Winter Cover Crops for Corn Production in the Northeast: N Balance and Soil Moisture Status
Winter annual legumes can provide most or all of the N required by no-tillage corn. Small grain covers can recycle more unused fertilizer nitrogen (FN) than legumes, thus reducing potential for leaching and groundwater contamination, but the high C:N ratio of cereals can lower N availability to subsequent crops. When spring rainfall is low, cover crops can deplete soil moisture and jeopardize corn germination and early growth. This project will evaluate the management of hairy vetch, cereal rye and vetch/rye mixtures in cover crop-corn systems in terms of cover N production, N recycling, groundwater quality and soil moisture in order to optimize profits without damage to the environment. Research plots will be established at Maryland Coastal Plain and Piedmont locations. Demonstrations on three commercial grain farms and two Experiment Station farms will include field-scale plantings of selected treatments from research plots. Field days and twilight meetings will be held at research locations and on-farm demonstration locations.
(1) Extend field plot research findings to field-sized research/demonstration programs on commercial farms.
(2) Determine effects of kill dates of hairy vetch, cereal rye and vetch/rye mixtures, plus no-tillage corn planting dates on nitrogen status of soils and crops, soil moisture availability during germination and early growth, and shallow groundwater quality.
(3) Develop predictive models to identify viable management alternatives for cover crop use in corn production systems.
Replicated small-plot studies were conducted over a two-year period at Coastal Plain and Piedmont locations to evaluate the effects of cover crop kill dates, corn plant dates, and corn fertilizer nitrogen (FN) rates following hairy vetch, cereal rye, and a vetch/rye mixture in a no-tillage corn production system. Research evaluated cover crop yield and N production, corn N uptake and yield, soil moisture use efficiency, and soil N status.
Results substantiate that vetch can fix most of the N required for high corn yields. When more N is required N responses are greater following vetch than following rye or no cover. This synergistic response appears to be related to more efficient soil water utilization. Research has shown that fall-seeded rye will immobilize more soil N than vetch, thus, reducing the potential for winter nitrate leaching. Data from these studies support the thesis that vetch/rye mixtures can maximize N production, minimize the potential for N leaching, and enhance corn yields.
Cover crop kill dates and corn plant date are critical in terms of N fixation, N recycling, and soil moisture utilization. The ideal kill date will vary with location, soil, and annual climatic pattern but will usually fall between April 20 and May 10 and the best kill date should be what is best for the dominant species in the mixture.
Composition of a fall-seeded legume/grass mixture will adjust to the soil N status in that the grass will dominate when the residual N is high while the legume will dominate when the N level is low. This offers good environmental protection while reducing fertilizer N costs to the producer. Shallow ground water samples show lower nitrate concentrations under rye or vetch/rye mixtures, but more study is needed since data are noisy and may reflect previous cropping history.