The 2010 ASHS Annual Conference

Two field experiments were conducted in two years 2008 and 2009 at the Agricultural Research Station of King Abdulaziz University in Hada Al-Sham, North East of Jeddah, Saudi Arabia  to test the effects of different concentration levels of nitrogen fertilizer (urea) and irrigation water intervals (water deficit stress) on plant growth of some tomato cultivars at different stages of plant growth and production. The results showed that water deficit regime caused reduction in plant growth (plant height, stem diameter, number of branches/plant and number of leaves/plant).

Water deficit also reduced number of clusters, flowers, and fruits/plant and reduced fruit mean weight and total yields of tomato cultivars. It also affected fruit length, diameter and sizes as well as wall thickness and number of lacules/fruit. Water deficit influenced vitamin C contents, acidity and total soluble solids in the fruit juice. The dry matter of vegetative and roots system was reduced due to the stress of water deficit.

Nitrogen fertilizer increased the vegetative growth of tomato plants, such as plant height, diameter, number of leaves and number of branches/plant. Number of clusters, flowers, fruits/plant were also increased with increasing the concentration levels of nitrogen. Fruit mean weight and yield of tomato cultivars and fruit length, diameter and sizes increased with high level of nitrogen. Dry matter of vegetative and root system increased with nitrogen fertilizer.

The responses of the tomato cultivars to water deficit stress and nitrogen concentration levels were greatly varied. Further investigations are needed using more (other) tomato cultivars to make better choice in selecting a cultivar, line, or hybrid for breeding program leading to the selection of a water deficit tolerable cultivar and to get the best efficiency of nitrogen utilization.