Influence of Groundwater Irrigation on Chemical Properties of Soils in the Vicinity of Wastewater Drainage Canals in Al-Ahsa Oasis, Saudi Arabia

摘要

Presently, irrigated agriculture in the Oasis is facing problems of high water infiltration rate, poor drainage, low rainfall and high evaporative conditions resulting in the formation of sabkha lands and above all of that a degradation in irrigation water quality. A field study was carried to determine the influence of groundwater irrigation on chemical properties of soils in the vicinity of main drainage canals. Soil and water samples were collected from 19 irrigated farms and 18 wells. The total salinity of 42% soil samples was less than 4 dS m-1 (a category of non-saline soils) and that of 58% soil samples was above 4 dS m-1 (a category of medium to highly saline soils). Inter-ions relationship was strong among major cations and anions such as Ca, Mg and Na with HCO3, Cl and SO4 radicals. Well waters were classified as C4S1 (very high salinity and low sodium) to C4S4 (very high salinity and very high sodium) waters for irrigation purpose. The order of abundance of cations was Na>Ca>Mg>K while those of anions was Cl>SO4>HCO3. The inter-ions relationship of well waters was very poor. In conclusion, irrigating soils with high salinity well waters can develop saline soils and need to adopt certain soil and water management practices such as leaching application, cultivation of salt tolerant crops and improved irrigation systems.