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United States Department of Agriculture

Agricultural Research Service

Title: Spatial and Temporal Variation in Economically Optimum N Rate

Authors
item Mamo, M - UNIVERSITY OF NEBRASKA
item Malzer, G - UNIVERSITY OF MINNESOTA
item Mulla, D - UNIVERSITY OF MINNESOTA
item Huggins, David
item Strock, J - UNIVERSITY OF MINNESOTA

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2003
Publication Date: June 20, 2003
Citation: Mamo, M., Malzer, G.L., Mulla, D.J., Huggins, D.R., Strock, J. Spatial and temporal variation in economically optimum N rate. Soil Science Society America Journal. 2003. v. 95. p. 958-964.

Interpretive Summary: Requirements of N fertilizer for corn can vary substantially across a given field. Improvements in N fertilizer use efficiency may be realized if N rates can be tailored to actual requirements within a field. Our objective was to determine the effects of applied N fertilizers on yield of corn as it changed across a field and to evaluate the potential for variable N rate management. A production field near Revere, Minnesota was cropped from 1995 through 1999 in a corn-soybean rotation. Treatments consisted of different N rates in long strips across the field. Measurements of corn grain yield in response to N fertilization rates allowed derivation of economically optimum N rates and potential profitability of variable N management. On a whole field basis, corn yield was increased with N applications; however, only one-half of the field actually responded to applied N. Current recommendations based on whole field N application would over-fertilize non-responding areas and under-fertilize high-response areas. Overall, using variable N rates across the field would have reduced fertilizer N use by 70 kg ha-1 and increased profits by $18 ha-1 as compared to uniform N rates. Therefore, adoption of variable N rate technology could achieve significant reductions in fertilizer N use and increase corn profitability in Southern Minnesota.

Technical Abstract: Spatial and temporal variability of N requirements are important to maximize potential economic-returns of N application and minimize environmental N losses. The objective of this study was to determine the effects of N application on yield of corn and to evaluate the potential for variable N rate management. A 3.1 ha production field near Revere, Minnesota was cropped from 1995 through 1999 in a corn-soybean rotation. A randomized complete block design with four replications was established with main plots (strips 225 m long and 6.1 m wide) consisting of four N rates (0, 67, 134 and 202 kg ha-1). Measurements of grain yield in response to N fertilization rates allowed derivation of economically optimum N rate and potential profitability of variable N management. On a whole field basis, corn yield was increased with N applications; however, only one-half of the field actually responded to applied N. Current recommendations based on whole field N application would over-fertilize non-responding areas and underfertilize high-response areas. In 1997 and 1999, the variable N rate resulted in 67 and 75 kg ha-1 less applied N than the field average N rate for the same yield and $8 and $28 ha-1 greater profit than uniform N rates, respectively.

Last Modified: 11/26/2014
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