Soil Quality and Landscape. Soil and water ... Geologist â Weathered rock particles contains minerals .... such as food production, water quality, and flood control, which have value ..... states or iron oxides, which are reflective of predominant aeration and ... Organic colloids exhibit much greater CEC than silicate clays.
Unit - 1
Dr. PALANIVEL, K CENTRE FOR REMOTE SENSING, BHARATHIDASAN UNIVERSITY, TIRUCHIRAPPALLI-23.
SEMESTER – VII GEOINFORMATICS IN SOIL SCIENCE
ELECTIVE PAPER-VIII 3 Credits
1. Introduction to Soil Science Nature and Importance of Soil, Soil formation, Soil survey, Physical, chemical and biological characters of soil, Relationship between Soil, plants and animal. 9 Hrs 2. Soil Types Soil types and classification, Soil genesis, Soil mineralogy and geochemistry of soil types: laterites, bauxites, aridisols, vertisols, camborthids. Application of soil micromorphology and landscape evolution. Radiometric age determination of soils. 12 Hrs 3. Soil Nutrients and Crop Production Elements essential for plants and animals, Soil nutrients - Nitrogen, Phosphorous, Potassium, Calcium, Magnesium and Sulphur in soil and its significance in plant growth, Micronutrients. 9 Hrs 4. Soil Quality and Landscape Soil and water relations, organic matter in soil, functions of organic matter, organic matter and soil structure, organic matter and essential elements, tillage, cropping systems and fertility and case studies. 12 Hrs 5. Geoinformatics in Soil Mapping, Management and Conservation Introduction, irrigation, drainage and soil management for field crops, gardens, lawns, pastures, range lands and forests. Conservation factors and implementation methods using Geoinformatics. 6 Hrs
Unit – 1
Introduction to Soil Science
Nature and Importance of Soil, Soil formation, Soil survey, Physical, chemical and biological characters of soil, Relationship between Soil, plants and animal. 9 Hrs.
What is soil?
– in view of various persons… thoughts /views, descriptions are different. Following are the views of various scientists and Engineers….
Geologist – Weathered rock particles contains minerals Mining Engineer – Over burden – debris Highway Engineer – Platform Civil Engineer – Foundation media
Agriculturist – Habitat for plants Hydrogeologist – Aquifer – Catchment, Reservoir, Media for GW occurrence, etc. A DYNAMIC NON-RENEWABLE NATURAL RESOURCE ON THE SURFACE OF THE EARTH COMPOSED OF MINERALS, ORGANIC MATTER AND LIVING ORGANISMS; UNCONSOLIDATED, IN WHICH PLANTS GROW;
Soil is obviously important because we wouldn’t have anything to stand on without soil. Without soil, we wouldn’t be able to plant trees, food crops hence, we wouldn’t be able to eat or have shelter to rest from the sun. In short, our soil is just as important as any other element in our planet. We are all connected in this planet and our soil is one of the most basic elements in our lives. Soil acts as a filter for our groundwater Some soils can support the massive weight of buildings and airports, while other are best for crops or rangeland Soil is the foundation for civilisation. Healthy soil is requisite for sustainable production of food, which allows a civilisation to exist. In fact, loss of soil fertility has been a contributing factor to every civilisation in history that has collapsed. (This is particularly frightening when one considers how we have damaged soil with modern, industrial approaches to agriculture.)
Our soil is also a very big link in the chain of life and death in our planet. Living things like animals, leaves, seeds and other organic matter decompose on the soil providing organic matter that fatten up the soil. These in turn make plants grow healthier which in turn are eaten by animals that are eaten by humans. The cycle resumes when the animal dies or something decomposes with a very big help from our soil.
Soil is important for many reasons: ==> soil provides physical support for plants; plant roots anchor themselves in the soil to prevent the plant from falling over or blowing away ==> soil has pores (air spaces) that (1) allow plant root respiration from which plants obtain energy; (2) absorb rainwater for plant root uptake; and (3) allow ventilation to rid soil of toxins (that occur naturally from plant products or are caused by anthropogenic pollution) ==> soil has insulating properties that protect plant roots from extreme weather conditions ==> fertile soil provides a continuous supply of dissolved mineral nutrients for plant growth ==> soil is the site for organic matter decomposition, where everything that dies is recycled back into the earth (the cycle of life) – it is therefore home to many organisms that take part in this decomposition (i.e. bacteria, fungi (mycorrhizae), earthworms)
We depend on soil to perform many functions. Healthy soil gives us clean air and water, bountiful crops and forests, productive rangeland, diverse wildlife, and beautiful landscapes. Soil does all this by performing five essential functions. Nutrient Cycling - Soil stores, moderates the release of, and cycles nutrients and other elements. During these biogeochemical processes, analogous to the water cycle, nutrients can be transformed into plant available forms, held in the soil, or even lost to air or water. Water Relations - Soil can regulate the drainage, flow and storage of water and solutes, which includes nitrogen, phosphorus, pesticides, and other nutrients and compounds dissolved in the water. With proper functioning, soil partitions water for groundwater recharge and for use by plants and soil animals. Biodiversity and Habitat - Soil supports the growth of a variety of plants, animals, and soil microorganisms, usually by providing a diverse physical, chemical, and biological habitat. Filtering and Buffering - Soil acts as a filter to protect the quality of water, air, and other resources. Toxic compounds or excess nutrients should be degraded or otherwise becomes dangerous to human and other living plants and animals. Physical Stability and Support - Soil has the ability to maintain its porous structure to allow passage of air and water, withstand erosive forces, and provide a medium for plant roots. Soils also provide anchoring support for human structures and protect archaeological treasures.
Value of Soil Social issues and soil quality Nutrient cycling, water regulation, and other soil functions are normal processes occurring in all ecosystems. From these functions come many benefits to humans, such as food production, water quality, and flood control, which have value economically or in improved quality of life. People can increase or decrease the value of soil benefits because land-management choices affect soil functions. Thus, it is important to understand what benefits we derive from soil and their value so we can appreciate the importance of managing land in a way that maintains soil functions. What are the social benefits of soil? People tend to emphasize benefits with the most direct, private economic value. In rural areas, this is usually plant growth especially as crops and rangeland, but also as recreation areas. In urban/suburban areas, the most direct economic benefits of soil relate to structural support for buildings, roads, and parking. Landscaping, gardening and parklands may also be valued economically. Those are all on-site, short-term benefits. That is, the landowner who decides how to manage the soil also reaps the benefits (and costs) of those management decisions. In contrast, many important benefits are long-term or go beyond the land being managed. The landholders who make the management choices and pay the costs of managing land may not be the same people who are affected by the landholders decisions. Society should discuss the value of these off-site benefits and to what extent the land owner or society should pay to maintain these soil functions.
Public, off-site benefits of soil relate to the following resource issues: Water quality of streams, lakes, oceans, and groundwater Air quality, especially particulates Greenhouse gases, including carbon dioxide, methane, and nitrous oxide. Biodiversity Water flow and flood control
Sustainability of land productivity Aesthetics
Soil Function
Benefit of Value to Humans On-site
Off-site
Nutrient cycling
Delivery of nutrients to plants Enhances water and air quality Carbon storage improves a variety of soil Storage of N and C can functions greenhouse gas emissions
Maintaining biodiversity and habitat
Supports the growth of crops, rangeland plants, and trees May increase resistance and resilience to stress Reduces pesticide resistance
Water relations
Provides erosion control Allows on-site water recharge of streams Provides flood and sedimentation control and ponds Groundwater recharge Makes water available for plants and animals
Helps maintain genetic diversity Supports wild species and reduces extinction rates Improves aesthetics of landscape
Can maintain salt, metal and micronutrient levels within Improves Filtering and buffering range tolerable to plants and quality animals Physical stability and support
Acts as a medium for plant growth Supports buildings and roads
Multiple functions
Sustains productivity
reduce
water
and
air
Stores archeological items Stores garbage
Maintains or improves air and/or water quality
SOIL COMPOSITION Organic
5% 20 - 30 % Air 45 % 20 - 30 % Water
Mineral
Major Soil forming factors (Jenny 1941)are :
Climatic effects Biological factors
Shape of the landscape – Topography Geologic factors Chronological factors
s = f (cl, o, r, p, t, ......)
The dots indicate that factors of lesser importance such as mineral accession from the atmosphere, or fire, might need to be taken into account.
To simplify the application of the above equation, it has been practice to solve it for changes in a soil property s when only one of the control variable (e.g. climate) varies, the others being constant or nearly so. The relationship is then called a climofuntion (climate = control variable):
s = f (cl) o, r, p, t, ...
and the range of soils formed is called a climosequence. Biosequences, toposequences, lithosequences and chronosequences of soils have been recognized in various parts of the world. The term toposequence is synonymous with Milne's catena concept (Milne, 1935). Indeed, the main virtue of Jenny's attempt to quantify the relationship between soil properties and soil forming factors lies not in the prediction of exact values of s at a particular site, but rather in identifying trends in properties and soil groups that are associated with readily observable changes in climate, parent material, etc.
DETECT DESCRIBE DEFINE DELINEATE DEDUCE
RRSS : 2000 ha / day RSS
: 400 ha / day
SDSS : 200 ha / day
DSS
: 80 ha / day
- identify - examine - classify - trace boundaries - inferences
SOIL SURVEY WHAT IS?…. - DETECT
: IDENTIFY
- DESCRIBE
: THE CHARACTERS OF SOIL
- DEFINE
: ITS TAXANOMICAL UNIT
- DELINEATE : ITS BOUNDARY and - DEDUCE
: INFERENCES TO BEST USE
TYPES OF SOIL SURVEYS :
• RRSS
: RAPID RECCONNAISSANCE SOIL SURVEY - 2000 Ha / day
• RSS
: RECCONNAISSANCE SOIL SURVEY - 400 Ha / day
• SDSS
: SEMI DETAILED SOIL SURVEY - 200 Ha / day
• DSS
: DETAILED SOIL SURVEY - 80 Ha / day
• A soil survey describes the characteristics of the soils in a given area, • classifies the soils according to a standard system of classification, • plots the boundaries of the soils on a map, and • makes predictions about the behavior of soils. • The different uses of the soils and • how the response of management affects them are considered. • The information collected in a soil survey helps in the development of land-use plans and • evaluates and predicts the effects of land use on the environment.
SOIL MAPPING BY CONVENTIONAL SURVEY
• BASE MAP PREPARATION • PLAN TRAVERSING • FIX SOIL LEGENDS USING ROAD-CUTS, WELL-CUTS, FOUNDATION PITS, AUGER BORINGS • OPEN PROFILE AND DEFINE
• TRACE BOUNDARY FOLLOWING TOPOGRAPHY, VEGETATION, CULTURAL PRACTICES, ETC. • FIX MASTER PROFILE AND DESCRIBE • COLLECT SOIL SAMPLES AND ANALYSE • MODIFY SOIL NAME BASED ON ANALYSIS • PREPARE SOIL SURVEY REPORT
SOIL MAPPING THRO RS DATA
Base map preparation
Selection of proper season satellite data
Delineation of soil boundaries using VI keys and collateral data
Name the polygons by number or alphabet
Plan field visit – open soil profile, examine and classify
Improve VI keys and substitute class name to soil polygons
Check accuracy and area calculation
SOIL COLOUR
MINERAL CONTENT
ORGANIC MATTER
SOIL MOISTURE
TEXTURE
STRUCTURE
PARTICLE SIZE
VEGETATION
STATE : PUNJAB GEOGRAPHICAL AREA : 50.3 L.ha By conventional method : Per day coverage Per year (200 WD) To cover 50.3 L.ha
2000 ha 4 L.ha 12.6 Field Party Years (FPY)
By RS Technique : Time spent 310 man days which corresponds to 1.5 FPY Efficiency : 12.6 / 1.5 = approx. 8 times Remote Sensing Tech thus affords 8 times more efficiency than conventional method ( Sehgal and Karale, 1998 )
Physical properties of soil
Texture – Size distribution of primary mnls
Structure – arrangement of primary particles into secondary particles – granular, blocky, platy, etc. Consistence – Soil’s Physical condition at various moisture content – hard, loose, friable, firm, plastic, sticky Colour – determined by minor components
Soil Texture The texture of a soil is its appearance or “feel”
and it depends on the relative sizes and shapes of the particles as well as the range or distribution of those sizes. Coarse-grained soils:
Fine-grained soils:
Gravel
Silt
Sand
Clay
0.075 mm (USCS) 0.06 mm (BS) (Hong Kong)
Sieve analysis
Hydrometer analysis
Unified Soil Classification System (USCS)
Soil texture, has a strong influence on the properties of a soil.
Particles larger than 2 mm in diameter are considered inert. Little attention is paid to them unless they are boulders that interfere with manipulation of the surface soil.
Particles smaller than 2 mm in diameter are divided into three broad categories based on size.
