Growings On: University of Georgia researchers evaluate the benefits of cover crops

Published 8:00 am Thursday, January 20, 2022

For row crop producers in Georgia, corn, cotton and peanut were planted in the spring and harvested in the fall. After harvest, the ground is left relatively bare, with only the residue of the harvested crop remaining to protect the soil. Many farmers have adopted cover crops to “armor” the surface of the ground following harvest until the next crop emerges.

Cover crops are non-crop plants like crimson clover and rye planted after cash crops are harvested and allowed to grow until producers prepare for spring planting. Cover crops provide living roots in the ground over the winter, and a mat of residue on the soil surface until the following crop is planted. During the last few decades researchers have found that cover crops improve various soil properties and contribute positively to weed management.

Fields left with only the residue of harvested cotton plants remaining are conspicuously subject to soil erosion. Now, University of Georgia weed scientist Nicholas Basinger and doctoral candidate David Weisberger, researchers in the University of Georgia’s College of Agricultural and Environmental Sciences, are studying the use of both annual and perennial cover crops called “living mulches” in cotton. Weisberger developed a program to test the use of living mulches and annual cover crops in cotton production in Georgia based on previous work using living mulches in corn production conducted by UGA Professor Emeritus Nick Hill.

“It seemed like a natural extension of the work to try this with one of the state’s most economically relevant row crops,” said Weisberger, who received funding for the three-year project from Cotton Inc. “Cover cropping and even the use of living mulches is not that new, but it is something that’s fairly new to cotton production.”

In fall 2019 Weisberger, Basinger and a team of soil scientists from the Department of Crop and Soil Sciences including soil pedologist Matthew Levi, doctoral student Chandler Greuner and soil physicist Nandita Gaur established a study at the J. Phil Campbell Sr. Research and Education Center in Watkinsville. Research plots were planted with a bare ground control, two annual cover crops — cereal rye and crimson clover — and a living mulch. Durana white clover, a variety originally developed by UGA scientists as a forage for livestock, serves as the living mulch.

“Being able to do studies like this, bringing in other students and faculty from our department to get a really full picture both from above and below ground, can help drive a better understanding of what’s actually happening in the system and what the true benefits and drawbacks of each system are,” Basinger said. “That helps us have more understanding about where we would prescribe this and where it will best fit.”

The goal of the study is to quantify both above-ground and below-ground effects of these annual cover crops and a living mulch compared to a standard no-till bare ground system. The researchers are measuring cotton yield and weed suppression as well as changes in the soil’s physical and chemical properties.

Weed monitoring has focused on Palmer amaranth, a costly and problematic weed that has developed resistance to herbicides like Roundup and Atrazine.

“The goal has been to incorporate more cover crops so that there’s a blanket on the soil that suppresses those little Palmer amaranth seeds that are down in the ground and keeps them from waking up,” Weisberger said.

In the weed-control studies, researchers are calculating how well the cover crop or living mulch suppresses weed emergence, and survival and adult seed production, in cotton plots pre-seeded with this problematic species.

“The idea was to start at the same level of infestation and to look at how those different covers, or lack thereof, affect the weed population over time,” Weisberger said.

Led by Weisberger, UGA researchers are quantifying both above-ground and below-ground effects of annual cover crops and a living mulch compared to a standard no-till, bare ground system. According to Basinger, it is important to balance long-term and short-term goals with a study like this.

“So many of these properties, especially from the soil perspective, are slow to change, so that’s one of the big challenges we have. Soil properties tend to change much more slowly, but from a weed perspective we can determine some important findings each year,” Basinger explained.

Initial findings were promising. In the first year of the study both the cover crop and living mulch plots showed a major reduction in the number of Palmer amaranth weeds that emerged.

Roger Gates is the agricultural and natural resources agent for University of Georgia Extension, Whitfield County. Contact him at roger.gates@uga.edu.