Water Economy and Saline Water Use by Drip Irrigation1

Abstract In arid regions water is scarce and efficient use of poor quality water by means of drip irrigation has become a necessity. Drip irrigation with good quality water at 1.0, 0.75, and 0.5 and with saline water at 1.0 times the daily evapotranspiration (ET) rate was compared with furrow irrigation using sweet water applied at the rate 1.0 ET with respect to the yield of potatoes ( Solanum tuberosum L.) on a loamy sand soil. Drip irrigation with sweet and with saline water at the rate equal to 1.0 ET was also evaluated with respect to the yield of tomatoes ( Lycopersicon esculentum Mill.). Water was applied daily by drip irrigation and at intervals of about 7 days by furrow irrigation in amounts equal to 63% of Class A pan evaporation. Drip irrigation at a rate less than the ET rate decreased the yield of potatoes compared with the rate equal to ET. To obtain identical yields, drip irrigation required 50% less water than furrow irrigation. Saline water at 3,000 μmhos/cm applied by drip irrigation did not limit yields but at 10,000 μmhos/cm it reduced potato yields by 91% and tomato yields by 35%. The soil water content was about 15% beneath the emitter, 7% at a point 20 cm from the lateral, and 3 to 4% near the wetting front located 40 cm from the lateral. The wetted zone, extending 20 cm on either side of the lateral, could be used for twin‐row configurations. Salts were concentrated in the surface 15 to 20 cm of soil at the midpoint between the emitters and towards the wetting front. Salts were not leached to lower soil horizons with the treatments used in these experiments.