CHANGES IN THE ORGANIC-MATTER MINERALIZATION RATES OF AN ARID SOIL AFTER AMENDMENT WITH ORGANIC WASTES

This study examined the changes in organic matter mineralization when sir amendment rates of municipal solid waste, sewage sludge, and compo st were added to an arid soil. Short-time incubation assays were carri ed out in which the amount of CO2 emitted was measured. The kinetic an d mineralization constants of the organic matter were studied, as was the influence, of this amendment on the soil organic matter content. P otentially mineralizable C (C-0) in the municipal solid waste-amended soil was significantly higher than in the soil amended by sewage sludg e and compost and it increased (is the amendment rate of compost and s avage sludge increased. There was no direct relation between the incre ase in organic matter decomposition rate and the amount of organic ame ndments that were applied to the soil. The CO2 loss/total organic carb on (CO2 loss/TOC) ratio in the soils amended with fresh organic waste was significantly higher than in that amended with compost. The CO2 lo ss/TOC ratio also differed with amendment rare between fresh and compo sted wastes. The ratio rose slightly as the amendment rate of fresh wa stes increased up to 2%, after which it stabilized, whereas it decreas ed ar the amendment rate increased in the soils amended with compost. Linear fittings were made of the CO2 evoked as a function of dose for the different sampling rimes. The carbon mineralized increased in all treatments, more so in the soils amended with fresh wastes than in tho se amended with compost. The organic amendments resulted in a priming effect that was more pronounced during the first days of incubation an d differs according to the nature of the material added.