Agronomic and Economic Assessment of Planting Date and Plant Density for Corn.

Corn (Zea mays L.) grain yield is closely related to plant density and is typically maximized in the northern Corn Belt when planting occurs in late-April. However, spring precipitation events often result in wet and cold soil conditions that delay planting. The objective of this research was to determine whether the economically optimum seeding rate for corn differs with planting date in order to help growers better manage a late-planted crop. In 2008 and 2009, corn response to plant density was evaluated for three planting dates at two locations in southern Minnesota. Planting dates occurred on 2-wk intervals beginning in late-April. Within each planting date, there were six plant densities ranging from 38,400 to 107,900 plants ha^-1 on 5,600 plants ha^-1 intervals. The response of corn grain yield to plant density did not differ with planting date. Yield was maximized at 91,400 plants ha^-1, but was within 1% of the maximum at 79,800 plants ha^-1. Grain yield was similar with the first two planting dates, but was 14 to 16% lower with the late May planting date. Grain moisture at harvest was not significantly influenced by planting date or plant density. Partial budget analysis revealed that with grain prices of $128 Mg^-1 and seed costs of $250 80,000 seeds^-1, net returns within $2.50 of the maximum occurred with seeding rates ranging from 70,800 to 81,200 seeds ha^-1, assuming 5% overseeding. With grain prices of $167 Mg^-1 and seed costs of $200 80,000 seeds^-1, net returns within $2.50 of the maximum occurred with seeding rates between 78,500 and 87,400 seeds ha^-1. These results demonstrate that optimum corn seeding rates are significantly influenced by seed cost and corn price, and that within a given economic scenario a relatively wide range of seeding rates can result in similar net returns.