Particles of 2 to 0.05 mm diameter are called sand; those of 0.05 to 0.002 mm diameter are silt; and the 51
1.7 g/cm3 + low O2
Soil Structure Anyone who has ever made a mud ball knows that soil particles have a tendency to stick together. Attempts to make mud balls out of pure sand can be frustrating experiences because sand particles do not cohere (stick together) as do the finer clay particles. The nature of the arrangement of primary particles into naturally formed secondary particles, called aggregates, is soil structure. A sandy soil may be structureless because each sand grain behaves independently of all others. A compacted clay soil may be structureless because the particles are clumped together in huge massive chunks. In between these extremes, there is the granular structure of surface soils and the blocky structure of subsoils. Soil structure is the shape that the soil takes based on its physical and chemical properties. Each individual unit of soil structure is called a ped.
Structure
… contd…
In some cases subsoils may have platy or columnar types of structure. Structure may be further described in terms of the size and stability of aggregates.
Structural class is based on aggregate size, while structural grade is based on aggregate strength. Soil horizons can be differentiated on the basis of structural type, class, or grade. What causes aggregates to form and what holds them together? Clay particles cohere to each other and adhere to larger particles under the conditions that prevail in most soils. Wetting and drying, freezing and thawing, root and animal activity, and mechanical agitation are involved in the rearranging of particles in soils-including destruction of some aggregates and the bringing together of particles into new aggregate groupings or cracks form around soil masses, creating peds.
Peds are held together and in place through the adhesion of organic substances, iron oxides, clays or carbonates. Cracks and channels between peds are important for water, air, and solute transport and deep water drainage. Finer soils usually have a stronger, more defined structure than coarser soils due to shrink/swell processes predominating in clay-rich soils and more cohesive strength between particles.
Structure
… contd…
Organic materials, especially microbial cells and waste products, act to cement aggregates and thus to increase their strength. On the other hand, aggregates may be destroyed by poor tillage practices, compaction, and depletion of soil organic matter. The structure of a soil, therefore, is not stable in the sense that the texture of a soil is stable. Good structure, particularly in fine textured soils, increases total porosity because large pores occur between aggregates, allowing penetration of roots and movement of water and air.
1. Single-grained (windblown particles such as silt; sand) highly erodable 2. Massive (heavy clays) 3. Aggregated (ideal soil structure)
Soil Structure: type, class, & grade
Structure less (single grain) Grade (stability) weak moderate strong
Class (size) very fine fine medium coarse very coarse
Massive Type (shape) platy prismatic columnar angular blocky subangular blocky granular crumb
Compression of an unsaturated soil, resulting in reduction of fractional air volume Natural and human-induced compaction: Surface crusts Hardpans Clay pans Carbonates
Tillage pans Trampling by animals Machinery
Compaction measurements Bulk density
Penetrometer (indirect, and measures soil strength)
Soil Consistency Consistence is a description of a soil's physical condition at various moisture contents as evidenced by the behavior of the soil to mechanical stress or manipulation. Descriptive adjectives such as hard, loose, friable, firm, plastic, and sticky are used for consistence. Soil consistence is of fundamental importance to the engineer who must move the material or compact it efficiently. The consistence of a soil is determined to a large extent by the texture of the soil, but is related also to other properties such as content of organic matter and type of clay minerals.
Soil Color The color of objects, including soils, can be determined by minor components. Generally, moist soils are darker than dry ones and the organic component also makes soils darker. Thus, surface soils tend to be darker than subsoils. Red, yellow and gray hues of subsoils reflect the oxidation and hydration states or iron oxides, which are reflective of predominant aeration and drainage characteristics in subsoil. Red and yellow hues are indicative of good drainage and aeration, critical for activity of aerobic organisms in soils. Mottled zones, splotches of one or more colors in a matrix of different color, often are indicative of a transition between well drained, aerated zones and poorly drained, poorly aerated ones. Gray hues indicate poor aeration. Soil color charts have been developed for the quantitative evaluation of colors.
Soil Porosity and Permeability
Soil Particle Density and Bulk Density
Soil Temperature
Soil Tillage and Plant Growth
Soil Conservation Tillage
Soil moisture Soil particle size - texture Bulk density Color Organic matter Soil water retention properties
Field capacity - 1/3 atm Wilting point - 15 atm Hygroscopic water - 30 atm Available water = field capacity - wilting point Wilting point – A condition at which there is a loss of rigidity of non-woody parts of plants. This occurs when the turgor pressure in non-lignified plant cells falls towards zero, as a result of diminished water in the cells.
Chemical properties of soil
Major elements ◦ 8 Chemical elements ◦ Amongst 8, Oxygen – a negatively-charged ion (Anion) in crystal structures - most prevalent on both weight and volume basis ◦ The next common elements, all positively-charged ions (Cation) in decreasing order are silicon, aluminium, iron, magnesium, calcium, sodium and potassium. ◦ Ions of these elements combine in various ratios to form different minerals ◦ More than 80 other elements also occur in soils and the earth’s crust, but in much smaller quantities.
Soils contain less of the water soluble weathering products, Ca, Mg, Na, K, Fe, Al. Old and highly weathered soils normally have high concentrations of Al and FeO. Organic fraction of a soil is much less than 10% of the soil mass by weight But it has great influence on soil chemical properties. Soil organic matter is composed chiefly of carbon, hydrogen, oxygen, nitrogen and smaller quantities of sulphur and other elements.
Organic fraction • serves as a reservoir for the plant’s essential nutrients • Increases soil water holding capacities • Increases cation exchange capacities • Enhances soil aggregation and • Enhances soil Structure. Most chemically active fraction of soils consists of colloidal clays and organic matter
The most chemically active fraction of soils consists of colloidal clays and organic matter. Colloidal particles are so small (< 0.0002 mm) that they remain suspended in water and exhibit a very large surface area per unit weight with high adsorptive capacity. Montmorillonite, vermiculite, and micaceous clays are examples of 2:1 clays, while kaolinite is a 1:1 clay mineral. 2:1 CLAYS: Clays having a layer of Al₂ O₃(octahedral sheet) sandwiched between two layers of silicon oxide (tetrahedral sheets) 1:1 CLAYS: Clays having one tetrahedral sheet bonded to one octahedral sheet.
Cation exchange Capacity It is the ability of soil clays and organic matter to adsorb and exchange cations with those in soil solution (water in soil pore space). A dynamic equilibrium exists between adsorbed cations and those in soil solution. Cation adsorption is reversible if other cations in soil solution are sufficiently concentrated to displace those attracted to the –ve charge on clay and organic matter surfaces. The quantity of cation exchange is measured per unit of soil weight and is termed Cation Exchange Capacity. Organic colloids exhibit much greater CEC than silicate clays. Cation exchange capacity is an important phenomenon for two reasons:
1. Exchangeable cations such as calcium, magnesium, and potassium are readily available for plant uptake and 2. Cations adsorbed to exchange sites are more resistant to leaching, or downward movement in soils with water.
Various clays also exhibit different exchange capacities. Thus, cation exchange capacity of soils is dependent upon both organic matter content and type of silicate clays. Movement of cations below the rooting depth of plants is associated with weathering of soils. Greater cation exchange capacities help decrease these losses. Pesticides or organics with positively charged functional groups are also attracted to cation exchange sites and may be removed from the soil solution, making them less subject to loss and potential pollution.
Calcium (Ca++) is normally the predominant exchangeable cation in soils, even in acid, weathered soils. In highly weathered soils, such as oxisols, aluminum (Al+3) may become the dominant exchangeable cation. The energy of retention of cations on negatively charged exchange sites varies with the particular cation. The order of retention is: aluminum > calcium > magnesium > potassium > sodium > hydrogen.
o o o
o
o
Movement of cations below the rooting depth of plants is associated with weathering of soils. Greater cation exchange capacities help decrease these losses. Pesticides or organics with positively charged functional groups are also attracted to cation exchange sites and may be removed from the soil solution, making them less subject to loss and potential pollution. Calcium (Ca++) is normally the predominant exchangeable cation in soils, even in acid, weathered soils. In highly weathered soils, such as oxisols, Al+3 may become the dominant exchangeable cation.
Cations with increasing positive charge and decreasing hydrated size are most tightly held. Calcium ions, for example, can rather easily replace sodium ions from exchange sites. This difference in replaceability is the basis for the application of gypsum (CaSO4) to reclaim sodic soils (those with > 15% of the cation exchange capacity occupied by sodium ions). Sodic soils exhibit poor structural characteristics and low infiltration of water. The cations of calcium, magnesium, potassium, and sodium produce an alkaline reaction in water and are termed bases or basic cations. Aluminum and hydrogen ions produce acidity in water and are called acidic cations.
The percentage of the cation exchange capacity occupied by basic cations is called percent base saturation. The greater the percent base saturation, the higher the soil pH.
Cation exchange, in the soil. 1) Clay and organic matter have negative charges that can hold and release positively charged nutrients. (The cations are adsorbed onto the surface of the clay or humus.) That static charge keeps the nutrients from being washed away, and holds them so they are available to plant roots and soil microorganisms. 2) The roots and microorganisms get these nutrients by exchanging free hydrogen ions. The free hydrogen H+ fills the (-) site and allows the cation nutrient to be absorbed by the root or microorganism. 3) The unit of measure for this exchange capacity is the milligram equivalent, ME or meq, which stands for 1 milligram (1/1000 of a gram) of exchangeable H+. In a soil with an exchange capacity (CEC) of 1, each 100 grams of soil contain an amount of negative (-) sites equal to the amount of positive (+) ions in 1/1000th of a gram of H+.
Soil pH Soil pH is probably the most commonly measured soil chemical property and is also one of the more informative. Like the temperature of the human body, soil pH implies certain characteristics that might be associated with a soil. Since pH (the negative log of the hydrogen ion activity in solution) is an inverse, or negative function. Soil pH decreases as hydrogen ion (or acidity) increases in soil solution. Soil pH increases as acidity decreases. Soil pH refers to a soil’s acidity or alkalinity and is the measure of hydrogen ions (H+) in the soil A high amount of H+ corresponds to a low pH value and vice versa. The pH scale ranges from approximately 0 to 14 A soil pH of 7 is considered neutral. Soil pH values greater than 7 signify alkaline (basic) conditions, whereas those with values less than 7 indicate acidic conditions.
Soil pH typically ranges from 4 to 8.5, but can be as low as 2 in materials associated with pyrite oxidation and acid mine drainage. In comparison, the pH of a typical cola soft drink is about 3.
Soil
pH has a profound influence on plant growth. Soil pH affects 1. The quantity 2. Activity 3. Types of microorganisms in soils
which in turn influence
1. 2. 3. 4.
Decomposition of crop residues, Manures, Sludges Other organics.
It also affects other nutrient transformations and the solubility, or plant availability, of many plant essential nutrients. Phosphorus, for example, is most available in slightly acid to slightly alkaline soils, while all essential micronutrients, except molybdenum, become more available with decreasing pH. Aluminum, manganese, and even iron can become sufficiently soluble at pH < 5.5 to become toxic to plants. Bacteria which are important mediators of numerous nutrient transformation mechanisms in soils generally tend to be most active in slightly acid to alkaline conditions.
Macronutrients tend to be less available in soils with low PH. Micronutrients tend to be less available in soils with high pH.
A higher concentration of H+ (lower pH) will neutralize the negative charge on colloids, thereby decreasing CEC and increasing AEC. The opposite occurs when pH increases
It also affects Other nutrient transformations The solubility Plant availability of many plant essential nutrients. Phosphorus, is most available in slightly acid to slightly alkaline soils, while all essential micronutrients, except Mo, become more available with decreasing pH. Al, Mn and even Fe can become sufficiently soluble at pH < 5.5 to become toxic to plants. Bacteria which are important mediators of numerous nutrient transformation mechanisms in soils generally tend to be most active in slightly acid to alkaline conditions.
pH Cation exchange capacity - total amount of cations(including H+) that can be displaced Base saturation - the percent of the cation exchange complex occupied by exchangeable bases (mostly plant nutrients such as Ca, Mg, Na, K, etc.) Nutrients - amounts of macronutrients and micronutrients
The presence and concentration of salts in soil can have adverse effects on soil function and management. Salt-affected soils are most common in arid and semiarid regions where evaporation exceeds precipitation and dissolved salts are left behind to accumulate, or in areas where vegetation or irrigation changes have caused salts to leach and accumulate in low-lying places (saline seeps). The three main types of salt-affected soils are saline, sodic and saline-sodic.
Saline soils contain a high amount of soluble salts, primarily calcium (Ca2+), magnesium (Mg2+), and potassium (K+), whereas sodic soils are dominated by sodium (Na+). Saline-sodic soils have both high salt and Na+ content. Salts in soil can affect structure, porosity and plant/water relations that can ultimately lead to decreased productivity. Salt-affected soils needs proper management.
