495 Nitrate Accumulation, Growth, Yield and chemical composition of Rocket (Eruca vesicaria subsp. Sativa) plant as affected by NPK fertilization, Kinetin and Salicylic Acid * Hanafy Ahmed, A. H.; *Khalil, M.K. and **Farrag, Amal M. * Plant Physiology Section and **Vegetable Department, Faculty of Agriculture, Cairo University, Giza, Egypt. ABSTRACT In two field experiments, rocket (Eruca vesicaria subsp. sativa) plants were fertilized with low or high nitrogen level as the main plot. Sub-main treatments included; control, double phosphorus (2P), double potassium (2K) and 2K+2P as soil fertilization as well as kinetin (25 and 50 ppm) and salicylic acid (50 and 100 ppm) as foliar application. High level of nitrogen fertilization increased the fresh yield of rocket leaves by 50.0 and 16.4% in the 1st and 2nd cuts, respectively, while these increases in dry yield were 31.6 and 16.8%, respectively as compared to their low nitrogen levels control values. Sub-main treatments of 2P, 2K, 2P+2K, kinetin (25 and 50 ppm) and salicylic acid (50 and 100 ppm) increased both fresh and dry yield of rocket leaves in both 1st and 2nd cuts. The highest percentage increase in total fresh and dry yield were obtained from the treatment with kinetin at the rates of 25 and 50 ppm. Nitrate concentration in the leaf petioles of rocket plant was significantly increased by 41.2 and 75.0% in both 1st and 2nd cut, respectively when fertilized with the high level of nitrogen, while all sub-main treatments significantly decreased it in the 1st cut. Whereas the treatments kinetin (25 and 50 ppm) and salicylic acid (50 ppm) significantly decreased nitrate concentration in the 2nd cut. High nitrogen fertilization increased total nitrogen concentration in the leaves of rocket plant in both cuts. All sub-main treatments, increased total nitrogen concentration in the in the leaves of rocket plants in the 2nd cut. Phosphorus concentration in the leaves of rocket plants decreased as a result of high nitrogen fertilization in both cuts. Treatments of 2P, 2K, 2P+2K and kinetin at 25 ppm increased phosphorus concentration in the leaves of rocket plants in both cuts, while salicylic acid treatments decreased it only in the 2nd cut. Potassium concentration was slightly increased when plants were fertilized with the high nitrogen level, while the treatments kinetin (25 and 50 ppm) and salicylic acid (50 and 100 ppm) slightly resulted in decreasing it in the 1st cut. High nitrogen level fertilization and kinetin (50 ppm) slightly increased iron concentrations in both 1st and 2nd cut. Low values for both manganese and zinc concentrations were observed due to high nitrogen fertilization in the 2nd cut, while salicylic acid treatments at 50 and 100 ppm increased their concentrations, specially in the 2nd cut. Soluble sugars concentrations (reducing, non-reducing and total) in the leaves of rocket plant were decreased when fertilized with the high level of nitrogen, while kinetin at 50 ppm showed the highest increase in these components in both 1st and 2nd cuts. Total free amino acids were increased with the high level of nitrogen fertilization, while all sub-main treatments, except for salicylic acid in the 1st cut and 2P in the 2nd cut, decreased it. High nitrogen fertilization decreased soluble phenols in both 1st and 2nd cut, while the sub-main treatments, kinetin (25 and 50 ppm) and salicylic acid (50 and 100 ppm) increased it by 6.9, 6.9, 18.1 and 8.1%, respectively in the 1st cut. No differences were observed in soluble phenols concentrations in the 2nd cut, except for the treatment salicylic acid at 100 ppm where it was decreased by 28.0%. INTRODUCTION Rocket (Eruca vesicaria subsp. sativa) plant fresh leaves are consumed by the Egyptian public as fresh green salad. About 5000 feddan are cultivated with rocket plants in Egypt. Besides its importance as green salad available all over the year, rocket seeds contain oil which is promising to be medicinal oil. Recently, a problem facing the fresh vegetables is nitrate accumulation due to its uptake from the soil. A major source of nitrate in the soil is the nitrification process through the nitrifying organisms. Tests of nitrate accumulation in Egyptian vegetables showed considerable high values as compared to those found in vegetables grown in several European countries (Blom-Zandstra, 1989; Kheir et al., 1991; Hanafy Ahmed, 1996 and Hanafy Ahmed, et al., 1997), in spite of the high intensity and long duration of light in Egypt which favors nitrate redution in plants. This could be mainly due to the intensive application of nitrogen fertilizers carried out by the Egyptian farmers which results in imbalance nutritional status of the plants and consequently high nitrate accumulation. Nitrite may be accumulated from NO 3 after ingestion, causing methaemoglobinemia (Wright and Davison, 1964). Presence of NO 2 in blood might result also in the formation of nitroseamines, which are carcinogenic (Craddock, 1983). Reduction of nitrate accumulation in fresh vegetable crops became an important task which might be affected through specific treatments. Such treatments include the application of A. H. HanafyAhmed et al. / ICEHM2000, Cairo University, Egypt, September, 2000, page 495- 508