Organic Amendment for the Recovery of Vineyard Soils: Effects of a Single Application on Soil Properties over Two Years

Spent mushroom substrate (SMS) is the organic residue generated during mushroom cultivation, and it is being produced in ever-greater quantities around the world. Different applications for this residue have been proposed for its valorization, but its application as a soil amendment could be one of the most sustainable. SMS improves soil quality by increasing its organic matter (OM), thereby enhancing the sustainability of agricultural systems. The objective of this work was to evaluate the effect of the application of two doses of SMS on the chemical, biochemical, and microbiological characteristics of two degraded vineyard soils in La Rioja (Spain) with different textures, as a new regenerative agricultural practice. The variations in organic carbon (OC), micro- and macronutrients, soil microbial biomass (BIO), respiration (RES), dehydrogenase activity (DHA), and the profile of phospholipid fatty acids (PLFAs) extracted from the soils were evaluated over two years. An initial increase in soil OC content was recorded in both soils, although the content that remained over time differed for each site. In general, SMS enhanced DHA, RES, and BIO in the soils, but the effect varied, possibly being conditioned by the availability of OC for soil microorganisms. In general, changes in the soils' microbial structure after SMS application were not very significant over the two-year experimental period.