Mow-plow crop residue management influence on soil erosion in north-central Oregon

Soil loss from dryland farms on the Columbia Plateau in Oregon and Washington (USA) results primarily from rain falling on frozen, cultivated soil. Soils are most susceptible to erosion when moldboard plowed, summer-fallowed, repeatedly rod-weeded or cultivated, and fall planted to winter-wheat. These tillage practices are used because they help control weed and disease infestations and consistently produce good crops. Unfortunately, they also destroy soil structure and lead to considerable soil loss by water erosion. Conservation-tillage-practices have not been widely accepted because of associated weed and disease problems. A new conservation system using crop residue management, the mow-plow system, has shown promise for weed control. The moldboard plow is the primary tillage tool, but standing crop residue is cut ahead of the plow and distributed onto the adjacent plowed surface. The system requires a single pass of the equipment. We evaluated runoff and erosion responses in two levels of residue application in the mow-plow (L∼23% and H∼36% cover), traditional moldboard plow, and chisel plow winter-wheat/summer-fallow systems near Pendleton, OR, USA. Following extended periods of sub-freezing air and soil temperatures, we simulated rainfall at 9, 13, and 19 mm h −1 and collected runoff to evaluate water and soil loss as the soil thawed. Runoff was not significantly different among treatments. For each of the three rainfall intensities, the chisel plow treatment provided the best protection against soil erosion at 0.11, 0.39, and 0.95 Mg ha −1 h −1, followed closely by the mow-plow (H) 0.26, 0.55, and 0.90 Mg ha −1 h −1. The moldboard plow treatment was the least effective treatment for erosion control (0.57, 1.38, and 3.76 Mg ha −1 h −1). The erosion response from the mow-plow (L) treatment was variable and not statistically different from the moldboard plow treatment (0.33, 2.49, and 1.71 Mg ha −1 h −1). These results demonstrate the importance of maintaining cover on the soil surface. The mow-plow system, where adequate straw residue is available, is superior to moldboard plow system for soil conservation.