Organization: University of Minnesota, Department of Soil, Water and Climate
The availability of new sweet corn varieties with higher nitrogen (N) efficiency means researchers should revisit N recommendations for non-irrigated sweet corn production. This research also examined the impact of split N applications, as well as “smart fertilizer” products like coated urea, on sweet corn yields.
The specific objective is to determine the effects of N rate/rate/timing, hybrid, plant population density, and planting date on sweet corn yield, N uptake, and residual soil N
C646 yield and ear length were consistently higher than the other hybrids across all treatments, and the data suggest that elevated competition for N (low N rates) at high plant populations generates shorter ears.
Overall, yields were highest in May 2015 (5 T cut corn/A) and lowest in May 2014 (3.6 T/A). No consistent benefit in cut corn yield from using elevated populations or higher N rates earlier in the season for any of the hybrids studied. In fact, the only population effect was elevated yield at lower plant density in the May 2014 planting.
In 2014, we found no yield benefit from using split application or slow-release nitrogen compared to pre-plant urea at 120 lb N/A, even in planting dates with substantial rainfall after planting. In 2015, yields with split urea and ESN were numerically higher than preplant urea, but the differences were not statistically significant.
In only one of 4 planting dates (June 2014), did 180 lb N/A generate more cut corn yield than 120 lb N/A, and in 2 of 4 planting dates (May and June 2015), 60 lb N/A generated statistically indistinguishable yields from 120 lb N/A. Residual soil N at the end of the 2014 season was highest for 120 lb N/A split-applied urea (12.5 ppm), but this was not statistically different from pre-plant application of urea at 180 lb N/A or 120 lb N/A, or ESN at 120 lb N/A.
There was no apparent difference in lb N/A in the stover or harvested kernels between 120 lb N/A and 180 lb N/A in 2014 (2015 results are not yet available).
A third and final year for the study is planned for 2016.