Effect of land management on incorporation of prickly pear crop residues in different soil organic matter fractions of a Sicilian soil under desertification risk

The return of organic amendments and plants residues to the soil is a fundamental measure for carbon (C) accrual in soil, in particular in agroecosystems of Southern Mediterranean areas, where aridity limits plant growth and litter inputs as well as soil organic matter (SOM) decomposition, often resulting in land degradation and desertification risk. The allocation of this residual C in SOM fractions which are more prone to fast mineralization, at the onset of the rainy season, might significantly vary with the quality of the residues and the type of land management. The extent of residues incorporation is also relevant as it increase the SOM-microbial interactions responsible of SOM processing, mineralization and stabilization. We investigated the effect of two types of land management, no tillage and minimum tillage, on the incorporation of C from a list studied soil amendment, pruned prickly pear cladode residues, in the SOM of the same crop site, and its distribution in the particulate organic and mineral associated organic matter fractions. The characteristics ¹³C signature of the Opuntia ficus-indica (L.) Mill, which is an obligate CAM plant, was used to identify which of the two soil management practices was more effective in storing more C and of a more stable form along the soil profile (0-30 cm). Two adjacent cactus plantation located in southern Sicily, were used, where the different land management was maintained in the last 10 years. The analysis was part of the measures of adaptation investigated by the project Desert-Adapt (LIFE16 CCA/IT/000011) in areas under desertification risk.