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Yield determining factors and row spacing in corn

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"Oftentimes, we struggle with making decisions about whether to plant or even abandon planting intentions due to not being able to plant early, but I encourage producers to focus on other management factors, like getting a good stand," Erick Larson said.
These management factors can ultimately determine crop outcome in corn. In addition, research shows soybeans and corn are both more responsive in narrow rows (30-inch rows).

Thinking ahead to planting season in 2021, consider yield determining factors for corn planting such as variety selection, plant stand, and soil fertility. Also, consider row spacing when thinking about management practices.

Row spacing

There is a lot of row spacing research available in corn. Erick Larson, corn specialist with Mississippi State University Extension, said that, while row spacing can be a useful management addition to a farm, it may be hard to implement in a cotton rotation.

"The Midsouth is unique in that cotton is the predominant crop and has been for a long time," said Larson. "Cotton rows have been a wide-row system (38- or 40-inch rows) for a long time, and it will take a broad and serious commitment to make a change to narrow rows (30-inch rows) where soybeans and corn both are more responsive."

 The row width is one of the more difficult management inputs to change on a whole farm because it affects a lot of equipment and row crops planted.

"Because it is a more difficult management change to make on a farm that grows cotton, it's one factor that is probably underutilized, particularly in the Mississippi Delta because of the predominance of cotton," he said.

In general, 30-inch rows are well-known to be 8-10% more responsive and have higher yield potential than 38- or 40-inch rows.

"The benefits of narrow rows in corn is, by improving the plant spacing geometry in a field, each plant has more light, water, and nutrients since there is more elbow room between plants," Larson said. "The plant spacing for corn in wide rows is normally somewhere between 5 and 5 ½ inches between plants. A similar plant population in 30-inch rows is going to be 6 ½ to 7 inches between plants, so they have more room to utilize their resources like water and nutrients more efficiently."

The size of a corn plant determines light interception, and light interception is more problematic in wide rows since the plants have a harder time capturing all the available light in row middles.

"The plants are going to naturally be crowded together closer in a wide row than what they will be in a narrow row," he said. "That is why they're more inefficient, and there is more competition between plants for various resources, limiting yield potential.

"A narrow row allows you to grow higher plant populations, and the corn should be more responsive to plant population in narrow rows than in wider rows."

Three factors

For yield determining factors, there are three general areas to focus on: variety selection, plant stand, and soil management.

"The number one factor is variety selection, and you could lump crop rotation into this," Larson said. "The second is your plant stand, which would be comprised of planting date, plant population, row spacing, and emergence uniformity. All those things interact to affect what kind of stand the corn plant has, and corn is not very forgiving if it doesn't achieve a good stand or has plant growth disparity.

"One thing I emphasize in educational programs is for growers to try to improve management beyond picking an appropriate plant population and planting as early as possible. Trying to achieve a uniform stand is as critical as those other two factors, and it is likely the most important factor determining your yield or your yield-limiting factor.

"Midsouth corn growers always struggle with planting date, but this year there were some amazing results, despite delayed planting, which is contrary to conventional wisdom. The National Corn Growers Association just released their yield contest winners, and the state yield winner from Mississippi produced a 294 bushel an acre yield, which was planted on May 1."

The highest yielding plot for the Corn Hybrid Demonstration Program was also planted the first week of May this year.

"A lot of growers had problems planting corn in 2020 due to spring rainfall," he said. "We deal with weather issues every year, but a lot of growers change their planting intentions in April because they didn't have the opportunity to plant in March or early April. From an educational standpoint, there's a lot of other management factors that ultimately determine crop outcome, so realize you can still be successful if you manage your crop well."

This past spring, there wasn't a decent planting window until the last few days of April and the first week of May for many regions.

"Oftentimes, we struggle with making decisions about whether to plant or even abandon planting intentions, but my point is to focus on other management factors, like getting a good stand," Larson said.

The third part of the yield determining factors is soil management and fertility.

"When you plant during adverse conditions, a poor stand is one of the main concerns," he said. "Also, if the soil is marginally wet, you are going to create soil compaction from the tractor and equipment going through the field, which can have a significant negative impact on the crop.

"Cool, saturated soils hinder seedling establishment by causing seedling mortality and uneven emergence. Soil compaction further stunts corn plants and root development, which is necessary to feed and support the plants. Both these issues persist through the entire growing season and reduce yield because corn cannot compensate for poor stands or growth disparity nearly as well as other crops."

Hybrid programs

 In the 2020 MSU Corn for Grain Hybrid Trials, around 85 corn hybrids representing 14 companies were tested in Mississippi.

"We also have a Corn Hybrid Demonstration Program which increases public exposure and evaluation of premier corn hybrids. These premier hybrids are planted in over 20 growers' fields around the state," Larson said. "This provides a unique opportunity for growers, consultants, and everyone to observe and evaluate plant characteristics and environmental responses of our best corn hybrids grown in local production systems. These university variety testing programs serve an important role in generating sound, third-party data from which our growers can better identify superior genetics."

For further resources on corn hybrid selection, check out the links below for the 2020 MSU Corn Hybrid Trials and associated recommendations for 2021.

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