Calcareous soils often form from the weathering of carbonate-rich parent material, such as limestone or lime-enriched glacial till, and generally occur in areas where precipitation is too low to leach the minerals from the soil. Carbonates can be found throughout a soil profile or concentrated in the lower horizons due to downward leaching. The subhorizon letter ‘k’ denotes a calcareous horizon layer (e.g., Bk). Calcareous soils can be distinguished in the field by an effervescence (fizz) reaction that occurs when a drop of dilute acid (10% hydrochloric acid or strong vinegar) is applied (Brady and Weil, 2002). The presence of carbonates in soil can affect soil productivity by influencing soil pH, structure, WHC and water flow. Calcareous soils have a high ‘buffering capacity,’ or resistance to changes in pH. This is due to free carbonates being able to effectively neutralize acids in the soil. Thus, the pH of calcareous soils changes very little and is maintained near 8. Because calcareous soils are so well-buffered, reducing the pH with acidifying amendments (NM 10) is often difficult and costly. N.B.: Leaching (Soil/agriculture), the loss of water-soluble plant nutrients from the soil; or applying a small amount of excess irrigation to avoid soil salinity
Carbonates can alter soil structure by affecting texture and promoting aggregation. Carbonate deposits can be of varying size, ranging from very fine clay-like powder to coarser, silt-like deposits, which can impact texture. If carbonates are not removed prior to analysis, soils may be incorrectly classified. For instance, a soil analyzed for texture without the removal of CaCO3 may classify as a clay loam, however after removing carbonates it may classify as a sandy loam. Thus, it is important to consider the presence of carbonates when analyzing the texture of calcareous soils, both in the field and laboratory. Additionally, Ca2+ and Mg2+ in soil causes soil particles to ‘flocculate,’ or clump together, thus increasing the formation of stable aggregates (SW 2). The influence of carbonates on soil structure can cause calcareous soils to have different water relation properties than non-calcareous soils. WHC can be affected by the size and concentration of carbonates. Very fine carbonate particles can coat clay and silt particles and reduce their surface tension with water, and when a large percentage of CaCO3 is present in the clay fraction (30% or higher), the soil’s WHC can be reduced (Massoud, 1972). Diffusivity, a measure of how well water moves through soil, may also be affected by carbonates.
Base saturation is the percent of the exchange sites that are occupied by exchangeable bases (Ca++, Mg++, K+), which are important plant nutrients.
Soil Biota Soil Microorganisms Nutrient cycling by soil microbes
“Soil is not a dead mass but an abode of millions
of organisms, which includes crabs, snails, earthworms, mites, millipedes, centipedes”
These feed on plant residues burrow the soil and help in aeration and percolation of water. The soil organisms are of two types: 1. Microflora & 2. Macrofauna
Bactro Actinomycetes, Fungi and Algae relate to former and Protozoa, Nematodes relate to some
of these have symbiosis with other organisms. They act on plant and animal residue and release the food material which in turn used by plants.
The soil contains a vast array of life forms ranging from submicroscopic (the viruses), to earthworms, to large burrowing animals such as gophers and ground squirrels. Microscopic life forms in the soil are generally called the "soil microflora" (though strictly speaking, not all are plants in the true sense of the word) and the larger animals are called macrofauna.
Soil animals, especially, the earthworms and some insects tend to affect the soil favorably through their burrowing and feeding activities which tend to improve aeration and drainage through structural modifications of the soil solum. In general, they affect soil chemical properties to a lesser extent though their actions indirectly enhance microbial activities due to creation of a more favorable soil environment.
(within a depth range of a few meters)
Soil micro organisms occur in huge numbers and display an enormous diversity of forms and functions. Major microbial groups in soil are bacteria (including actinomycetes), fungi, algae (including cyanobacteria) and protozoa. Because of their extremely small cell size (one to several micrometers), enormous numbers of soil microbes can occupy a relatively small volume, hence space is rarely a constraint on soil microbes.
Soil microbes can occur in numbers ranging up to several million or more in a gram of fertile soil (a volume approximately that of a red kidney bean). Note that the bacteria are clearly the most numerous of the soil microbes. Perhaps more important than the numbers of the various soils microbes is the microbial biomass contributed by the respective groups. It is the soil fungi which tend to contribute the most biomass among the microbial groups. In fact, it is because of their large contribution to the biomass that they are generally regarded as being the dominant decomposer microbes in the soil. You might find it surprising that there are literally "tons" of microbes beneath your feet as you walk across a grassland in Africa or Australia or through a cornfield in the American Midwest. Interestingly, a fungus discovered in the state of Michigan may be one of the largest living organisms on the planet.
A fungus, Armillaria bulbosa, discovered in the U.S. in the state of Michigan, could turn out to be earth's largest creature or at least among the largest. Scientists discovered the fungus growing among the roots of hardwood trees in a forest. The microscopic, branched filaments (called hyphae) of the fungus occupy a 14.8 ha (37-acre) area of land. Careful genetic analysis has shown the filaments constitute a single organism. Fungi generally radiate outward in a circular pattern as they grow through the soil. In fact, the fairy rings (a ring of darker grass caused by fungi) of mushrooms (named because ancient peoples thought they represented the paths of fairies dancing in the night) often seen in lawns or on golf courses actually represent the outer boundary of a developing fungus. Scientists estimate that the portion of the Michigan fungus they have been able to identify, may weigh as much as 100 tons, slightly less than a blue whale. Imagine the biochemical capacity of a soil micro organism this large!
Soil microbes influence much in controlling the quantities of chemical elements. The mineralization of organic materials by soil microbes liberates carbon dioxide, ammonium (which is rapidly converted to nitrate by soil microbes), sulphate, phosphate and inorganic forms of other elements. This is the basis of nutrient cycling in all major ecosystems of the world. John Burroughs once said, "Without death and decay, how
could life go on?“
This pool of microbial biomass constitutes a portion of the soil organic matter which turns over (cycles) fairly quickly and therefore represents a "fertility buffer" in the soil. The liberation of carbon dioxide through microbial respiration makes possible the continued photosynthesis (i.e. carbon dioxide fixation) by algae and green plants which in turn produce more organic materials which may ultimately reach the soil, thereby completing the cycle.
In the world's agricultural soils, the source of our food supply, mineralization of nitrogen by soil microbes is a most important process. In those soils not receiving external inputs of fertilizer nitrogen the liberation of ammonium from organic debris makes possible the continued growth of new plant matter. Therefore, it is the soil microbial population which controls the productivity of these soils if other environmental factors (moisture, temperature) are suitable. Nitrogen tied-up (assimilated into cell constituents) in microbial cells is not available for plants or other microbes until that tissue has been decomposed by other microbes. In other words, nitrogen contained in tissues is said to be immobilized. Microbes are the keys for the remobilization of these nutrients.
Soil bacteria, can control the forms of the ions in which these nutrients occur. For example, ammonium (NH4+) in the soil is usually rapidly oxidized by bacteria first to nitrite and then to nitrate (NO3-) which may readily leach through soil. Ammonium is oxidized to nitrite and then to nitrate by the bacteria Nitrosomonas and Nitrobacter, respectively. Similarly, reduced sulfur compounds such as thiosulphate, elemental sulphur and even iron pyrite (FeS2, "Fool's Gold") can be oxidized to sulphuric acid by soil bacteria. Unlike the decomposer microbes which use organic carbon compounds from organic matter for energy and to make cell matter (e.g. they are called heterotrophs), these specialized bacteria called chemoautotrophs obtain their carbon for cell synthesis from carbon dioxide or from dissolved carbonate.
o
o
o
o
Nitrogen and sulphur may be converted to gaseous forms (volatilized) and lost to the atmosphere. Nitrogen in the form of nitrate can be converted to gases such as nitrous oxide (N2O) and dinitrogen (N2) through the process of denitrification (the bacterial reduction of NO3to N2O or N2) by soil bacteria under anaerobic conditions. A consequence of denitrification is that nitrogen, a precious nutrient for plants, is lost from the soil. On the other hand, this process is a useful way to remove excess nitrate from wastewater.
Rhizobium - legume root-nodule symbiosis.
Soil bacteria belonging to the genera Rhizobium and Bradyrhizobium are capable of inducing the formation of nodules on roots of specific legumes (plants like peas, beans, peanuts, soybeans, alfalfa, etc.) and fixing large quantities of nitrogen in these structures. In the nodule, the bacteria are supplied with carbon sources that they need in order to fix nitrogen. In return for this carbon, the bacteria fix atmospheric nitrogen which is converted to amino acids used by the plant for growth. Nearly two-thirds of the world's nitrogen supply is from biological nitrogen fixation. Legumes have been used since the beginning of recorded history as "soil improving" crops known as "green manures". Green manuring is the practice of growing a legume species for the sole purpose of returning it to the soil to serve as a source of nitrogen for an ensuing crop.
Bioremediation may be defined as the controlled use of microorganisms for the destruction of chemical pollutants. A large number of processes have been developed to handle various wastes and for the cleanup of spilled organic materials. At the heart of all of these processes lies the premise that the metabolic activities of bacteria or fungi can be used to degrade many of the organic chemicals of commerce (solvents, pesticides, hydrocarbon fuels, etc.).
In biostimulation the environment into which the material has been spilled or otherwise introduced is made favorable for the rapid development of microbes. Adding sufficient nitrogen and phosphorus fertilizer to overcome nutrient limitations to microbial growth and providing some mechanism for increased aeration of the system. Development of the indigenous microbial population which usually contains microbes able to degrade the compounds of interest. In the practice of bioaugmentation, an external microbial population is added in order to speed up the degradation process.
It is probable that in due time useful microbial products or processes will be developed for use in the clean-up of oil or other chemical spills. What is certain is that successful bioremediation will require detailed knowledge of the factors which make some microbes more competitive than others in a given environment. Only when these details are established will we know “how to use sound ecological principles to
add microbes to these complex environments to insure their establishment and function in the clean-up process”.
All the plants are uptaking its maximum essential macro and micro nutrients from soil solutions only. Different plant species requires different nutrients in different quantities. It is really a difficult task of estimating the amount of nutrients for the better growth of plants Though a lots of research have brought out different information on plant’s nutrition.
Plant nutrition is a difficult subject to understand completely, partially because of the variation between different plants and even between different species or individuals of a given clone The macronutrients are consumed in larger quantities and are present in plant tissue in quantities from 0.2% to 4.0. Micronutrients are present in plant tissue in quantities measured in parts per million, ranging from 5 to 200 ppm, or less than 0.02% dry weight. Each of these nutrients is used in a different place for a different essential function.
Carbon, nitrogen, oxygen, phosphorus, potassium, calcium, magnesium, sulphur and the micronutrients are boron, chlorine, cobalt, copper, iron, manganese, molybdenum, nickel and zinc are the mineral needed for animal growth. In addition to this, some elements such as selenium and iodine, though not required by plants, are essential nutrients for animals.
Over the millions of years animals have been on the planet, there has been ongoing adjustment in a particular period to changing soil and climatic conditions. In each climatic period, generally there has been a balance created between the nutrient needs of the animals and the ability of the soil to supply it. Nutrient cycling is essential ultimate sustenance for plants and animals.
Web of Life
Selenium is among the rarer elements on the surface. Selenium occurs naturally in the environment.
Well fertilized agricultural soil generally has about 400 mg/ton since the element is naturally present in phosphate fertilizers and is often added as a trace nutrient. selenium is more readily absorbed by animals through the digestive tract. It has been estimated that lactating dairy goats absorb about 65% of ingested selenomethionine Selenium substances in soil are usually broken down to selenium and water fairly quickly, so that they are not dangerous to the health of organisms.
Iodine compounds are found in seawater, soil, and rocks. Once in the air, iodine can combine with water or with particles in the air and can enter the soil and surface water, or land on vegetation when these particles fall to the ground or when it rains Iodine can remain in soil for a long time because it combines with organic material in the soil. It can also be taken up by plants that grow in the soil Cows or other animals that eat these plants will take up the iodine in the plants. The reason that iodine ultimately concentrates in the soil is the result of its chemistry. Iodine is one of the halogens. The halogens are prominent anions in the environment. "The horse has a high sensitivity for iodine” Even just an extra of 35 mg iodine per day (adult horses, dry matter intake: 10 kg) can cause severe health risks,
Unit - 2
Dr. PALANIVEL, K CENTRE FOR REMOTE SENSING, BHARATHIDASAN UNIVERSITY, TIRUCHIRAPPALLI-23.
Soil types and classification, Soil genesis, Soil mineralogy and geochemistry of soil types: laterites, bauxites, aridisols, vertisols, camborthids. Application of soil micromorphology and landscape evolution. Radiometric age determination of soils. 12 Hrs
Soils can be classified in many ways. Based on its location / occurrence, soils are classified as follows:
soil Insitu
Drifted
a) Residual
a) Colluvial
b) Cumulose
b) Alluvial c) Glacial d) Aeolian e) Laccustrine
Clayey Soil Silty Soil Loamy Soil Sandy Soil Peat Soil Chalky Soil
Clay soils contain very fine, flat particles which tend to stick together. They feel heavy and sticky and form a little ball when you rub a small amount between finger and thumb. A handful of damp clay will retain the impression of your fingers and may appear shiny on the surface.
