Winter Legume Cover Crop Benefits to Corn: Rotation vs. Fixed-Nitrogen Effects
- H. Allen Torbert *,
- Donald W. Reeves and
- Richard L. Mulvaney
The use of winter legume cover crops for erosion control and to provide additional N to the soil is well established. Other potential benefits to legume cover crops besides N additions have been recognized, but have not been quantified. The objective of this study was to separate the fixed-N effects from the rotation effects in a winter legume cover cropping system. A field study was initiated in 1989 on a Norfolk loamy sand (fine, loamy, siliceous, thermic Typic Kandiudult) in east-central Alabama. Corn (Zea mays L.) was grown following (i) ‘Tibbee’ crimson clover (Trifolium incarnatum L.), (ii) a partially ineffective-nodulating crimson clover, CH-1, (iii) rye (Secale cereale L.), and (iv) winter fallow. The plots were split into four rates of fertilizer N (0, 56, 112, and 168 kg N ha−1) in a split-plot experimental plan. An evaluation of different methods of distinguishing fixed-N vs. rotation effects of the winter annual legume cover crop to a subsequent corn crop was made. Regression analysis of the effect of N application rates on N2 fixation by crimson clover (fertilized with 45 kg N ha−1) indicated that CH-1 clover biomass contained approximately 40 and 101 kg N ha−1 and Tibbee clover contained approximately 51 and 119 kg N ha−1 in 1990 and 1991, respectively. In both years of the study, crimson clover substantially increased corn yield compared with winter fallow, with a yield increase at the highest fertilizer N application level of 7 and 22% for 1990 and 1991, respectively. Estimates of yield increases due to rotation ranged from negative to 40%. The data indicated that winter cover crops improve corn yield and that besides soil N availability, there was very little difference between the beneficial effects of clover and the rye cover crops to corn.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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