ABSTRACT
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[-1]season[-1] resulting from the decomposition of plant root residues. The above-ground plants provided the orchards with 95-665.7 kg ha[-1]season[-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
ABSTRACT
The Central Bekaa plain constitutes the main region with prime agricultural land in Lebanon. The agricultural sector is the main consumer of available water resources [up to 70%]. Intensive agriculture, urban expansion and industrial activity have been increasingly stressing the limited soil and water resources. In the Central Bekaa, farmers are enforced to use contaminated water to recompense water shortage during the peak crop demands. Water scarcity and mismanagement increased contagion hazards and pressure on soil and groundwater quality. The objective of this study was to provide a synopsis of the assessment methodologies and analyze the soil-groundwater vulnerability to contamination by heavy metals as based on the risks of metal transfer and the degree of protection offered by the soil cover and soil-metal interaction. The soils of the area are distinguished by a high content of clay and relatively high pH that would reduce the danger of heavy metals transfer and mobility. However, throughout the study area, the perched groundwater table is relatively high with a depth varying between 60 and 500 cm making it highly vulnerable to pollution. Metals might be more mobile under reducing conditions. The area of high, medium and low soil and groundwater table vulnerability were determined and spatially located according to international standards. Referring to the German Concept on soil protection effectiveness, the residence time of percolating water carrying soluble pollutants in the unsaturated soil zone was assessed. It varied between several months and 10 years. Zones of high soil and ground water vulnerability risk require special management to establish pollution prevention programs. Results can help land use planning oriented to the choice of suitable crops, promulgate sustainable use of natural resources and environmental preservation