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.