The soil ecology effort has concentrated on understanding how soil physical and biological factors change when tillage is reduced or stopped. Our goal is to help farmers exploit positive and avoid negative changes. Investigations have included the effects of surface residue and seed-soil contact on germination and crop establishment, effect of tillage on earthworm populations, vertically connected soil pores, soil temperature, water storage, nutrient dynamics and pH.
Stewart Wuest, Soil Scientist
Tami Johlke, Biological Science Technician
Bill Schillinger, WSU
Larry Lutcher, OSU
Effect of soil and residue management on soil productivity, soil biopores, water infiltration, and stand establishment
Over the last five years, we have made a major effort to explain how reduction in tillage tends to result in increased water infiltration capacity. The use of no-till cropping systems involves changes in crop residue distribution in addition to reduced soil disturbance. We need to know whether the lack of soil disturbance, the amount of surface residue, or both are important for producing good water infiltration. With this knowledge, farmers can design soil management practices that optimize goals of sustainable production.
Preliminary results indicate that, in our weakly aggregated soils, surface residue and near-surface soil organic matter plays a very important role in reducing runoff and improving water infiltration capacity. Soil disturbance plays a role in destroying pathways for water infiltration left by the crowns of the previous crop, and by mixing surface residues and surface organic matter deeper into the soil where they are less effective.
Future plans are to understand exactly how soil mulches preserve seed-zone moisture for early planting in winter wheat/summer fallow systems. This century-old practice has been a mainstay of dryland agriculture in arid regions, and is being replaced by no-till annual cropping in many areas which receive summer rainfall. Our goal is to add in-depth scientific understanding to the current conventional wisdom and experience being used by farmers to come up with erosion-resistant summer fallow practices for areas which receive too little summer rain to sustain spring crops.