Silty soils fall between clay and sand in terms of particle size, and feel smooth, silky or soapy when rubbed between your fingers.
Loam is one of the ideal soil types for plant growing purposes. It comprises proportionate amounts of sand, silt and clay in the ratio . Generally, loam soil is fertile (unlike sandy soil) and has no water drainage problems like clayey soil and silty soil.
Chalk soils were described by Geoff Hamilton as 'pale and hungry looking' which sums them up really well! They feel dry and crumbly in your hand, are usually greyish white in colour, and contain fragments of white chalk.
Peat soils have a very high organic content so are very dark, almost black, in colour. In your hand they feel moist and spongy and are hard to roll into a ball.
In India diverse natural environment has engaged various
types of soil. Number of soil classifications has been adopted for soils of India. Based on physiography, climatic conditions, and Geological formations soil has been grouped into
Alluvial Soils Mountain Soils Red and Yellow Soils Black soils Lateritic soils Saline Soils Desert Soils
Red Soil Red soils, one of twelve soil orders in USDA classification
known as Ultisols.
The red and yellow colors result from the accumulation
of iron oxide (rust) which is highly insoluble in water.
Major nutrients, such as calcium and potassium, are typically
deficient.
They generally cannot be used for sedentary agriculture
without the aid of lime and other fertilizers such as superphosphate.
Crops grown in Red soil includes Groundnuts, mullet, Ragi,
rice, potatto, sugarcane, wheet etc
They are less clayey and sandier and are poor in important minerals like lime, phosphorous and nitrogen. Red soil is acidic like that of the Lateritic soil. This soil is mainly cultivated during the monsoon rainy season. Red soils also develop in Manipur, Shillong Plateau and Mizoram.
Black Soil The colour of the soil is black because of the presence of certain salts. However, in some places, presence of humus in the soil imparts its black colour. Black soils, also called regur or black-cotton soil, This soil becomes sticky when is wet owing to the high quantity of clay deposition. Black soils are generally thin and sandy in the hilly regions of the country. It does not contain adequate nitrogen but it contains sufficient phosphorous required for the growth of the plants. These soils are spread mostly across the Deccan Lava Plateau, the Malwa Plateau, and interior Gujarat, where there is both moderate rainfall and underlying basaltic rock. Black soils are highly argillaceous, very fine-grained and dark and contain a high proportion of calcium and magnesium carbonates. These soils have high plasticity and stickiness.
their iron-rich granular structure makes them resistant to wind and water erosion.
They are also highly moisture-retentive, thus responding well to irrigation.
Red Soil
Black Soil
alluvial soils are mainly found in the plains of northern India. These soils have low phosphorous and nitrogen content. These soils are sandier in their composition. Even in the north western regions of the country which are drier these soils are found.
Lateritic Soil Lateritic soil formed due to seasonal variations in
tropical temperature and humidity.
The color of the soil indicates the soils fertility. Despite a typically dense vegetation, little
decomposed plant material (humus) passes into the soil due to its rapid decay.
Lateritic soils are rich in Iron and aluminium and
poor in potash, nitrogen, phosporic acid and lime.
Laterite soils are mainly found in capings of flat
Lateritic soil
Alluvial soil
Desert Soils Desert soils are basically sandy texture, poor
clay content and lacks in moisture. They are saline soils and evaporation is quite rapid. Desert soils are generally brown or reddish color
These soils are favourable for vegetation if there is water content. These soils contain an important mineral
that is nitrogen.
They are regions of extremely low rainfall and
level of precipitation is below 250 mm per Year.
Desert Soils
Saline soils develop in the coastal plains of Kerala and Orissa. In some regions of the country, salt content is in toxic doses. Saline soils are basically black in colour. They are highly acidic.
Mountain soils are considered as a significant variety of soil in the Himalayan region of the country. They are mainly found in dry and cold district in the northern region of India.
Mountain soil
Textural Classification of Soils
Soil Texture Triangle Source: USDA Soil Survey Manual Chapter 3
Characteristics
(Holtz and Kovacs, 1981)
It is important to understand the soil units used for general classification of soils
Soil Units Pedon – smallest three-dimensional unit /volume of soil; natural aggregates; that displays the full range of properties characteristic of a given soil. (1-10 m2 of area) - the fundamental unit of soil classification Polypedon – collective of such pedons; group of closely associated pedons in the field Soil Series – class of soils world-wide which share a common suite of soil profile properties Pedology - study of soil profiles Horizon - a layer of soil that can be differentiated from below and up above
Profile - a vertical section of soil through all its horizon down to rock
Diagnostic Soil Horizons Epipedons
Mollic Umbric Ochric Histic Melanic Plaggen Anthropic
Subsurface Soils Albic Kandic Argillic Spodic Oxic
Epipedons
Mollic Epipedon Thickness Color Organic Carbon Base Saturation Structure
> 18-25 cm value < 3.5 moist chroma < 3.5 moist > 0.6 % > 50 % strongly developed
Organic carbon = organic matter x 0.5
Umbric Epipedon
Ochric Epipedon
Meets all criteria of the
Too: thin light low in
Mollic epipedon, except base saturation < 50%. Chemically different than Mollic
Orrganic Matter. Ochric = pale Extremely common
Histic Epipedon Organic horizon Formed in
wet areas Black to dark brown Low bulk density = 20-30 cm thick. Organic = > 20% - 35% Organic Matter.
Histic Epipedon Similar in properties to
Mollic Formed in volcanic ash Lightweight, Fluffy.
Anthropic Horizon •
Resembles mollic (color, orgainc matter.) • Use by humansas well as Shells and bones
Plaggen Epipedon Produced by long-term
(100s yrs.) manuring Old, human-made surface horizon > 50 cm thick
Subsurface Pedons
Horizon
Description of detailed soil horizons
O
consists mainly of organic matter from the vegetation, which accumulates under conditions of free aeration.
A
eluvial (outwash) horizon consisting mainly of mineral matter mixed with some humified (decomposed) organic matter.
E
strongly eluviated horizons having much less organic matter and/or iron and/or clay than the horizons underneath. Usually pale coloured and high in quartz.
B
illuvial (inwashed) horizon characterised by concentrations in clay, iron or organic matter. Some lime may accumulate, but if the accumulation is excessive, the horizon is named K.
K
horizon containing appreciable carbonate, usually mainly lime or calcium carbonate.
G
gleyed horizons which form under reducing (anoxic) conditions with impeded aeration, reflected in bluish, greenish or greyish colour.
C
weathered parent material lacking the properties of the solum and resembling more the fresh parent material.
R
regolith, the unconsolidated bedrock or parent material.
Albic (white) Horizon Light-colored (Value > 6 moist ) Elluvial (E master horizon*) Low in clay, Fe and Al oxides Generally sandy textured Low chemical reactivity (low CEC) Typically overlies Bh or Bt horizons
albic
Argillic Horizon Illuvial accumulation of silicate clay Illuvial based on overlying horizon Clay bridges Clay coatings
Spodic Horizon • Illuvial accumulation of organic matter and aluminum (+/- iron) • Dark colored (value, chroma < 3) • Low base saturation (acidic) • Formed under humid acid conditions
Spodic
Oxic horizon • Highly weathered (high temperatures, high rainfall)
- High in Fe, Al oxides - High in low-activity clays activity (kaolinite < smectite < vermiculite)
Elluviation (E horizon)
Organic matter
Clays
A
A
E E
Bh horizon
Bt horizon Bt
Bh Spodic horizon
Argillic horizon
O
- Organic horizon
A
- elluvial horizon
B
- illuvial horizon
C
- weathered gneiss
R
- rock
Soil profile This solid rock give rise to the number of
horizons. Soil profiles look different in different areas of the world.
Desert
Prairie
Temperate
Soil Profile The soil profile is an important tool in nutrient management. By examining a soil profile, we can gain valuable insight into soil fertility. As the soil weathers and/or organic matter decomposes, the profile of the soil changes.
Soil horizons
O - organic horizons. A - predominatly mineral horizon that is mixed with humified organic material (an eluvial horizon, i.e. a source of organic material, clay, and cations to lower horizons). E - light colored, bleached mineral horizon underlying the A horizon that occurs only in highly leached acidic soils. B - mineral horizon that shows little or no evidence of the original rock structure and which has been altered by oxidation, and illuviation (addition of minerals, clays, and organic matter from the A horizon). K - a subsurface horizon that is characterized by accumulation of calcium carbonate. Occurs mostly in desert and dry areas. C - a subsurface horizon that is basically the material from which the soil formed (loess, alluvium, till, etc.). It lacks most of the properties of the A or B horizon, but can be somewhat oxidized (Cox horizon). R - regolith (consolidated bedrock ).
US COMPREHENSIVE SOIL CLASSIFICATION SYSTEM
CATEGORY ORDER
DIFFERENTIATING CHARACTER PRESENCE OR ABSENCE OF MAJOR DIAGNOSTIC HORIZON
SUBORDER
GENETIC HOMOGENITY, SOIL MOISTURE REGIMES AND TYPE OF PARENT MATTERIAL
GREATGROUP
SOIL COLOR, SOIL MOISTURE,TEMPERATURE AND DIAGNOSTIC LAYERS
SUBGROUP
TYPIC – REPRESENT CENTRAL CONCEPT INTERGRADE – HAS PROPERTY THAT TEND TOWARDS OTHER GREAT GROUP OR SUBORDER EXTRAGRADE – HAS PROPERTY THAT TEND TOWARDS OTHER ORDER
FAMILY
TEXTURE, MINERALOGY AND SOIL TEMPERATURE
SERIES
PLACE NAME
Soil Taxonomy - Scientific grouping of similar soils
U.S. Soil Classification System The US System classification scheme contains 6 categories: 1. Order – the most general grouping – 10 – 12 orders 2. Suborder - defined by moisture, temp, dominating chemical or textural features – 47 nos. 3. Great Group - by differentiating horizons – 185 nos. 4. Subgroup - three types: typical (typic), intergrade, not one of the other two – 970 nos. 5. Family - plant growth or engineering properties – 4500 nos. 6. Series – common name / local area name – 10,500 nos. Soil orders are categorised by the nature of the developed pedogenic horizons they contain, - by the degree of weathering (Oxisols and to some extent ultisols), - by the importance of swelling clay contents (Vertisols) and - by being organic soils (Histosols).
SIMPLIFIED KEY TO SOIL ORDERS SOILS WITH >30% OM; HISTIC EPI-PEDON
HISTOSOLS
(ist)
SOILS WITH A SPODIC HORIZON
SPODOSOLS
(od)
SOILS WITH AN OXIC HORIZON AND NO ARGILLIC
OXISOLS
(ox)
SOILS WITH >30% CRACKING CLAY
VERTISOLS
(ert)
SOILS THAT ARE DRY FOR >6 MONTHS A YEAR
ARIDISOLS
(id)
SOILS THAT HAVE ARGILLIC HORIZON BUT B.S Oxisol)
Soil micromorphology is concerned with the description, measurement of soil components and pedological features at a microscopic to sub-macroscopic scale. soil micromorphology begins in the field with the routine and careful use of a 10x hand lens, But, much more can be described by careful description of thin sections made of the soil with the aid of a petrographic polarizing light microscope. The soil can be impregnated with an epoxy resin, but more commonly with a polyester resin (crystic 17449) and sliced and ground to 0.03 millimeter thickness and examined by passing light through the thin soil plasma. Soil micromorphology is the study of size, shape, aggregation, etching, coating, accumulation, and depletion of minerals associated with various soil processes.
Application of soil micromorphology and landscape evolution. Soil formation is a dynamic process with material continually being added, removed, and transformed. For example, water moving through a soil profile will pick up fine-textured material and deposit it as a coating along channels formed by the faces of adjacent peds Human activity can interrupt these processes and result in subtle differences in morphology. Water infiltration in the soil around a structure would be less than that in adjacent soil, because the structure would divert water away from it and compact the soil beneath it. Consequently, coatings on soil peds beneath the structure would be thinner, less well oriented, and have a different ratio of fine to coarse material than in the adjacent undisturbed soil. Some features occur within peds, such as manganese concretions, and others occur on ped surfaces, such as clay films
For features within peds, record the percent (or class) of the volume of the ped occupied by the feature. Illustrations of silt coats, clay films, carbonate coats, Mn concretions, and depletions and concentrations associated with a root channel are to be studied in detail, along with their form description. These kinds of additional features are common in Indiana soils.
Determination Examine ped surfaces or near surfaces to learn if they differ from the adjacent material in the interior of the peds in texture, color, orientation of particles, or reaction to various tests. A hand lens to magnify the feature is helpful. Cut a ped to observe features within the ped.
