Using soil incubations to interpret and predict soil-plant nitrogen dynamics under real field conditions

A proper management of Mediterranean agro-ecosystems should be aimed at building-up soil organic matter content, in order to cope with the decline of soil fertility due to high mineralization rates. Organic fertilization, like compost amendment, may be considered to reach this goal, but there is a need for specific tools to monitor N availability from fertilizers together with their effect on soil biological fertility. In this work, chemical and microbiological indices from soil incubations were evaluated as predictors of crop performance under real conditions. Results from field and laboratory experiments showed some discrepancies for organic fertilization, while mineral N availability and maize N uptake were found in accordance for non-fertilized soils and mineral fertilization. Cumulative mineral N from a 42-day incubation period was a good predictor of N availability to maize, showing that short-term incubations can be used to optimize fertilization management. Moreover, the dynamics of microbial populations involved in the N cycle were able to discriminate between soils with different N mineralization potential, highlighting the effect of fertilization and soil properties on biological fertility.