LONG-TERM USE EFFECT OF ORGANIC, INORGANIC FERTILIZERS AND CROP ROTATION THROUGH NINETEEN YEARS ON SOME SOIL PROPERTIES IN PERMANENT EXPERIMENT AT BAHTIM. 2. SOIL CHEMICAL PROPERTIES.

Representative disturbed soil samples of tow successive layers (0 – 30 and 30 – 60 cm) were collected from the permanent experimental plots at Bahtim to study the prolonged effect of permanent fertilization under two crop rotations namely, one and three years rotation on some soil chemical properties, i.e., electrical conductivity, soil reaction, soil organic matter content, total soluble ions and nutritional status (available N, P and K).
     The obtained results indicated that the plots of 3-year rotation recorded significantly higher values of EC, pH and OM content. Sodium ion was the dominant cation in soil followed by Mg⁺⁺, Ca⁺⁺ and K⁺, respectively, while SO₄^-- was the dominant anion followed by Cl^- and HCO₃^-. Also, all soluble cations except K⁺, and anions as well as available N and P were relatively higher under the three-years rotation than the one-year rotation. The adverse trend was found for soluble and available K. Organic manuring resulted in significantly higher values of EC and appreciable values of OM content than the other mineral fertilizers or unfertilized one while the adverse trend was true for pH. Also, soluble cations and anions were relatively higher due to applying organic manuring than the other fertilizers except for NPK fertilizer, which gave the same soluble anions. Farmyard manuring improved nutritional status in the soil compared with the other mineral fertilizers, where available N, P and K were higher due to applying organic manuring. The soil surface layer contained significantly higher OM as well as available N, P and K than the subsurface one, while the adverse trend was found for soluble cations, also, no clear trend was noticed for pH and soluble anions with soil profile depth.       
         No clear variation was occurred in the studied soil chemical properties such as available nutrients (N, P and K), soluble Ca⁺⁺ and Mg⁺⁺, soluble anions and soil organic matter content with a relative increase of such property as a result of crop rotation and long-term fertilization throughout the last nineteen years. On the contrary, an adverse trend of EC and soluble Na⁺ and K⁺ was found due to fertilization and crop rotation while pH value took different trends due to crop rotation only. Also, the dominant soluble ions in 2007 differed from those in 1989 where Na⁺ and So₄^-- were the dominant ions in 2007.