Climate smart farming practices and soil carbon cycle proxies Restricted; Files Only

Abstract

Climate-smart agriculture practices can enhance the ability of small-scale farmers to adapt to issues posed by climate change and meet the growing demand for food, fiber, and fuel. By embracing perennial agriculture, minimizing soil disturbance, and enhancing soil biodiversity, soil microbial activities and the potential for soil carbon (C) sequestration can be increased. While changes in long-term C storage occur over extended timescales, biological parameters provide more immediate insights into these processes.

I evaluated soil C dynamics and associated microbial proxies under different climate-smart agriculture practices (e.g., cover crop, agroforestry, conservation/reduced tillage, and soil amendments such as biochar and compost) within the Southeast USA. Study sites included an annual vegetable farm in Georgia and a perennial agroforestry system in North Carolina. I measured total C and nitrogen (N), potential C mineralization, microbial biomass C and N, microbial necromass, and potential extracellular enzyme activities to improve our understanding of how climate-smart agriculture practices affect soil organic matter (SOM) dynamics and their ability to contribute to long-term C stabilization.

Results indicate that there are significant differences in microbial biomass C between soils using no-till and conservation-till practices, and in microbial biomass C, potential C mineralization, and enzyme activities between agroforestry with pecan vs. pine trees and across alley cover crop types. The main effect of amendment and an interaction effect between amendment and tillage depth on enzyme activities were also observed. This is relevant for comparing the utility of different climate-smart practices for the enhancement of soil biological health and climate change mitigation in a cropping system. This study may provide insights into precursory shifts in soil C dynamics and how they relate to long-term changes in C pools, which is important for agricultural decision-making and land use management.

Table of Contents

1. Introduction / Background.....................................................................................................................1

1.1 Climate Change and Agriculture...........................................................................................................1

1.2 Climate-Smart Agriculture ..................................................................................................................1

1.2.1 Cover Crops.....................................................................................................................................2

1.2.2 Amendments...................................................................................................................................4

1.2.3 Tillage ............................................................................................................................................4

1.2.4 Agroforestry ....................................................................................................................................4

1.3 Soil Health and Carbon Cycling............................................................................................................6

2. Materials & Methods ............................................................................................................................9

2.1 Experimental Design & Sample Collection............................................................................................9

2.1.1 Oxford Farm, Emory .........................................................................................................................9

2.1.2 University Research Farm, North Carolina A&T ................................................................................10

2.2 Treatment Details: Oxford Farm: Amendment.....................................................................................10

2.2.1 Amendments..................................................................................................................................10

2.2.2 Tillage ...........................................................................................................................................11

2.3 Treatment Details: NCA&T.................................................................................................................11

2.3.1 Agroforestry ...................................................................................................................................11

2.3.2 Tillage ...........................................................................................................................................11

2.3.3 Alley Cover Crop .............................................................................................................................12

2.4 Laboratory Analyses...........................................................................................................................13

2.5 Statistical Analyses ............................................................................................................................15

3. Results................................................................................................................................................15

3.1 Oxford Farm ......................................................................................................................................18

3.1.1 Microbial Biomass...........................................................................................................................18

3.1.2 Enzyme Kinetics..............................................................................................................................19

3.1.3 Necromass......................................................................................................................................21

3.1.4 Correlation Matrix...........................................................................................................................22

3.2 NCA&T ............................................................................................................................................23

3.2.1 Microbial Biomass...........................................................................................................................23

3.2.2 Respiration.....................................................................................................................................24

3.2.3 Enzyme Activities ...........................................................................................................................26

3.2.4 Necromass......................................................................................................................................31

3.2.5 Total C & N ....................................................................................................................................34

3.2.6 Correlation Matrix...........................................................................................................................35

4. Discussion .......................................................................................................................................... 36

4.1 Microbial Biomass..............................................................................................................................36

4.2 Respiration........................................................................................................................................38

4.3 Enzyme Activities & Kinetics..............................................................................................................40

4.3.1 Enzyme Kinetics (Oxford Farm)........................................................................................................40

4.3.2 Enzyme Activities (NCA&T) .............................................................................................................41

4.4 Necromass.........................................................................................................................................43

4.5 Correlation Matrices ..........................................................................................................................45

5. Societal Implications of Climate-Smart Practices ...................................................................................47

6. Conclusions.........................................................................................................................................48

7. References...........................................................................................................................................50

8. Appendix A: Additional Statistical Outputs ...........................................................................................66

9. Appendix B: Correlation Matrices..........................................................................................................77 

About this Honors Thesis

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School	Emory College
Department	Environmental Studies
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Environmental Sciences
Stichwort	biogeochemistry climate change soil agriculture
Committee Chair / Thesis Advisor	Sihi, Debjani, Emory University
Committee Members	Lonsdorf, Eric, Emory University Phillips, Kristin, Emory University Dari, Biswanath, North Carolina Agricultural and Technical State University

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