Will Adding N at Pod Fill Benefit High Yield Soybeans? - UNL CropWatch, July 7, 2011

Will Adding N at Pod Fill Benefit High Yield Soybeans? - UNL CropWatch, July 7, 2011

July 7, 2011

This content requires Flash Download the free Flash Player now!
Get The Code to Embed This Audio Clip

Also access this audio in Quicktime format (iPad, iPod, etc.)

Soybean demand for water and nitrogen (N) is greatest after the R3 (beginning pod fill) growth stage. Soybean meets much of its N need from fixation of atmospheric N, but 50% of the N may come from the soil. Nitrogen fixation typically peaks during podset and early pod fill (R3), and ends during late pod fill. Soil application of N at R3 may enhance N uptake with no negative effect on N fixation.

Research results have not been consistent but generally indicate a low probability of yield response to N applied at R3-R4 when yields are less than 60 bu/ac; a response is more likely when yields are  more than 60 bu/ac. We conducted 56 trials supported by the Nebraska Soybean Board to determine whether N fertilization at R3 is economical where yields are more than 60 bu/ac.

Mean yield increases with 27 lb/ac N applied and more than 60 bu/ac yield were 2.5 bu/ac in south central Nebraska, 1.6 bu/ac in the northeast, and 0.3 bu/ac (not significant) in southeast Nebraska. There was no added yield from applying 54 lb/ac N compared with applying 27 lb/ac N or when adding 4.5 lb/ac sulfur (S).

Variations in soil properties and in leaf N and S concentrations were not related to yield or the response to applied N. Depending on the grain to fertilizer price ratio, fertigation of 25 lb/ac N at early pod fill may be profitable if the pivot is already equipped for fertigation.

Charles Wortmann, Extension Nutrient Management Specialist, Lincoln
Charles Shapiro, Extension Soils Scientist - Crop Nutrition, Haskell Agricultural Laboratory, Concord
Richard Ferguson, Extension Soils Specialist, Lincoln