THE EFFECT OF SALINE IRRIGATION WATER ON SHAMOUTI ORANGES
- To study the effect of different water quality on salt accumulation and on the chemical and physical properties of the soil in the Mediterranean climate.
- To evaluate the response of Shamouti oranges to variable salinity in the irrigation water.
- To study the effects of the irrigation system (partial soil wetting with microsprayers versus complete wetting with sprinklers) and chemical amendments (potassium as K2SO4 and nitrate as KNO3) in minimizing the salinity hazard in citrus production.
The following results have been obtained till now:
After the heavy rainfall of the winter of 1982/83 (700 mm) almost all the salts accumulated during the irrigation season were leached out of the root zone. Low rainfall during subsequent years (300–360 mm) caused only partial leaching of salts. During the first two years no appreciable effects on tree growth, fruit yield and quality were found. During the summer of 1984 tree growth as measured by increase in cross-section of main branches was retarded in the plots receiving the high level of salinity (450 mg Cl/l). Leaf water potential before irrigation was lower in the high salinity treatment because of salt stress. Fruit yield in 1984/85 was lowered significantly by salinity -78, 73 and 68 Mg ha-1 for the 100, 250 and 450 mg Cl L-1 treatments, respectively. Chloride concentration in leaves and fruit juice were increased slightly by increased salt content of the irrigation water but fruit quality was not impaired.
It is not clear at this time whether these effects on trees and fruits were cumulative or caused by lack of complete salt leaching during the previous rainy season.