Leaching practices in the selected plots of Tabriz floodplain (Ghom-Tappe, Sofian) was investigated. The purposes of investigation were: 1) to shorten the leaching period in the reclamation of heavy textured saline soils, 2) save water where the high quality water resource is limited in the area, 3) bring the reclaimed lands under cultivation and to produce reasonable yield. To achieve these goals a one- hactar piece of land was leveled and divided into three plots. The first plot was plowed regularly, of 25 - 30 cm depth (treatment 1). the second plot plowed into a depth of 45 - 50 cm (treatment 2). and the third plot was subsoiled to a depth of 75 - 80 cm (treatment 3). Considering the physical nature of the soils in the area, a drainage canal to a depth of 2 meters was digged. The quantity of water required for reclamation was calculated from Valabieve equation and an apropriate desalinization coefficient was determined. Desalinization in each treatment was accomplished by three times leachings a 3000 m3 of water application at each time (totally to 9000 m3). The indices of salt leaching nature including pH, EC, TDS, soluble anions and cations, and the ionic relations such as SAR, ESP and RSC all were evaluated. At each treatment plot a soil profile to a depth of 150 cm was examined and the same indices were determined in the soil samples taken from the profile. Gapoti’s equation was used and the effects of SAR of leaching water on ESP was determined. The quantity of drainage water from each plot conveyed into the main drainage canal was measured and their water samples were analyzed for various anions and cations. Piezometer wells were drilled in each treatment plot The depth of water table , and the dynamic of salt movement were monitored during the various stages of leaching. The water and salt balance were computed in order to check the results of chemical data anlysis. All parameters promoted or retarded leaching (precipitation) it (water consumed to raise soil moisture content to the FC level) are all included as the water balance component. Similar to water balance, salt balance was also carried out. After accomplisbment of the leaching program, the salt content of the soil
profile within top 100 Cm layer reduced from %2.4 to %1.59, %1.92 to%O.95, and %2.14 to %0.37 in the treatments 1, 2 and 3 respectively, Comparison of these figures indicates that in treatment 1, with normal plowing depth, the leaching has not been carried out so successfully. In treatment 2, about %50 of salts has been removed out, whereas in treatment 3 with deep subsoiling, leaching has reduced the salt content of the soil to a such level that not to create salinity problem for plant growth. The leaching period for this purposes were 146, 45, and 58 days for treatments 1, 2 and 3 respectively.
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