Residue May Be Key Infiltration Factor

John Church, Extension Educator – Natural Resources, Rockford Extension Center, 815-397-7714, churchj@uiuc.edu

During and after planting can be a good time to compare the impact of various tillage and conservation practices on soil erosion and water infiltration in fields. Residue left on the soil surface from no-till and other high-residue tillage systems helps protect the soil from raindrops, which reduces the breaking apart of soil particles and ultimately the erosion of soil. Residue's impact on protecting the soil surface from erosion is well accepted. However, there is also growing interest in the impact of residue and less tillage on increasing water infiltration, which can reduce runoff as well as maintain moisture supplies.

Purdue studies have shown that fields with no residue on the surface similar to conventional tillage can have a 45 percent runoff rate as compared to no-till fields with high residue that have runoff rates as low as 0.5 percent of the rainfall. At about 40 percent residue cover, which is comparable to many mulch tillage systems, the runoff rate was about 40 percent. The same study shows about 12 tons per acre soil loss with no surface residue as compared to 3.2 tons at 40 percent residue and 0.3 tons at 93 percent residue levels. Runoff velocity rates for the same three residue levels were 26, 14, and 7 ft./min., respectively. Less runoff means less soil erosion and more water infiltration, which can enhance groundwater supplies, reduce stream volumes and velocities, and reduce streambank erosion and lessen sedimentation. Increased infiltration also is a good indicator that soil structure is improving for better rooting, less compaction and better air, water and nutrient movement.

While evaluating the field residue for sheet erosion and water infiltration, be sure to check other erosion structures for necessary maintenance or need for new construction to reduce gully erosion or streambank erosion.