Impact of Global Warming and Climate Change on ...

Impact of Global Warming and Climate Change on Human and Plant Health

Editors

Dr. Arun Arya Prof. V.S. Patel

2015

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2015, Impact of Global Warming and Climate Change on

Pages 352–363

Human and Plant Health

Editors: Dr. Arun Arya and Prof. V.S. Patel Published by: DAYA PUBLISHING HOUSE, NEW DELHI

Chapter 34

Silvopastoral Systems and their Contribution to Carbon Sequestration and Livestock Methane Emissions Reduction under Tropical Conditions S. F. J. Solorio1*, S.B. Solorio1, S.K. Basu2, L.F. Casanova1, V.J.C. Ku1, P.C. Agilar1, A.L. Ramírez1, and B.A. Ayala1 1

Campus de Ciencias Biológicas y Agropecuarias. Universidad Autónoma de Yucatán. Carretera Mérida-Xmatkuil Km. 15.5. C.P. 97100, Mérida, Yucatán, México 2 Department of Biological Sciences, University of Lethbridge, T1K 3M4 Lethbridge, Alberta, Canada

ABSTRACT Silvopastoral system is an efficient and integrated land use management system that has emerged as a valuable strategy to develop livestock systems. There is also, evidence that silvopastoral systems have an important role in providing environmental services; it involves interactions of woody perennial species with grasses or other crops and livestock. The objective of this review is to discuss the role of silvopastoral systems in providing environmental services, including more diverse and sustainable livestock (milk and meat production), increased carbon stocks, biodiversity conservation, improved soil fertility and ––––––– * Corresponding author: E-mail: [email protected]

Silvopastoral Systems and their Contribution to Carbon Sequestration and Livestock

353

atmospheric nitrogen fixation. The adoption of silvopastoral systems contributes to reduced carbon dioxide emissions, diminishes the pressure on vulnerable ecosystems and substantially improves forage quality and livestock production. Keywords: Carbon sequestration, Forage, Silvopastoral systems, Livestock, Methane, Monoculture, Nitrogen fixation, Soil fertility.

List of Abbreviations AFS: Agro forestry; GHG: Greeenhouse Gases; ISPS: Intensive Silvopastoral Systems

34.1 Introduction Silvopastoral systems combine fodder plants such grasses and leguminous herbs with shrubs and trees for animal production and environmental services. The silvopastoral systems provide a diverse ecosystem services, they favor biodiversity by creating complex habitat that can support a wide variety of species of plants and animals (Castro, 2009; Moreno and Pulido, 2009). Under humid, tropical conditions, the silvopastoral systems can sequester more carbon and fix atmospheric nitrogen than traditional monocrop pasture systems (Nair et al., 2009). The combination of grasses and trees contribute comprehensively to retain soil and water, there by supporting soil and watershed protection (Ibrahim et al., 2006). Silvopastoral systems are an excellent way of reforestation and recuperation of degraded lands. Evidence supporting these benefits have been gathered only recently (Murgueitio et al., 2011). Although scientific reports supporting these benefits have increased noticeably within the last few decade, they have generally focused on single agroforestry ecosystem services; for instance, impacts on biodiversity conservation in tropical landscapes (Schroth et al., 2004), soil fertility (Schroth and Sinclair, 2003) or potential carbon sequestration (Montagnini, 2006). Recently in Mexico, there has been an increasing interest towards intensive silvopastoral systems or ISPS. This is an important approach in recovering degraded pastures or dry tropical areas, increasing the availability and quality of fodder generated and holds great opportunities for economic value addition resulting from sustainable and healthy animal production (milk, cheese and meat) further contributing to environmental protection and sustainable ecosystem generation. In this context, there have been significant advances in the understanding of the methodologies used for the silvopastoral systems benefitting integrated systems with joint ruminants and tree crop production, especially in association with citrus members, coconuts palm and mangoes among others. The main areas in which research have been currently undertaken include: P Characterization of environmental and soil conditions within plantations. P Assessment of forage availability and quality, as well as seasonality of production. P Carbon sequestration and atmospheric nitrogen fixation.

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P Measurement of animal performance for milk and meat production and quality. P Measurement for animal behavior. P Analyses of the economic benefits of the silvopastoral systems.

