EFFECT OF SALINITY OF SOIL OR IRRIGATION WATER ON THE MICROBIAL ACTIVITY UNDER DESERT SOIL CONDITIONS

Abstract

possible enhancement due to organic matter amendment and biofertilization with the phosphate dissolving B. megaterium were also reported. Data showed that densities of the above mentioned microorganisms were generally decreased with increased soil salinity. Spore formers generally found in higher counts than the other tested groups of microorganisms. However, phosphate dissolving bacteria gave the lowest recorded figures for soil microbial colonization. Nodulation, growth and N & P uptake showed maximum perfonnance when alfalfa was grown on non-saline soil (500 ppm). Increased soil salinity to 2000 ppm did not strongly affect the above recorded parameters but the higher levels (4000 and 8000 ppm) considerably reduced them. Combining B. megaterium var. phosphaticum with R. meliloti in soil with 4000 ppm salinity has shown some positive effects on nodulation, growth and N & P uptake. However, the effects of organic matter amendment with either sheep dung or rice straw were superior to biofertilization with B. megaterium var. phosphaticum. In this respect, sheep dung induced higher levels of stimulation compared to rice straw. The most pronounced enhancement was recorded in plants inoculated with R. meliloti, B. megaterium and amended with sheep dung. Plants grown on soil with 8000 ppm salinity gave the lowest response to the above mentioned treatments.