Among the four rollers that were evaluated, the two-stage roller/crimper performed best.
Photos courtesy of Ted Kornecki, USDA-ARS.
The use of organic practices has continued to expand in vegetable and fruit production. At the same time, more and more growers are going pesticide- free without being certified organic. As interest in organic produce increases, technology is helping to make production more efficient.
Dr. Ted Kornecki has conducted field trials following extensive research on mechanically killing off cover crops using a roller/crimper he developed, along with trials of other machines. The roller/crimper trials offer encouraging results, with benefits in terms of soil enhancement and weed control for both organic and pesticide-free growers. Benefits to the soil are increased when roller/crimpers are used to mechanically kill off cover crops, leaving a biomass mat into which future crops can be planted about three weeks later.
Kornecki, an agricultural engineer at the U.S. Department of Agriculture Agricultural Research Service (USDA-ARS) National Soil Dynamics Laboratory in Auburn, Ala., cited a number of benefits from cover crops.
"In addition to enhancing soil properties by adding organic carbon to the soil, legumes are able to fix nitrogen from the air," he stated, adding that cover crops are an important source of nitrogen for organic farming, in which commercial, nonorganic nitrogen fertilizers are not permitted. Kornecki explained, "Legumes contain beneficial bacteria rhizobia within their root systems. These bacteria have the ability to fix nitrogen from atmospheric nitrogen into ammonia that is then converted to ammonium, a form usable by plants."
He said, "Cover crops that are used by growers are traditionally incorporated into the soil, but all benefits that cover crops can provide are lost with traditional incorporation, such as plowing or disking." Soil erosion and runoff occur from the energy of rainfall. Soils in southern states have low organic carbon levels, and growing cover crops can protect soil surfaces from erosion and increase organic carbon levels.
Ted Kornecki adjusts the smooth-bar roller/crimper.
Over a four-year period, Kornecki evaluated four roller/crimpers that he developed with patents held by the USDA. The following rollers were evaluated at the E.V. Smith Research Center and in commercial fields: a smooth roller with a crimping bar, a one-piece assembly prototype; a two-stage roller/crimper with two drums; a roller/crimper developed for elevated bed culture to kill off cover crops grown in furrows and hills; and a powered roller/crimper for walk-behind tractors, designed for small organic operations.
On-farm no-till project
Kornecki directed a multiyear, on-farm no-till vegetable project as part of a Conservation Innovation Grant (CIG). The project evaluated a two-stage roller/crimper on the farm of grower Frank Randle. Kornecki specially designed the two-stage roller as an 8-foot model to fit the farm's needs. Randle, 62, operates a 210-acre farm near Auburn with his sons, Franklin, 33, and Zach, 30. Though not a certified organic grower, Randle produces food crops on 20 acres without pesticides.
Randle maintains a year-round greenhouse where transplants are produced. And for more than a decade, the Randle farm has included a community-supported agriculture (CSA) operation. In addition to growing crops for the CSA, Randle sells produce at an on-farm market.
"Here in the South, our soils have low carbon. With our high heat and high humidity, we have a lot of weed pressure, and we grow our crops pesticide-free," Randle explained. "We see the no-till operation with the cover crops killed off mechanically as another tool in our toolbox to grow crops."
Side view of the smooth-bar roller/crimper.
He uses cover crops of crimson clover and cereal rye. He found tilling necessary to control perennial weeds after the fourth year, but noted that the roller/crimper could subsequently be used continuously.
Randle noted that the effectiveness varies with the crop. He cited increased yields with the rye cover crop, and added that the no-till, roller/crimper process worked particularly well with okra, tomatoes and squash.
"Earlier, original roller/crimpers generated a lot of vibration," Kornecki said. He designed his rollers to improve on the crimping action and reduce the vibration of models. Kornecki explained, "The rollers were evaluated for three or four years at different locations to account for different soil and weather conditions. All of these rollers performed as well or better than the original straight-bar roller, with average termination rate 90 to 100 percent three weeks after rolling."
