EFFECTIVENESS OF OPEN DRAINS IN RECLAIMING SALTY CLAY LOW PERMEABLE SOIL

Abstract

A field study was carried out at Khalid Ibn Al Walid village, Hessanya, Sharkia Governorate during the winter season of 2006/07 where barely crop was grown toinvestigate the possibility of restoring the deteriorated soil through open field drains. The field served by open drains at a depth of 90 cm with length of 100 m. and the drain spacing treatments were at 10 and 20 m. The results indicated that drain spacing treatments reduced the watertable level. The recession percentages of watertable level were 60, 47, 29 and 28 % after 5, 10, 15 and 20 days, respectively in the treatment of 10 m drain spacing compared to the one of 20 m. Generally, close drain spacing relatively was more effective on lowering watertable level than the wider spacing. Watertable salinity during the recession of watertable increased with depth to reach the maximum value at deeper layers. Closer drain spacing caused a considerable reduction in soil moisture content with days after irrigation more than the obtained reduction under wider drain spacing. The reduction in the moisture content of soil profile was 11.69, 13.08, 25.88 and 24.74 % after 5, 10, 15 and 20 days from irrigation, respectively in 10 m drain spacing treatment compared to that of 20 m. The reduction in soil salinity for the treatment of narrow drain spacing was more obvious than that in wider one especially in the surface layer and short time after irrigation (5 days). The reduction in the salinity of soil profile was 14.71, 8.00, 9.52 and 7.14% after 5, 10, 15 and 20 days from irrigation, respectively in 10 m drain spacing treatment compared to that of 20 m. It might be concluded that drainage alone is not enough for control of the twin menace of waterlogging and salinity. Therefore, supplementary practices to improve drainage efficiency such as subsoiling can be used periodically. Subsoiling will enhance downward movement of irrigation water carrying off excess salts from surface layers. After wards, regular subsequent irrigations will gradually reduce the salt content in groundwater at least when it comes close to soil surface. The percolating water will constitute a temporary front preventing the saline groundwater in subsurface layers from linking with the upper ones.