Source: Bill Cox and Phil Atkins, Department of Crop & Soil Sciences, Cornell University

Assuming soil conditions are conducive to a 90 percent emergence rate, we currently recommend seeding rates of 30,000 kernels/acre for grain corn on silt loam soils in New York, based on studies at the Aurora Research Farm from 2003 to 2005 (Table 1). Recent hybrid releases, however, have been selected at higher plant populations and lodge less because of the Bt trait so there is a general belief that seeding rates should exceed recommended rates, based on hybrid releases from the early 2000s. On the other hand, most corn seed is now treated with soil-applied insecticide/fungicide, which results in greater stand establishment today than hybrids planted in the early 2000s. Consequently, the higher emergence rate may offset the need to plant the new hybrid releases at higher seeding rates. We have been conducting field-scale studies at the Aurora Research Farm since 2006 on fields following soybean and planted in early May under strip tillage to validate our small plot research. When averaged across years (2006 to 2010), optimum yields occurred at seeding rates of 29,600 kernels/acre (Table 2), close to our recommended seeding rate. We initiated another field-scale study in Cayuga County as well as a small-plot hybrid by seeding rate by N rate study in 2010 to further evaluate seeding rates for grain corn.

Planting Rates for New York Grain Corn

Two hybrids were planted at four seeding rates ranging from 30,000 to 38,000 kernels/acre with four replications at the Du Mond Farm in Cayuga Co. on 18 May. Each subplot averaged 0.9 acres so the entire study represented about 28 acres of research. Plant populations at the 8th leaf stage (V8) in late June ranged from about 28,000 to 34,500 plants/acre (Table 3). Neither hybrid responded to seeding rates in this study, possibly because the mid-May planting date resulted in emergence rates of 92 percent, so optimum seeding rates at this site was also at the recommended rate.

Planting Rates for New York Grain Corn

There is also a general belief that hybrids will not respond to seeding rates unless the N rate is high so we also tested two hybrids at four seeding rates (25,000 to 40,000 kernels/acre) with two N rates (the recommended 125 lbs/acre of total N for corn following soybeans and a high N rate of 175 lbs/acre of total N) in small plot research at the Aurora Research Farm. The planting date was 30 April and the emergence rate was 87 percent for the DEKALB hybrid and 79 percent for the Pioneer hybrid. Despite the differences in emergence rates between the hybrids, both showed similar responses to seeding rate, especially at the high N rate (Table 4). As in all previous studies, 30,000 kernels/acre was the optimum seeding rate, regardless of N rates. Such high yields in this study indicate that seeding rates or N rates do not have to be above recommended rates to achieve such high yields.

Planting Rates for New York Grain Corn

Planting Rates for New York Grain Corn

Conclusion
We have repeatedly seen that seeding rates of about 30,000 kernels/acre result in optimum yields on silt loam soils in Cayuga Co. Nevertheless, there is enough information out there to make us question whether this response is consistent across different soil types and farming operations in New York. Consequently, we will initiate field-scale studies on four to six farms across New York State at different row spacing for the next two years to further validate our current seeding rate recommendations for grain corn in New York.