Characterization and Classification of Some Soils Adjacent to the Southern of Al-Najaf Sea – Iraq

Abstract

The study area was selected in the Najaf Governorate. It's adjacent to the southern part of Al- Najaf Sea and its area ​​(17150.5 ha), located between the longitudes 425594E and 445138E and between the Latitudes 3521842N and 3538169N (UTM), it's covered the soil types and its geomorphological units which located within the sedimentary environment of Al- Najaf Sea. The semi details soil survey was carried out to selected area for study by grade soil system and according to soil texture examination results, ten heterogeneous sites were selected and geographically determined using a GPS device. In every study area, the pedon was digger and morphologically soil units soil units descripted. The samples were then taken from each diagnostic horizon and transferred to the laboratory for some chemical analysis and physical measurements. According to the results, the soil of the study areas was classified from the level of the order to level the family according to the American system (2014) and was completed to the level of the series based on the classification system of soil proposed by Al-Aqadi (1976 and 1982). The lands of the region were classified according to the productive capacity proposed by Klingebiel and Montgomery (1961).    The results showed that there is a variation in the morphological characteristics, whether within the single pedon or the study area, due to the effect of the topographic factor, which was reflected in the characteristics and thickness of the horizons and the nature of their arrangement and the accompanying characteristics of each horizon. The pidogenical  processes, mainly washing, loss and gain, salinization have been reflected in the presence of some subsurface diagnostic horizons like the calcic, gypsic and salic horizons, with the supremacy of the primordial evolution diagnostic surface horizon, represented by the Ochric horizon. The results of the texture class showed a difference in the soil content of  the soil separators indicated that there was a difference in the soil content of the soil from the main soil separators, depending on the topographical location. The results of the cartographic analysis of the texture class map for the first meter indicated the  dominance of moderately fine varieties (43.6%), while the coarse texture showed lowest percentage(5.3%). The studied soils was different with carbonate content and had a different distribution with depth due to the effect of situational conditions. The values ​​of this component ranged from 145 to 500 gm.Kg-1, the state of variation in the distribution pattern of this component in the study pedons is consistent with the state of variation in the calcification activity and the observed elevation of this component values in the sub-surface horizons due mainly to the nature of the parent material. The soil content of the gypsum ranged between 6 to 665 gm.Kg-1, with a general trend of high soil content of this component with depth. The percent of sodium exchange percentage was ranged between 3.2 to 8.4, and did not exceed the risk limits (15%). Classification of studied area showed existence two soil orders, The majority was within  Aridisols order, which formed (92.5%)from studied area. The most common great soil groups were Typic Calcigypsids(44.75%), followed by Gypsic Aquisalids (29.53%), Typic Aquisalids (5.76%), Leptic Haplogicids (6.42%) and Typic Hapiogpsids by 6.04%. The Entisol order formed  7.5%, diagnosed in great sub group under the Typic Torrifluvents. The classification of the study area lands according to the determinants of productivity indicated that the IV class had the highest percentage of the total area (48.19%), while the I class did not exceed (5.23%). The following determinants were recorded: the texture, the drainage, salinity and gypsum percentage, which emphasizes the need to take the necessary administrative measures when exploiting these agricultural lands in the future.