Comparison of different laboratory incubation procedures to evaluate nitrogen mineralization in soils amended with aerobic and anaerobic stabilized organic materials

Abstract

The suitability of three biological laboratory methods to assess N mineralization of differently amended soils was evaluated. In more detail, two representative soils of southern Italy agricultural area with different physico-chemical characteristics were amended with four organic materials (two composts, blood meal and an anaerobic digestate from wine industry) and incubated in laboratory conditions according to three different procedures: i) dynamic aerobic; ii) static aerobic and iii) anaerobic static incubation. Results obtained demonstrated that N mineralization in potential condition was affected by soil texture, the values obtained for the clay textured soil being significantly higher (9%) than those in the silty-clay textured one. Moreover, the two aerobic methods tested were able to differentiate potential N mineralization of organic materials characterized by a wide range of chemical properties, contributing to foresee the amendments potential to release available N to crops. Conversely, the aerobic static procedure did not always furnish interpretable outcomes since anaerobic procedure failed in evaluating N mineralization of anaerobically stabilized organic amendments. At the end of incubation, the soil-blood meal mixture mineralized the highest amount of N (211 mg kg-1 of soil), followed by the soil-anaerobic digestate mixture (72 mg kg-1 of soil). Furthermore, both the two different soil-compost mixtures showed net N immobilization. Hence, the four organic amendments studied were ranked on the basis of their potential to release mineral nitrogen.