$ Soil micromorphology can contribute a rich source of archaeological data that takes into account the effects of human activity on the cultural environment and the natural world. #Reference: Discussion of the Influence of Prehistoric Humans on soils in the British Isles - Virgil Yendell
$Ref.: The Use of Soil Micromorphology at Sylvester Manor By Eric Proebsting
# Soil Micromorphology has also been applied successfully to locate sites on the transition to agriculture by prehistoric humans
Within peds (Code consists of upper case letter + lower case letter) Carbonate concentrations (Ca) — Whitish concentrations that are identified by adding a few drops of HCl to the surface and watching for a fizzing reaction, as explained in the Reaction section. Clay bridges (Cb) — Clay particles that form bridges between sand grains in coarsetextured soils, usually Bt horizons. The clay grains are oriented like a pack of cards (as seen in micromorphology studies). Clay bridges, usually reddish brown color, provide evidence for clay illuviation processes and thus argillic horizons. They usually occur in the matrix of weakly developed peds [Ma]. Iron concentrations (Fe) — Reddish or dark reddish brown zones not associated with ped surfaces or pores. Manganese concretions (Mn) — Black specks or masses within peds. The presence of Mn can be identified by applying a few drops of 3% hydrogen peroxide to the feature. Mn catalyzes the conversion of H2O2 to H2O and O2. The production of oxygen gas is observed as release of small bubbles or fizzing. Rhizosphere concentration (Rc) — A circular brownish or reddish zone around the outside of gray rhizosphere depletion. Rhizosphere depletion — (Rd) A circular gray zone around a root channel or pore. Often there is rhizosphere concentration around the outside of this gray zone. Surface concentration (Sc) — A planar brownish or reddish zone associated with a planar void; often there is a surface depletion between this concentration and a void. Surface depletion (Sd) — A planar gray zone near the surface of ped; often found near the surface of a fragipan prism.
On ped surfaces (Code consists of two upper case letters) Carbonate coats (CC) — White or light gray calcareous coatings on ped surfaces usually in upper C horizons. They usually are very effervescent because the secondary carbonate minerals are very fine and react quickly with acid. Clay films (skins) (CF) — Thin layers of oriented, translocated clay that often appear to be waxy, with low luster. They seem to be painted on the ped and may have a color different from the matrix (interior) color. If there is sand in the matrix, the clay coating covers up the grains so they cannot be seen in the coating. Iron coats (FE) — Reddish or brownish coatings on ped surfaces not associated with clay skins. Manganese coats (MN) — Black coatings on ped surfaces that fizz with H2O2 application. Organic matter coats (OM) — Dark coatings, that do not froth with H2O2 application, on ped surfaces, usually immediately below A horizons. Silt coats (SI) — Coatings of silt grains on ped surfaces. They appear to be dusty and powdery, like sugar on a donut. Thin silt coats can be distinguished from clay films by moistening the sample. If the coating is silty, the color of the coating disappears and the underlying color comes through, like when you dunk the donut, but a clay skin keeps its color when moist. Silt coats often originate by removal of clay from a silty clay ped coating. Slickensides (SS) — Outer surfaces of peds that have been altered when one surface slides across another surface, as shown by small ridges, valleys, grooves, striations, etc. In contrast to clay films, they are not coatings. If the ped contains sand, sand grains may show on a slickenside surface, and this surface is usually the same color as the ped interior.
* The distribution of soil pores within a faulted soil is different than the distribution of soil pores in the normal soil for the area. A cutan "is a modification of the texture, structure, or fabric at natural surfaces in soil materials due to concentration of particular soil constituents or in situ modification of the plasma" (Brewer, 1960). If the samples having the cutans which are composed dominantly of clay minerals, called argillans, then these argillans are clay minerals which have been translocated to the Bt horizon of the pre-Holocene soil in an area. Although the paleosoil was characterized by well developed argillans, only small remnants of argillans were found in the fault zone. It must be assumed that highly oriented pedologic structures will get destroyed at the time of movement of the fault. * Reference: SOIL MICROMORPHOLOGY AND FAULTING by Lowell A. Douglas, Rutgers University, Department of Soils and Crops New Brunswick, New Jersey 08903 USGS CONTRACT NO. 14-08-0001-18320 Supported by the EARTHQUAKE HAZARDS REDUCTION PROGRAM
**Soil micromorphology is a technique well suited for analysing landscapes, supplemented by fundamental field descriptions and basic cartography of the geomorphologic units of the area. It can, for example, try to answer whether the pre-site soils were subjected to freshwater flooding and alluviation or not, as well as were they aggrading, disrupted by agriculture, and/ or affected by seasonal aridity or not? **Reference (above): Identifying Human Behaviour by using Soil Micromorphology— a geoarchaeological approach Sayantani Neogi
Reference: Micromorphology of a Soil Catena in Yucatán: Pedogenesis and Geomorphological Processes in a Tropical Karst Landscape By Sergey Sedov, Elizabeth SolleiroRebolledo, Scott L. Fedick, Teresa Pi-Puig, Ernestina Vallejo-Gómez, and María de Lourdes FloresDelgadillo
REFERENCE: MICROMORPHOLOGICAL STUDY OF SOIL POROUS SYSTEM AFFECTED BY ORGANISMS AND ITS IMPACT ON SOIL HYDRAULIC PROPERTIES Radka Kodesova1, Vit Kodes2, Anna Zigova1 Czech Republic a) b) Fig. 1. Micromorphological images of the soil sample characterizing the horizon at depths of 45–125 cm (a) and the image of krotovina soil structure at the depth of 100–110 cm (b)
Soil Water Retention Curve
Pressure Head [cm]
1000
100
10
Soil Sample A Soil Sample B
1 0.25
0.3
0.35
0.4
0.45
Soil Water Content [cm3/cm3]
a) b) Fig. 2. Micromorphological image of the soil sample characterizing the horizon at depths of 75–102 cm (a) and corresponding soil water retention curves (b).
The age of most persons are measured in years since birth. For people and soils, there are also ways to judge age in terms of “maturity”. The age of a soil is determined by the amount of weathering that has occurred; that is, to what extent the parent material has been converted to distinct horizons or soil layers. Soil age is based on three general criteria: • The more horizons that are present, the older the soil. • The thicker the horizons, the older the soil. • The more difference there is between adjacent horizons, the older the soil.
Radiometric dating (often called radioactive dating) is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates. Radiometric dating methods are used ingeochronology to establish the geological time scale.[2] Among the best-known techniques are radiocarbon dating, potassium-argon dating and uranium-lead dating.
Radiocarbon dating is considered to be the most reliable. The two main regularities observed are: ◦ (1) the upper horizons of a majority of soils are younger than the lower ones (exclusive of the humus-illuvial podzols);
(2) forest (“podzolic”) soils are younger than steppe (“chernozem”) soils. At the same time, the first regularity is absent in arable soils, where a sharp increase of soil age is observed at the lower boundary of plowing. Recent data on tropical black clays reveal a great age of humus throughout their profiles due apparently to peculiarities of the clay.
Every rock and mineral exists in the world as a mixture of elements, and every element exists as a population of atoms. One element's population of atoms will not all have the same number of neutrons, and so two or more kinds of the same element will have different atomic masses or atomic numbers. These different kinds of the same chemical element are called nuclides of that element. A nuclide of a radioactive element is known as a radionuclide. The nucleus of every radioactive element spontaneously disintegrates over time. This process results in radiation, and is called radioactive decay.
Losing high-energy particles from their nuclei turns the atoms of a radioactive nuclide into the daughter product of that nuclide. A daughter product is either a different element altogether, or is a different nuclide of the same parent element. A daughter product may or may not be radioactive. If it is, it also decays to form its own daughter product. The last radioactive element in a series of these transformations will decay into a stable element, such as lead.
While there is no way to discern whether an individual atom will decay today or two billion years from today, the behavior of large numbers of the same kind of atom is so predictable that certain nuclides of elements are called radioactive clocks. Ages may be determined on the same sample by using different radioactive clocks. When the age of a rock is measured in two different ways, and the results are the same, the results are said to be concordant.
Unit - 3 Soil Nutrients and Crop Production Dr. PALANIVEL, K CENTRE FOR REMOTE SENSING, BHARATHIDASAN UNIVERSITY, TIRUCHIRAPPALLI-23.
Unit - 3 Soil Nutrients and Crop Production Elements essential for plants and animals, Soil nutrients - Nitrogen, Phosphorous, Potassium, Calcium, Magnesium and Sulphur in soil and its significance in plant growth, Micronutrients. 9 Hrs
Plant nutrition is the study of the chemical elements that are necessary for growth. In 1972, E. Epstein defined a criteria for an element to be essential for plant growth In its absence the plant is unable to complete a normal life cycle Sixteen chemical elements are known to be important to a plant's growth and survival. The sixteen chemical elements are divided into two main groups: Non-mineral and Mineral
Elements essential for plants and animals Elements essential for plants
Elements essential for animals
16 out of the 90 elements of soil, are: 1. Carbon 2. Hydrogen 3. Oxygen 4. Phosphorous 5. Potassium 6. Nitrogen 7. Sulphur 8. Calcium 9. Iron 10. Magnesium 11. Boron 12. Manganese 13. Copper 14. Zinc 15. Molybdenum and 16. Chlorine
Animals are also in need of the same nutrients With the exception of Boron And the addition of 1. 2. 3. 4.
Sodium Cobalt Selenium and Iodine
Non-mineral and Mineral nutrients essential for plants
The Non-Mineral Nutrients are hydrogen (H), oxygen (O), & carbon (C). These nutrients are found in the air and water. Since plants get carbon, hydrogen, and oxygen from the air and water, there is little farmers and gardeners can do to control how much of these nutrients a plant can use.
In a process called photosynthesis, plants use energy from the sun to change carbon dioxide (CO2 - carbon and oxygen) and water (H2Ohydrogen and oxygen) into starches and sugars. These starches and sugars are the plant's food. Photosynthesis means "making things with light"
Nearly all nutrients are used in ionic forms Plant roots release hydrogen ions as they absorb other nutrient cations and exchange bicarbonate ions for nutrient anions from soil solution Nitrogen is most often the limiting element in plant growth
The 13 mineral nutrients, which come from the soil, are dissolved in water and absorbed through a plant's roots. There are not always enough of these nutrients in the soil for a plant to grow healthy. This is why many farmers and gardeners use fertilizers to add the nutrients to the soil. The mineral nutrients are divided into two groups: macronutrients and micronutrients.
MACRONUTRIENT
Nitrogen (N), Phosphorus (P) Potassium (k)
These major nutrients usually are lacking from the soil first because plants use large amounts for their growth and survival. These elements are generally required in quantities ranging from 10 to 400 pounds per acre.
Nitrogen in the soil is the most important element for plant development. Nitrogen is a major part of chlorophyll and the green color of plants. It is responsible for lush, vigorous growth and the development of a dense, attractive lawn. Although nitrogen is the most abundant element in our atmosphere, plants can't use it until it is naturally processed in the soil, or added as fertilizer.
Phosphorus is limited in most soils because it is released very slowly from insoluble phosphates. phosphorus is important for plant growth and flower/seed formation. Phosphate esters make up DNA, RNA, and phospholipids. Most common in the form of polyprotic phosphoric acid (H3PO4) in soil, but it is taken up most readily in the form of H2PO4.
Potassium is an essential nutrient for plant growth. Potassium is involved in many plant metabolism reactions, ranging from lighting and cellulose used for formation of cellular structural components, for the regulation of photosynthesis . It controls water loss from plants and is involved in overall plant health. Soils that have adequate potassium which allow plants to develop rapidly and outgrow . It protects plant disease, insect damage and protect against winter freeze damage.
Soil minerals are rich in potassium naturally. However, the plant available forms are classed as available , slowly available and the unavailable. Clay soils contain more minerals and tend to have higher levels of potassium and sandy textured soils tend to contain lower amounts of potassium.
calcium (Ca), magnesium (Mg), and sulfur (S). There are usually enough of these nutrients in the soil so fertilization is not always needed. Also, large amounts of Calcium and Magnesium are added when lime is applied to acidic soils.
CALCIUM - regulates transport of other nutrients into the plant and is also involved in the activation of certain plant enzymes. Calcium deficiency results in stunting. MAGNESIUM is part of the chlorophyll in all green plants and essential for photosynthesis. It also helps activate many plant enzymes needed for growth.soil minerals, organic material, fertilizers, and dolomitic limestone are sources of magnesium for plants. SULFUR is usually found in sufficient amounts from the slow decomposition of soil organic matter.
Easily identified by the plants that grow in that soil The plants grow with the deficiency of certain important nutrients with some defects in their growth Affected growth is represented in plants through – it’s stems, leave, flowers, fruits, and roots. In the form of colour change, stunted growth, curled leave, rotten roots and stems, etc.
