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An Infiltration Equation to Assess Cropping Effects on Soil Water Infiltration

Soil Research Center, Abu-Ghraib, Baghdad, Iraq

D. Swartzendruber^*

Dep. of Agronomy, Univ. of Nebraska, Lincoln, NE 68583

*Corresponding author.

ABSTRACT

The effect of crop plants on the infiltration of water into soil has been difficult to characterize. This study was conducted to determine whether a new three-parameter infiltration equation, obtained from a recent infiltration quasi solution, could be validated and used for improved characterization of infiltration. For field plots under different cropping conditions of corn (Zea mays L.), sorghum [Sorghum bicolor (L.) Moench], soybean [Glycine max (L.) Merr.], and fallow, water-infiltration data from ponded double-ring infiltrometers were fitted by nonlinear least squares to the new equation, and, for comparison, to the two-parameter Philip form and to the strictly empirical Lewis equation. Physically problematic negative values of the sated (near-saturated) hydraulic conductivity K were yielded by the Philip form in well over half of the data sets, but all were superseded with positive K values by use of the new equation which, of the three, also gave the best fit to the data, in keeping with the additional fitted parameter. Statistically, by using orthogonal-contrast analysis of the several equation parameters, the new equation also produced the largest number of significant differences between crops and crop sequences (rotations). Grain sorghum created the largest sorptivity S, whereas corn decreased it. Soybean produced the smallest K, but corn and grain sorghum caused moderate and equal increases in K. The new equation and these findings offer promise for improved characterization and understanding of plant effects on water infiltration.

Contribution from the Agricultural Research Division, Univ. of Nebraska, Lincoln; Journal Series Paper no. 9085.

Received for publication December 10, 1992.