Lack of Hybrid, Seeding, and Nitrogen 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 sidedress N rates to determine if recommended rates (74,100 kernels ha −1 and 111 kg N ha −1 ) still optimize yield. Precipitation from June through August varied (389 mm in 2010 and 198 mm in 2011), so year × hybrid and year × seeding rate interactions existed for yield and yield components, but no two– or three‐way interactions existed among hybrid and 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 per plant 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 × 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 Mg ha −1 in 2010 and 11.1 and 11.3 Mg ha −1 in 2011, respectively). Overall, recommended seeding and sidedress N rates achieved close to optimum yield in this study.