Lack of Hybrid, Seeding, and N Rate Interactions for Corn Growth and Yield.

Corn (Zea mays L.) seeding rates have increased because new hybrids purportedly optimize yield at high seeding and N rates. Two hybrids were evaluated in New York at four seeding and two side-dress N rates to determine if recommended (74,100 kernels ha^-1 and 111 kg N ha^-1) rates still optimize yield. Precipitation from June through August varied (389 mm in 2010 and 198 mm in 2011) so year by hybrid and year by seeding rate interactions existed for yield and yield components but no 2 or 3-way interactions existed among hybrid, N and seeding rates. Quadratic regression analysis predicted maximum yield at 88,000 kernels ha^-1 in 2010, although yields varied by only 2% between 74,100 (18.5 Mg ha^-1) and 98,800 kernels ha^-1 (18.9 Mg ha^-1). Seeding rate did not affect yield in 2011. As seeding rates increased from 61,875 to 98,800 kernels ha^-1, kernel number plant^-1 had negative linear decreases in 2010 (818 to 694) and 2011 (567 to 383). Kernel weight had a negative quadratic response to seeding rates in 2010 but a linear response in 2011 (338 to 317 and 312 to 332 mg, respectively, from 74,100 to 98,800 kernels ha^-1). A year by N rate interaction existed for kernel weight (320 and 338 mg in 2010 and 318 mg in 2011 at 111 and 167 kg N ha^-1, respectively) but not for yield (18.2 and 18.4 and 11.1 and 11.3 Mg ha^-1, respectively). Overall, recommended seeding and side-dress N rates achieved close to optimum yield in this study.