|Torbert, Henry - Allen|
Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/25/1996
Publication Date: N/A
Citation: Interpretive Summary: The beneficial effects of using winter legumes as cover crops for corn production is well documented. Most of the benefits to the corn has been attributed to the additional soil N provided to corn following a legume crop. However, other benefits to the soil other than just the additional N may also benefit the corn crop. The object of this study was to separate the effects of additional N to the soil from any other potential benefit of a winter legume cover crops. Results indicate that while most of the benefit comes from additional soil N, from 5 to 17 percent of the increased yield following a clover cover crop could be attributed to factors other than N additions to soil. The results also indicated that the reduction in corn yield following a rye cover crop is due to reduction in available soil N. The data indicated that besides soil N availability, there was very little difference between the beneficial effects of a clover cover crop and a rye cover crop to corn.
Technical Abstract: The potential benefits of legume cover crops beyond soil erosion control and the addition of N to the soil system is not known. 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, USA. Corn (Zea mays L.) was grown following: (1) 'Tibbee' crimson clover (Trifolium incarnatum L.), (2) an ineffective-nodulating crimson clover, CH-1, (3) rye (Secale cereale L.), and (4) winter fallow. The plots were split into four rates of fertilizer-N (0, 56, 112, 168, kg N ha**-1) in a split plot experimental plan. 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 would contain approximately 40 and 101 kg N ha**-1 and Tibbee clover would contain approximately 51 and 119 kg N ha**-1 for 1990 and 1991, respectively. In both years of the study, crimson clover substantially increased corn yield compared to winter fallow, by an average of 30 percent and 33 percent for 1990 and 1991, respectively. 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, with estimates of yield increases ranging from slightly negative to 40 percent due to rotation effects. The data indicated that besides soil N availability, there was very little difference between the beneficial effects of clover and the rye cover crops to corn.