The Role of Mole Drainage in Degradation Soils Under Saline Groundwater Table, Egypt

摘要

Agricultural salt affected heavy textured lands of poor productivity are commonly found throughout the northern periphery of the Nile Delta. Clay-salt affected soils are known to be difficult to manage. The present work is conducted in El-Serw Farm, north Delta. The salinity is due to a shallow saline groundwater table (EC ≈ = 39dS/m at 40 cm depth). The aim is to develop suitable local techniques for land improvement in rootzone and sustainable agriculture. An experimental field was designed with different treatments of mole drain spacing 0, 3.0, 2.0 and 1.5 m combined without or with gypsum addition. Rice was cultivated in the summer of 1999 and 2000. AH agricultural practices are similar to that in neighbour fields. Irrigation water salinity ranges from 1.5 to 2.0 dS /m. In the first year, results revealed that only negligible reduction in salinity occurred in the plots under 3 m mole spacing with or without gypsum. Better desalinization is obtained in plots under 2 m and 1.5 m without gypsum up to 60 cm soil depth. Salinity reduction is clear enough under the same spacing with gypsum, since the EC dropped to values around 6 and 5 dS/m, respectively. For exchangeable sodium percentage, ESP, the soil at all depths is initially highly sodic ESP>40. The sodicity almost persists in the different treatments, even in plots under 2 and 1.5 m mole spacing either without or with gypsum, the sodicity is still high (ESP ～ 26). The rice yield in the control being 1 Ton/fd reached 2.6 and 1.75 Ton/fd under 1.5 m treatment with and without gypsum, respectively. Almost the same yield is obtained with 2 m spacing. In the second year, there is a progressive improvement in soil conditions. In general, salinity decreased with decreasing mole drain spacing; EC dropped to less than 4 dS/m in 1.5 m mole drain spacing with gypsum treatments comparing to the other treatments. Regarding exchangeable sodium percentage, there is a relative reduction in ESP at the soil surface than in the deeper depth especially with gypsum and narrow drain spacing. The ESP is still high. Concerning plant growth and production, there is a good cover plant for mole drain spacing especially with gypsum treatments compared to that without gypsum addition. The best treatment is 1.5 m mole drain spacing with gypsum. Data of rice yield follows the same trend to that in the first year with a relative increase in all treatments.