Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 7/10/2006
Publication Date: 7/10/2006
Citation: Kennedy, A.C., Schillinger, W.F., Stubbs, T.L. Soil Quality and Conservation Tillage in the Palouse and Dryland Farming Regions of the Pacific Northwest. ASABE Annual International Meeting. Interpretive Summary: The soils in eastern Washington and northern Idaho have been farmed for over 125 years. Farming in the Palouse is conducted on steep slopes and water erosion is an environmental concern. Also, soil organic carbon has declined to half the original values of the native soil since the onset of farming. We characterized the biological, physical and chemical soil quality parameters and monitored their changes over time as affected by tillage and crop rotation. Soil organic carbon increased over time with 20-year no-till. No-till also increased the proportion of aggregates in the larger sized soil fractions. Microbial community analysis often showed changes with long-term (20-yr) no-till and an increase in the fungal component. Data from these long-term experiments will allow us to better assess the health or quality of soils in dryland cropping regions to aid growers in the transition to no-till cropping. Long-term studies are needed to fully understand the subtle and often slow changes occurring in the soil environment with conservation tillage practices.
Technical Abstract: Soil quality was assessed at several dryland cropping systems research sites in eastern Washington and northern Idaho to further define management practices that build rather than degrade soil. The objective was to characterize soil quality changes over time as affected by tillage and cropping system at sites near Colfax, Ritzville, and Lind, WA and Genesee, ID. We found that soil quality changes during the transition from tillage-based farming to no-till are less dramatic and more variable in the low precipitation (150– to 300– mm annual) zone compared to the higher precipitation (300– to 550– mm annual) zone. Tillage impacts soil quality more than surface residue management or crop rotation. Soil organic carbon (SOC) slowly increased in long-term no-till and approached or exceeded that of nearby undisturbed native soil. Long-term no-till also increased the proportion of aggregates in the larger sized soil fractions. We also see that long-term (20-yr) no-till results in microbial community changes and an increase in the fungal:bacterial ratio. Data from these long-term experiments will allow us to better assess the productivity and quality of soils in the Palouse and other dryland cropping regions of the Inland Pacific Northwest. This information will allow identification of soil quality parameters that can be used in the development of best management practices for conserving soil quality and enhancing crop production.