Carbon and nitrogen balances and CO₂ emission after exogenous organic matter application in arid soil

Addition of organic amendments (OAs) could be a means to sequester carbon (C) in soils. However, the efficiency of C sequestration depends on how OAs evolve in the soil. A field study was installed in arid soil to which was added one of five OAs – olive husk-based compost (CM), palm leaf-based compost (CP), crushed olive pruning (GW), fresh olive mill wastewater (OMW) or fermented ovine manure (OM) – at an equivalent fixed level of 350 g of C/m2. C and N mineralization were followed for 112 days by measuring the evolution of released CO2 and mineral N evolution. The results showed that CM and CP did not disturb soil respiration, with a very low CO2 emission or almost no respiration for the CM, while CO2 release reached 7.6 g of CO2/m2 for GW and OMW. Soil organic carbon (SOC) was sustainably improved by 0.54% and 0.50%, respectively, for CM and CP. N mineralization showed no significant difference between amended and untreated soils. Based on these results, compost amendment was the most efficient for C sequestration to enhance soil fertility and consequently reduce the rate of CO2 emission.