Assessing nitrogen mineralization from soil organic matter by routine procedures

Careful management of N in agriculture is important for plant and environment since both N deficiency and surplus of mineral N after crop harvest need to be avoided. As mineralization of N from soil organic matter remains an important source for plant uptake, reliable prediction of N from this pool is crucial to meet nutrient availability and crop needs. This study was developed working on nine dissimilar agricultural soils collected across Europe, in Italy, Poland, Denmark, Portugal, Slovakia, Czech Republic. Aerobic incubation was performed in triplicate over 24 weeks at 25°C. Net N mineralization was determined each two weeks. After 3 weeks of pre-incubation, cumulative values of mineral N showed a linear trend over the 24 weeks period. The relationship between N mineralization rate and organic C of the soil, representing the quantity of the organic pool, was poor, especially due to the three soils whose mineralization rates were much lower than the other soils. For the nine dissimilar soils, the net mineralization was very well explained (r2=0.98) by 2 parameters that can be measured in a laboratory routine basis: the organic N content (quantity of the pool) and the C/N ratio of the organic matter (quality of the pool).