Nitrogen - growth of plant is stunned; plants become pale yellow in color; leaf edges become reddish brown. Phosphorus - root growth is stunted; thin stalk; maturity of plant is delayed; plant becomes purplish in color. Potassium -plant stems are weakened; leaf edges appear brown and dry.
Element
Soil Factor Causing Deficiency
N&K
Excessive leaching on coarse-textured low organic matter soils
P
Acid low organic matter soils Cold wet soils such as occurs during early spring Newly cleared soils
S
Excessive leaching on coarse-textured low organic matter soils in areas where air pollution is low (minimal levels of SO2 in the air)
Ca & Mg
Excessive leaching on coarse-textured low organic matter soils Soils where large amounts of K have been applied
Pale yellow
Nitrogen deficiency
Stunned growth-phosporous deficiency
General chlorosis. Chlorosis progresses from light green to yellow. Entire plant becomes yellow under prolonged stress. Growth is immediately restricted and plants soon become spindly and drop older leaves.
http://plantsci.sdstate.edu/woodardh/soilfert/Nutri ent_Deficiency_Pages/soy_def/SOY-N1.JPG
Leaves appear dull, dark green, blue green, or red-purple, especially on the underside, and especially at the midrib and vein. Petioles may also exhibit purpling. Restriction in growth may be noticed.
http://wwwunix.oit.umass.edu/~psoil120/images/tomatox2.jpg
http://www.ext.vt.edu/news/periodic als/viticulture/04octobernovember/p hoto3.jpg
Potassium deficient banana; older leaves become chlorotic, then necrotic, and the tip of the midrib bends downward. Potassium deficient corn; margins of older leaves become chlorotic and necrotic.
Leaf margins tanned, scorched, or have necrotic spots (may be small black spots which later coalesce). Margins become brown and cup downward. Growth is restricted and die back may occur. Mild symptoms appear first on recently matured leaves. http://www.ipm.iastate.edu/ipm/icm/files/images/antoni o004f.jpg
Calcium deficiency
Growing points usually damaged or dead (die back). Margins of leaves developing from the growing point are first to turn brown.
http://hubcap.clemson.edu/~blpprt/acid_photos/B lossomEndRot.JPG
Calcium - leaf edges become curly; terminal buds may die; blossoms lose their petals prematurely. Magnesium - leaves become thin and brittle; leaves lose their color at the tips and the areas between the veins. Sulfur - lower leaves of the plant becomes yellowish in color, roots and stems are small.
Boron - terminal buds are light green; dark spots appear on the roots; stems crack. Copper - plants develop bleached appearance. Iron - leaves become yellow but veins remain green; leaves curl upward. Manganese - spots of dead tissue on the leaves may drop out, giving the leaves a ragged appearance. Molybdenum - symptoms are similar to those of nitrogen deficiency. Zinc - terminal leaves are dwarfed; bud formation is reduced.
Sulfur deficient sorghum; young leaves are uniformly chlorotic.
Marginal chlorosis or chlorotic blotches which later merge. Leaves show yellow chlorotic interveinal tissue on some species, reddish purple progressing to necrosis on others. Younger leaves affected with continued stress. Chlorotic areas may become necrotic, brittle, and curl upward. Symptoms usually occur late in the growing season. http://quorumsensing.ifas.ufl.edu/HCS200/images/ deficiencies/-Mgcq.jpg
Leaves uniformly light green, followed by yellowing and poor spindly growth. Uniform chlorosis does not occur
http://www.ces.ncsu.edu/plymouth/crop sci/graphics/sulfur2.jpg
http://www.ag.ndsu.nodak.edu/aginfo/e ntomology/ndsucpr/Years/2007/june/7/ soils.jpg
Sulphur deficiency
Young leaves become chlorotic
Carbon, nitrogen, oxygen, phosphorus, potassium, calcium, magnesium, sulphur and the micronutrients are boron, chlorine, cobalt, copper, iron, manganese, molybdenum, nickel and zinc are the mineral needed for animal growth. In addition to this, some elements such as selenium and iodine, though not required by plants, are essential nutrients for animals.
Over the millions of years animals have been on the planet, there has been ongoing adjustment in a particular period to changing soil and climatic conditions. In each climatic period there has been generally been a balance created between the nutrient needs of the animals and the ability of the soil to supply it. nutrient cycling is essential ultimate sustenance for plants and animals.
Selenium is among the rarer elements on the surface. Selenium occurs naturally in the environment Well fertilized agricultural soil generally has about 400 mg/ton since the element is naturally present in phosphate fertilizers and is often added as a trace nutrient.
selenium is more readily absorbed by animals through the digestive tract. It has been estimated that lactating dairy goats absorb about 65% of ingested selenomethionine Selenium substances in soil are usually broken down to selenium and water fairly quickly, so that they are not dangerous to the health of organisms. http://www.lenntech.com/periodic/elements /se.htm#ixzz1YYU1twR6
Iodine compounds are found in seawater, soil, and rocks. Once in the air, iodine can combine with water or with particles in the air and can enter the soil and surface water, or land on vegetation when these particles fall to the ground or when it rains Iodine can remain in soil for along time because it combines with organic material in the soil. It can also be taken up by plants that grow in the soil Cows or other animals that eat these plants will take up the iodine in the plants.
The reason that iodine ultimately concentrates in the soil is the result of its chemistry. Iodine is one of the halogens. The halogens are prominent anions in the environment. "The horse has a high sensitivity for iodine” Even just an extra of 35 mg iodine per day (adult horses, dry matter intake: 10 kg) can cause severe health risks,
Plant nutrition is a difficult subject to understand completely, partially because of the variation between different plants and even between different species or individuals of a given clone The macronutrients are consumed in larger quantities and are present in plant tissue in quantities from 0.2% to 4.0% .Micronutrients are present in plant tissue in quantities measured in parts per million, ranging from 5 to 200 ppm, or less than 0.02% dry weight. Each of these nutrients is used in a different place for a different essential function
Micronutrients are elements which are essential for plant growth, but are required in much smaller amounts than those of the primary nutrients; nitrogen, phosphorus and potassium. The micronutrients are boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), zinc (Zn), and chloride (Cl). While chloride is a micronutrient, deficiencies rarely occur in nature, so discussions on supplying micronutrient fertilizers are confined to the other six micronutrients.
Deficiencies of micronutrients have been increasing in some crops. Some reasons are higher crop yields which increase plant nutrient demands, use of high analyses NPK fertilizers containing lower quantities of micronutrient contaminants, and decreased use of farmyard manure on many agricultural soils. Micronutrient deficiencies have been verified in many soils through increased use of soil testing and plant analyses.
Through
leaves (foliar) or through soil High nutrient demand - soil active uptake of specific nutrients Micronutrients
can be foliarly applied
mechanism is primarily diffusion good quick fix methods in greenhouses etc. Most
soil nutrients enter through roots
The term micronutrient is encouraged by the American Society of Agronomy and the Soil Science. They are needed in trace amount. They generally required in quantities of about 6 grams per hectare of molybdenum to 280 kg per hectare of iron and manganese. The micronutrients are boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn).
Helps in the use of nutrients and regulates other nutrients. Aids production of sugar and carbohydrates. Essential for seed and fruit development. Sources of boron are organic matter and borax. Secondary roles may be in sugar transport, cell division, and synthesizing certain enzymes. Boron deficiency causes necrosis in young leaves and stunting.
Important for reproductive growth. It competes with zinc and copper in the soil for position (availability) to plants. Without zinc and copper plants wont grow either. Available copper in soil is held as a cation(cu++) on surface of clay mineral. Aids in root metabolism and helps in the utilization of proteins.
Iron
Essential for formation of chlorophyll. Iron is also used by enzymes to regulate transpiration in plants. It competes with zinc and copper in the soil for position (availability) to plants. Without zinc and copper plants wont grow eithe
Essential for the transformation of carbohydrates. Regulates consumption of sugars. Part of the enzyme systems which regulate plant growth. Sources of zinc are , zinc oxide, zinc sulfate, zinc chelate.
Manganese
Functions with enzyme systems involved in breakdown of carbohydrates, and nitrogen metabolism. It aids in the synthesis of chlorophyll and in nitrate assimilation.
Molybdenum Helps in the use of nitrogen Soil is a source of molybdenum. Legumes need more molybdenum than other crops, such as grass or corn, because the symbiotic bacteria living in the root nodules of legumes require molybdenum for the fixation of atmospheric nitrogen
The deficiencies of micronutrients have become major constraints to productivity, stability and sustainability of soils A brief discussion of micronutrient functions and nutrient deficiency symptoms in plants and soil conditions affecting micronutrient availability serves to help understand their importance in crop production and to recognize symptoms of possible deficiencies. Deficiencies of these elements in crops are widespread in the region due to one or more of the following main reasons
Cultivating poor sandy soils with low contents of micronutrients High pH values of the soil negatively influencing the availability of these nutrients. Occurrence of high salt contents affecting adversely the uptake of nutrients High content of CaCO3 in the soil Prevailing agronomic practices hindering continuous supply of nutrients (e.g. periods of wet/dry soils) Continuous intensive cropping without adding micronutrients to the soil (nutrient depletion)
Element
Soil Factor Causing Deficiency
Fe
Poorly drained soils, Low organic matter soils, pH>7.0, Soils high in P
Zn
Cold wet soils low in organic matter and highly leached, High pH soils (pH>7.0), Soils high in P, Exposed subsoils
Cu
Peat and muck soils, High pH, sandy soils, Soils heavily fertilized with N
B
Excessive leaching on coarse-textured low organic matter soils, Soils with pH>7.0
Mn
Excessive leaching on coarse-textured low organic matter soils, Soil with pH>6.5
Mo
Soils high in Fe oxides, high adsorption of molybdenum, Soil cropped for a long time
Leaves wilt, become chlorotic, then necrotic. Wilting and necrosis are not dominant symptoms.
http://images.google.com/url?q=http://ipm.ncsu.e du/Scouting_Small_Grains/Grain_images/fig4.jpg&u sg=AFQjCNE2vzRwrqp65VR_xKRlo2LQOgWI3g
Distinct yellow or white areas appear between veins, and veins eventually become chlorotic. Symptoms are rare on mature leaves.
http://bexartx.tamu.edu/HomeHort/F1Column/2003 Articles/Graphics/iron%20chlorosis.jpg
Chlorosis is less marked near veins. Some mottling occurs in interveinal areas. Chlorotic areas eventually become brown, transparent, or necrotic. Symptoms may appear later on older leaves.
http://www.ca.uky.edu/HLA/Dunwell/KHC/110122.JPG
Leaves may be abnormally small and necrotic. Internodes are shortened.
http://agri.atu.edu/people/Hodgson/Fiel dCrops/Mirror/Nutrient%20Def_files/slid e24.jpg http://plantsci.sdstate.edu/woodardh/soil fert/Nutrient_Deficiency_Pages/corn_def/C ORN-ZN1.JPG
Young, expanding leaves may be necrotic or distorted followed by death of growing points. Internodes may be short, especially at shoot terminals. Stems may be rough, cracked, or split along the vascular bundles.
http://www.canr.msu.edu/vanburen/ffc12.j pg
1. Soil treatment • Adding fertilizers containing micronutrients 2. Crop treatment • Adding fertilizers containing micronutrients to the soil • Breeding cultivars for high micronutrient efficiency • Spraying crops/fodder with micronutrients
3. Animal treatment : • Addition to water • Feeding blocks • Supplementation • Injection • Producing fodder with high micronutrient
content
4. Human treatment : • Food fortification • Supplementation (capsules … etc.) • Increasing natural contents in food produced There is no only one way to overcome micronutrient deficiencies. Treatments differ from preventive and curative measures.
Unit – 4 Soil Quality and Landscape & Unit - 5 Geoinformatics in Soil Mapping, Management and Conservation
Dr. PALANIVEL, K CENTRE FOR REMOTE SENSING, BHARATHIDASAN UNIVERSITY, TIRUCHIRAPPALLI-23.
Unit – 4 Soil Quality and Landscape Soil and water relations, organic matter in soil, functions of organic matter, organic matter and soil structure, organic matter and essential elements, tillage, cropping systems and fertility and case studies.
Water is held in soil by strong cumulative forces of the H-bonds that are between the water and the oxygen atoms of soil mineral surfaces. These adhesive forces are very strong near the mineral surface; cohesive forces (between water molecules) occur throughout the water films. Because water held to soil particles has less freedom than free water (potential = 0), it is measured in negative bars. The strength with which water is held in the soil is called water potential.
Water infiltration is the movement of water from the soil surface into the soil profile. Soil texture, soil structure, and slope have the largest impact on infiltration rate. Water moves by gravity into the open pore spaces in the soil, and the size of the soil particles and their spacing determines how much water can flow in.