34.2 Intensive Silvopastoral Systems (ISPS) ISPS refers to the integration of shrubs mainly leguminous plants at high densities in association with grasses and trees species for animal production. Fodder production and accessibility is improved by using high density Leucaena shrubs at narrow spacing (Figure 34.1). Rows are established about 1.6 m apart and the row spacing of shrubs varies from 20-30 cm. Ideally, rows are oriented along the contours in east-west direction. Once the Leucaena are well established, grass should be allowed to grow in the area between the rows.

A

B Figure 34.1: ISPS Established with A. Leucaena leucocephala (Lam.) de Wit and B. Panicum maximum Jacq.


355

Figure 34.2: ISPS Examples. A. High density L. leucocephala and guinea grass (P. maximum) farm, Ejido la Concha.); B. Livestock for milk production, Huarinches farm, Tepalcatepec; C. Steer for meat production, Uricho farm, and D. P. maximum farm, La Concha municipality.

A

B

C

Contd...

356


Figure 34.2–Contd...

D There must be a significant positive interactions between shrubs-trees and grasses in the system ecologically and economically. The integration of shrubs and tree crops or timber trees with pastures can increase soil fertility, reduce soil erosion, favor biodiversity and increase carbon capture and fixation of atmospheric nitrogen. Among ruminants, cattle are well suited to integration with tree crops such coconuts, citrus species and mango trees (Figure 34.2). Murgueitio et al. (2011) described intensive ISPS as an advanced form of agroforestry (AFS) for animal production that integrates fodder shrubs planted at high densities (>10,000 plants/ha), intercropped with improved, highly productive pastures and timber trees all combined in a systems that can be directly grazed by livestock.

34.3 Environmental Services from Agroforestry Systems Carbon Sequestration and Methane Emissions Carbon sequestration is the capture and storage of atmospheric carbon into carbon sinks (e.g. oceans, vegetation, or soils) through physical and biological processes (Ibrahim et al., 2005). Incorporating trees and shrubs into ISPS will increase carbon sequestration, compared with other systems like monoculture pastures. Besides storing important amounts of carbon in above ground biomass, they can also store greater amounts of carbon in below ground biomass (Casanova et al., 2010). However, this is an area that has not been addressed in Mexico, the expanding areas under tree crops will provide good opportunities for carbon sequestration trough more widespread use of leguminous shrubs in association with grasses including the improved forage management practices which will result in decreased carbon atmospheric emissions and global warming. Casanova et al. (2011) has calculated that in silvopastoral systems (mixed fodder bank systems) the carbon sequestered per hectare was from 14.9 to 21.8 t C/ha/yr using a combination of leguminous with non-leguminous shrubs, root biomass is estimated to be 20-30 per cent of the aboveground shrubs carbon stock. This is an area


357

has not been fully addressed in Mexico concern carbon sequestration, the expanding land areas under silvopastoral systems with tree crops provide good opportunities for carbon sequestration through more widespread use of grasses and legumes shrubs, with resultant decreased carbon atmospheric emissions and global warming. On the other hand the wide, deep root systems of L. leucocephala (Figure 34.3) in the ISPS increases the available area for nutrient capture and help maintain nutrient stock by reducing leaching losses or by taking up nutrient from deeper soil layer

A

B

Figure 34.3: Leucaena leucocephala Lam. A: Root Nodule and B: Root Architecture.

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including the C storage, (Casanova, 2012). In addition, organic matter is incorporated gradually into the soil, this help to improve soil stability, mineralization and availability of soil nutrients, (Petit, 2012). Associated with above is the issue of Greeenhouse Gases (GHG) emissions mainly methane (CH4) and its effects on climate change. Improved monocrop pastures with leguminous shrubs to feed grazing ruminants will have beneficial effect, the CH 4 yield tends to decrease as feed quality increases (Moss et al., 2000). In response to possible effects on climate change, mitigation efforts have therefore concentrated on ways of reducing the GHG emissions in which some strategies to include enhance feed quality, supplemental with foliage and pods of tropical legumes may contributed to improvement of ruminant productive performance. The secondary metabolites (such as tannins and saponins) present in the pods of Acacia pennatula (Schlecht. and Cham.) Benth and Enterolobium cyclocarpum (Jacq.) Griseb. may contribute towards reducing CH4 production in the rumen (Briceño-Poot et al., 2012). To reiterate, more widespread use of high quality grass-legume (such as the association of guinea grass with L. leucocephala) and improved forage management practices (grazing rotation, adequate stocking rate); including the introduction of best, available animal breeds (genotypes) for grazing under tropical conditions will be necessary. Recently, it has been reported that it is possible to reduce CH 4 production by 27 per cent in the rumen of sheep fed with saponin from tea leaves (Mao et al., 2010). As millions of cattle graze low nutritive quality tropical pastures in Central and South America, contributing to global GHG emissions, there is scope to reduce enteric CH4 production in grazing ruminants under ISPS based in the association of leguminous shrubs with tropical grasses. Thus, mitigation of CH4 emissions in ruminants could reduce their contribution to GHG emission while improving feed efficiency for ruminants. However, better understanding is necessary for the relative GHG emissions from improved grass-legume pastures. Hence, strategies including the use of leguminous shrubs with the capacity to fix atmospheric nitrogen in order to reduce fertilizer-related emissions and for reducing GHG emissions from land use through better carbon sequestering, ISPS offer promising sustainable alternatives both for the local economy as well as environment.

