Fall 2008, No. 4


The following table provides average nutrient removal rates for field crops commonly grown in the northcentral USA. To use the values in the table, simply multiply the table value by the yield of the crop, making sure that the yield units match those in the table. For instance, to estimate the amount of K2O removed by 200 bu/A of corn grain, multiply 200 by 0.27 to get 54 lb K2O/A.

Stover or straw values in the table are reported on a ton or a bushel basis. The bushel basis is used when the grain yield is known but the amount of stover removed is not. This value assumes that all of the stover is recovered during harvest. In reality, only a percentage of the stover is harvested. Therefore, if the bushel basis is used, the percent recovery must be factored in. For instance, assume 200 bu/A of corn is harvested and about 50% of the stover is removed later. First, if all of the stover could have been harvested from the field, the amount of K2O removed would be 200 bu/A times 1.1 lb K2O per bushel, or 220 lb K2O/A. However, since only 50% of the stover was removed, we multiply 220 lb K2O/A by 0.50 to get 110 lb K2O/A. This is the amount of K2O estimated to be removed by harvesting 50% of the stover remaining after a 200 bu/A corn grain crop.

Estimating nutrient removal helps farmers and advisers assess whether nutrient applications are exceeding or are falling short of what the crops take off when they are harvested.

Pocket-sized, field-ready cards containing this information as well as many more field crops may be ordered for US$0.20 (20 cents) each by calling IPNI Circulation at (770) 825-8082, or e-mail: circulation@ipni.net.
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For more information, contact Dr. T. Scott Murrell, Northcentral Director, IPNI, 2422 Edison Dr., West Lafayette, IN 47906. Phone: 765-463-1012. E-mail: smurrell@ipni.net.

Abreviations in this article: N = nitrogen; P = phosphorus; K = potassium; Mg = magnesium; S = sulfur.