MAXIMIZING USE EFFICIENCY OF MINERAL NFERTILIZATION FOR SPINACH an‎d ROCKET PLANTS

Two field experiments were conducted at the experimental farm of Faculty of Agricultural., Mansoura Univ. during the successive winter seasons of 2009-2010 and 2010-2011 to investigate some of the available options to reduce the losses and increase the efficiency of N-fertilization for Spinach (Spinacia Oleracea) and Rocket (Eurco Visicaria L.) plants. Thirty treatments were arranged in split-split block design, which were the simple possible combination between five treatments of mineral N, i.e ammonium nitrate (AN), AN+inhibitor (DCD), Urea (U), U+DCD and calcium nitrate (Ca-N) as a control treatment at the rate of 60 kgN/fad were arranged in the main plots. Treatments of N-fertilization were divided into 2, 3 or 4 doses and adapted as subplots. Two methods of N-applied were allocated as sub-sub plots, once as side dressing (SD) and the other as deep placement (DP). The results of these investigation indicated that ; the highest safe yield of spinach and rocket plants and the most suitable treatment for realizing the highest use efficiency can be obtained due to applying N-fertilizer in the form of urea plus nitrification inhibitor (DCD) as deep placement in four doses. The obtained data, also revealed that under any form of N-fertilization the contents of nitrate in the leaves of spinach and rocket plants in the absence of (DCD) were higher than that obtained in the presence of (DCD) as a nitrification inhibitor. The study highlighted that; the heighest NUE values were recorded for the plants fertilized with U+DCD and splitting N-fertilizer to four doses and applied using deep placement method for realizing the highest safe yield for spinach and rocket plants.