Soil water dynamics and nitrate leaching under corn-soybean rotation, continuous corn, and kura clover

Authors: OCHSNER, TYSON - Oklahoma State University; Schumacher, Todd; Venterea, Rodney - Rod; Feyereisen, Gary; Baker, John

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2017
Publication Date: 5/17/2018
Citation: Ochsner, T., Schumacher, T.W., Venterea, R.T., Feyereisen, G.W., Baker, J.M. 2018. Soil water dynamics and nitrate leaching under corn-soybean rotation, continuous corn, and kura clover. Vadose Zone Journal. 17:170028. https://doi.org/10.2136/vzj2017.01.0028.
DOI: https://doi.org/10.2136/vzj2017.01.0028

Interpretive Summary: Improving the water quantity and water quality impacts of corn (Zea mays L.)- and soybean (Glycine max L.)-based cropping systems is a key challenge for agriculture in the US Midwest and similar regions around the world. Long-term field experiments are important for documenting those effects and exploring possible solutions. This study presents water quantity and quality measurements from a long-term field experiment in southeastern Minnesota, the Rosemount experiment. The main objective was to quantify differences in soil water dynamics and nitrate-nitrogen (N) leaching between cropping systems and N fertilizer sources. Drainage and leachate concentrations were measured for four years using automated equilibrium tension lysimeters installed below the rooting zone in a replicated, large plot experiment on a well-drained silt loam soil. Soil water storage was monitored continuously using water content reflectometers. Corn-soybean (C/S) and continuous corn (C/C) cropping systems exhibited similar soil water dynamics, drainage rates (145-202 mm yr-1), leachate nitrate-N concentrations (21.3-25.6 mg L-1), and nitrate-N leaching loads (30-75 kg ha-1 yr-1). Nitrate-N concentrations in the leachate were lower (P < 0.10) when urea (21.2 mg L-1) rather than anhydrous ammonia (25.7 mg L-1) was used as the N source. A perennial kura clover (Trifolium ambiguum M. Bieb)-based cropping system significantly altered soil water dynamics and resulted in lower (P < 0.10) drainage rates (53 mm yr-1), nitrate-N concentrations (7.1 mg L-1), and nitrate-N leaching loads (2-5 kg ha-1 yr-1) compared to C/S or C/C. Those reductions are generally consistent with a growing body of literature showing substantial environmental benefits of a kura clover living mulch system for corn production, but the economic viability of such a system has not yet been proven. These results will be of interest to scientists, land managers and policy-makers interested in developing crop production practices that maintain productivity while reducing envrionmental impacts.

Technical Abstract: Improving the water quantity and water quality impacts of corn (Zea mays L.)- and soybean (Glycine max L.)-based cropping systems is a key challenge for agriculture in the US Midwest and similar regions around the world. Long-term field experiments are important for documenting those effects and exploring possible solutions. This study presents water quantity and quality measurements from a long-term field experiment in southeastern Minnesota, the Rosemount experiment. The main objective was to quantify differences in soil water dynamics and nitrate-nitrogen (N) leaching between cropping systems and N fertilizer sources. Drainage and leachate concentrations were measured for four years using automated equilibrium tension lysimeters installed below the rooting zone in a replicated, large plot experiment on a well-drained silt loam soil. Soil water storage was monitored continuously using water content reflectometers. Corn-soybean (C/S) and continuous corn (C/C) cropping systems exhibited similar soil water dynamics, drainage rates (145-202 mm yr-1), leachate nitrate-N concentrations (21.3-25.6 mg L-1), and nitrate-N leaching loads (30-75 kg ha-1 yr-1). Nitrate-N concentrations in the leachate were lower (P < 0.10) when urea (21.2 mg L-1) rather than anhydrous ammonia (25.7 mg L-1) was used as the N source. A perennial kura clover (Trifolium ambiguum M. Bieb)-based cropping system significantly altered soil water dynamics and resulted in lower (P < 0.10) drainage rates (53 mm yr-1), nitrate-N concentrations (7.1 mg L-1), and nitrate-N leaching loads (2-5 kg ha-1 yr-1) compared to C/S or C/C. Those reductions are generally consistent with a growing body of literature showing substantial environmental benefits of a kura clover living mulch system for corn production, but the economic viability of such a system has not yet been proven.