4.3 Evolution rates of CO2-C at days 1, 8, 57, and 149 of incubation. Values ...... The cores were taken with a manual hammer- driven core sampler from random ...
INFLUENCE OF TILLAGE ON SOIL PROPERTIES UNDER AGRICULTURAL AND NATURAL PRAIRIE SYSTEMS
By JUAN-PABLO FUENTES
A dissertation submitted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY WASHINGTON STATE UNIVERSITY Department of Crop and Soil Sciences December 2003
To the Faculty of Washington State University: The members of the Committee appointed to examine the dissertation of JUAN-PABLO FUENTES find it satisfactory and recommend that it be accepted.
Chair
ii
ACKNOWLEDGEMENTS
I have to give my sincere and immense gratitude to my advisor, Dr. David F. Bezdicek, which has given me all his support and extraordinary academic advice throughout this worth–living experience at the Washington State University. Similarly, I would like to express my great appreciation to Dr. Markus Flury. He has enriched my perception of what constitutes an example of an eminent scientist and extraordinary educator. With no doubt, I will follow the advice of Dr. Bezdicek and Dr. Flury in my work, and in my day to day life. My recognition also to Dr. Jeffrey Smith for his suggestions and comments during the revision of this dissertation, as well as for his invaluable help with the laboratory equipment. I thank Dr. Stephan Albrecht, who provided excellent and accurate comments to this dissertation. I acknowledge Debbie Bikfasy, Ron Bolton, Mary Fauci, David Uberuaga, and Shawn Wetterau for their help and assistance during sampling, collection, and data analysis in the laboratory. My sincere appreciation also to the Washington State University, the STEEP Project, and the USDA-ARS for their financial and logistic support. My particular thanks to Dr. David R. Huggins, who assisted and advised me during this dissertation. I extend my appreciation to Frank Lange and Larry Hood for the soil samples taken from their land. Finally, I acknowledge Claudia Reyes-Quilodr´an, my wife, for her strong support during all these years. She has been a major key for the successful completion of the dissertation. iii
INFLUENCE OF TILLAGE ON SOIL PROPERTIES UNDER AGRICULTURAL AND NATURAL PRAIRIE SYSTEMS Abstract by Juan-Pablo Fuentes, PhD. Washington State University December 2003 Chair: David F. Bezdicek Over the last 130 years, agriculture practices in the Palouse region of Washington State have caused remarkable changes in soil properties and soil processes. No-till (NT) is an alternative to conventional tillage (CT), mainly with the objective of reducing soil erosion. However, the impact of NT practices on soil hydraulic properties and increased soil acidity in the seed zone is not completely known. Surface application of lime to correct for soil acidification may not be practical under NT. One alternative is to place the lime near the seed zone. Soil hydraulic properties were studied in a longterm NT soil, a long-term CT soil, and a never-tilled natural prairie (NP) soil. The effect of sample size on the near-saturated K of a NT silt loam soil was also analyzed. Finally, laboratory experiments were conducted to characterize the effect of lime on chemical and biological soil properties in a long-term NT soil. Hydraulic conductivities under the NP soil were about one order of magnitude larger than for cultivated soils. Under NT, saturated K in the top 5 cm of soil was significantly higher than under iv
CT. No-till and CT soils had similar unsaturated K, indicating that restoration of original hydraulic properties in these soils may take a long time. Determination of K in an undisturbed soil core was affected by the length of the soil column. The heterogeneity of the soil with depth affected mostly the saturated K. Unsaturated K at low hydraulic heads was less affected by the length of the soil core due to increased homogeneity of the porous media. Lime increased soil NO− 3 -N consistently at only at the highest rate of 17.6 Mg ha−1 . Greater microbial respiration rates and greater microbial biomass-C were found in lime-treated than in non-limed soils. When soil was limed and mixed over larger depths (0-10, 0-20 cm), NO− 3 -N, soil respiration rates, and microbial biomass-C, decreased significantly. Organic mater turnover was faster in the lime-treated than in the non-limed soil.
v
Table of Contents
1 Introduction 1.1
1
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
1.1.1
The effect of soil management on hydraulic conductivity . . . .
1
1.1.2
Effect of sample size on hydraulic conductivity . . . . . . . . . .
7
1.1.3
Correction of soil acidification under no-till systems . . . . . . .
9
1.2
Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14
1.3
Dissertation Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15
2 Variation of Hydraulic Properties in a Silt Loam Soil under Natural Prairie, Conventional Till, and No Till
16
2.1
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16
2.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17
2.3
Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . .
21
2.3.1
Site selection and characterization . . . . . . . . . . . . . . . . .
21
2.3.2
Soil sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23
2.3.3
Measurement of hydraulic properties . . . . . . . . . . . . . . .
23
2.3.4
Data analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26
vi
2.4
Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . .
27
2.4.1
Temporal variation of hydraulic properties . . . . . . . . . . . .
27
2.4.2
Effect of soil management on hydraulic properties . . . . . . . .
29
2.5
Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . .
31
2.6
Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33
3 Near-Saturated Hydraulic Conductivity of a Silt Loam Soil as Affected by Sample Size
51
3.1
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
51
3.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
52
3.3
Material and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . .
55
3.3.1
Sampling and preparation of soil core . . . . . . . . . . . . . . .
55
3.3.2
Measurement of hydraulic properties . . . . . . . . . . . . . . .
56
3.3.3
Data analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . .
58
Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . .
