|Kramer, Larry - RETIRED USDA/ARS/NSTL|
Submitted to: Soil Conservation and Water Quality Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 3, 2005
Publication Date: November 28, 2005
Citation: Tomer, M.D., Burkart, M.R., Cambardella, C.A., Meek, D.W., James, D.E., Kramer, L.A. 2005. Conservation practices: short term decisions with long term effects. Soil Conservation and Water Quality Symposium Proceedings. Available: http://www.swcs.org/en/swcs_international_conferences/2005_annual_conference/index.cfm?nodeID=7455&audienceID=1 Technical Abstract: Conservation practices have effects that can be recognized and measured only through long-term research. By reviewing lessons from 35 years of research on four field-scale watersheds near Treynor, IA, our objective is to show the time frame of conservation-practice influences on natural resource properties and processes. Since the 1960s, tillage, N-fertilizer rate, and more recently crop rotation treatments were evaluated on deep-loess soils representing Major Land Resource Area 107. Recent analyses show that some responses to the treatments persisted for decades, and/or were revealed by patterns that can only be recognized with datasets that span decades. Watershed hydrology, groundwater quality, and soil quality and water storage all showed long-term responses. Specifically, we found that stream discharge of baseflow not only increased under ridge tillage compared to conventional tillage, but also that impacts of drought on baseflow were consistently less severe under ridge till. Also, an experiment involving large N-fertilizer applications, conducted in the early 1970s, continues to influence current groundwater nitrate concentrations. Finally, we found that differences in soil organic matter and bulk density created by contrasting tillage practices during a 25-year period persisted for at least eight years after the conventionally tilled watershed was converted to no-till. These differences in soil properties influenced the amounts and spatial patterns of water stored in the surface soils of these watersheds. These results help document the value of long-term research and emphasize the importance of a sustained research commitment to understand effects of conservation practices.