An integrated system of reduced tillage practices and conservation structures is needed for successful soil and water conservation. Crop residues on the soil surface reduce the effect of rainfall intensity and help somewhat to keep sediments in place. However, conservation structures such as diversions, grade control measures, terraces, grass waterways, contour strips and conservation buffers are needed to reduce the velocity of water and sediment transport off fields.
Farmers need to combine tillage systems with crop rotations and conservation structures to control surface runoff and soil erosion effectively. For a corn-soybean rotation in the Karst area, contour farming, contour buffer strips and grass waterways in combination with no-till corn into soybean residue and chisel-plowing corn residue could provide sufficient erosion control. However, if tillage is done both after growing corn and growing soybeans, it may be necessary to compensate for the increased erosion potential from the additional tillage by using contour farming and terraces and adding hay or small grain to the rotation. In the loess-cap region, con-servation tillage in combination with grass waterways or terraces often can control soil erosion in a corn-soybean rotation. Even if corn is planted no-till into soybean stubble, grass waterways or terraces will often be needed to handle erosion on steeper or longer sloping fields. If tillage reduces residue cover to 20 percent or less, terraces may be needed on steeper or longer slopes.
These typical conservation systems show how combinations of management practices and conservation structures can successfully control erosion in southeastern Minnesota. Individual farms may need site-specific designs that differ from these typical systems. Farmers can contact their local Soil and Water Conservation District/Natural Resources Conservation Service office for help in determining which combination of conservation tillage, crop rotation and conservation structures is best for their farm.
Grass buffers at the edge of a field, drainage ditch or stream should be considered supplemental erosion control for the upper portions of the field, not a replacement for conservation practices. In fact, field buffers are effective mainly against sheet and rill erosion, and can be easily breached by gully erosion that is the result of insufficient erosion control on the uplands.
Figure 1. Major watersheds in Southeastern Minnesota
Figure 2. Minnesota Land Resource Area (MLRA) Soils (Major Land Resource Areas 104 and 105).
Source: Austin, M.E., 1965, "Land Resource Region and Major Land Resource Areas in the United States," Agriculture Handbook 296, Soil Conservation Service, United States Department of Agriculture, Washington, D.C.
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