Soil organic matter (SOM) quantity and characteristics strongly affect soil fertility, crop production, soil microbial community composition and carbon sequestration in terrestrial ecosystems. Distinct SOM fractions that are extractable with chemical salt solutions (e.g. organic carbon and nitrogen fractions extractable with 0.01 M CaCl2, 2M KCl, or water) have been used to assess the biochemical properties of SOM, in particular its ability to supply N.

However, none of these extractable OM fractions has been proven as an universally applicable indicator of the soils’ capacity to supply N by mineralization and still substantial uncertainty exists on the role of these extractable fractions in the N cycle. Hence, in spite of the significant efforts during last decades, one of the major goals of soil N research, that of being able to predict soil N supply and fertilizer N needs, has not been adequately achieved. The lack of universal adoption of an extraction method as a predictor of soil N mineralization may be due to the huge variation among study methods, temporal and spatial variation in agricultural fields and climatic, soil and farming conditions, a lack of mechanistic research, and unsuitable statistical analysis of the data. Although numerous papers have been published, a lack of consensus on the most appropriate method for predicting N mineralization from soils remains, largely due to these challenges.

An interdisciplinary approach that combines perspectives from soil chemistry, soil physics, microbiology, plant sciences, and computer modelling, may provide a way forward to address this issue. We solicit presentations that address relationships between measures of extractable organic matter and soil N supply, and address the dependency of these measures on climate, soil properties, management history, and cropping systems. Presentations addressing the issue how to measure soil N supply (e.g., incubation or field studies, determination of gross or net mineralization rates, or potentially mineralizable N pools) are also welcome.

We are particularly interested in mechanistic approaches to research that explore the biochemical basis for observed relationships, innovative approaches to improve the accuracy of predictions of mineralizable N in the field, application of new analytical and statistical methods to identify appropriate extractable OM fractions, and modelling tools to match crop demand with soil N supply. In addition to soil scientists, we encourage plant scientists, ecologists, environmental microbiologists, and others interested in this topic to submit their work.