ABSTRACT

Soil organic carbon (SOC) is the part of carbon (C) in the soil that is derived from living organisms and plays an important role in the C cycle (Paustian et al. 1997). Soil is a major reservoir of soil C, at 3.3 times the size of the atmospheric pool of 760 pentagrams (Pg) and 4.5 times the size of the biotic pool of 560 Pg (Lal 2004). Soils act as a reservoir of SOC and the level of storage within an ecosystem is mainly dependent on the soil type, climate, land use history, and current management practices. The quantity of SOC stored in a particular soil is dependent on the quantity and quality of organic matter returned to the soil matrix, the soil’s ability to retain SOC (a function of texture

CONTENTS

2.1 Introduction ............................................................................................................................ 41 2.2 Factors Affecting SOC ........................................................................................................... 42

2.2.1 Climate ....................................................................................................................... 42 2.2.2 Soil Type ..................................................................................................................... 43 2.2.3 Land Use ..................................................................................................................... 43

2.3 Effect of Agricultural Management on SOC ..........................................................................44 2.3.1 Conservation Agricultural Practices...........................................................................44 2.3.2 Crop Residue and Its Quality for SOC Stabilization ..................................................44 2.3.3 Crop Residue Management ......................................................................................... 45 2.3.4 Crop Residue and Tillage ...........................................................................................46 2.3.5 Fertilizer Management................................................................................................ 47 2.3.6 Organic and Conventional Farming Systems ............................................................. 47

2.4 Pools of C and C Stabilization Mechanisms ..........................................................................48 2.4.1 Labile and Particulate Organic C ...............................................................................48 2.4.2 Soil C Stabilization through Aggregation ..................................................................48 2.4.3 Physicochemical Stabilization .................................................................................... 49

2.5 Conclusion and Summary ....................................................................................................... 49 Acknowledgments ............................................................................................................................50 References ........................................................................................................................................50