Soil management and crop biomass removal impacts on soil organic matter content

Abstract

A well-recognized soil quality indicator is soil organic matter (SOM) content (SOMC), a soil component upon which agroecosystems and agricultural production are dependent. Agricultural practices greatly influence SOMC (Larson and Pierce, 1994) and SOMC affects crop production (Guernsey et al., 1969). Research has shown positive relationships between increased SOMC and appropriate management practices with organic carbon added to the soil (Peterson et al., 1998; Robinson et al., 1996). Removing residues increases soil erosion losses (Gupta et al., 1979), and residue harvest removes with it plant nutrients that must be replaced with fertilizer (Rasmussen and Rode, 1988) or manure applications (Sommerfeldt et al., 1988). Even with these negative impacts, it seems residues, or part of the residues, can be removed from selected soils without decreasing soil quality if appropriate management practices are used, i.e., reduced tillage, manure application, and crop rotations (Havlin et al., 1990). These practices are known to attenuate the effect of residue removal. Stevenson (1965) reported that rotations including legumes maintained a higher SOM level than continuous cropping with no leguminous crops. Few studies have explicitly measured the effect of com (Zea mays L.) residue removal on soil organic carbon (SOC; SOC = 1.6 x SOM). Karlen et al. (1994) found that normal and doubled residue addition treatments resulted in higher SOMC than the residue removal treatment within no-till continuous com in Iowa. Changes in SOMC occur slowly over periods of decades so long-term experiments are necessary to measure these changes. However, no SOMC analysis of long-term experiments designed to evaluate the effects of residue removal on SOMC when using a variety of crop and soil management practices has been located. Understanding the net effect of management alternatives on SOMC with residue removal, and the soils for which they will best work, requires research. The objective of this study is to evaluate impacts of manure and mineral fertilization application and crop rotations on soil carbon change when crop biomass is incorporated vs. when it is removed.