Effect of wheat residue and evaporative demands on intermittent evaporation

Abstract

Evaporation with time was measured from wetted columns of loam (fluventic Camborthids) soil treated with 7 application rates of straw, either surface applied or incorporated into the top 10 cm. The application rates were 0, 1, 2, 3, 4, 6 and 10 Mg ha −1. The experiment was conducted in a growth chamber under low (4.5 mm day −1) and high (16.0 mm day −1) evaporative demand conditions. Soil moisture profiles were also measured. Incorporated residue treatments did not show any significant advantages over the control, under both evaporative demands. In general, evaporation decreased and thus the amount of water conserved increased with increasing surface-residue rates under both evaporative demands. Those evaporation reductions were clearly reflected in soil-moisture profiles. However, it has been concluded that 4 Mg ha −1 was the most efficient surface residue rate in water conservation. The amount of water conserved with the rate of 4 Mg ha −1 was 1.7 times that of the control under low evaporative demand. Whereas the amounts of water conserved were 1.4, 1.5 and 1.3 times that of the control by the end of the first, second and third cycles, respectively, under high evaporative demand. Highly significant ( P = 0.01) linear relationships were established between the evaporation reductions and the square root of surface-residue rates for both evaporative demands. These relationships may prove useful as a guide for water conservation. The results of this study may be used as a guide for further field investigation.