INFLUENCE OF ORGANIC AND INORGANIC FERTILIZERS ON SOIL NUTRIENTS AVAILABILITY AND WHEAT PRODUCTIVITY.

Soils degraded physically and nutritionally due to continuous use of chemical fertilizers under intensive agricultural. Management of N is the key for sustainable and profitable wheat production in a low N-soil availability. So a field experiment was conducted on a clay soil using wheat (Triticum aestivum) Giza 168 variety during 2008 / 2009 season at Agricultural Experimental Station of Fac. Agric, Mansoura Univ., to study the influence of combined use of mineral fertilizers (urea) and organic fertilizers in the form of farmyard manure (FYM), composted rice straw (CRS) and their combinations on wheat productivity, nutrients availability and monitoring soil organic matter (SOM) status in soil at certain times 45, 88 and 155 days from wheat planting. The randomize complete blocks design with three replications was used. The mineral fertilizer (urea) was applied at the rate of N₁=60 and N₂=120 kg urea fed^-1.The amounts of various organic fertilizers used were (10 and 20 m³ fed^-1), for both FYM and CRS. Organic fertilizers added either alone or in combinations with urea to the soil. Results indicated that the maximum increase in grain yield (54.66 and 56.55 % over untreated control) and straw yield (1660.50 and 1710.99 g.m²) were recorded with N₂FYM₂ and N₂CRS₂ respectively. All combination of organic (FYM or CRS) and inorganic fertilizers gave the optimum availability of NH₄⁺, NO₃^-, P, K concentration in soil beside the enhancement of soil organic  matter percentage (SOM) as compared to the other treatments.