AVAILABILITY OF SOME NUTRIENTS an‎d RICE YIELD ASAFFECTED BY RICE STRAW FERTILIZATION UNDER CONTINUOUS FLOODING an‎d SATURATION.

A field experiment was conducted during the two successive summer seasons of 2009 and 2010 in using clayey soil at the farm of Rice Research and Training Center, Sakha District, Kafer El-Sheikh Governorate, Egypt, to investigate the effect of rice straw incorporation in the soil under continuous flooding and continuous saturation on availability of some nutrients in the soil (ammonium, nitrate, phosphorus and potassium) and rice yield. Utilization of 165 kg N ha-1 gave the highest values of rice grain yield but without any significant differences with 5 tons rice straw ha-1 + 110 kg N ha-1. The largest amounts of nutrients (NH4+ and P) availability were found with continuous flooding. While, the highest values of NO3- and K availability were found under continuous saturation. The continuous flooding treatment gave more grain yield as compared with continuous saturation treatment.