University of Minnesota Extension
/
612-624-1222
Menu Menu

Extension > Agriculture > Crops > Corn Production >Planting > Think carefully about corn plant population to maximize profits

Think carefully about corn plant population to maximize profits

By Jeff Coulter, Extension Corn Agronomist

With support from the Minnesota Corn Growers Association and others, we have been able to conduct a number of trials to determine how corn yield responds to plant population for various situations in Minnesota.

Figure 1. Corn response to plant population for three planting dates. Data are averages from Lamberton and Waseca, MN in 2008. Red triangles indicate the optimum plant population based on a corn price of $4.00 per bushel and a seed cost of $250 per 80,000 seeds.

In 2008, research was conducted at Lamberton and Waseca, MN to determine how planting date impacted optimum plant population. In this study, the economically optimum plant population was not consistently influenced by planting date (Figure 1). However, yield potential was greatest with early planting, and the optimum plant population with the early planting date was 2,400 plants per acre higher than that with the mid-May planting.

From 2005 to 2007 at Lamberton and Waseca, MN, corn plant population was evaluated in 20- and 30-inch rows for a single full-season hybrid (Figure 2). In this set of trials, there was no yield increase with narrow rows at any plant population, and the economically optimum plant population was similar (within 1,000 plants per acre) for both row widths. In 2008, these trials were repeated with four hybrids. Averaged across hybrids and locations, yield response to plant population was similar for both 20- and 30-inch rows (Figure 3), supporting the results from 2005 to 2007. However, yield with 20-inch rows in 2008 was consistently 9% higher than that with 30-inch rows for all hybrids. It is unclear why there was an advantage to narrow rows in 2008, but not in 2005 to 2007.

Of the four hybrids evaluated in the row spacing study in 2008, two hybrids had a relative maturity (RM) of 94 and 96 days, and the other two hybrids had a RM of 102 days. Averaged across locations and row widths, the economically optimum plant population was 3,400 plants per acre higher for the 94 to 96 day RM hybrids than for the 102 day RM hybrids (Figure 4). Since earlier-maturing hybrids tend to be shorter and have less leaf area than full-season hybrids, it is possible that they may require higher plant populations for optimum light interception. However, we did not find that one of the maturity groups or hybrids was better suited to narrow rows than the others.

Figure 2. Corn response to plant population for two row widths. Data are averages over Lamberton and Waseca, MN from 2005 to 2007. Red triangles indicate the optimum plant population based on a corn price of $4.00 per bushel and a seed cost of $250 per 80,000 seeds.

Figure 3. Corn response to plant population for two row widths. Data are averages over four hybrids at Lamberton and Waseca, MN in 2008. Red triangles indicate the optimum plant population based on a corn price of $4.00 per bushel and a seed cost of $250 per 80,000 seeds.

Of the four hybrids evaluated in the row spacing study in 2008, two hybrids had a relative maturity (RM) of 94 and 96 days, and the other two hybrids had a RM of 102 days. Averaged across locations and row widths, the economically optimum plant population was 3,400 plants per acre higher for the 94 to 96 day RM hybrids than for the 102 day RM hybrids (Figure 4). Since earlier-maturing hybrids tend to be shorter and have less leaf area than full-season hybrids, it is possible that they may require higher plant populations for optimum light interception. However, we did not find that one of the maturity groups or hybrids was better suited to narrow rows than the others.

Another consideration with regard to optimum plant population is yield potential. Using data from Illinois, Nafziger (2002) reported that as yield potential increased from 135 to 225 bushels per acre, the economically optimum plant population increased from about 25,000 to 32,000 plants per acre. In other words, the optimum plant population increased by about 800 plants per acre for each 10 bushel per acre increase in yield potential.

In the last four years, there have been a total of 34 plant population comparisons conducted in 10 experiments at Lamberton and Waseca, MN. Averaged across all of these trials, yield was maximized at 36,000 plants per acre (Figure 5), and a final stand of 32,000 to 34,000 plants per acre was necessary to maximize economic return (Table 1). With generous support from the Minnesota Corn Growers Association, we will be able to further evaluate corn response to plant population for various row widths, planting dates, and maturity groups over the next few years at multiple locations.

Figure 4. Corn response to plant population in 2008. Data for each maturity group are averages over two hybrids and two row widths at Lamberton and Waseca, MN. Red triangles indicate the optimum plant population based on a corn price of $4.00 per bushel and a seed cost of $250 per 80,000 seeds.

Figure 5. Response of corn yield potential to plant population, averaged over 34 comparisons from 2005 to 2008 at Lamberton and Waseca, MN.

 

 

Table 1. Economically optimum plant population for various seed costs and corn prices. Optimum plant populations were calculated based on data from 34 comparisons between 2005 and 2008 at Lamberton and Waseca, MN.

Seed cost ($/unit)* Corn price ($/bu)
3.00 3.50 4.00 4.50 5.00
175 33,600 34,100 34,500 34,800 35,000
200 33,100 33,700 34,100 34,400 34,700
225 32,600 33,200 33,700 34,100 34,400
250 32,100 32,800 33,400 33,800 34,100
275 31,600 32,400 33,000 33,400 33,800
300 31,100 31,900 32,600 33,100 33,500

A more in-depth fact sheet on optimum plant population for corn in Minnesota is available. Additional information on corn production from the University of Minnesota is available on our new corn website: www.extension.umn.edu/corn.

References:

Nafziger, E.D. 2002. Corn. p. 22-34. In R.G. Hoeft and E.D. Nafziger (ed.) Illinois agronomy handbook. 23rd ed. University of Illinois, Urbana.

  • © 2013 Regents of the University of Minnesota. All rights reserved.
  • The University of Minnesota is an equal opportunity educator and employer. Privacy