Rates of Nitrogen Mineralization of Meat and Bone Meals in Mediterranean Soils
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Animal by-products such as meat and bone meals are now certified as free from bovine spongiform encephalopathy (BSE), and their use as organic fertilizers is considered safe again. Given that knowing the rates at which their nutrients are released is key to efficient use, nitrogen (N) mineralization in Mediterranean soils fertilized with meat and bone meals (MBMs) has been studied by means of 12 incubation experiments using three soils of different textures and organic-matter contents and five MBMs of varied origin and characteristics. After the application of the organic products, the amounts of mineral N released after 2, 4, 8, 12, 16, 20, and 35 weeks of aerobic incubation at 25 degrees C were measured and the data were adjusted to first-order reaction kinetics. In all cases, the results were consistent with the assumption of N mineralization being a first-order reaction with k constants ranging from 0.177 week(-1) to 1.603 week(-1). Mineralization was fast, with most of the N release taking place during the first 5-10 weeks of the incubations. Despite the different origin and characteristics of the MBMs compared in the experiment, soil type was the most influential factor in the mineralization process. The N mineralization rates were greater in the loam soil, suggesting a relevant role of enzymes immobilized in inorganic colloids such as clay.