Corn plant population considerations
The optimal period for corn planting, in our area, begins April 15 and runs through May 5. Research shows that planting after that period likely incurs some reduction of yield potential. Small reductions are apparent at first, then larger reductions begin to accrue as planting is delayed beyond May 20.
Another aspect of optimizing corn yields (and production economics) is optimizing corn plant populations. Dr. Peter Thomison, Ohio State University Extension corn production specialist, recently summarized recent research data concerning corn plant populations. Excerpts from that research summary follow.
Corn response to population is continuously changing with seeding rates increasing about 280 plants/A/yr according to the National Agricultural Statistics Service (2010). Plant populations in Ohio have increased 16 percent in the past 10 years (56 percent since the early 1970s). Plant population for corn in Ohio averaged 28,200 plants/A in 2010, which is lower than most Corn Belt states (e.g. Minnesota - 29,900 plants/A; Iowa – 29,950 plants/A; Illinois – 29,650; Indiana- 28,350 plants/A).
Research has demonstrated that the superiority of modern hybrids is fully expressed only at higher plant populations (Duvick, 2005). When hybrids of different eras (from the 1930s through 2001) were planted at a very low population (4,000 plant/A – a low stressenvironment), there was little to no difference in the yields of hybrids from different eras. However, when established at a higher plant population (32,000 plants /A) more typical of that required to maximize yields in recent years, hybrids exhibited progressively higher yields with each era of genetic improvement. The genetic improvements that have facilitated the positive interaction between hybrids and increasing seeding rates include increased yield stability across a range of environmental conditions, greater tolerance to drought (and higher plant populations), enhanced stalk and root strength, and resistance to diseases and insects.
Most corn agronomists recommend adjusting seeding rates by using the yield potential of a site as a major criterion for determining the appropriate plant population. Seed companies recommend final stands as high as 35,000 to 36,000 plants/A for some hybrids in high yield environments. Average seeding rates of hybrids entered in the Ohio Corn Performance Test have increased from about 25,000 seeds/A in the early 1970s to over 35,000 seed/A in 2010 (with final stands ranging from about 23,000 to 33,000 plants/A). Ohio Corn Performance Test sites generally represent production environments with high yield potential.
When yield potential is reduced due to stresses including to late planting, drought, root and stalk lodging, disease and insect injury, and harvest delays, yield response to plant population is often limited. Under severe drought conditions, yield may even decrease at higher plant population due to increased barrenness and greater stalk lodging, but this is relatively rare in hybrids developed in recent years.
Based on OSU studies to date, a seeding rate of 31,000-33,000 seeds/A will be adequate for optimal yields in most production environments planted in late April and early May. For fields with low yield potential, seeding rates of 24,000-26,000 seeds/A will probably be sufficient. For fields with very productive soils and high yield (180 bu/A level and higher), seeding rates of 36,000-37,000 seeds/A may be necessary. (These seeding rate estimates are based on 10 percent mortality). The planting rate can be cut to lower seed costs, but this approach typically costs more than it saves. In the absence of major environmental stresses, most research suggests that planting a hybrid at suboptimal seeding rates is more likely to cause yield loss than planting above recommended rates. Because of differences in genetic backgrounds for various traits, especially stalk quality, seed company recommendations should be followed to adjust seeding rates for specific hybrids.
Another aspect of optimizing corn yields (and production economics) is optimizing corn plant populations. Dr. Peter Thomison, Ohio State University Extension corn production specialist, recently summarized recent research data concerning corn plant populations. Excerpts from that research summary follow.
Corn response to population is continuously changing with seeding rates increasing about 280 plants/A/yr according to the National Agricultural Statistics Service (2010). Plant populations in Ohio have increased 16 percent in the past 10 years (56 percent since the early 1970s). Plant population for corn in Ohio averaged 28,200 plants/A in 2010, which is lower than most Corn Belt states (e.g. Minnesota - 29,900 plants/A; Iowa – 29,950 plants/A; Illinois – 29,650; Indiana- 28,350 plants/A).
Research has demonstrated that the superiority of modern hybrids is fully expressed only at higher plant populations (Duvick, 2005). When hybrids of different eras (from the 1930s through 2001) were planted at a very low population (4,000 plant/A – a low stressenvironment), there was little to no difference in the yields of hybrids from different eras. However, when established at a higher plant population (32,000 plants /A) more typical of that required to maximize yields in recent years, hybrids exhibited progressively higher yields with each era of genetic improvement. The genetic improvements that have facilitated the positive interaction between hybrids and increasing seeding rates include increased yield stability across a range of environmental conditions, greater tolerance to drought (and higher plant populations), enhanced stalk and root strength, and resistance to diseases and insects.
Most corn agronomists recommend adjusting seeding rates by using the yield potential of a site as a major criterion for determining the appropriate plant population. Seed companies recommend final stands as high as 35,000 to 36,000 plants/A for some hybrids in high yield environments. Average seeding rates of hybrids entered in the Ohio Corn Performance Test have increased from about 25,000 seeds/A in the early 1970s to over 35,000 seed/A in 2010 (with final stands ranging from about 23,000 to 33,000 plants/A). Ohio Corn Performance Test sites generally represent production environments with high yield potential.
When yield potential is reduced due to stresses including to late planting, drought, root and stalk lodging, disease and insect injury, and harvest delays, yield response to plant population is often limited. Under severe drought conditions, yield may even decrease at higher plant population due to increased barrenness and greater stalk lodging, but this is relatively rare in hybrids developed in recent years.
Based on OSU studies to date, a seeding rate of 31,000-33,000 seeds/A will be adequate for optimal yields in most production environments planted in late April and early May. For fields with low yield potential, seeding rates of 24,000-26,000 seeds/A will probably be sufficient. For fields with very productive soils and high yield (180 bu/A level and higher), seeding rates of 36,000-37,000 seeds/A may be necessary. (These seeding rate estimates are based on 10 percent mortality). The planting rate can be cut to lower seed costs, but this approach typically costs more than it saves. In the absence of major environmental stresses, most research suggests that planting a hybrid at suboptimal seeding rates is more likely to cause yield loss than planting above recommended rates. Because of differences in genetic backgrounds for various traits, especially stalk quality, seed company recommendations should be followed to adjust seeding rates for specific hybrids.
Published: March 31, 2011
