When it comes to winter cover crops, more is usually better, especially in the case of rye, according to researchers with the USDA-ARS National Soil Dynamics Laboratory at Auburn University.
But handling a rye cover crop in a no-till or strip-till cotton or corn field brings problems of its own — such as what do you do with all that biomass in the narrow window between when the rye reaches its full growth potential and planting time?
“You need to get the rye head high to do any good,” says Kip Balkcom, research agronomist with the USDA Agricultural Research Service laboratory in Auburn. “We generally try to plant it early to get it up higher and have more biomass when we plant the summer crop.”
On a cool, cloudy day at the Pee Dee Research and Education Center near Florence, S.C., Balkcom is standing on the back of a trailer discussing cover crops and equipment for handling them with participants in the 2005 Southern Conservation Tillage Systems Conference.
The trailer contains an 18-inch-diameter roller with 6-inch blades protruding from its surface at 7- to 8-inch intervals. The implement, which was manufactured in Brazil, is used to “roll” standing rye cover crops onto the ground. Once the rye is dead, farmers can plant into the rye mat.
“Farmers in Brazil have been using this technology for about a decade,” says Ted Kornecki, an agricultural engineer with the USDA-ARS laboratory. “The straight blades on the roller crimp the rye after it hits the ground, injuring the rye so that it will be terminated in time for planting.”
Balkcom, Kornecki and fellow researchers, Randy Raper, Francisco Arriaga and Andrew Price, all with the USDA-ARS at Auburn, have been conducting a study on the effects of rolling/crimping rye and the direction and use of different row-cleaning attachments on no-till or strip-till cotton.
Cover crops, the topic of several papers at this year's SCTSC, have long been recognized as a vital part of conservation systems, but researchers generally agree they should produce maximum biomass to be effective in protecting the soil from erosion and providing a mulch layer on the soil surface for conserving moisture.
The USDA-ARS researchers selected rye for their study because it typically produces a large amount of biomass and is popular with conservation-tillage producers in Alabama. The study took place in two locations (in central and northern Alabama.)
After planting a rye cover crop in early November and watching it grow all winter, producers need to know the best time to terminate the rye, says Kornecki.
“Our study indicates the proper growth stage is the soft dough or early milk stage of development,” he said. “Rolling it earlier or later did not provide the same crop yields as the early milk stage.”
But terminating the cover crop needs to be tied to when the grower intends to plant the summer crop. Researchers found it was better to roll and crimp the rye three weeks before planting.
“In general, three weeks from rolling, the grower can plant, but it depends on the spring,” said Kornecki. “Some years are more conducive than others.”
“You can have a problem with the rye wrapping around the planter,” said Balkcom. “One of the keys to successful planting is to make sure the rye is dead three weeks ahead of planting. You want it to be crunchy when you walk on it.”
Balkcom said researchers also found that row cleaners help with planting, particularly in strip-till systems. “You need row cleaners for strip-till to help clear the planting strip, but you want to just barely scratch the rye trash to move it out of the way.”
Growers may also have to increase the pressure on their no-till planter's down-pressure springs to help the planter openers place the seed at the proper depth, he said. “It's important with cotton — because you plant shallow — that you have a good mechanism for closing the row to keep the seed in the ground.”
The study also indicates growers may be able to save from $2.77 to $3.69 per acre in herbicide application costs depending on the type of roller implement used to roll and crimp the rye. (The study used the Brazilian-style roller with straight blades ($2.77) and a smooth roller with a crimping bar ($3.69).
Other scientists have been looking at rollers for use on other cover crops, including wheat. “We don't know if the roller is right for wheat,” says Balkcom. “Wheat does not produce as much biomass, and wheat does not give good weed suppression. It's better with rye.”
The Brazilian roller is not the favorite tool with the USDA-ARS researchers. “You can have a problem with vibration (from the blades), and you can't cover as many acres because of the roller width (13.5 feet),” Kornecki notes.
“We're working on a smooth roller with a crimping bar that we believe will be as effective, but can go much faster. This unit would be 30 feet wide. We're trying to design a machine that the farmer wants.”
The researchers tried rolling the rye parallel, perpendicular and at a 45-degree angle to the direction the planting rows. Preliminary results showed rolling the straw parallel to the rows produced the highest emergence and yield at both locations.
“This is from the 2003/04 study, but we need to have more data to prove it,” says Kornecki. “The first and second years of the study, unfortunately, were not the best years for cover crops.”
Other papers presented at the Southern Conservation-Tillage Systems Conference show that rye may not be the best cover crop for suppressing winter weeds. Black oats, another import from South America, appears to be more allelopathic or antagonistic to winter weed species.
Another group of researchers from the USDA Soil Dynamics Research Laboratory, the USDA-ARS J. Phil Campbell Sr. Natural Resource Conservation Center at Watkinsville, Ga., and the Department of Agronomy and Soils at Auburn University presented the results of a study on the use of mixtures of black oats and ryes compared to other cover crops on winter weed suppression.