This smooth-bar roller/crimper is used to kill a cereal rye cover crop.
He noted, "The two-stage roller performed the best compared to other rollers. It can successfully be operated at different speeds without generating harmful vibrations." Adjustable compression springs can release enough energy to kill the cover crop by providing appropriate crimping force. Kornecki explained that the first drum flattens the cover crop, and the second drum with crimping bar crimps the cover crop. The second drum is isolated from the first to minimize vibrations and is preloaded by two compression springs. The two-stage roller/crimper can be designed with a single or multiple sections to accommodate different farm and tractor sizes.
Rolling/crimping must be done in the same direction as planting of a future crop to minimize residue interference and possible buildup of residue on the planting units. During the operation, a thick mat of cover crop residue is created on the soil surface, and the cover is crimped at equal intervals. Kornecki said, "The idea is to damage the plant without cutting stems. The original rollers typically consist of a steel drum with attached crimping bars equally spaced on the drum's perimeter."
He said, "It is important to know that to maximize benefits from cover crops, the crops must be in an appropriate growth stage to produce an optimum biomass and to be effectively killed mechanically using roller/crimpers." Kornecki noted that the appropriate growth stage for cereal rye is from early milk to soft dough stage, and for crimson clover it's late bloom stage.
Ted Kornecki during a roller/crimper technology presentation at a field day at Frank Randle's farm.
Reducing glyphosate amounts
Kornecki said, "In conservation tillage systems, rolling/crimping plus glyphosate application may be needed, particularly when there is a cold, wet spring, because rolling/crimping alone might not be fast enough to efficiently and timely terminate a cover crop." He emphasized that the combination of rolling/crimping and glyphosate applications is for use in conservation tillage systems and not for organic growing systems, where multiple rolling operations may be necessary.
A specially designed 8-foot roller/crimper is used in a field test on Frank Randle's farm.
Studies were conducted using different glyphosate applications to determine just how much glyphosate is actually needed when a roller/crimper is used. The smooth roller with crimping bar was used. Results indicated that spraying every fourth crimp using a high-speed solenoid valve for discharge control provided an effective rate of killing the cover crop at 87 to 99 percent one week after rolling. Reduced herbicide and water use produced savings of up to $17.50 per acre.
A modified no-till tomato transplanter displaces compacted soil.
Cover crops reduce compaction
Southern soils are sometimes prone to compaction from wheel traffic as well as natural soil consolidation. Kornecki said, "Cover crops left on the soil surface after rolling dissipate rainfall energy while preserving moisture. The cover crops act as 'sponges' to hold water, and water gradually infiltrates deeper into the soil, preserving soil structure. Without cover crops, rainfall energy causes the soil structure to collapse on the soil surface and causes soil crusting - a hard compacted topsoil."
No suitable subsoilers are attached to transplanters to deal with compaction issues. Kornecki noted, "Commercial no-till vegetable transplanters usually are equipped with a coulter to cut through residue cover. The RJ transplanter, from RJ Equipment in Canada, is a typical example of a no-till transplanter. The RJ transplanter was modified by adding a subframe between the toolbar, with a mounted plastic tank for water and starter fertilizer, and the parallel linkage."
Frank Randle discusses improved yields on his farm using roller/crimper technology.
The subframe accommodated both commercially available and custom-made shanks as well as row cleaners for managing cover crop residues while transplanting. The subsoiler shank enabled the transplanter to disrupt a naturally occurring compacted soil layer to a depth of 12 to 16 inches beneath heavy residue in a conservation system.
Numerous benefits to growers
The four-year study indicated that roller/crimper technology offers real benefits to growers. With efficient roller/crimpers, cover crops can be effectively killed and left on the soil to provide the many benefits that are lost with incorporation. Weed control is enhanced - an important consideration for organic growers who cannot use chemicals. Substantial savings can be realized by other growers who can reduce the amount of glyphosate applications when used in combination with roller/crimpers.
Nancy Riggs is a freelance writer and frequent contributor. She resides in Mount Zion, Ill.