Nitrogen dynamics in a calcic petrocalcid soil from the SE Spain treated with an anaerobic sewage sludge compost

Addition of organic waste into the soil induces several changes under semi-arid ecosystem such as nutrient increase and improvement of physical and microbiological properties. Assessing the mineralisation dynamics of organic wastes is very important to establish the nutrient input, especially of N, to the soil. The mineralisation of N from anaerobic sewage sludge compost was studied in a semi-arid soil (sandy-clay-loam) treated with four different rates of this compost: 0, 5, 15 and 30 g compost kg(-1) soil. The N mineralisation from the organic compost was determined during 19 weeks incubation period by measuring the inorganic nitrogen produced. The increase rate of the amendment has increased the soil total and inorganic N ignificantly. The initial release of inorganic N was slow in the S+C-5 and S+C-15 treatments. The N mineralisation dynamic in amended soils followed the model proposed by Smith et al. (1980), with a high level of correlation between experimental and calculated values. Overall the potentially mineralisable N and N mineralisation rate increased with the rate of compost application.