14 September 2015 • PDPW • Dairy’s Bottom Line
Figure 1
Erosion Continued from page 13
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• S edimentation in lower areas of the field, • R ills running down hillsides, and • Soil-covered emerging crops. If any of these signs are seen, it might be time to consider adjusting management strategies. Checking for signs of loss during these critical months is an important practice no matter what type of management. There might be areas on the farm that are particularly prone to loss, like fence lines, and the top or bottom of waterways. These areas may need special attention. Even no-till farms contain critical sites and might suffer from soil losses.
MATCH TILLAGE TO LANDSCAPE
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Discovery Farms programs of Wisconsin and Minnesota have collected water-quality information for more than 12 years from farms with tillage systems ranging from intensive to no-till. There are other differences between monitored fields, which include location, soils, slopes, crop rotation, study period and manure application. Long-term Discovery Farms edge-of-field surface-runoff data suggests the
main soil-loss difference between no-till and intensively tilled farms is in the higher ranges of soil loss. There are no years where no-till farms had more than 1,000 pounds per acre of soil loss, meaning that no-till sites have maintained a sustainable level of soil loss. Loss from no-till sites ranged from almost no loss to just under 1,000 pounds per acre, compared to tillage sites that ranged from almost no loss to upward of 6,000 pounds per acre. Seventy-five percent of tillage sites also maintained a sustainable level of loss – area under the top line of orange box in Figure 2. Although no-till reduces variability, on average no-till and tillage sites did not lose substantially different amounts of soil. The points on the tillage boxplot that fall above the 75 percent mark are examples of systems where the tillage practices did not appropriately match the landscape. No-till systems are good at limiting soil loss and controlling for weather variability, but no-till may not be appropriate on every landscape or desirable for every farmer. There are instances where low levels of loss can be maintained even if some tillage is involved. The key is finding a level of tillage that works for a producer’s management and matches the landscape.