MAXIMUM SURFACE STORAGE PROVIDED BY CROP RESIDUE

Small ponds created by crop residue serve to store water on upland areas. The present study is conducted to identify the maximum surface storage provided by crop residue. Equations for estimating surface storage arc derived assuming that residue elements were oriented end to end, at uniform intervals, in a direction perpendicular to flow. Separate equations are developed for conditions where average slope was greater than or equal to residue cover, or less than residue cover. Both equations relate average surface-storage depth to residue cover, residue diameter, and average slope. Data to test the reliability of the equations are obtained in a laboratory investigation. Artificial residue elements are glued onto a 1-m2 test section positioned at slopes of 1%, 10%, or 20%. Four sizes of residue elements and three surface-cover conditions are examined. Surface-storage depth for each experimental condition is measured. Close agreement is found between predicted and measured surface-storage values. Surface storage occurring under field conditions may bc substantially less than the estimates obtained using the predictive equations.