Residue Cover and Surface‐Sealing Effects on Infiltration

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Abstract
Surface sealing of bare soils often reduces rain infiltration, and crop‐residue cover is commonly used to reduce surface sealing. We conducted numerical experiments to quantify effects of the percentage and distribution of residue cover on infiltration, and to provide guidelines for residue management. Residue cover was simulated over the soil surface in circular patches. Excess surface water from the bare surface‐sealed areas was available for infiltration in nonsealed areas. Numerical simulations were conducted for combinations of (i) soil type, either a clay loam or loamy sand soil; (ii) percentage residue cover (Prc); (iii) saturated hydraulic conductivity of the surface seal (Kc) relative to bulk soil (Ks); (iv) residue‐patch size with a constant Prc; and (v) rainfall intensity. The Kc values had the greatest influence on infiltration as a function of Prc This influence increased with rainfall intensity. For a given Prc, smaller patches gave greater relative infiltration due to differences in the lateral redistribution of infiltrated water. The target values of Prc that provided 95% relative infiltration varied from 40 to 80% for most combinations. Changing the geometry of the residues made no significant difference. We also tested a one‐dimensional model with a spatially averaged saturated hydraulic conductivity (Kce) for both covered and surface‐sealed areas, and found that infiltration into a partially residue‐covered soil could be estimated by the one‐dimensional model for all cases of this study, when Kc > 0. Finally, simulated infiltration qualitatively agreed with data sets of two independent field experiments under similar soil and rainfall conditions.