Coarse sand 0.25–0.75 Fine sand 0.75–1.00 Loamy sand 1.10–1.20 Sandy loam 1.25–1.40 Fine sandy loam 1.50–2.00 Silt loam 2.00–2.50 Silty clay loam 1.80–2.00 Silty clay 1.50–1.70 Clay 1.20–1.50
Soil is the major source of water for plants. The plants absorb water through root hairs from the soil. The total water content present in the soil is called ‘holard’. Out of this, the water which can be absorbed by plants is ‘chresard’ and the remaining is called ‘echard’.
Where rainfall lands on the soil surface, a fraction infiltrates into the soil to replenish the soil water or flows through to recharge the groundwater. Another fraction may run off as overland flow and the remaining fraction evaporates back into the atmosphere directly from unprotected soil surfaces and from plant leaves. The above-mentioned processes do not occur at the same moment, but some are instantaneous (runoff), taking place during a rainfall event, while others are continuous (evaporation and transpiration).
Soil Organic Matter (SOM) SOM - is a Living or dead plant and animal residue which is very active and forms important portion of the soil. Why Soil Organic Matter (SOM) matters Soil organic matter contributes to a variety of biological, chemical and physical properties of soil and is essential for good soil health. Functions of soil organic matter Optimising the benefits of soil organic matter
Soil health is important to optimise productivity in agricultural systems. Healthy, productive soil is a mixture of water, air, minerals and organic matter. In turn, soil organic matter is composed of plant and animal matter in different stages of decay, making it a complex and varied mix of materials.
Humus Humus has a characteristic black or dark brown color, due to an accumulation of organic carbon
Humin The strong base insoluble fraction. The carbon cycle describes how carbon is circulated through the atmosphere, biosphere, pedosphere, and hydrosphere. The dead organic matter of the soil is colonized by (micro)organisms, which derive energy for growth from the oxidative decomposition of complex organic molecules. Decomposition is the biochemical breakdown of mineral and organic materials. During decomposition, inorganic elements are converted from organic compounds, a process called mineralization. For example, organic-N and -P is mineralized to NH4+ and H2PO4-, and C is converted to CO2.
The amount of organic matter in soil The amount of carbon (the measure of organic matter) in a soil depends on a range of factors, and reflects the balance between accumulation and breakdown. •Climate – For similar soils under similar management, carbon is greater in areas of higher rainfall, and lower in areas of higher temperature. The rate of decomposition doubles for every 8 or 9oC increase in mean annual temperature. •Soil type – Clay helps protect organic matter from breakdown, either by binding organic matter strongly or by forming a physical barrier which limits microbial access. Clay soils in the same area under similar management will tend to retain more carbon than sandy soils. •Vegetative growth – The more vegetative production the greater are the inputs of carbon. Also, the more woody this vegetation is (greater C:N ratio), the slower it will breakdown. So, the crop system can strongly affect carbon concentrations.
Role of Organic Matter in Soil Fertility Organic matter forms a very small but an important portion and it is obtained from dead plant roots, crop residues, various organic manures like farmyard manure, compost and green manure, fungi, bacteria, worms and insects. Measuring soil organic matter While living organisms, particularly the plants we grow, are of vital importance to us, it is the non-living organic matter that we measure as 'soil organic matter'. The most common methods for measuring soil organic matter in current use actually measure the amount of carbon in the soil. This is done by oxidising the carbon and measuring either the amount of oxidant used (wet oxidation, usually using dichromate) or the CO₂ given off in the process (combustion method with specific detection).
Essential functions performed by different members of soil organisms (biota)
Human interventions that influence soil organic matter Various types of human activity decrease soil organic matter contents and biological activity. However, increasing the organic matter content of soils or even maintaining good levels requires a sustained effort that includes returning organic materials to soils and rotations with high-residue crops and deep- or dense-rooting crops Soil organic matter levels can be maintained with less organic residue in fine textured soils in cold temperate and moist-wet regions with restricted aeration. a decrease in biomass production; a decrease in organic matter supply; Increased decomposition rates.
Effect of soil organic matter on soil properties Organic matter affects both the chemical and physical properties of the soil and its overall health. Properties influenced by organic matter include: soil structure; moisture holding capacity; diversity and activity of soil organisms, both those that are beneficial and harmful to crop production; and nutrient availability.
Organic matter deposition The reduction of soil disturbance through zero-tillage, the use of cover crops and the preservation of crop residues on the soil surface result in increased activity of the soil and in the accumulation of organic matter, mainly in the topsoil An argument often heard in the discussion on conservation agriculture is that it is only feasible in the humid and subhumid tropics and that the generation of sufficient biomass in semi-arid regions is the limiting factor to start implementing conservation agriculture
Organic matter affects both the chemical and physical properties of the soil and its overall health. Properties influenced by organic matter include: ◦ soil structure; ◦ moisture holding capacity; ◦ diversity and activity of soil organisms, both those that are beneficial and harmful to crop production; and ◦ nutrient availability.
The less the soil is covered with vegetation, mulches, crop residues, etc., the more the soil is exposed to the impact of raindrops.
When a raindrop hits bare soil, the energy of the velocity detaches individual soil particles from soil clods. These particles can clog surface pores and form many thin, rather impermeable layers of sediment at the surface, referred to as surface crusts
They can range from a few millimetres to 1 cm or more; and they are usually made up of sandy or silty particles. These surface crusts hinder the passage of rainwater into the profile, with the consequence that runoff increases.
This breaking down of soil aggregates by raindrops into smaller particles depends on the stability of the aggregates, which largely depends on the organic matter content.
Benefits of soil organic matter Organic matter can be considered a pivotal component of the soil because of its role in physical, chemical and biological processes Many of these functions interact. For example, the high cation exchange properties of organic matter are a major means by which organic matter is able to bind soil particles together in a more stable structure.
The reactive regions present in humus are numerous, and give these molecules a capacity to bind to each other and to mineral soil particles, It supplies major soil aggregate-forming cements, particularly long sugar chains called Polysaccharides also to react with cations (positive charge, e.g. Ca2+, K+) in the soil solution.
The density of cation exchange capacity (CEC) of organic matter is greater than clay minerals . While a high CEC is an important attribute of soil organic matter, please note that organic matter does not have an anion (negative) exchange capacity, and is therefore not able to bind anions like phosphate and sulphate.
SOM is the source of 90-95% of nitrogen in unfertilized soils SOM is the major source of both available phosphorous and available sulphur, if soil humus is present It increases water contents at field capacity When left on top of soil as a mulch, it reduces soil erosion, keeps the soil cooler in very hot weather and warmer in winter. Organic matter is a carbon supplying material for many microbes.
Organic mater and soil structure Organic materials, especially microbial cells and waste products, act to cement aggregates and thus to increase their strength.
Crop residue mulch, in situ or brought in, also improves soils structure by eliminating the raindrop impact and enhancing activity of soil macrofauna. (The pen points to earthworm casts beneath the mulch layer.)
A multidisciplinary approach to soil structure
Structural Resilience The ability of soil structure to recover following a major disruption in the aggregation process is known as Structural Resilience
The disruption may be caused by alterations in land use, cultivation,or soil management practices that change the composition of cations on the exchange complex, decrease quantity and quality of the humus fraction, and reduce effectiveness of the bio tic factors. Numerous soils exhibit selfmulching properties
Surface layer of some vertisols and andisols have selfmulching characteristics with fine- to medium-crumb structure.
Cropping and Farming Systems
• In other soils, aggregation is restored only when taken out of cultivation and put under a restorative fallow. • Inevitably, soils with structural resiliency are better suited for intensive management under different land uses than those that do not possess these characteristics. • Structural resiliency depends on numerous factors including soil organic matter content, clay mineralogy, wettability characteristics, and biotic factors. • Root systems and canopy cover have an important influence of soil structure. • Grasses with their dense and fibrous root system and legumes with their deep tap roots have a profound effect on aggregation characteristics. • It is because of these and other differences in legumes and cereals that crop rotations and farming systems have a profound effect on soil structure. • Crops affect structural properties through their impacts on root biomass, amount and rate of water extraction from different depths, total biomass produced, and C:N ratio of the biomass that affects its persistence. • From a long-term study in Ohio, Lal et al. (1990) observed that relative aggregation for different rotations was 1.00:1.66:2.1 for corn-oats-meadow, continuous corn, and corn-soybean. • The MWD was 1.34 mm for corn-soybean, 1.0 mm for continuous corn, and 0.7 mm for corn-oats meadow rotation. Perennial forages, both legumes and grasses, improve soil structure (Wilson et al., 1947; Low, 1972; Lal et al., 1979; Lal, 1991).
Soil Organic Matter and essential elements, tillage, cropping systems and fertility Relation of soil organic matter content with soil properties Consequently, the organic fraction affects timing and nature of tillage, rate and type of fertilizers to be used, fate of pesticides, and transport of water and pollutants into the soil
Beneficial effects of organic fraction on plant growth and yield are also related to improvement in soil quality and decrease in susceptibility to degradative processes. With a strong interaction with texture and clay minerals, the organic fraction affects soil’s
Texture influences soil compaction through its effect on aggregation and porosity, absorption of water and other organic/inorganic compounds by altering surface area, water and nutrient storage through charge properties, transport of solute and gaseous exchange through porosity, etc. Soil Properties and Processes Affected by Soil Organic Component Soil properties 1. Color 2. Surface area 3. Charge density
Processes -Heat absorption, warming -Adsorption, aggregation -Cation exchange, chelation, aggregation, buffering capacity -Transport of solute and solids, leaching
4. Porosity and pore size distribution 5. Bulk density, particle density -Compaction, erosion, bearing capacity 6. Gaseous composition of soil air -Soil respiration, gaseous emission to the atmosphere 7. Microbial biomass and activity -Mineralization, aggregation, soil respiration, nutrient immobilization
Tillage • Structural effects of tillage depend on the type, frequency, and timing of tillage operation. • The antecedent soil moisture content is an important parameter that affects structural properties, because it influences dispersibility of clay. • Conservation tillage and mulch farming techniques are beneficial to aggregation and soil structure formation (Lal, 1989; Carter, 1994). • Lal et al., (1994) reported that in Ohio, tillage effects on total aggregation and MWD were in the order of no tillage > chisel plowing > moldboard plowing. • Agricultural practices that enhance biomass production have also favorable effects on aggregation and soil structural development. • Use of organic manures, compost, and mulches improve aggregation (soil structure) more than chemical fertilizers (Tisdall et al., 1978). • Decrease in soil pH due to chemical fertilizers may adversely affect aggregation, especially in soils of low activity clays. • Otherwise, use of chemical fertilizers has beneficial effects on aggregation (Emmond, 1971; Hamblin, 1985).
Importance of Soil Organic Matter - case studies
Unit - 5 Geoinformatics Management and Conservation
in
Soil
Mapping,
Introduction, irrigation, drainage and soil management for field crops, gardens, lawns, pastures, range lands and forests. Conservation factors and implementation methods using Geoinformatics. 6 Hrs
REMOTE SENSING is the process of sensing and measuring objects from a distance without physical contact with them
REMOTE SENSING is largely concerned with the measurement of electro - magnetic energy from the sun which is reflected, scattered or emitted by the objects on the surface of the earth
Basic interactions between EMR and an earth surface feature
Different surface objects return different amounts of energy
in different wavelengths of the electro - magnetic spectrum
Soil Vegetation Water
Spectral Signature Curves of Vegetation Classes DIGITAL NUMBERS 80 70 60 Rice Sugarcane Groundnut Scrub
50 40 30 20 10 0 BLUE
GREEN
BANDS
RED
NIR
Detection and measurement of these spectral signatures enable identification of surface objects from air- borne and space - borne sensors
MSS scan line
Water
Sand
Forest
Urban
Corn
Hay
DATA ACQUISITION
DATA ANALYSIS Reference Data
Pictorial
Visua l
Numeric al
Digital Users
Source of energy Propagation through the atmosphere
Sensing Systems Earth Surface Features
Data Products
Interpretation Procedures
Information Products
Electromagnetic remote sensing of earth resources
Resolution - resolving power to distinguish between signals that are spatially near or spectrally similar SPECTRAL
: Sensitive to specific wavelength intervals
SPATIAL
: Smallest unit that can be resolved
TEMPORAL
: Revisit of sensor to same area
RADIOMETRIC
: Ability to detect slight radiance difference
It is generally believed that improvements in resolution increases the probability that phenomena may be remotely sensed more accurately.
The trade-off is that any improvement in resolution usually will require additional data - processing capability for either human or computer - assisted analysis.
