Application of different organic wastes on soil properties and wheat yield
Fresh and composted organic wastes [beet vinasse (BV), sewage sludge (SS), and a cotton gin crushed compost (CCGC)], were applied for 4 yr to a Typic Xerofluvent in dryland conditions near Seville, Spain. Organic wastes were applied at rates of 5, 7.5, and 10 Mg organic matter ha–1, respectively. The effect on the soil's physical properties, soil microbial biomass, and six soil enzymatic activities (dehydrogenase, urease, protease, ß-glucosidase, arylsulfatase, and alkaline phosphatase activities) and the yield parameters of wheat (Triticum aestivum cv. Cajeme) were ascertained. The application of CCGC compost improved the soil's physical (structural stability, bulk density), chemical (exchangeable sodium percentage, ESP), and biological properties (microbial biomass, soil respiration, and enzymatic activities) and the wheat yield parameters; however, the application of SS adversely affected the soil biological properties and reduced the wheat yield, probably because high of amounts of heavy metals. The application of fresh BV also adversely affected the soil's physical, chemical, and biological properties and the wheat yield, probably because high amounts of Na and fulvic acids were introduced into the soil by the vinasse, which destabilized its structure. Wheat yield decreased 22.5% in BV with respect to CCGC-amended soil, 13.6% in SS with respect to CCGC-amended soil, and 7.9% in BV with respect to SS-amended soil. These results suggest that the chemical composition of the three organic wastes notably influenced the soil properties and therefore the wheat yield parameters. Of the three organic wastes studied, alone the application of CCGC originated a positive effect in the soil and in the wheat yield parameters, while the application of BV and SS originated a negative effect in the soil properties and therefore in the wheat yield parameters.