34.4 Soil Fertility It is indisputable that decreasing vegetation cover has caused a reduction in nutrient cycling and soil fertility (Iridiondo et al., 1998). Livestock production is frequently referred to as a major driver of tropical deforestation. Mexico is a representative example within the regional context. The estimates for the rate of deforestation in Mexico ranged from 400,000-1,500,000 ha/year and there is much more deforestation in the tropical region than in the temperate areas. The dominant impact of forest conversion has been made by the rapid expansion of livestock production and the increased demand for pasture land, particularly in tropical areas (Barbier and Burgess, 1996). Forest ecosystems are closed and efficient systems (Petit et al., 2009). They have high rates of return and low rates of losses, and are thus selfsustaining. On the other hand, many conventional agroecosystems (e.g., monocrops)


359

are open or permeable, with relatively low rates of return and high rates of losses (Nair, 1993). Agroforestry (AFS) is positioned between these two extremes, with more efficient nutrient cycling than conventional agricultural systems and similar productivity to forest ecosystems. Nair (1993) claimed that the difference between AFS and other agricultural land use practices lies in the transference or recovery of nutrients into the system from one component to another and the possibility of managing the system or its components to increase nutrient recycling rates without affecting total productivity. The incorporation of shrubs and trees in the silvopastoral systems increases soil fertility, and improves soil structure. Trees have deep root systems which serve as an underground net through which nutrients can be captured from deep within the soil profile. These nutrients are returned to the soil via leaf litter, increasing the nutrient recycling efficiency of the system (van Noordwijk et al., 1996; Allen et al., 2004). The incorporation of L. leucocephala in pastures led to an increase in the content of soil nutrient such as nitrogen (N), phosphorus (P) and carbon (C). These results have been explained by the amount of good quality litter decomposition by tropical shrubs in silvopastoral systems. Moringa shrubs (M) residue decomposed significantly faster than the other shrubs followed closely by the combination of Leucaena + Moringa, (Figure 34.4) Leucaena leaves released their organic matters at intermediate rates. These differences in organic matters released have grave importance with respect to synchronization with nutrients demand by either crops or grass in silvopastoral systems. 120 mixture L+G pure L pure G mixture L+M pure M

100

80

60

40

Organic matter rem

20

0 0

2

4

6

8

10

12

14

16

18

Time in field (weeks) Figure 34.4: Litter Decomposition from different Tropical Shrubs Species under Silvopastoral Systems Arrangement. Guazuma ulmifolia Lam. (G), L. leucocephala (L), Moringa oleifera Lam. (M) and the combinations of Leucaena with Guazuma (L + G) and Moringa with Leucaena (L + M).


360

Additionally, most shrubs and trees used in silvopastoral systems are legumes that have the capacity to fix nitrogen through the association of bacteria living in the roots nodules. These bacteria can change inert N 2 to biologically useful NH3, which is then converted to protein in the plant. Under ISPS, L. leucocephala provide the main input of nitrogen for pastures. Furthermore, there is a reduction in the use of nitrogen fertilizers in pastures and have the extra benefit of improving feed quality for grazing animal. Bacab et al. (2012) found high productivity of forages without using fertilizer with the introduction of high density ISPS using L. leucoephala in combination with guinea grass (Table 34.1). Table 34.1: Fodder Production under ISPS and Monocrop Based Pasture Indicator

ISPS (L. leucocephala + P. maximum)

P. maximum

Fodder production (t DM/ha/) dry period

14.5

5.0

Fodder production (t DM/ha/) wet period

24.2

7.0

2100-3500

360 -600

Crude protein production (kg/ha) Source: Modified from Bacab et al. (2012).

