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Ag Notes: Cover crops following a drought

October 01, 2008|JERRY LITTLE

This year's dry weather will have implications for future crops long after drought conditions are over. Farmers planting wheat after a low-yielding corn crop will see the most immediate effects.

Because of severe water limitations, corn plants were not able to produce up to their genetic yield potential. Nitrogen that would have been taken up in the plant under normal growing conditions is left in the soil. Residual nitrogen will be lost through the winter months if the farmer doesn't plant anything on these fields this fall.

Much of the loss occurs when the soil begins to rehydrate. Under water-saturated conditions, soil microbes convert nitrate nitrogen into nitrous oxide, a greenhouse gas, and nitrogen gas. Wheat can scavenge the remaining nitrogen and protect it from loss. For wheat producers, that means there is no reason to apply nitrogen this fall. If the soil doesn't become saturated during the winter, farmers can cut spring nitrogen by 20 to 30 pounds per acre.

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Grain producers who will plant corn again next year, second year or continuous corn also should consider planting a cover crop of wheat. Just like growing it for grain production, the wheat will take up nitrogen that would otherwise be lost through the winter months.

As wheat decomposes after the spring herbicide application, nitrogen will be released and become available to the corn crop. Research has shown that at least 30 pounds of nitrogen can be recycled using a wheat cover crop following drought conditions. In addition to nitrogen, the cover crop will help increase soil organic matter, reduce winter annual weeds, help break up surface compaction and improve overall yield of the following corn crop.

Cover crops are more economically viable now because of the increased cost of nitrogen fertilizer and other agricultural inputs. If you have not planted cover crops in the past, this would be a good year to try them on all or part of this year's corn ground. For more information on crop management, you can contact your local University of Kentucky extension service office. In Boyle County, call (859) 236-4484.

Jerry Little is Boyle County extension agent for agriculture/natural resources.

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