الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Egyptian soils are deficient in nitrogen, therefore nitrogenous fertilizers must be applied to supply the grown plants with their nitrogen requirements. Urea is one of the commonly used nitrogenous fertilizers in Egypt. It is hydrolysed by the enzyme urease secreted by soil organisms and plant roots. upon the application of urea to solis some of its nitrogen is expected to be lost due to ammonia volatilization as the result of the biological hydrolysis and the alkalinity of the soil enhance such process. Therefore precotions should be undertaken to avoid or at least minimize suouldosses .
Therefore hydrolysis of urea by soil Microorganisms was studied. Soil samples representing different Egyptian soil types were collected from three governorates [ loamy and sandy-calcareous soils from Minia, saline soil from Dakahlia and alkali and alkali saline soils from kafer El Sheikh].
The addition of 500 ppm urea to each of the soil types under study resulted in rapidly increase in the total bacterial densities during the first seven days, reaching the maxima on th 7th day in all the soil types. loamy, Alkali saline and Alkali soils appeared to have the highest bacterial load other seven day