Evaporation Reduction from Soil with Wheat, Sorghum, and Cotton Residues

Abstract

AbstractWheat (Triticum aestivum L.), grain sorghum [Sorghum bicolor (L.) Moench], and cotton (Gossypium hirsutum L.) are major irrigated crops on the Southern Great Plains. While irrigated wheat residue mulches increase soil water storage and decrease evaporation, very limited data are available regarding the effectiveness of grain sorghum and cotton (stalk) residues for this purpose. Therefore, this study was conducted to compare the effectiveness of wheat, grain sorghum, and cotton residues for decreasing evaporation under three potential evaporation conditions and to determine which residue characteristics are most effective for decreasing evaporation.The laboratory tests were conducted on Pullman elay loam soil columns at potential evaporation rates of 0.66, 0.92, and 1.29 cm/day. Besides a bare soil (check) treatment, residue treatments were 4, 8, 16, and 32 metric tons/ha for sorghum and cotton, and 8 metric tons/ha for wheat. About 16 metric tons/ha of sorghum and more than 32 metric tons/ha of cotton residues were needed to decrease evaporation to levels obtained with 8 tons/ha of wheat residue. Multiple regression analyses indicated that residue thickness most strongly affected cuniulative evaporation and evaporation rates at selected days of the study. Other independent variables considered were potential evaporation, relative humidity, and residue specific gravity, application rate, and surface coverage.