Submitted to: Proceedings Great Plains Soil Fertility Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/14/2008
Publication Date: 3/4/2008
Citation: Wienhold, B.J., Wilhelm, W.W. 2008. Wheat roots and residue effects on soil aggregation and carbon. Proceedings Great Plains Soil Fertility Conference. 12:232-237. Interpretive Summary: Crop residue is being harvested or a number of off-field uses. While we know that these residues are important for maintaining soil aggregation and organic matter content we do not have a good understanding of the role of surface residue versus roots in these processes. This study compared aggregation and soil carbon for five years in soils receiving surface residue and roots, surface residue only, roots only, or no residue. Aggregation declined in soils receiving roots only or no residue. A measure of readily available soil carbon also decline in soils receiving no residue. Surface residue protects the soil from rainfall and serves as a carbon source for the surface soil. Roots alone are unable to provide physical protection.
Technical Abstract: Crop residues have been identified for a number of off-field uses. Poor understanding of the role of crop residues in key soil processes limits our ability to predict sustainable crop residue removal rates. A study was conducted to compare aggregate size distribution, aggregate stability, and soil organic carbon fractions in the 0 to 3 inch depth of soils receiving surface residue and roots, surface residue only, roots only, or no residue for five years. Aggregate size distribution was similar among treatments in 2002. After five years there was a loss of aggregates from the largest size class and a gain in aggregates in smaller size classes for the roots only and no residue treatments likely resulting from poor physical protection from rainfall. Aggregate stability declined in the no residue treatment in 2004 and 2006 likely the result of declining available nutrient and energy resources for soil biota. There was trend for lower labile carbon concentration in soils from the root only and no residue treatments likely resulting from limited carbon addition to the soil of these treatments. Crop residue provides energy and nutrients for soil biota and provides physical protection to the surface soil. Roots alone were unable to maintain soil aggregation.