Corn Response to Seeding Rate: The Implications for Variable Rate Seeding.

More site-specific management has been adopted by farmers to increase field productivity and profitability, although successful prediction of input response within management zones remains challenging. For some inputs, like plant density, the economic optimum plant density (EOPD) changes as new genetics become available. The objective of this research is to determine whether an EOPD could be determined for one soil type given that genetics constantly change. The experiments were conducted from 1987 to 2013 on a Plano silt loam (fine-silty, mixed, mesic, Typic Argiudoll) near Arlington, Wisconsin. In 46% of the site*years no significant relationship between plant density and grain yield was found, while in 50% of the site*years a positive relationship occurred, and in 4% of the site*years a negative relationship was detected. When significant relations were observed, the maximum yield plant density (MYPD) for the Plano silt loam soil series varied by year and site and ranged from 72 000 to 101 000 plants ha^-1. The EOPD was lower the MYPD and also varied by year and site ranging from 65 400 to 88 000 plants ha^-1. An algorithm using edaphic (i.e., organic matter, P, K, and pH) measurements did not find any relationship to MYPD or EOPD for grain yield. Since MYPD and EOPD varied widely between sites and years for a Plano silt loam it would be difficult to predict site-specific seeding rate prescriptions within a management zone.