34.5 ISPS for Cattle Production: Fodder Availability and Quality Ruminants raised in the tropics of Mexico largely depend on seasonal grass feed resources which are relatively low in quality in terms of low crude protein. The introduction of L. leucocephala in pastures improves the forage quality of associated grasses compared to grasses under monocrop system. In one study carried out by Bacab et al. (2011) in the Tepalcatepec Valley, Michoacán, Mexico, an ISPS of L. leucocephala in association with P. maximum cv Tanzania showed a forage production of 8.2 t DM/ha/year without fertilization compared to 3.2 t DM/ha/year under traditional pasture system. These results demonstrate the great potential of ISPS to produce high quality biomass and iradicate problems of fodder scarcity. Bacab-Perez and Solorio-Sánchez, (2011) evaluated the animal performance (milk production and daily weight gain) for cattle grazing under ISPS. In all these cases, the stocking rate and milk productivity was reported increased. The increase in acerage of land use with high density ISPS L. leucocephala with P. maximum has led to an increase in the stocking rate and milk production substantially (Table 34.2). Silvopastoral systems can remain productive for longer periods than conventional pastures, thus reducing the pressure to clear more forests for agricultural purposes (Steinfield et al., 2006). In case of ISPS, cattle grazing under the shade of trees suffer less heat stress than in open pastures (Table 34.3). The animals graze more efficiently and have lower respiratory rates, thereby producing more milk and meat. In addition, the combination of trees, shrubs and grasses help to retain and use water more efficiently and help in proper soil and nutrient cycling. All the above conditions provide suitable habitat for insects and other litter decomposers that can quickly recycle the nutrients and for beneficial insects (predator and parasitoids) that control harmful insect in a biological


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control system without the application of expensive and non-environment friendly chemical pesticides (Murgueitio et al., 2011). Table 34.2: Animal Parameters under ISPS and Traditional Monoculture System Parameters

SSPi (Ll* + Pm**)

Traditional System (Pm monoculture)

Milk production (L/cow./day)

8.0

3.5

Weight gain (g/día)

900

500

Stocking (AU/ha/year)

4.0

2.0

* Ll: L. leucocephala cv Cunningham; ** Pm: P. maximum cv. Tanzania. Source: Bacab-Perez and Solorio-Sánchez (2011)

Table 34.3: Environmental Indicators under Traditional Monoculture System and ISPS in the Apatzingan Valley, Michoacán Indicators

Traditional System (Grass monoculture)

ISPS

Environmental temperature (°C)

34-38

30-34

Nutrient recycling (kg/ha N-P-K).

Less 15, 6, 17

More 22, 4, 2

Efficiency of water (per cent)

30

80-90

Organic Matter (kg/ha)

320

1000

N fixation (kg/ha/year)

0

300-500

120

220

Carbon storage (t/ha/year)

34.6 Conclusions Silvopastoral systems are very important and implementation of silvopastoral systems on cattle farms has resulted in significant improvements in livestock productivity and environmental sustainability. Well managed silvopastoral systems increase biological diversity, soil and biomass carbon sequestration; as well as increase the capacity to fix atmospheric nitrogen more efficiently. The use of leguminous shrubs in combinations with grasses can replace the use of nitrogen fertilizer for sustaining pasture yields and reducing the impact on the local ecosystem and environment. A combination of clear polices and increased technology diffusion of silvopastoral systems can further accelerate the adoption of this innovative and sustainable approach among farmers in developing and under developed countries. Future research and development efforts are still expanding with enhanced emphasis on environmental protection and sustainability. Grazing management and socioeconomic analysis on the adoption of this approach on local rural economy level will be important to properly asses the success of this approach under low input agricultural systems. Further research and developments will also be necessary under different dry tropical agro-ecosystems as well as in the proper and scientific integration of livestock management with tree crop productions for making ISPS a viable solution for dry and tropical agriculture.

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Acknowledgments We are grateful to the National Council of Science and Technology (FordecytCONACyT) for their generous support, to Fundacion Produce Michoacan funded our research.

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