Effect of some climatic factors and irrigation regimes on tomato growth and chemical constituents

This work was performed in 2012 and 2013 seasons at El- Bostan Protected Cultivation Experimental Site, Agricultural Research Center. The aim of the study was to investigate the growth of tomato plants under  various shading densities and water regimes. Tomato variety (V.T.916) F1 hybrid was used. Tomato seeds were sown on 1^st of March during both seasons of 2012 and 2013, in multi-pot transplant. Treatments used were four different levels of shade net (73%,60% and 40%) in addition to the control( without shading).  Three water regimes which were tested as follow: 120%, 100% and 80% from class A pan. Results indicated that the application of 73% shading was the most effective in reducing average air temperature and radiation, followed by 60%, and finally 40%. On the other hand, the highest values of air temperature and radiation were observed in the control treatment throughout the two growing seasons. In addition, 73% of shade density reflected the highest values of all growth aspects such as plant height, stem diameter, number of leaves and stems, fresh and dry weight of leaves and except stem diameter compared to the unshaded treatment. As for the effect of irrigation regime on vegetative growth parameters, using the highest level of irrigation water (120% of water requirement) reflected the highest values in all determined growth parameters. With regard to the effect of the interaction between shading densities and irrigation regimes on the vegetative growth traits of tomato plants grown under sandy soil conditions. Shaded plants at 73% shade density and irrigated with the highest level of irrigation water (120% of water requirement) exhibited the highest vegetative growth measurements except stem diameter. Moreover, shaded plants with the highest used level of shade (73%) exhibited the highest content of total nitrogen, phosphorus, potassium and carbohydrates content compared with the medium (60%) and low level of shading 40%.  In addition, the highest levels of irrigation water (120% of water requirement) reflected the highest values of such elements. In this connection, the highest shading density (73%) combined with the highest level of irrigation water (120% of water requirement) led to the highest concentration of all assayed mineral macronutrients (N, P and K) or organic constituents (carbohydrates) in tomato leaves