Crimping Cover Crops

Cover crops outcompete many troublesome weeds but cover crop needs to be terminated. Most farmers kill cover crop with herbicides but crimper crop rollers can terminate naturally. Selecting the right cover crop to crimp and timing are critical for getting good crimping results.

The most common grass crops that are crimped are cereal rye, oats, triticale, and wheat. Avoid trying to crimp soft flexible plants like annual ryegrass because they do not have enough lignin in the stems to cause the plant to crimp properly. For legumes, hairy vetch, winter peas, cowpeas, Balansa and crimson clovers have been successfully terminated by crimping.

The best time to crimp grass cover crops are when the seed heads are emerging and for legumes when they are blooming. The crimper crop roller mechanically rolls down plants and “crimps” or kinks the stem so that water and nutrients can not move up the xylem or sugars down the phloem. Crimper blades are blunt and spaced about 7 inches apart at a 15-degree angle to crimp the stem several times. The goal is not to cut the stem, just severely crimp and roll the plant flat, so that it dies naturally.

Cereal rye is the most common cover crop crimped, either before or after planting soybeans. Crimping before planting, make sure you plant in the same direction and the crimper should be the same width as the planter. Planting across crimped cover crops may cause twisting, binding, wrapping, and hair pinning to occur. Planting green and then crimping at a later date works well. Soybeans can be crimped up to 4-5 inches tall and corn up to V4. Be careful not to crimp when soybean cotyledons are emerging. Clipping off cotyledons causes soybean to die Once 1 to 2 trifoliate soybean leaves emerge, it is generally safe to crimp. Generally, about like rotary hoeing, the damage looks worse than it really is when crimping.

The amount of cover crop biomass is important for good weed control. A study in Weed Science found that cover-crop biomass and the ratio of carbon to nitrogen influenced weed suppression and its duration. For example, a 9 to 1 ratio of carbon to nitrogen (legumes) suppressed pigweed by 50 percent at four weeks after treatment, while a 20 to 1 ratio (grasses) delivered the same level of control eight weeks after treatment. A cover-crop biomass of 2,500 pounds per acre was needed for 50% weed suppression for four weeks, while a biomass of 5,900 pounds per acre was needed for the same level of suppression at eight weeks.

In fields where the cover crop was the only weed control measure used, corn and soybean yields increased as both cover crop biomass and carbon to nitrogen ratios increased. Cover crop mixtures were beneficial. Mixtures grew extra biomass to suppress weeds, increased moisture later in the growing season, and if legumes were used, increased soil nitrogen. Cereal rye and Daikon radish produce natural herbicides which suppress many weeds. The extra crop residue also supports many beneficial insects and pollinators, helping to increase yields.

Crop rollers can crimp about 1 acre per foot of implement when traveling 8-10 mph. A 15- footer can crimp 15 acres/hour and a 30-footer, 30 acres/hour. When conditions are dry, adding water or oil to the drum reduces bouncing and increases crimping effectiveness. Make sure you drain the drum before winter to avoid cracking the drum. Crimping effectiveness can also be improved by driving at a slight angle. Sometimes there is a slight elevation difference on the row compared to the area between the rows, and driving at an angle allows the crimper to roll across the row for a better crimp.

For safety, make sure you have a big enough tractor to handle the weight and to easily lift and turn on the ends. On 3-pt hitch models, extra weight may be needed on front of the tractor to prevent the front wheels from coming off the ground. On trailed crimpers, hydraulic tractor lift is the most limiting factor. It takes very tittle horsepower to roll the crimper but it takes some power to lift it up on the ends. If you leave the crimper down while turning, its hard on the equipment and drags up soils as it turns. Watch out for ground hog holes, sink holes, and turning too fast. Crimping does not work every single year but crimping is a lot of fun!