Farmers who have tried growing cover crops during the months when no commercial crops are in the field have found they provide substantial benefits, especially in no-till or reduced tillage planting systems.
So why don’t more growers plant them? Fear of the unknown is one issue. Cost of cover crop seed is another. And dealing with the cover crop when it’s time to plant the commercial crop is another. But there are ways to work around that, experts say.
“Our very erodible landscape in Tennessee really needs some protection,” said Tyson Raper, Extension cotton and small grains specialist with the University of Tennessee. “No-till advances that protection but having an additional cover crop growing out there to hold the soil in place can really provide some benefits.”
Raper, a speaker at this year’s online Milan No-Till Field Day, said erosion control during the winter months can be crucial not only in west Tennessee, but in other parts of the Mid-South where winter rains on bare soil can remove soil. There are also in-season benefits, including weed control.
“One of the things I’m interested in since we are predominantly a no-till state, a dryland state, is that having a cover crop out there can increase our infiltration rate and provide some water efficiency in the middle of the growing season,” he said. “We can capture the rainfall and hold it in place for the crop for when it needs it most.”
But there are also potential issues in cotton production, such as terminating the cover crop at a time when farmers can get the maximum benefit from the biomass left by the cover crop and it not be detrimental to crop emergence.
Managing cover crops
“Along the northern edge of the Cotton Belt, anything that we do that can increase the risk of losing a stand can hurt our bottom line,” he noted. “So, we want to make sure we’re managing this cover crop as best as we can to establish a profitable cotton crop the first time.”
Raper and his colleagues have been looking at termination timing, termination method and different types of planter attachments that can process the biomass of cover crops and create a uniform seedbed they can plant into and achieve a successful stand.
The three-year study involved terminating cover crops six weeks prior to the expected planting date, four weeks prior, two weeks prior and at planting. The earliest termination treatment can improve the ease of planting, but it may also negate the benefits of the cover crop.
“When you terminate six weeks prior, this biomass here – and there’s not a lot of biomass to begin with – it almost melts,” said Raper, who was standing in one of the test plots when his presentation was recorded. “By the time we get to planting there will be very little sign that a cover crop was ever here.
“If we wait until planting, we obviously will get a tremendous amount of biomass, but there are some negative impacts of having all that biomass in the system,” he said. “We’ll have a green bridge (for insects) if we wait until planting. We can have some inconsistent moisture issues, and we can also have issues with the planter processing that green, lush material at that quantity.”
Researchers have typically seen the best results with a two- to three-week prior to plant termination, he said.
“That allows us to get as much biomass as possible out of the cover crop and minimize the negative impacts we can see of having too much biomass or green biomass present right in front of the planter.”
For more information on the field day, visit https://milannotill.tennessee.edu/research-tours/.