Crimping is a soil conservation technique in which crops that cover and protect the soil during the winter season are flattened with a roller to create an organic mulch. Commercial crops are planted into that mulch three weeks later. Crimping is a no-tillage technique that terminates winter cover crops as effectively as chemical herbicides and is appropriate for organic gardening. With crimping, clear tillage is not necessary, either prior to planting or for weed control during the growing season.
Crimping, crusher rolling or knife rolling was developed in South America in the 1980s as a method of introducing mulch or green manure without disturbing the soil. The rollers had thin metal bars over the full width of the roller surface that flattened and bend the plant stems, but did not cut them. Unlike mown plants, crimped plants decompose, rather than sprouting again.
Creating and conserving healthy soil is the guiding paradigm in organic gardening. Conventional conservation agriculture and alternative organic gardening both prevent soil loss with cold season cover crops. Cover crops increase rainwater infiltration by preventing compaction, and reduce soil erosion by preventing rapid run-off. Conventional mowing and clear tillage to turn under the winter cover exposes soil to drying and wind or water erosion. Crimping preserves winter cover as mulch and increases organic matter content.
Conservative Tillage and Global Warming
Soil sequesters an amount of carbon equal to the total amount of atmospheric carbon plus the total amount of global above-ground vegetation. Conservative tillage practices such as crimping preserve carbon in the soil as mulches and manures, while they also prevent loss of soil through erosion. Conserving carbon in the soil reduces the atmospheric carbon-loading that influences global warming.
Types of Crimpers
Commercial crimpers are manufactured in Brazil, with three roller designs available in the U.S. market. All designs are pulled behind a tractor. The least sophisticated design has long, straight, blunt blades attached to the outer surface of a round roller. In an advanced design, the blades on the roller are gently, elliptically curved at an angle of about 15 degrees relative to the ends of the roller, so that contact with the soil is sifted along the curve as the tractor advances. The most complex design has a completely smooth roller that flattens the plants, followed by a detached oscillating bar that crimps them.
Problems at Commercial Scale
Crimping rollers create vibration that can potentially damage tractor frames. Vibrations increase as speed increases, but percent of crop termination decreases as speed decreases. Ted S. Kornecki and others at Alabama's Auburn University looked at three roller designs operated at 1, 3 and 5 mph. They found that elliptically curved blades conveyed the least vibration, or half as much as long blunt blades. Smooth rollers with an oscillating crimping arm attachment terminated only slightly more effectively than other rollers. They noted a significant difference in termination rate between 1 and 5 miles per hour, but not between 3 and 5 mph.