COVER CROPPING TO REDUCE NITRATE LOSS THROUGH SUBSURFACE DRAINAGE IN THE NORTHERN CORN BELT

Authors: STROCK, JEFFREY - UNIV OF MINNESOTA; PORTER, PAUL - UNIV OF MINNESOTA; Russelle, Michael

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2003
Publication Date: 5/15/2004
Citation: Strock, J.S., Porter, P.M., Russelle, M.P. 2004. Cover cropping to reduce nitrate loss through subsurface drainage in the northern corn belt. Journal of Environmental Quality. 33:1010-1016.

Interpretive Summary: An enormous amount of farmland in the midwest must be drained to allow timely farm operations. This drainage generally is achieved by underground pipes that carry water away from the field to ditches and streams. Unfortunately, much of this drainage water contains high concentrations of nitrate, which can impair the environment. Even using best management practices, large amounts of nitrate are lost in drainage water beneath corn and soybean fields. Much of this loss occurs when these warm-season crops are not growing. One way to limit nitrate losses is to plant another crop to provide ground cover and to use both soil water and nitrate. These cover crops are grown in fall and early spring, and have been very successful in warm areas of the U.S., such as the southeastern states. In the northern midwest, low temperatures reduce cover crop growth. Even though a cover crop of cereal rye did not consistently reduce nitrate losses, we found that it was highly successful in some years, so that its average effect was substantial. The main problems still needing research are effective establishment of the cover crop under northern U.S. conditions and inexpensive methods of crop termination in late spring. In the meantime, farmers can begin using winter cover crops, like cereal rye, to help protect water quality.

Technical Abstract: Despite the use of best management practices for nitrogen (N) application rate and timing, significant losses of nitrate-nitrogen (NO3-N) in drainage discharge continue to occur from row crop cropping systems. Our objective was to determine whether a fall-seeded winter rye (Secale cereale L.) cover crop following corn (Zea mays L.) would control NO3-N losses through subsurface drainage in a corn-soybean [Glycine max (L.) Merr.] cropping system on a moderately well-drained Normania clay loam (fine-loamy, mixed, mesic Aquic Haplustolls) soil with improved drainage at Lamberton, MN. Four cropping systems [soybean-corn (S-C), corn-soybean (C-S), soybean-corn+rye (S-C+rye), and corn+rye-soybean (C+rye-S)] were established in 1998. Cover cropping did not affect subsequent soybean yield but reduced drainage discharge, flow-weighted mean NO3-N concentration (FWMNC), and NO3-N loss relative to winter fallow, although the magnitude of the effect varied considerably with annual precipitation. Three year average drainage discharge was higher with the S-C cropping system compared to the C+rye-S and the S-C+rye cropping systems (p = 0.06). Subsurface drainage discharge was reduced by 19% in the S-C+rye cropping system versus the S-C cropping system over the 3-yr period. Losses of NO3-N in drainage discharge during the 3-yr study were reduced by about 23% with a rye cover crop from the 32 kg/ha losses for S-C. Cover cropping with rye has the potential to be an effective management tool for reducing NO3-N loss from subsurface drainage discharge despite challenges to establishment and spring growth in the north-central U.S.