PROTECTING SURFACE AND GROUND WATERS IN EMERGING FARMING SYSTEMS OF THE NORTH CENTRAL UNITED STATES
Location: Soil and Water Management Research
Title: Water Balance and Nitrate Leaching for Corn in Kura Clover Living Mulch
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 6, 2010
Publication Date: May 12, 2010
Citation: Ochsner, T.E., Albrecht, K., Baker, J.M., Schumacher, T.W. 2010. Water Balance and Nitrate Leaching for Corn in Kura Clover Living Mulch. Agronomy Journal. 102:1169-1178.
Interpretive Summary: Conventional corn production has been implicated as a contributor to several important environmental problems due to erosion and leaching losses of nutrients that can impair ground and surface waters. New management practices are needed to reduce these impacts without adversely affecting corn yield. One potential practice is the use of kura clover as a continuous living mulch, into which corn can be planted. We tested this system to determine if it would indeed reduce nitrate losses, and to determine whether it would have a negative impact on corn by depleting soil water. An experiment was conducted over a 2.5 year period at Arlington WI, in which corn clover living much systems, one with no added nitrogen and one with 90 kg ha-1 of added N, were compared to a conventional corn treatment. Soil water contents in all three treatments were similar over the duration of the experiment, but the clover did cause a depletion of moisture in the spring, when ET was higher in the clover than it was for the conventional field, which was still bare. Nitrate leaching was 70% lower in the living mulch treatments and 35% lower in the mulch treatment with added N than in the conventional corn treatment. We conclude that the living mulch system can offer important environmental benefits, but with an added risk of early season moisture stress for the corn. If this risk can be reduced or eliminated, this could be an important new cropping system for farmers in the corn belt, that could reduce N fertilizer needs and nitrate contamination of groundwater.
Cropping systems with improved environmental performance are needed in the Midwestern United States. Corn (Zea mays L.) grown in kura clover (Trifolium ambiguum M. Bieb.) living mulch is a relatively new cropping system which may have potential to meet that need. Our objectives were to determine the impact of kura clover living mulch on the soil water balance and nitrate leaching under corn. Treatments were no-till corn as the control and no-till corn in kura clover living mulch with 0 and 90 kg ha-1 added N. Soil water content for the top 1 m of soil was similar in the control and the living mulch treatments for the majority of the 2.5 yr experiment. However, the living mulch temporarily reduced soil water storage by 37 to 50 mm in the late spring, and the control caused 29 to 36 mm greater soil water depletion in mid- to late summer. Evapotranspiration estimates were similar for the control and the living mulch systems, except in May when the modeled evapotranspiration for the living mulch was consistently greater by 11 to 41 mm. The living mulch did not appreciably reduce drainage below the root zone. Nitrate-N storage in the soil profile and nitrate-N concentrations in the soil solution at 1 m depth were significantly reduced (p = 0.10) in both living mulch treatments relative to the control. Flow-weighted nitrate-N concentrations were 22 mg L-1 for the control, 15 mg L-1 for the living mulch with 90 kg ha-1 added N, and 7 mg L-1 for the living mulch with no added N. Total nitrate-N leached under the living mulch with no added N was reduced 70% relative to the control, and the total nitrate-N leaching under the living mulch with 90 kg ha-1 added N was reduced 35% relative to the control. We conclude that the kura clover living mulch offers valuable environmental benefits, but also increases the risk of water stress on the corn.