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ARS Home » Pacific West Area » Pullman, Washington » Northwest Sustainable Agroecosystems Research » Research » Publications at this Location » Publication #105270
Title: Subsurface drain losses of water and nitrate following conversion of alfalfa and conservation reserve land to row crops

Author
item Huggins, David
item RANDALL, GYLES - UNIVERSITY OF MINNESOTA
item Russelle, Michael

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2000
Publication Date: 5/1/2001
Citation: Huggins, D.R., Randall, G.W., Russelle, M.P. 2001. Subsurface drain losses of water and nitrate following conversion of alfalfa and conservation reserve land to row crops. Agronomy Journal. 93:477-486.

Interpretive Summary: The conversion of annual row crops to alfalfa (ALF) and perennial grasses achieved with Conservation Reserve Program (CRP) plantings has reduced losses of nitrate nitrogen through subsurface tile drains in the Upper Midwest. Conversion of alfalfa or CRP back to row crops could have rapid, adverse affects on water quality of tile drainage. Our objectives were to evaluate how prior perennial crops affect water and N use efficiency of annual row crops, and losses of water and nitrate to subsurface tile drains. Tile flow volumes increased to levels similar to row-crops during the first season following conversion of ALF and CRP to corn. Residual soil nitrate (RSN) in the root zone increased by 125% in first year corn following CRP and was 32% greater than continuous corn (CC) after 3 years. High N uptake efficiencies of corn following ALF helped to slow buildup of RSN, but levels were equal to row crop systems after two years. Nitrate losses and concentrations in tile drainage remained low during the initial year of conversion, but were similar to row crop systems during the subsequent two years. Thus, low tile flows and nitrate losses will likely require a rotation of perennial and annual crops in the Upper Midwest.

Technical Abstract: Nitrate losses through subsurface tile drains pose a serious threat to surface water quality. Large reductions in drainage losses of nitrate can be achieved with alfalfa (Medicago sativa L.)or perennial grasses often used in Conservation Reserve Program (CRP). Conversion of alfalfa or CRP back to row crops could have rapid, adverse affects on water quality. Our objectives were to evaluate how prior perennial crops affect water and N use efficiency of annual row crops, and losses of water and nitrate to subsurface tile drains. Four cropping systems [continuous corn (Zea mays L.), corn-soybean [Glycine max (L.) Merr.], alfalfa (ALF), and CRP] were established in 1988. ALF and CRP were converted to a corn-corn-soybean sequence from 1994 through 1996 while continuous corn (CC) and corn-soybean (CS) rotations were maintained. Beneficial rotation effects occurred following CRP including a 14% increase in corn yield and a 20% increase in water use efficiency (WUE) as compared to CC. Yield was 19% and WUE 21% greater for soybean following corn in CRP and ALF as compared to CS. Tile flow volumes were correlated to water supplies (Ws) and drainage differences were small following conversion of CRP and ALF to row crops. Residual soil nitrate(RSN) in the top 1.5 m increased by 125% in first year corn following CRP and was 32% greater than CC by 1996. High N uptake efficiencies of corn following alfalfa helped to slow buildup of RSN, but levels were equal to row crop systems after two years. Nitrate losses and concentrations in tile drainage remained low during the initial year of conversion, but were similar to row crop systems during the subsequent two years. Thus, low tile flows and nitrate losses will likely require a rotation of perennial and annual crops in the Upper Midwest.