Carbon Mineralization in Soils Irrigated with Treated Swine Wastewater

Abstract

Treated swine wastewater agricultural use can promote environmental and agronomical improvements, however, the inappropiate management of this organic load added on soil can cause unbalances in soil fertility and in availability of nutrients and/or contaminants. Thus, this study aim was evaluate the organic matter biodegradation of treated swine wastewater (WB) and diluted swine wastewater (WBD) applied in Oxisol clayey texture (CS) and in Ultisol (SS) with medium-sandy texture. The treatments studied were: R1 – CS control; R2 – irrigation with WB on CS; R3 – irrigation with WBD on CS; R4 – SS control; R5 – irrigation with WBD on SS; R6 – irrigation with WBD on SS. Three applications were done in flasks containing 500 g of soils sampled from depth of 0-20 cm, the C-CO2 evolutions and degradation fractions were quantified after each application. The results obtained were adjusted to first-order chemical kinetics model. More than half organic matter was biodegraded between 4 and 10 days of incubation, when higher WB amount was applied (33.3 mm). Sucessive WBD use caused degradation of organic matter remaning of previous application. Higher CO2 evolutions were obtained for Oxisol treatments due to higher carbon contents of this soil. SW use caused depletion of Ultisol native organic matter. However, the WB use in Oxisol provided accumulation of organic matter. Soon, the respirometry test evidenced the importance of evaluate the soil depuration capacity before agricultural use, since that this process can affect the contents of organic matter native of these soils and the availabity of nutrient/contaminant for soil-water-plant system.