An agropastoral system as a practice to enhance organic matter in Lebanese inland mountainous soils

Organic matter (OM) is an essential soil component that results from the decomposition and decay of plant and animal materials. Decomposition processes are influenced by several biotic and abiotic factors. The Lebanese inland regions are characterized by low rain and elevated temperature. Soil formation and evolution occur under dry conditions and rare vegetation cover. Due to the absence or insufficiency of plant residues and frequent cultivation, the soils of the eastern mountain chain are characterized by low OM content. Given the importance granted to carbon sequestration in view of climate change and the importance of OM in soil fertility and resilience to erosion, the aim of this work is to assess the soil organic matter (SOM) levels by following an agropastoral system consisting of growing feed crops between the fruit trees as winter cover crops. A two-year study between 2009 and 2010 was conducted in Jurd Aarsal, Anti- Lebanon, to assess the biomass production from cover crop in orchards and to estimate the potential increase of SOM content in plots planted with legume species (Vicia sp., Lathyrus sp.) and barley (Hordeum vulgare). Soil and plant samples were taken from 7 orchards ranging in altitude between 2016m and 2 236m. SOM was analyzed in composite samples before and after the experiment. Plant samples were collected throughout the season to assess the dry matter production. Result showed that the sites were supplemented with OM varying between 140 and 250 kg ha-1season-1 resulting from the decomposition of plant root residues. The above-ground plants provided the orchards with 95-665.7 kg ha-1season-1 of OM. It is suggested to follow the practice of winter cover leguminous fodder crop between fruit trees, in dry Lebanese regions, in order to provide additional biomass for small ruminants, enrich the soils with OM and fixed nitrogen and better use of surface soil moisture.