Tillage and Surface Residue Effects on Evaporation from Soils

Abstract

AbstractMany crop growth models require modification for dryland farming systems because they do not predict an effect of residues on the soil water balance. Daily evaporation (E) from a Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll) was measured in three experiments using laboratory cores or field microlysimeters to determine effects of tillage and residues on cumulative E and on E rate. The first experiment showed that the disk treatment had the highest rate of Stage 1 E and a lower slope of the Stage 2 E curve than sweep and no‐tillage treatments. Effects of tillage on surface wheat (Triticum aestivum L.) residues and on soil physical properties both seemed related to E. In a subsequent experiment, no effect of tillage‐induced differences in soil properties on daily E was measured when wheat residues were removed before tillage. In the third experiment the effect of cotton (Gossypium hirsutum L.), sorghum [Sorghum bicolor (L.) Moench], or wheat residue (x, m3 m−2) on the initial, energy‐limited rate of E (y, the potential E at the surface relative to bare soil E) was described by a logarithmic relationship [y = −0.99 − 0.236 (ln x), n = 36, r2 = 0.87]. With residues described on a mass/unit area basis, crop‐specific curves were obtained; but with residues described on a thickness or volume/unit area basis, the curves obtained with the different crop residues were very similar to the pooled relationship given above. This simple relationship between residue level and daily E can be incorporated into water balances of commonly used crop growth models to increase the accuracy of water balance prediction for different cropping systems.