|Kaspar, Thomas - Tom|
Submitted to: Integrated Crop Management Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 11/10/2005
Publication Date: 12/1/2005
Citation: Singer, J.W., Kaspar, T.C. 2005. Cover crop selection and management for agronomic farming systems. In: Proceedings of the Integrated Crop Management Conference, Nov. 30-Dec. 1, 2005, Ames, IA. p. 197-198. Interpretive Summary:
Technical Abstract: Cover crops are literally “crops that cover the soil” and may be used to reduce soil erosion, reduce nitrogen leaching, provide weed and pest suppression, and increase soil organic matter. Winter cover crops are planted shortly before or soon after harvest of the cash crop and are killed before or soon after planting of the next cash crop. Cereal grains, such as oat, winter wheat, barley, winter triticale, and winter rye, are excellent cover crops because they grow rapidly in cool weather, withstand moderate frost, and their seed is relatively inexpensive or can be produced on site. Many varieties of winter rye, triticale, and wheat can overwinter in the upper Midwest and continue growing in the spring. Legumes are also used as cover crops and they fix nitrogen as an added benefit. Legumes, however, usually do not grow as well as cereal grains during the fall and winter months, they accumulate less soil nitrogen than cereal grains, their seed is relatively expensive, and most must be killed with tillage or herbicides in the spring. Grasses (such as annual ryegrass) and brassicas (such as oilseed radish, oriental mustard, and forage radish) are also potential cover crops. Reductions in nitrate load using a rye cover crop ranged from 13% in Minnesota to 94% in Kentucky. A study in Indiana reduced nitrate loads by 61% with a reduction in fertilizer nitrogen rates and a winter wheat cover crop following corn. Effectiveness of cover crops varies with growth of the cover crop, weather, and management of the cash crop. In Iowa, rye and oat cover crops reduced rill erosion following soybean in a no-tillage system by 79% and 49%. Losses of phorphorus (P) to surface waters, which are linked to sediment losses, might be reduced by a similar amount relative to no-tillage. Reductions in total P losses ranged from 54% to 94% from research experiments using cover crops. Corn yields may be reduced following winter-hardy cereal grain cover crops that are killed immediately before corn planting. Yield reduction can be minimized by killing cover crops more than 14 days prior to corn planting and using starter fertilizer. Corn yields following an oat cover crop, which dies when the ground freezes in the fall, or a legume that overwinters, are not reduced. Soybean yields are not reduced following cereal grain cover crops unless low soil water content limits soybean germination and emergence.