These changes may include the type and number of tillage operations, or reducing the amount of water applied per irrigation event. Moderate runoff problems may require alterations to the irrigation system design in conjunction with changes in cultural and management practices. For example, reducing the peak water application rate or increasing the sprinkler wetted radius and reducing tillage operations may control a moderate runoff problem. In severe runoff situations, specialized tillage practices, used in conjunction with other changes, may be necessary. Cultural Practice Changes Leaving crop residue on the soil surface generally reduces the amount of water runoff, particularly for water applications of one inch or less.
Crop residue works in a number of different ways to reduce runoff and erosion.
When water droplets strike a bare soil surface, energy contained in the droplets is transferred to the soil, often forming a crust. Although this crust is normally less than 0.1 inches thick, it can reduce the infiltration rate by more than 50 percent. Residue effectively absorbs much of this impact energy, reducing crust formation. Residue increases the soil surface roughness, which helps dissipate the energy from flowing water. This, in turn, reduces the amount of erosion that occurs.