62
3.4.1
Hydraulic conductivity as function of core length . . . . . . . .
62
3.4.2
Calculation of effective hydraulic conductivity . . . . . . . . . .
63
3.4.3
Tensiometer readings and time to steady-state . . . . . . . . . .
63
3.4.4
Fitting of hydraulic models to soil water retention and hydraulic
3.4
conductivity data . . . . . . . . . . . . . . . . . . . . . . . . . .
66
3.5
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
68
3.6
Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
70
vii
4 Microbial Activity Affected by Lime in a Long Term No-Till Soil
88
4.1
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
88
4.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
90
4.3
Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . .
93
4.3.1
Soil sampling and processing . . . . . . . . . . . . . . . . . . . .
93
4.3.2
Initial soil NO− 3 -N and liming treatments . . . . . . . . . . . . .
93
4.3.3
Soil pH, nitrate and ammonium . . . . . . . . . . . . . . . . . .
94
4.3.4
Soil respiration and microbial biomass–C . . . . . . . . . . . . .
95
4.3.5
Statistical analysis . . . . . . . . . . . . . . . . . . . . . . . . .
97
Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . .
99
4.4.1
Soil pH
99
4.4.2
Soil nitrate and ammonium . . . . . . . . . . . . . . . . . . . . 100
4.4.3
Soil respiration and microbial biomass–C . . . . . . . . . . . . . 101
4.4
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
4.6
Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
Bibliography
117
A Analysis of Biological Soil Properties for the 5-10 and 10-20 cm Depths Following Lime Application
viii
136
List of Tables
2.1
Agronomic practices under the CT and NT sites during the course of the study. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
34
2.2
Selected properties of the three soils. . . . . . . . . . . . . . . . . . . .
35
2.3
Significant differences in hydraulic conductivities for the different treatments: management system (MS), sampling time (TIME), sampling depth (DEPTH), and the interactions between treatments.
2.4
. . . . . .
36
Arithmetic mean, M (cm day−1 ), standard deviations, S (cm day−1 ), and coefficients of variation, CV (%), for hydraulic conductivity at different hydraulic heads, sampling times, and sampling depths (n = 8). .
2.5
Fitted van Genuchten parameters of soil moisture characteristics for the natural prairie soil.
2.6
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
39
Fitted van Genuchten parameters of soil moisture characteristics for the conventional till soil. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.7
37
40
Fitted van Genuchten parameters of soil moisture characteristics for the no-till soil.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ix
41
3.1
Differences in K (cm d−1 ) between direct measurement of large core and calculation with the harmonic mean of individual dissected cores. Values in parentheses are the relative variations expressed as percentage of the direct measurement of large core. . . . . . . . . . . . . . . . . . .
3.2
Parameters θr , θs , α, n, and m obtained from the curve fitting of soil water retention data with the van Genuchten model. . . . . . . . . . .
3.3
71
72
Parameters θr , θs , α, and n obtained from the curve fitting of soil water retention data with the van Genuchten model and the restriction m = 1 − 1/n. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4
Model fit comparisons for simultaneous fitting of soil water retention and hydraulic conductivity data. . . . . . . . . . . . . . . . . . . . . . .
3.5
73
74
Parameters θr , θs , α, n, and λ obtained from the simultaneous fitting of soil water retention and hydraulic conductivity data using the van Genuchten–Mualem models (m = 1 − 1/n, λ fitted parameter). . . . . .
3.6
75
Parameters θr , θs , α, n, and m obtained from the simultaneous fitting of soil water retention and hydraulic conductivity data using the van Genuchten–Mualem models (m and n independent parameters, λ = 0.5). 76
3.7
Parameters θr , θs , α, n, and λ obtained from the simultaneous fitting of soil water retention and hydraulic conductivity data using the van Genuchten–Mualem models (m = 1 − 1/n, λ=0.5). . . . . . . . . . . .
x
77
3.8
Parameters θr , θs , α, and n, obtained from the simultaneous fitting of soil water retention and hydraulic conductivity data using the van Genuchten–Burdine models (m = 1 − 2/n and, λ = 2). . . . . . . . . .
4.1
78
Selected soil properties previous to experimental treatment. Numbers in parentheses are standard deviations of the mean. . . . . . . . . . . . 108
4.2
+ Significant differences for NO− 3 -N, NH4 -N, and microbial biomass by
Substrate Induced Respiration (SIR) for the factors: liming rate (Lime), sampling time (Time), depth of application (Depth), and their interactions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 4.3
Evolution rates of CO2 -C at days 1, 8, 57, and 149 of incubation. Values in parenthesis are the standard error of the mean (n=6). . . . . . . . . 110
4.4
Fitted parameters C0 , Ce , and k for cumulative CO2 -C in time, and coefficients of determination R2 obtained by non-linear parameter estimation. Values in parenthesis are the standard errors of the fitted values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
+ A.1 Significant differences for NO− 3 -N, NH4 -N, and microbial biomass by
Substrate Induced Respiration (SIR) for the factors: liming rate (Lime), sampling time (Time), depth of application (Depth), and their interactions. Statistical analysis made for sampling depths 0-5, 5-10, and 10-20 cm (effect of lime at different depths). . . . . . . . . . . . . . . . . . . . 137
xi
A.2 Evolution rates of CO2 -C at days 1, 8, 57, and 149 of incubation in the 5-10 and 10-20 cm depths. Values in parenthesis are the standard error of the mean (n=6). Letters indicate Least significant differences of paired t-test (P
