What are the concerns for fall applied nitrogen?

Tuesday, April 10, 2012


University of Missouri Extension agronomy Specialist

Seed placement may affect yield in corn

There are questions every year about seed placement.

This includes depth of planting as well as uniformity of planting.

First, we will consider how uniform the distance between plants can affect yield.

Research in the past indicated that there was a potential for a 1 to 3.4 bushel per acre decrease in yield for every 1-inch deviation in plant spacing.

More recently, research indicates there is little reduction from non-uniform stands as long as the final population is within 15 percent of the target population.

This research along with research from other workers indicates that reduced population and non-uniform emergence have more potential to negatively influence yields than non-uniform plant spacing.

Individual corn plants have enough flexibility in yield components to make use of the small changes in available resources resulting from non-uniform plant spacing. Try to obtain plant spacing's that are consistent as possible. As long as the plant spacing between plants is within two or three inches of the desired plant spacing and the final population is not substantially lower than was desired, yield should not be affected.

The next concern is depth of planting and uniformity of emergence.

Establishing uniform stands with plants that emerge at close to the same time will increase the probability of maximizing corn yields assuming favorable growing conditions.

Uniform emergence can be delayed by non-uniform moisture in the seed zone, crusting, non-uniform planting depth, or non-uniform crop residue.

Research has shown that if one out of six plants is delayed by two leaf stages, yields can be reduced by 4 percent. If one out of six plants is delayed by four leaf stages, yields can be reduced by up to 8 percent.

Other research has indicated that if plants emerged within a period of two weeks, yield reductions were 3 percent or less.

Research at Kansas State University indicates that deeper planting results in more uniform emergence. Results showed that corn planted on April 11 with a soil temperature of 61 degrees F. resulted in the time to 90 percent emergence increased by about two days for each additional inch of depth of planting. Corn planted on May 3 with a soil temperature of 66 degrees F. all emerged within 7 to 9 days of planting, regardless of planting depth.

The results indicate the 1.5 to 2.0 inch planting depth resulted in some of the most consistent yields with both planting dates.

These results support current recommendations that corn be planted at 1.5 to 2.5 inches depending on soil conditions. Depending on soil conditions, corn can be planted deeper than 2.5 inches or shallower than 1.5 inches in certain conditions with minimal impact on yield.