Factors Continued...Soil Cover

Soil Cover

Bare soil is exposed to the full erosive power of raindrops and runoff water. Vegetative canopy helps stabilize soil and controls runoff. The vegetative canopy intercepts raindrops and reduces the erosive energy of the raindrops. Dense canopies that cover much of the soil surface intercept a large proportion of the rainfall. The roots of vegetation, such as grass, bind soil particles together to resist erosion. Vegetation can also help lessen or deflect wind, intercept wind-borne sediment, and keep soils moist, making them less susceptible to wind-related erosion.

Crop or plant residue dissipates the energy available to cause erosion. A mulch or crop residue absorbs the energy of falling raindrop, lessens detachment, reduces sealing of pores in the soil surface, and promotes good water infiltration. The chart below shows residue cover effects from 0 to 100% on soil erosion reduction. For example, a residue cover of 20% will reduce erosion by 50% compared to field with no residue cover.

Chart of the effect of residue cover on soil erosion. Image by UNL

Thinking Question:

Using the graph above, describe the relationship of % residue cover and soil loss? Would this relationship be expected for all residue types? Why or Why not?

Crop residue at various percentages of cover. Image by Iowa State University

Soil loss due to water erosion in relation to percent residue cover for Iowa, based on the Universal Soil Loss Equation. Image by Iowa State University



Using the graph above, describe the relationship of % soybeans residue and corn residue covers and soil loss? Is there a difference between corn and soybean residue on soil loss? Why and Why not? What general conclusion can you make about residue (mulch) type in its effect to reduce soil loss by erosion? Justify your conclusion.

Looks Good! Soil loss decreases for both residue types decreases as the amount of residue increases. However, the rate of soil loss is higher with soybeans compared to corn until the residue coverage reaches 50%. This is because of the smaller plant size and less thick soybean covers less of the soil surface.