M.S. Level Student
University of Illinois Urbana-Champaign
darbyd2@illinois.edu
Advised by Dr. Fred Below

Managing Decomposition of Cereal Rye Residues in No-Till Soybean for Timely Nutrient Release 

There has been a notable rise in the adoption of cover crops within agricultural production systems to mitigate non-point source nutrient pollution caused by leaching and runoff from fields during fallow periods. However, delayed decomposition of cover crop residues can lead to nutrient immobilization and reduced availability for the following row crop, potentially influencing subsequent yield and deterring the adoption of this sustainable farming practice. The inclusion of products that promote biomass degradation along with the foliar termination of the cover crop may be a feasible approach for increasing the rate of decomposition and the release of nutrients into the soil of no-till fields. The objective of this study was to investigate the efficacy of chemical and biological approaches to enhance the decomposition and nutrient release from the residue of a cereal rye (Secale cereale L.) cover crop for the subsequent soybean [Glycine max (L.) Merr.] crop. Ammonium thiosulfate (ATS) was applied alone as the chemical approach or with either of two biological approaches: a living microbial blend or a sugar-humic acid mixture to serve as a carbon addition. At the soybean R3 or R7 growth stages, cereal rye residue decomposition was not increased by any of the chemical or biological treatment combinations. When soybean was grown with untreated cereal rye, grain yield decreased by 0.53 Mg/ha, but using ATS, regardless of biological additive, mitigated this yield penalty. Additionally, all chemical and biological treatments to cereal rye numerically increased the soybean grain yield compared to untreated cereal rye, although these yield increases were not consistently related to the degree of residue decomposition. Therefore, when using a cereal rye cover crop with soybean, applying ATS or the biologicals mitigated expected yield losses, but did not directly affect residue decomposition.