Energy and economic savings from the use of legume cover crops in Virginia corn production

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Abstract
Energy analysis provides a measure of the effectiveness of sustainable agricultural systems in reducing inputs purchased from off-farm sources. This study compares the total (direct plus indirect) energy costs of growing corn for silage using manufactured N fertilizer or N-fixing legume cover crops. The cover crop either was killed with herbicide in a no-till system or disked in the spring. Economically competitive alternative crop production practices are identified.In both the no-till and the disked versions, cover-cropped treatments used about half as much energy per hectare as the corresponding winter fallow N-fertilizer treatments. Using vetch to provide N significantly lowered energy use per unit of crop output compared with the N-fertilized treatments. For the treatments that used hairy vetch, either alone or in combination with big/lower vetch, net revenue was statistically equivalent to that of standard-practice treatments in each year of the study.