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This graph compares the tillage intensity scores of 123 tilled fields with the amount of soil organic matter in each field. (We excluded fields with organic matter inputs, because many of our growers who till intensively to control weeds also add a lot of organic matter to offset the effects of their tillage.) The graph’s red trend line shows that as tillage becomes more intense, soil organic matter tends to decrease. Our data also shows that increased tillage intensity is correlated with decreased organic carbon and decreased soil health scores.
Tillage can degrade soil structure and organic matter, but it can also be a valuable tool for weed management and incorporating cover crops and other organic material. We use a Natural Resources Conservation Service soil erosion model to assign a soil disturbance score to all farm operations that compact or disturb soil. For example, NRCS assigns a single pass with a subsoiler-chisel plow a score of 52.6, a disc harrow gets a score of 11.67, and hay cutting equipment gets a score of 0.15. We total all the scores from each implement used in a field in a calendar year to compute the tillage intensity score for each site.
Elizabeth Black is the producer of the Citizen Science Soil Health Project