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Optimal corn plant populations in Minnesota

Quick facts

  • To maximize profitability, the final plant population should range from about 32,000 to 34,000 plants per acre. The economically optimum plant population varies with seed costs and corn prices. Too high of a planting rate generally does not reduce corn yield, but it does reduce net return.

  • Optimum plant population does not change if corn is planted by mid-May. However, when planting is delayed until late May, a higher plant population is needed to maximize yield.

  • Optimum plant population is generally not affected by row width. However, narrow rows can provide a modest yield increase for early-maturity hybrids.

  • Optimum plant populations are generally not affected by relative maturity for mid- and late-hybrids. However, optimum plant populations for early maturity hybrids tend to be near or above the recommended planting rate guidelines.

With increasing corn production costs and fluctuating grain prices, it’s critical that corn growers make sound decisions about planting to maximize profits. Decisions related to planting rate are especially important, since seed represents about 15 percent of the total cost of corn production according to an Iowa State University report.

From 2005 to 2011, researchers evaluated how corn yields in southern and central Minnesota responded to plant population, and whether planting date, hybrid maturity and row width affected this.

Maximizing profit

To maximize profit, research shows Minnesota growers need a final stand of 32,000 to 34,000 plants per acre (Figure 1), although this varies with the cost of seed and corn price. Corn yields were maximized near a final stand of 33,000 plants per acre and were not reduced as plant population increased to 44,000 plants per acre.  

Graph with corn yield on the y-axis and final plant population on x-axis.  Corn yield levels out at slightly over 175 with a plant population of 33,000 per acre
Figure 1: Corn response to plant population in Lamberton, Morris, Rochester and Waseca from 2009 to 2010. Each dot in the average of 228 plots.

Planting rates

Planting rates should be higher than the optimum plant population to compensate for early season stand losses. Based on Figure 1, planting rates of 34,000 to 36,000 seeds per acre maximize net return in most fields.

Like the final stand needed to maximize profit, economically optimum seeding rates vary with corn price and seed costs. We calculated seeding rates (seeds per acre) to get within $1 of the maximum net return in Table 2. These seeding rates are 5 percent above the targeted population to compensate for early season losses.

 

Table 1: Seeding rates (seeds per acre) to maximize net return

Seed cost $4/bushel corn price $6/bushel corn price $8/bushel corn price
$225/bag 30,700 to 33,700 32,100 to 34,400 32,700 to 34,700
$275/bag 30,100 to 32,900 31,700 to 34,000 32,400 to 34,400
$325/bag 29,400 to 32,300 31,200 to 33,500 32,100 to 34,100

Factors affecting optimum plant population

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Jeff Coulter, Extension agronomist

Acknowledgements

Thanks to the Minnesota Corn Growers Association, the Minnesota Corn Research and Promotion Council, National Crop Insurance Services and Monsanto for generously supporting the majority of the research in this summary, and to Tom Hoverstad and Steve Quiring for conducting much of the research.

Reviewed in 2018

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