Corn Grain and Silage Response to Plant Density and Hybrid.

Harvest plant densities that produce maximum yield (MYPD) of corn have been steadily increasing over time. However, the range in seed cost among commercially available hybrids is large. The economic optimum plant density (EOPD) is affected by both seed cost and corn price. Our objective was to determine the MYPD and EOPD for corn grain and forage. Experiments were established at five locations in Wisconsin. Each experiment used three to nine corn hybrids ranging in maturity from 93 to 108 d RM and planted at 64200, 79100, 93900 and 108700 plants ha^-1. Location MYPD and EOPD differences were measured indicating that plant density recommendations should vary by location (field). Hybrid interactions to plant density were measured for grain and forage yield. For most hybrids, forage yield increased linearly over the range of plant densities tested. Forage milk per ton decreased linearly resulting in a MYPD for milk per area between 93900 and 105000 plants ha^-1 depending upon hybrid. For most hybrids, grain yield increased linearly to a maximum and then declined over the range of plant densities tested. The grain MYPD averaged 93900 plants ha^-1. The forage and grain EOPD was typically 9.9 to 12.4 plants ha^-1 lower than the MYPD. Future agronomic research must continually evaluate MYPD and EOPD and will likely need to make recommendations on a site-specific basis.