IMPACT OF WATER STRESS DURING DIFFERENT GROWTH STAGES ON TOMATO YIELD UNDER VARIOUS IRRIGATION SYSTEMS

Field experiment was carried out at Maryout Experimental Station Farm, Desert Research Center during summer season 2007. The field experiment amid to study the impact of water stress levels of 100, 75 and 50 % from crop evapotranspiration, ETc during development, flowering and harvesting stages on some plant growth parameters and yield of tomatoes (Lycopersicon esculentum, mill., cultivator 888) in calcareous sandy clay loam soil. Drip and gated-pipe irrigation systems were used in this investigation. Generally, the obtained results revealed that the plant height values at harvesting growth stage under drip irrigation system were not significantly lower than those obtained under gated pipe irrigation system. The plant height values subjected to irrigation water stress levels 100, 75 and 50 % ETc during different growth stages were significantly decreased with increasing irrigation water stress levels under the studied irrigation systems. Tomatoes leaf water potential values,-kPa, at harvesting growth stage were significantly increased with increasing irrigation water stress levels subjected during different growth stages under studied irrigation systems. The fruit yield of tomatoes as affected by irrigation water stress levels subjected during different growth stages under drip irrigation system were significantly higher than that obtained under gated pipe irrigation system. Also, fruit yields of tomatoes were significantly decreased with increasing irrigation water stress levels under studied irrigation systems, especially at water stress level of 50 % ETc. For the fruit yield, the results showed that the flowering growth stage of tomatoes subjected to irrigation water stress levels is more sensitive than other growth stages under studied irrigation systems. Consequently, tomato plants subjected to water stress levels during flowering growth stage achieved the lowest net revenues and invested pound return.