Inconsistent Responses of Corn to Seeding Rates in Field-Scale Studies.

Corn (Zea mays L.) seeding rates have increased because new hybrids lodge less, have improved drought tolerance, and may respond to higher rates in narrow rows. Farmer-researcher partnerships were formed to evaluate two hybrids at two 0.76 m row sites and a twin row site at four seeding rates (61,750, 74,100, 86,450, and 98,800 kernels ha^-1); and a narrow row site (0.51 m rows at ~5000 more kernels ha^-1 across seeding rates) in field-scale studies in 2011 and 2012 in New York. Partial budget analyses were conducted to aid in future seeding rate decisions based on 2011-2012 market grain prices ($265.76 Mg^-1) in New York and grower seed ($225 80,000^-1 kernels) costs, in addition to drying and hauling costs. Yields averaged 11.8 Mg ha^-1 in 2011 and 10.5 Mg ha^-1 in 2012, but yield and relative profit responded inconsistently to seeding rates across sites, between hybrids, and between years at the narrow row site. Maximum relative profit exceeded the recommended seeding rate of 74,100 kernels ha^-1 at the twin-row site (76,000 kernels ha^-1), at the narrow row site in 1 year (85,000-95,000 kernels ha^-1), but not at 0.76 m row sites. Lack of consistent responses to seeding rates is probably related to dry July conditions in both years, contributing to decreases of 4 to 5 kernels plant^-1 and 0.5 to 1 mg in kernel weight with each 1000 kernel ha^-1 seeding rate increase at most sites. Based on these field-scale studies, recommended seeding rates in New York will not change.