While it's been known for a long time that young corn plants are typically shorter in continuous no-till corn fields, Tony Vyn maintains this doesn’t mean there is an overall lack of plant height across a field.

Instead, the Purdue University agronomist says residue left over from the previous year’s corn crop can result in changing soil conditions, which can create a disadvantage for some plants when it comes to competing for sunlight and nutrients.

Vyn has found that no-till yield reductions in corn have little to do with any overall height reduction early in the growing season. Instead, decreased yields have more to do with height variability during the crop’s vegetative growth stage.

14% Yield Difference

He’s attributed yield losses of up to 14% to plant competition when corn is no-tilled after a previous corn crop.

In these fields, the remaining corn residue creates patches with lower soil temperatures and varying water and nutrient content. Corn plants in these areas of a field are at a distinct disadvantage with conditions created by the residue having an impact on root development.

“Plants that have better access to resources grow faster and then dominate their smaller neighbors,” Vyn says.

By evaluating plant height data over 14 years, Vyn found significant height differences among plants stretching out as long as 4 weeks.

“For example, competition for nitrogen increases as crowding increases,” he says. “The higher the density, the greater the intensity of the competition for all resources.”

Vyn says one misconception among growers is that barren plants or ears with only a few kernels at the end of the growing season are a result of when the plant first emerged from the soil back in the very beginning of the growing season. He says corn plants that have been dominated by their neighbors will still tend to shed pollen on time, but they will have delayed silk emergence.

“So the main reason for barrenness in corn plants has to do with the long interval between pollen shed on the tassel and silk development of the ear,” Vyn says.

Weather conditions, such as a lack of rainfall during critical plant development, will definitely affect the final yield among those corn plants that are competing for limited resources.

While some of the corn plants dominate and reach their full potential, other plants tend to dominate smaller plants.

What Should You Do?

Vyn says no-tillers need to make sure corn residue is spread uniformly, fields are adequately drained, surface soil compaction is avoided and all nutrients are evenly distributed.