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Towards an exergy methodology to assess the fertility of topsoil

Abstract:

Feeding a growing world population is threatened by soil degradation, which currently affects around 38% of the world's cropland. Soils are complex systems constituted by physical, chemical and biological properties. Due to the soil's complexity, the measure of degradation or fertility represents an unsolved problem. The degradation of soils is an important issue currently faced by humanity that can be accounted for using exergy. A methodology to calculate the exergy value enclosed in a fertile soil due to its inorganic, organic and biological components is developed in this study and will be used to assess soil fertility, degradation and quality. As a starting point, the exergy of an ideal topsoil with optimal attributes called "OPT soil" is established. The "OPT soil" is based on agronomic knowledge and will allow to establish a theoretical general line useful to perform exergy evaluations of the soil and compare the degradation degree of any soil with respect to the optimum. This paper establishes the factors that define the inorganic part of "OPT soil" and the methodology to calculate its exergy from Thanatia. Accordingly, we establish the first steps in order to allow the quantification of the quality of any soil and its degradation.