A COMPARISON BETWEEN CONTROLLED RELEASE an‎d SOLUBLE N-FERTILIZERS ON YIELD an‎d QUALITY OF TWO SUBSEQUENT VEGETABLE CROPS.

With increasing nitrogen unit price, the growers are begining to search about new methods for increasing nitrogen use efficiency. Consequently, this study was carried out to evaluate the efficiency of slow release nitrogen fertilizers on yield quantity and quality of two consecutive crops i.e., lettuce (Lactuca sativa L.) and jew's mallow (Corchorus olitorus L.) under furrow irrigation system. Two filed experiments were conducted at Kaha Hort. Res. Station, Kalyoubia Governorate, during two consecutive growing seasons (winter and summer seasons) 2007/2008 and 2008/2009. Results showed that sulfur coated urea (SCU) caused an increase in plant fresh weight and dry weight, yield as well as nitrogen and nitrate content of lettuce plants as compared with Ureaformaldehyde (UF) and traditional urea. The residual effect for Ureaformaldehyde increased the plant growth parameters, yield, nitrogen and nitrate content for jew's mallow. But, nitrate content in both crops did not exceed the critical concentration tolerated for human. On the other hand, the results show generally that increasing N-level from 30 to 90 kg/ fed. caused a marked increase in parameters under study for the two crops It can be concluded to use sulfur coated urea at 90 kg N/fed. is recommended to obtain the optimum yield with highest quality for lettuce plant. Also, the residual effect for this fertilizer was sufficient to obtain the optimum yield and quality of jew's mallow.