SOIL COLOUR
MINERAL CONTENT
ORGANIC MATTER
SOIL MOISTURE
TEXTURE
STRUCTURE
PARTICLE SIZE
VEGETATION
Elements of Image Interpretation TONE / COLOUR PATTERN TEXTURE SIZE SHAPE SHADOW LOCATION ASSOCIATION SCALE RESOLUTION
Interpretation Key Selective Key Elimination Key
FACTORS INFLUENCING REFLECTANCE AND EMITTANCE CHARACTERISTICS OF SOILS Numerous soil properties influence the reflectance and emission of the electromagnetic energy. The factors that influence soil reflectance act over less specific spectral bands. Some of the factors affecting soil reflectance are soil texture, soil colour, organic matter content, presence of iron oxide, structure and surface roughness. These factors are complex, variable and inter-related. 3.1 Soil moisture content Presence of moisture in soil will decrease its reflectance. As with vegetation, this effect is greatest in the water absorption bands at about 1.4, 1.9 and 2.7 un (clay soils have hydroxyl absorption bands at about 1.4 and 2.4 gn). Soil moisture content is strongly related to soil texture . Coarse, sandy soils are usually well drained, resulting in low moisture content and relatively high reflectance. Poorly drained fine textured soils will generally have lower reflectance. In the absence of water, however, the soil itself will exhibit the reverse tendency i.e, coarse textured soils will appear darker than fine textured soils. Thus, the reflectance properties of a soil are consistent, only within particular ranges of conditions. 3.2 Soil particle size Increasing particle diameter results in the decrease of reflectivity. The determining factor that influences the reflectivity is the diameter of the aggregates and the form of their surface and not the characteristics chemical composition. 3.3 Soil texture Soil texture or the composition of soil particles present in soil aggregates appears to have an influence on spectral response. Sand (light textured) has higher reflectance. Clay (fine textured) soil has the lower reflectance.
3.4 Soil Colour The different reflectance of light is associated with soil colour. The red region of the visible spectrum and the near infrared region are most favorable for a qualitative and quantitative description of soils. 3.5 Organic matter and iron oxide The organic matter content of the soil affects the soil colour, heat capacity, water holding capacity, cation exchange capacity, structure and corrodibility of soils. It is observed that soils with high iron content and soils with high organic matter content are easily distinguishable by the reflection characteristics. The presence of iron oxide in a soil significantly decreases the reflectance, at least in the visible wavelengths. 3.6 Structure and Surface roughness Structure and surface roughness on account of tillage operation has a substantial influence on reflectance of soils. Soil surface disturbed by tillage exhibit a decrease in reflectance. Structureless soils reflect 15 - 20% more light than soils with well defined structures.
4. IMAGE INTERPRETATION METHODS FOR SOIL MAPPING The techniques for satellite imagery interpretation can be divided into two: 1. Visual interpretation 2. Computer aided digital analysis (Digital Image Processing : DIP) 4.1. Visual interpretation Success in visual interpretation or manual interpretation varies with the training and experience of the interpreter, the nature of object or phenomena being interpreted, and the quality of data products being utilised. Generally the most capable interpreters have keen powers of observation coupled with imagination and great deal of patience. In addition, it is important that the interpreter have a through understanding of the phenomenon being studied. Visual interpretation always needs the presence and careful observation of interpreter for every scene of imagery to be interpreted. 4.2. Computer Aided Digital Analysis Digital image processing involves the manipulation and interpretation of digital images with the aid of a computer. The computer aided techniques utilise the spectral variations as fundamental to analysis. The central idea behind digital image processing is quite simple. The digital image is fed into a computer one pixel at a time. The computer is programmed to insert these data into an equation or series of equations, and then store the results of the computation for each pixel. These results form a new digital image that may displayed or recorded in pictorial format or may itself be further manipulated by additional programme.
Image Data Set Categorised Set Water Sand Forest Urban
Corn Hay
Training Stage
Classification Stage
Typical spectral pattern recognition process
Output Stage
MONITORING SALT AFFECTED LANDS . . . STUDY AREA : Karnal District, Hariyana G.A. : 3721 Sq.Km. Data used
Year
Area affected in ha.
Percentage to G.A
Landsat MSS FCC
1973
47810
12.85
Landsat TM FCC
1986
11,460
3.08
IRS 1A LISS I FCC
1988
11,250
3.02
Result : 76.46% reclaimed (Source: Hooda & Manchanda, 1992)
MONITORING SALT AFFECTED LANDS . . . STUDY AREA : Sangrur District, Panjab
Data used
Year
Scale
Aerial Photo
1965
Semi Detailed SS Landsat TM FCC enlarged to 1:50000
1973 1988
Salt Affected land % to G.A 1:25000 13.1
1:50000 1:250,000
9.6 2.5
•
Reduction is due to supply of gypsum to farmers at a subsidised rate by state Agri Dept.
•
Reclaimed land put to agriculture 1965
Rice Wheat
1988 16,000
224000
1,84,500
3,77,000
(Source:Bajwa et al., 1990)
EFFICIENCY OF SOIL MAPPING BY RS TECHNIQUE STUDY AREA : PUNJAB G.A : 50.3 L. Ha BY CONVENTIONAL METHOD :
PER DAY COVERAGE PER YEAR (200 EWD) TO COVER 5.03 L.Ha
: 2000 Ha. : 4.0 L.Ha : 12.6 Years
BY RS TECHNIQUE : TIME SPENT FOR PREPARING BASE MAPS, NTERPRETATION, FINAL MAPPING : 310 MAN DAYS WHICH CORRESPONDS KEEPING 200 EWD/YEAR : 1.5 Years EFFICIENCY
= 12.6 / 1.5 = 8 TIMES (Sehgal and Karale, 1988 )
HYDROLOGICAL SOIL GROUPS CHARACTER
A
B
C
D
Infilteration rate
High
Moderate
Slow
Very Slow
Texture
Sand or Gravel
Moderately Coarse to fine
Moderately fine to fine
Clay
Depth
Deep
Moderately Deep
Deep
Shallow over an impervious layer / clay
Drainage
Well to excess
Moderately well drained
Moderately slow
Slow
Water Transmission
High
Moderate
Slow
Very Slow
Soil List
Entisols
Inceptisols
Alfisols
Vertisols
Remarks : Runoff Recharge
Low High
- Moderate - Moderate -
High Low
SOME RESEARCH WORK ON SOILS USING REMOTE SENSING DATA * Soil characteristics and properties that are most important in classification as well as in assessment of use capability lie below the surface and stretch well into the substrata. But the fact that soil surface manifestation more often than not, has a correlation with nature of deeper layers, forms a basis for many a successful attempts on use of remote sensing in this field. Use of indirect means like the one based on the relationship between the soil and landform has been equally & extensively used. * There is a close relationship between the kinds of soil and the nature permeability, relief, climate, vegetation and age of landforms. Soil boundaries can also be revealed by differences in permeability, relief which are all detectable visually from Landsat images.(B5/B7). * Krishnamurthy and Srinivasan (1974) compared the small scale soil map for a part of Barnagar Tehsil, Ujjain District, Madhya Pradesh prepared by the adoption of a systematic Aerial Photo Interpretation procedure with the Soil map for the same area resulting from a previous Rec. Soil Survey using toposheets as base maps. It has been shown that the soil boundaries of the Photo-interpretation map are both more accurate and natural in shape; delineation of gullied lands has been achieved more accurately by Aerial Photo Interpretation procedures: soil erosion could be mapped more consistently and accurately through Aerial Photo Interpretation. Apart from the increased accuracy and diminished costs the Aerial Photo Interpretation procedure will be helpful in modernising previously prepared Reconnaissance Soil maps.
Venkataratnam (1979) has shown the ability of digital analysis to bring out subtle variations in soils such as discrimination of Entic Chromusterts from Typic Chromusterts and a resolution of broad group of red soils into Ultic Haplustalfs, Typic Rhodustalfs, Udic Haplustalfs and plinthudalfs. He has also shown that a linear stretched data is superior to a FCC or band ration products. * Singh (1980) used Landsat images in conjunction with topographical and geological information to prepare soil map of Mudhol taluk in Bijapur district, Karnataka State. The map has been compared with the Reconnaissance maps prepared by conventional method using 1:1 mile scale Survey of India toposheets. The study reveals that more accurate soil maps in terms of boundary delineation and composition of soil mapping units could be prepared by (Visual) interpretation of Landsat images with adequate ground data. The method can thus be used in revising and improving many of the existing reconnaissance soil maps prepared by conventional method. * Mapping of salt affected soils has been carried with greatest ease using remote sensing techniques. Manchanda and Hilweg (1981) and Venkataratnam (1983) have found digital analysis particularly useful in sub-classification of salt affected soils
Singh (1983) has shown that an FCC was quite useful in differentiating soils developed on parent materials of varied mineralogy. Use of digital analysis enabled separation of weekly contrasting soils. Over 15 mapping units belonging to nearly 15 groups and subgroups were identified. * Karale et al (1985) concluded based on comparative study of various remote sensing techniques in Chitradurga district of Karnataka that whereas 302 mapping units were recognised on FCC, the digitally linear stretched product could show only 256 such units but the results of latter were more convincing and comparable with Aerial Photo Interpretation. * Sengal & Karale (1988) reported: Time spent on different operations for preparation of a broad Reconnaissance soil map of Punjab involving a total Geographical area of about 5.03 million ha in 310 man days. This corresponds to about 1.5 field party years assuming 200 days effective work in a year. Conventional approach of field work for this area would necessitated 12.6 field party areas with National norms of 4 Lakhs ha / field party year even at rapid Reconnaissance level. The remote sensing technology therefore offers about 8 time more efficiency compared to conventional system. Karale et al (1978) earlier presented evidence to show that the computer aided remote sensing technology affords 10 times more efficiency at reconnaissance level mapping compared to conventional surveys.
MONITORING SALT AFFECTED SOILS . . . STUDY AREA : Karnal District, Hariyana G.A. : 3721 Sq.Km. Data used
Year
Area affected In ha.
Percentage to G.A
Landsat MSS FCC
1973
47810
12.85
Landsat TM FCC
1986
11,460
3.08
IRS 1A LISS I FCC
1988
11,250
3.02
Result : 76.46% reclaimed (Source: Hooda & Manchanda, 1992)
MONITORING SALT AFFECTED SOILS . . . STUDY AREA : Sangrur District, Panjab
Data used
Year
Scale
Aerial Photo
1965
Semi Detailed SS Landsat TM FCC enlarged to 1:50000
1973 1988
Salt Affected land % to G.A 1:25000 13.1 1:50000 1:250,000
9.6 2.5
•
Reduction is due to supply of gypsum to farmers at a subsidised rate by state Agri Dept.
•
Reclaimed land put to agriculture 1965
Rice Wheat
1988 16,000
224000
1,84,500
3,77,000
(Source:Bajwa et al., 1990)
Application of Remote Sensing and GIS on Soil Erosion Assessment at Bata river basin, India M. H. Mohamed Rinos1, S. P. Aggarwal2, Ranjith Premalal De Silva3 1 & 3Department of Agricultural Engineering, Faculty of Agriculture, University of Peradeniya, Peradeniya, Sri Lanka.
• A number of parametric models have been developed to predict soil erosion at drainage basins, yet Universal Soil Loss Equation (USLE) (Wischmeier and Smith, 1978) is most widely used empirical equation for estimating annual soil loss from agricultural basins. • While conventional methods yield point-based information, Remote Sensing (RS) technique makes it possible to measure hydrologic parameters on spatial scales while GIS integrates the spatial analytical functionality for spatially distributed data. • Some of the inputs of the model such as cover factor and to a lesser extent supporting conservation practice factor and soil erodibility factor can also be successfully derived from remotely sensed data. • Further, Modified USLE (MUSLE) uses the same empirical principles as USLE. • However, it includes numerous improvements, such as monthly factors, influence of profile convexity/concavity using segmentation of irregular slopes and improved empirical equations for the computation of LS factor (Foster & Wischmeier 1974, Renard et al. 1991). • In this study, IRS-1D LISS III and ID Pan data were used to identify the land use status of the Bata river basin. • Based on maximum likelihood classifier, the area was classified into eight land use classes namely, Dense Forest, Moderate Forest, Open Forest, Wheat, Sugarcane, Settlement, River Bed, Water Body. • A 12-day intensive field checking was undertaken in order to collect ground truth information.
• Digital Elevation Model (DEM) of Bata river basin was created by digitizing contour lines and spot heights from the SOI toposheets at 1:50,000 scale. • Modified Fournier index was used to derive parameters for modified erosivity factor. • The modified LS factor map was generated from the slope and aspect map derived from the DEM. • The K factor map was prepared from the soil map, which was obtained from the previous studies done at Geo-Science Division of IIRS, Dehradun. • The P and C factor values were chosen based on the research findings of Central Soil and Water Conservation Research and Training Institute, Dehradun and spatial extent was introduced from land use/ cover map prepared from LISS III data. Maps covering each parameter (R, K, LS, C and P) were integrated to generate a composite map of erosion intensity based on the advanced GIS functionality. • This intensity map was classified into different priority classes. Study area was further subdivided into 23 subwatersheds to identify the priority areas in terms of soil erosion intensity. • Each subwatershed was analyzed individually in terms of soil type, average slope, drainage length, drainage density, drainage order, height difference, landuse/landcover and average NDVI with soil erosion to find out the dominant factor leads to higher erosion.
