Leaching and Water Requirement Studies in a Gypsiferous Desert Soil
1985
Russo, David
The relationships among irrigation regime, salt leaching and water uptake, and their effect on yields of bell pepper (Capsicum frutescens var. ‘Maor’) and tomatoes (Lycopersicon esculentum var. ‘Naama’) were studied in a gypsiferous desert soil. Trickle irrigation treatments (two irrigation frequencies: daily irrigation and irrigation every 4 d; and four different amounts of water, ranging from 0.6 to 2.2 times the Class A pan evaporation) were used to establish different leaching regimes. The changes in soil water content within the root zone were monitored by the neutron probe technique, and the vertical flux at the bottom of the root zone was determined from the hydraulic gradients (using tensiometers) and hydraulic conductivity values. Soil solution within the root zone was sampled by soil suction probes and was analyzed for electrolytic conductivity (EC), Cl⁻, and SO²⁻₄. The soil exchangeable sodium percentage (ESP) as well as the crop yields were also measured. Results showed that the different irrigation regimes produced different soil water profiles and different leaching fractions ranging from 0.09 to 0.53 which, in turn, affected the soil salinity profiles. Analysis of the soil solution ionic composition showed that with the higher levels of leaching, the excess chloride was essentially removed, whereas considerable sulphate concentration was maintained as a result of gypsum dissolution which was dominated by the changes in the soil's ESP. Both water uptake (evapotranspiration) and crop yields were closely correlated with the soil water and salinity profiles. This indicated that the effect of both salinity stress and water stress is to reduce crop water uptake and, concurrently, to reduce crop yield.
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