Agricultural lands in upper Egypt had been brought under perennial irrigation
after the construction of Aswan High Dam (1960-1968). The natural drainage system
that had sustained permanent agriculture for millennium could no longer cope with
increased percolation from irrigation, and large areas had become waterlogged and
salinized. An area of 2.21 million feddans in the Nile Delta was provided with tile
drainage at the end of 1998. Fifteen soil profiles were chosen from five regions of alluvial soils. They
mainly differed i n t he age 0 f implemented tile drainage network at EI-Minofiya and
Kafr EI-Sheikh Governorates, representing both middle and north Delta soils. In each
region, three profiles were selected where the first the profile is surface drainage, the
second is beside the lateral and the third profile is located just in the midway between. The relation between the microbiological activities (total bacterial counts,
dehydrogenase and nitrogenase activities) and the prevailed drainage conditions had
been studied. The results showed that the biological activity has been pronounced in the
old tile drainage specially the total bacterial count. In the newly tile drainage (Sid i-
Salim region I) and (Sidi-Salim region II), the bacterial count in the surface drainage
soil was higher than that of the tile drainage. The high values of dehydrogenase
activity were recorded in Mahalat Alkassab region profile 3P2 (beside the lateral). The
nitrogenase activity mostly decreased with increasing soil depth. Total nitrogen in soil profiles, decreased gradually with depth. The highest
value of total nitrogen (0.53%) was found in profile 1P2.