Effects of crop residue cover and architecture on heat and water transfer at the soil surface

Different residue types and standing stubble versus distributed flat residues affect heat and water transfer at the soil surface to varying degrees. Understanding the effects of various residue configurations can assist in better residue management decisions, but this is complex due to various interacting influences. Therefore, modeling the effects of crop residues on heat and water movement can be an effective tool to assess the benefits of differing residues types and architectures for various climates. The purpose of this study was to test the ability of the Simultaneous Heat And Water (SHAW) model for simulating the effects of residue type and architecture on heat and water transfer at the surface and to evaluate the impacts of differing residue types and architectures on heat and water transfer in significantly different climates. The model was tested on bare tilled soils and corn, wheat and millet residues having varying amounts of standing and distributed flat residues for three separate locations: Ames, IA, Akron, CO and Pullman, WA. Modifications to the model were necessary to correctly simulate the effect of wind on convective transfer through a flat corn residue layer. Model efficiencies for simulated soil temperature approached or exceeded 0.90 for nearly all residue treatments and locations. The root mean square deviation for simulated water content compared to measured values was typically around 0.04 m3 m?3. Satisfied that the model could reasonably simulate the effect of residue type and architecture, the model was applied to simulate the effects of differing residue architectures to 30 years of generated weather conditions for four diverse climate stations: Boise, ID; Spokane, WA; Des Moines, IA; Minneapolis, MN. Simulated frost depths for bare and standing residues were typically deeper than for flat residues. Bare soil had the highest evaporation at all sites, and flat wheat residue generally had the lowest evaporation. The wetter climates (Des Moines and Minneapolis) tended to favor flat residues for reducing evaporation more so than the drier climates. Near-surface soil temperature under standing residues warmed to 5 °C in the spring by as much as 5–9 days earlier compared to bare and flat residue cover depending on location, which can have important ramifications for early seedling germination and plant establishment.