MITIGATING AGRICULTURAL SOURCES OF PARTICULATE MATTER AND GREENHOUSE GAS EMISSIONS IN THE PACIFIC NORTHWEST
Location: Land Management and Water Conservation Research
Title: Residue Management Impacts on Field-Scale Snow Redistribution and Soil Water Storage
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 16, 2011
Publication Date: N/A
Interpretive Summary: In northern environments, snow can be a substantial contributor to available soil water and enhance crop yields in water-limited environments. Snow, however, is subject to redistribution across fields as a consequence of wind drifting that can result in field areas with large snowpacks as well as areas with virtually no snow. This field variability in snowpacks can have adverse consequences as upon melting, areas with concentrated snowpacks can promote soil erosion while areas with no snow do not accumulate stored soil water. We evaluated the impact of leaving crop residues standing after harvest as is practiced with no-tillage to see if this could influence field patterns of snow drifting and amounts of available soil water in different areas of a field. We found that standing crop residues did reduce field drifting of snow which resulted in more uniform storage of soil water as compared to a conventionally tilled field. In fact, for no-tillage, soil water storage was 60, 29 and 13 cm more than conventional tillage on ridge top, south slope and valley field positions, respectively. The greater soil water storage increases potential wheat yield by 900, 435 and 195 kg grain ha-1 for no-tillage compared to conventional tillage in ridge top, south slope and valley positions, respectively. These results can be used by NRCS and University extension personnel to promote the adoption of no-tillage thereby reducing soil erosion as well as enhancing crop yields and agricultural sustainability. Furthermore, results will allow hydrologists to improve models of snow drifting behavior to better predict soil erosion, soil water storage and other field-scale water-related processes.
Spatial variation of soil water affects crop performance, fertilizer use efficiencies and other important economic and environmental factors. Soil water storage could be increased and field variability reduced by residue management practices such as no-tillage (NT) as surface residues can retain more snow, enhance water infiltration and reduce evaporation as compared to conventional tillage (CT). Our objectives were to evaluate residue effects on snow redistribution and the spatial variation of soil water storage for two adjacent fields near Pullman, WA, one under NT, the other under CT. The fields were surveyed during the winter and spring of 2007–2008 to assess topographic variations in snow depth, snow water equivalent (SWE) and soil water storage. Standing stubble under NT retained 10–20 cm more snow on ridge-top and steeply sloped ground than CT and the snow pack was distributed more evenly with less spatial variation. SWE followed the same pattern of larger spatial variation in CT than NT. Soil water (0-1.5 m) in the spring was lowest for ridge top areas and highest in valleys for NT and CT. Under NT, however, soil water varied less across different field locations than CT and overall water storage was 60, 29 and 13 cm more for NT than CT on ridge top, south slope and valley positions, respectively. Although many factors can contribute to the spatial variation of soil water, standing wheat residue under NT retarded the generation of runoff, retained more snow on ridge top and steep-sloped areas, reduced soil water spatial variation and increased soil water recharge.