Emergy Synthesis as a Tool to Assess Soil Quality Change

The concern about soil quality has increased, since its use and intense mobilization may decreased its ability to keep a biological and sustainable production. However, since soil quality cannot be comprehensively measured by a single indicator, emergy synthesis rises as an alternative to assess this issue. This study aimed to present a comparative method for soil quality vis-a-vis the resource demand on intensified biomass production. For this purpose we used environmental accounting, converting inputs (environmental, material and labor) to emergy units. The largest contributions for the total purchased emergy inputs in sugarcane production (3.8E+15 sej) were diesel, limestone, gypsum, nitrogen and phosphorus with 27.38 %, 25.45 %, 13.25 %, 11.52 % and 11.31 % respectively. Diesel and limestone are obtained from petroleum and mining deposits, explaining the largest fractions of emergy, and gypsum, obtained from the manufacture of phosphoric acid, used for the production of triple superphosphate, monoammonium phosphate and diammonium phosphate. The higher biomass production due to the use of inputs shows lower embodiment of resources per unit of mass (sej Mg), whose yield increase is higher. Typic Hapludox soil presented 11.7 % more additional biomass production and 13.2 % less additional input demand than Arenic Hapludult soil, due to better fertility conditions. Indicators based on emergy synthesis are able to support analyses of land use change for intensive biomass production, since it showed to be a promising tool for evaluating soil quality change.