NITROGEN BALANCE IN SOIL PROFILE AS AFFECTED BY DIFFERENT SOIL TYPE, SOIL WATER REGIMES, NITROGEN RATE AND APPLICATION METHODS USING 15N TRACER TECHNIQUE

The interaction effect of “Soil type, Soil water regime, Nitrogen fertilizer application Rates and Timing” on Nitrogen balancein soil were studied; in terms of nitrogen gained by plant portions, remained in soil, and losses through different ways under wheat (Triticum aestivum L. Giza 168), in order to identify the most proper and effective combinations of above-studied variables that provides a satisfactory grain wheat yield and minimizes the use of chemical nitrogen fertilizers, to save the surrounding environment and to achieve good water saving. Two fields of experiments were carried out during November and December –April 2012-13, under Egyptian conditionsrepresents two different textured soils, i.e clay located at (30o 16- N latitude, 30o 56- E longitude), and sand soils located at (30o 24- N latitude, 31o 35- E longitude) as growth media of wheat crop. The application methods of Nitrogen rates, 100, 80 and 60% of recommended rates (Clay, 178 kg N & Sand, 238 kg N), were applied as Mode A, 25% at seedling, 25% and tillering, 50% at jointing AND Mode B, 35% at seedling, 65% at tillering.