ESTIMATING ACTUAL EVAPOTRANSPIRATION AND WATER STRESS COEFFICIENT FOR GROUNDNUT CROP UNDER DIFFERENT SALT CONCENTRATIONS IN SANDY SOIL

Abstract

Field experimental was conducted to study the influence of different irrigation water salinity levels on actual evapotranspiration, water stress coefficient, yield and water use efficiency for groundnut crop under trickle irrigation system in sandy soil located at 30o 24` N latitude, 31o 35` E longitude while the altitude is 20m above the sea level. Four irrigation water salinity levels were used; 2.4 (S1), 2.7 (S2), 3.3 (S3) and 4.4 (S4) dS m-1, beside a fresh water (FW) as a control (0.5 dS m-1). Cattle manure was added as a soil amendment as a rate of 48 m3 ha-1. Neutron moisture meter was used to determine soil moisture content and depilation through the soil depths of 30, 45, 60, 75 and 90cm. Soil moisture content of 15 cm soil depth was determined gravimetrically. The applied irrigation water was 700 mm/season based on 100 % of recommended crop water requirements according to FAO Irrigation and Drainage Paper No.33. The obtained results showed that actual evapotranspiration (ETa) and water stress coefficient (Ks) were slightly deceased by increasing the salinity of irrigation water especially under S4 salinity treatment (4.4 dS m-1). Regarding the yield, water use efficiency (WUE) and irrigation water use efficiency (IWUE) of groundnut crop, the high salinity of irrigation water reduced both yield; WUE and IWUE. The yield of groundnut follows the order FW (3.89 ton ha-1) > S1 (2.19 ton ha-1) > S2 (1.63 ton ha-1) > S3 (1.54 ton ha-1) > S4 (1.19 ton ha-1). Concerning soil chemical properties; the salinity of irrigation water significantly increased soil (ECe). This increment was reached 6 fold of that found for soils irrigated with fresh water.