Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/21/2002
Publication Date: 7/1/2002
Citation: LOGSDON, S.D., KASPAR, T.C., MEEK, D.W., PRUEGER, J.H. NITRATE LEACHING AS INFLUENCED BY COVER CROPS IN LARGE SOIL MONOLITHS. AGRONOMY JOURNAL. 2002. V. 94(4). P. 807-814. Interpretive Summary: Cropped fields in the upper Midwest are usually bare from fall through spring. During this period any unused nitrogen from the previous crop or biologically released nitrogen is subject to leaching because there is no crop to use either water or nitrogen from the soil profile. Small grain crops can be used as cover crops, for this period of the year, when interseeded into the soybean crop in the late summer. There is a question about how much nitrogen small grain cover crops would extract from the soil profile and the effect of these crops have on leaching during the fall and spring period. To address this question we used large blocks of soil in a controlled environmental chamber to grow cover crops in a corn-soybean rotation. Small grain cover crops reduced nitrate leaching during and following the growth of the cover crops. This information will help farmers, extension and NRCS personnel, and agricultural consultants, evaluate best management practices that involve cover crops for reducing loss of nitrate from fields.
Technical Abstract: Nitrate leaching to groundwater and subsequent drainage systems can be unacceptable under corn-soybean rotations. Cover crops have the potential to reduce nitrate leaching, but this process has not been documented. Lysimeters utilizing large soil monoliths are an excellent approach for studying nitrate leaching because inputs can be controlled and outputs can be accurately measured. In our study we used six large soil monoliths set up as lysimeters to examine the influence of fall cover crops on nitrate leaching. We used three large (1 x 1 x 1.5 m deep) monoliths in each of two controlled climate chambers for a corn / soybean rotation with fall cover crop interplanted into soybean in mid August. The treatments were oat, rye, or no cover crop. The study was continued for two cover crop cycles in each chamber. In chamber one, drainage was significantly reduced due to oat or rye cover crops for the fall through summer part of the cover crop cycle, and nitrate loss was reduced for most or all of the same time period. Ther were no significant drainage differences in chamber two, but nitrate loss was reduced for the spring through summer part of the cover crop cycle. The soil monoliths were useful for showing that oat and rye cover crops can reduce nitrate leaching.