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Research Shows N Rate in Sweet Corn Higher than Current Recommendations

By Carl Rosen, Professor and Head Department of Soil, Water and Climate
Vince Fritz, Professor, Horticultural Science

New research conducted at the Southern Research and Outreach Center in Waseca shows that the optimal N application rate for new sweet corn hybrids following soybeans in non-irrigated, on medium- to high-organic matter soils is higher than the current recommended rate of 110 lbs N/ac.

In a study funded by the Agricultural Fertilizer Research and Education Council (AFREC), and conducted by the University of Minnesota, we sought to determine the effects of N management, hybrid, population density and planting month on sweet corn yield and N use. By evaluating three hybrids – DMC 21-84, GSS 1477 and GM Code 646 – planted at two times –May and June, with six different N treatments, we were able to evaluate how N applications affected each scenario.

What you need to know:

  • Despite pronounced differences in yield potential due to hybrid, the hybrids evaluated in this study responded similarly to N rate in terms of yield. 
  • At 120 lbs N/ac, there was almost no effect of N source or timing on yield - applying N as urea preplant, ESN (a polymer-coated urea product) preplant or split applications of urea resulted in similar yields. 
  • With adequate N application, yields were greater with high population density than low population density. 
  • Approximately 70 to 77 lbs N/ac remained in the field after harvest as stover with a C to N ratio of 32 to 35. 
  • Planting time effects on yield depended on the year.  Therefore, generalizations about the effect of planting time on sweet corn N requirements could not be made.

While the current recommended application rate of N for sweet corn in soils with medium- to high-organic content following soybeans is 110 lbs/ac, our results indicate that the optimal rate is between 120 and 180 lbs/ac. Until the sweet corn N recommendations are revised, an application of 10 to 20 percent more N than current recommendations is suggested to optimize yields.

Based on our N uptake data and N remaining in sweet corn stover after harvest it is possible that the stover can provide an N credit for a following field corn crop. However, the data from this study do not allow us to advise on what that N credit might be for the following season. Future research will shed further light on this question.

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Support for this project was provided in part by the Agricultural Fertilizer Research & Education Council (AFREC).

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