Building a Maximum Yield Cropping System for Corn, Wheat and Double-cropped Soybeans


28 Mar 2007

2006 Annual Interpretive Summary

Building a Maximum Yield Cropping System for Corn, Wheat, and Doublecropped Soybeans, 2006

The goal of this study is to develop a management program that increases crop yield, input efficiency, and profit potential in a predominantly no-till cropping system. This cropping system consists of four crops planted over 3 years: no-till soybeans in corn stubble, followed by minimum-till wheat doublecropped with no-till soybeans, and then no-till corn.

The rotation clearly improved corn and soybean yields compared to continuous cropping. Starting in 2000, N use efficiency has appeared to improve when ammonium sulfate (AS) was blended with either urea or ammonium nitrate (AN). In 2003, with AS supplying one-third of the N, no-till and strip-till corn yield increased by 30 bu/A, particularly with split application, compared to broadcast urea. In 2004, doublecrop soybeans responded to N applied to the preceding winter wheat crop. Soybean yields were 4 to 5 bu/A higher where 120 lb N/A had been applied to wheat, regardless of whether the N had been supplied as urea or a urea-AS blend. The same N sources applied directly to single-crop soybeans produced no yield response at all. In 2004, N applied to winter wheat increased yields by 26% in no-till and by 53% in tilled soil, with an advantage of 3% to 6% from including AS in the blend. Urea plus Agrotain® boosted wheat yields by 5% compared to urea alone. Blends of fertilizers containing AS tended to produce higher wheat yields than either urea or AN alone. In contrast, a 2004 trial evaluating dry and liquid N sources for corn found little benefit to including AS in the blend, but showed some promise for several inhibitors and efficiency enhancers. In 2005, various N sources were broadcast-applied to corn at the 4-leaf stage. AN produced the highest corn yield as each pound of added N boosted yield by a bushel. Yields under urea were only 62% as high, but blending in AS or a urease inhibitor boosted yields by 30 to 50%. Liquid urea-ammonium-nitrate (UAN) produced yields about 45% higher than those with urea, but little benefit was observed from blending UAN with either AS or a urease inhibitor.

In 2006, yield responses were not as large, but two N combinations stood out in terms of their positive influence on corn yields: a granular blend of 75% urea and 25% AS, and liquid UAN with Agrotain. In wheat, granular blends of AN or urea with AS and a liquid blend of UAN with AS produced peak yields close to 90 bu/A. MD-06F