Root mass may affect soil water infiltration more strongly than the incorporated residue

Abstract

This Brief Report includes a single-finding that is reported with descriptions of an unexpected observation. Crop residue incorporation increases stable soil pores and soil water infiltration, consequently, reduces surface water runoff and soil erosion. However, to our knowledge, quantitative studies for the relation between incorporated residue and infiltration rate has not been conducted. We examined the relationship between the quantity of crop residue of the prior crop and the water infiltration rate. We continuously grew corn (cleaning crop), rhodes grass, and okra under greenhouses. The water infiltration rate was measured on the ridge at similar soil moisture conditions, on the day incorporating the prior crop residue. A strong correlation was found between the quantity of inputted residue and the soil water infiltration rate ( r = 0.953); however, that of corn, had no prior crop, is the outlier. The outliner is nonnegligible because the infiltration rate per input residue is two fifth of other crops. By contrast, aboveground biomass of the prior crop showed a stronger correlation with water infiltration rate ( r = 0.965), without outliers. Previous studies have revealed the logarithmic relation between plant root mass and soil erosion resistance. Our data also show a positive relationship between resistance to erosion and root mass when assuming that the aboveground biomass is proportional to the underground biomass. The result also showed that the effect of the prior crop root mass disappears within the next crop period. This suggests that maintaining a large root mass is crucial for reducing soil erosion.