Abstract
Secondary salinization of irrigated lands in Uzbekistan has been caused by excessive irrigation and rising groundwater level due to drainage system malfunction. Measures, such as maintenance of drainage system or leaching, had been conducted, but there are still fields where salinity levels remain high. The use of a shallow sub-surface drainage system has been proposed to ensure complete removal of percolation water after leaching, but it is considered as an expensive option. Therefore, the possibility of introducing a drain drilling machine (Cut-drain) which has been developed recently in Japan was investigated. Employing Cut-drain has presented some problems; it rises up to the soil surface and causes the occurrence of preferential flow under dry soil conditions. In this study, we examined the soil moisture conditions suitable for the construction of Cut-drain and the effectiveness of a method for mitigating preferential flow. The results showed that there was a border soil moisture condition needed in the construction of Cut-drain. More than 9-11% moisture was required in the first soil layer (from the surface to 20 cm below it) and 12-15%, in the second layer (from 20 to 40 cm). Furthermore, it was found that the preferential flow could be mitigated by irrigating the furrows before the construction.
