Labile, recalcitrant and stable soil organic carbon: comparison of agronomic management in a vineyard of Trentino (Italy)

Abstract

The intensive exploitation of agricultural land has caused a depletion of soil organic carbon (SOC) and a decline in soil fertility, with a consequent decrease in the productivity of agroecosystems, also contributing to atmospheric GHG emissions. The ability of soil to storage organic carbon (OC) depends on its persistence and susceptibility to decomposition. SOC is generally partitioned into fractions differing in protection mechanisms and in turn decomposability. This study aimed to compare the OC pool repartition in soils managed with three different fertilization practices (mineral – CONV, manure – ORGM and green manure – ORG-GM) during a medium-term trial in vineyard, in order to understand the best solution in increasing C sequestration. The OC fractionation by acid hydrolysis allowed separating three fractions of OC: a labile, quickly mineralizable pool, a recalcitrant pool with a slower turnover and a stable pool protected by microbial attack. The results showed that the periodic application of organic matrices (manure and green manure), although did not increase total OC, enriched the soil along time with readily available OC, thus promoting the release of nutrients. Green manure has also been shown to promote the accumulation of stabilized OC, able to improve the structure of the soil and, therefore, its fertility.