Comparison of Some Land Suitability Evaluating Methods for a Selected Gypsiferous Part in the Northern Karma Region for Irrigated Agriculture

To compare the efficiency of three systems to evaluate the suitability of Gypsiferous land for irrigated agriculture, an area of 8885.4 hectares was selected in the Tharthar region – Iraq within the Euphrates terrace, which formed at Pleistocene period and mainly consisted of gypsum, the study included a semi-detailed survey of the area's soil using the Free-lance method, by selecting three parallel transects, according to the variations in texture class, soil salinity and content of gypsum, five representative pedons locations were identified and morphologically described, also soil samples from each horizon were obtained, as well as we obtained water samples from the Euphrates river-Tharthar canal and every wells located in the study area, it's transferred to the laboratory and the required analyzes were performed. The result showed the predominance of the medium soil texture class and slightly saline soil class (S1) in the study area, with a decrease in the soil carbonate content, on the contrary the soil gypsum content was increased. All wall waters was salinity, which poses a danger to agricultural use, compared to the water of the Euphrates river. A discrepancy was observed between the obtained land suitability classes. While the Sys and Verheye, 1972 system showed two poor suitability classes, Sys et al. 1991 and Al-Baji et al. 2010 has improved the appropriateness of the varieties, but the Kadhim, 2012 system was the best in terms of application in order to include the quality of irrigation water within the classification, so its results were more close to the reality diagnosed during the field visits to the study area and the questionnaire from the land users of the region