NITROGEN FERTILIZATION OF ONION IN SANDY SOILS

This investigation was conducted at Ismailia, Agricultural Resea‌rch Station, during the two growing seasons 1994/95 and 1995/96 to study the response of onion plants (Allium cepa L.) grown in sandy soil to nitrogenous fertilization as urea foliar spray at the rate of 2.30, 3.45 and 4.60 kg N/f alone or in combination with soil applied N (60, 90 and 120 kg N/f.) comparing with the N recommended rate (150 kg N/f) in the form of ammonium sulphate (20.6% N). The results revealed the following: 1.Nitrogenous fertilization as soil application in combination with foliar application at high N level significantly increased plant hieght, num‌ber of leaves, fresh and dry weights of the whole onion plant, com‌pared to foliar application of urea only. However, bulbing ratio was higher with foliar application alone followed by soil N recommended level (1 50 kg/f). 2.Total yield and average weight of bulb were also significantly in‌creased with the combination of the highest N (4.6 kg N foliar as urea + 120 kg N/f.). However, the highest value of dry weight per‌centage was achieved with the highest level of urea as foliar applica‌tion (4.45 kg N/f.) in combination with the lowest level of soil appli‌cation N (60 kg N/f.) Foliar application of 4.6 kg N as urea with soil N application at any level gave the highest values of total soluble solids (T.S.S.). 3.Soil N application in combination with foliar spray at higher level (4.6 kg N/f.) significantly increased nitrogen percentage at harvest and N, P and K uptake of onion plant after 100 days from sowing. How-ever, at harvest, P percentage was significantly increased only by fo‌liar spray, but K percentage was not significantly affected.