Agronomic responses of corn to planting date, row width, and plant density.

Abstract

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 first objective of this research was to determine whether the economically optimum seeding rate for corn differs with planting date. From 2008 to 2010, the response of corn grain yield 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. The response of corn grain yield and economic return to plant density did not differ with planting date, and yield was maximized with a final stand of 81,700 to 107,900 plants ha-1. Grain yield was similar with the first two planting dates, but averaged 15% lower with the late May planting date. Based on a partial budget analysis for net return to seed cost and assuming 5% over-seeding from final stand, seeding rates of 82,700 to 83,900 seeds ha-1 were all within $2.50 ha-1 of maximum net return for four different scenarios of low and high seed costs and grain prices. In addition to possible interactions with planting date, increased seed costs and the availability of hybrids with greater stress tolerance than in the past make it important for growers to know whether plant density for corn grain production differs with row width or hybrid maturity. A second objective of this research was to determine; a) the optimum plant density and row width to maximize corn grain yield and economic return, and b) whether hybrid maturity influenced these responses. In 2009 and 2010, the response of corn grain yield to plant density was evaluated for two row widths and three hybrids of differing maturity at two locations in southern Minnesota. Three hybrids of 95-, 101-, and 105-d relative maturity were planted on both 51- and 76-cm row widths. Each combination of row width and hybrid was evaluated at six plant densities ranging from 41,700 to 108,700 plants ha-1. The response of corn grain yield and economic return to plant density did not differ with row width or hybrid, and yield was maximized with a final stand of 84,500 to 108,700 plants ha-1. Grain yield did not differ between 51- and 76-cm row widths and increased with increasing hybrid relative maturity. This research found that in southern Minnesota, corn grain yield can be maximized by planting from late April to mid-May, on either 51- or 76-cm row widths, with 105- or 101-d hybrids, and at plant densities from 81,700 to 108,700 plants ha-1.