Corn Hybrid Response to Plant Population and Planting Date in Northwestern Minnesota
- The far-northern U.S. Corn Belt is characterized by a short and cool growing season that is often further compressed by delayed planting, since many of the soils are high in clay content and poorly drained. This requires the use of short-season corn hybrids in this region.
- Previous research has shown that short-season corn hybrids often have a greater economic optimum planting rate than longer-season hybrids. However, there is limited information from the far-northern U.S. Corn Belt on how economic optimum planting rate for corn varies with changes in hybrid comparative relative maturity (CRM) planting date, and growing conditions.
- A 3-year field research study was conducted as part of the DuPont Pioneer Crop Management Research Awards (CMRA) Program with Dr. Jeff Coulter at the University of Minnesota.
- The objective of this study was to evaluate corn response to plant population and planting date for 3 hybrids of differing CRM in the far-northern U.S. Corn Belt.
- A replicated small-plot research trial was conducted from 2013 through 2015 in northwestern Minnesota at Crookston.
- In each year, 3 Pioneer® brand corn products of differing CRM were planted in 22-inch rows at 3 planting dates (early, normal, and late; Table 1) to 5 plant populations ranging from 22,000 to 44,000 plants/acre.
- 74 CRM - P7443R (RR2)
- 80 CRM - 39V07 (HX1, LL, RR2)
- 86 CRM - P8640AM™ (AM,LL,RR2)
|Early||May 7||May 5||April 23|
|Normal||May 23 (165)||May 16 (28)||May 6 (134)|
|Late||June 3 (286)||May 30 (241)||May 20 (189)|
- In 2013, only 2.2 inches of precipitation occurred during July and August. With these unusually dry conditions, corn grain yield in 2013 averaged 99 bu/acre and was not affected by planting date or plant population. Due to the dry conditions and low yields experienced in 2013, this summary focuses primarily on results from 2014 and 2015.
- Precipitation during in 2014 and 2015 was more abundant and evenly distributed compared to 2013. Corn grain yield in this study averaged 174 bu/acre in 2014 and 167 bu/acre in 2015.
- In 2014 and 2015, the response of corn grain yield to planting date differed among hybrids (Figure 1). Yield of the 86-CRM hybrid was greatest with the early and normal planting dates, and averaged 12% less when planting was late. Planting date did not affect yield of the 80- and 74-CRM hybrids. Grain moisture at harvest averaged 6.3, 7.1, and 7.7 percentage points greater with late compared to normal planting for the 74-, 80-, and 86-CRM hybrids, respectively.
- Grain yield in 2014 and 2015 was 11% greater with the 86-CRM hybrid compared to the 80-CRM hybrid for the early and normal planting dates (Figure 1). Yield did not differ between the 86- and 80-CRM hybrids for the late planting date. Lowest yield occurred with the 74-CRM hybrid for each planting date.
Figure 1. Corn grain yield in 2014 and 2015 at Crookston, MN as affected by planting date for 3 hybrids of differing comparative relative maturity (CRM), averaged across 5 plant populations. Bars with different letters indicate yields that were statistically different at the 5% probability level.
- The response of corn grain yield to plant population differed with planting date in 2014 and 2015 (Figure 2). When planting was early, yield was greatest with 38,500 to 44,000 plants/acre. With normal and late planting dates, yield was maximized with 33,000 plants/acre. In these years, grain moisture at harvest averaged 22.7, 21.8, and 21.5 percentage points with 33,000, 38,500, and 44,000 plants/acre.
Figure 2. Corn grain yield in 2014 and 2015 at Crookston, MN as affected by planting date and plant population, averaged across 3 hybrids of differing comparative relative maturity.
- The response of corn grain yield to plant population did not differ among the 3 hybrids with differing CRM in 2014 and 2015 (Figure 3). For all hybrids, yield was maximized with 33,000 to 38,500 plants/acre.
- Stalk lodging at harvest averaged less than 1% in all 3 years of this study and was not affected by planting date, hybrid, or plant population. Even in the dry year of 2013 when yield averaged 99 bu/acre, stalk lodging with 44,000 plants/acre was not greater than 1% for any combination of hybrid and planting date.
Figure 3. Corn grain yield in 2014 and 2015 at Crookston, MN as affected by plant population for 3 hybrids of differing comparative relative maturity (CRM), averaged across 3 planting dates.
- Differences in corn grain yield among treatments in this study were related to differences in the number of kernels per unit area and kernel weight. In all years, kernels per unit area were greatest with early and normal planting, and increased with plant population.
- The number of kernels per unit area was 18, 10, and 7% greater with the 74-CRM hybrid compared to the 86-CRM in 2013, 2014, and 2015, and did not differ between the 74- and 80-CRM hybrids during 2014 and 2015.
- There was an inverse relationship between the number of kernels per unit area and kernel weight. Heavier kernels were associated with treatments that produced fewer kernels per unit area.
- When compared to the 74-day hybrid, kernels from the 80-day hybrid were 3, 11, and 10% heavier in 2013, 2014, and 2015, respectively. Similarly, when compared to the 80-day hybrid, kernels from the 86-day hybrid were 19, 31, and 24% heavier in 2013, 2014, and 2015, respectively.
- Decisions regarding hybrid maturity and plant population are critical for successful corn production in the far-northern U.S. Corn Belt. In all years, the response of corn grain yield to plant population did not differ among hybrids, but the plant population for maximum yield was slightly greater with early planting.
- Greatest grain yield consistently occurred with the 86-CRM hybrid at 33,000 or more plants/acre with early to normal planting dates. In 2014, yield was 216 bu/acre with the 86-CRM hybrid at 38,500 plants/acre when planted early, demonstrating the great potential to produce high corn yields in the far-northern U.S. Corn Belt when growing conditions are favorable.
- Grain at harvest was wetter for hybrids with greater CRM, especially when planting was late. The limited or no reduction in grain yield with plant populations a great as 44,000 plants/acre, especially in the low-yielding dry 2013 season, indicates the great ability of modern corn hybrids to tolerate stress. Continued development and release of early-maturity hybrids for this region will help growers manage the risk of high grain moisture at harvest when planting is delayed and when the growing season is cool.
Author: Dr. Jeff Coulter, University of Minnesota
Research conducted by Dr. Jeff Coulter, University of Minnesota, as a part of the DuPont Pioneer Crop Management Research Awards (CMRA) Program. This program provides funds for agronomic and precision farming studies by university and USDA cooperators throughout North America. The awards extend for up to 4 years and address crop management information needs of DuPont Pioneer agronomists and customers, and Pioneer sales professionals.
2013-2015 data are based on average of all comparisons made in one location through Dec 1, 2015. Multi-year and multi-location is a better predictor of future performance. Do not use these or any other data from a limited number of trials as a significant factor in product selection.