ENZYMATIC-ACTIVITIES IN A SOIL AMENDED WITH ORGANIC WASTES AT SEMIARID FIELD CONDITIONS

A field experiment to determine changes in soil enzymatic activities responding to various fertilizer applications was carried out at semiarid climatic conditions in central Spain. The field was cultivated with barley, and compost of municipal solid waste at amounts of 20 and 80 Mg ha(-1) was added and compared with mineral fertilizer and cow manure (20 Mg ha(-1)) additions. Enzymatic activities ill the soil: urease, phosphatase, N-alpha-benzoyl-L-argininamide (BAA) hydrolyzing, and casein hydrolyzing activities were determinated at earing (April) and harvest rimes (end of June). Enzymatic activities were higher at earing than at harvest time, due to favorable environmental conditions. Soils with compost at two application amounts (20 and 80 Mg ha(-1)) displayed the highest values of urease and BAA hydrolizing activities, and the urease activity was positively correlated (p less than or equal to 0.05) with the C and N amount in the soil at earing lime. At harvest time, all enzymatic activity values decreased to levels equal to control soil, except for casein hydrolyzing protease. The latter activity was positively correlated (p less than or equal to 0.05) with the grain yield.