Spatial Variability of Soil Salinity in Mid of Mesopotamian Plain by Remote Sensing

Shaikh Sa'ad project, in Wasit province, was chosen to conduct the current study, which located between the two longitudes: 15' 46? and 35' 46?E, and between the two latitudes: 30' 32? and 45' 32?N, where the Iraqi-Iranian borders bounded it at the north, the borders of Ali Al-Gharbi, Maysan province, at the east, Tigris river at the south, and Al-Jabbab river at the west. The project area was about 75000 ha. Vegetative spectral indices of the saline soils were evaluated through evaluating non-vegetative indices of the saline soils. Saline soils mappings were according to Kriging and Cokriging for the following laboratory measurement of soil salinity and the data from the satellite images. 1- Soil salinity mapping from laboratory measurements. 2- Soil salinity mapping from the satellite images. GIS program was used for conducting Geostatistics to account effective area, spatial reliability, and the number of representative samples. The results showed the higher Salinity Index (SI) with high significant positive correlation of 0.68 followed by Normalized Difference Snow Index (NDSI) with significant correlation which indicated that increasing soil salinity values led to increasing SI values. The results indicated that most of the study region lands were salinity affected and the SI values ranged from the lower value of 0.002 to the higher of 0.334. Normalized Difference Vegetation Index (NDVI) values ranged from the lower to higher values of 0.34 to 0.52, respectively. The results of Kriging's study explained the ESP value for the class E0 which occupied 2.22 with ratio of 0.002% while the larger area was for the class E3 of 53562 ha with a ratio of 55.1%. The results of Cokriging's study explained salinity values and horizontal readings for the class S0 which had an area of 0 ha with a ratio of 0% while the class S5 had the higher area of 64082 ha with a ratio of 65.92%, but Cokriging indicated that of the relationship between the salinity and NDVI for the class S0 had an area of 0 ha with a ratio of 0% while the class S5 had the higher area of 64257.9 ha with a ratio of 66.1%. Crokriging's results, between salinity values and SI, showed that the class S0 had an area of 0 ha with a ratio of 0% while the class S4 had a higher area of 64241.49 ha with a ratio of 66.08%. Also, the results showed, ESP values with EM38 horizontal readings, that class E0 had an area of 2.38 with a ratio of 0.002% while the class E3 had the higher area of 54425.3 ha with a ratio of 55.98%. The results, between ESP values and NDVI, showed that the class E0 had an area with a ratio of 0.008 while the class E3 had the higher area of 53690.1 ha with ratio of 55.23%. The results, between ESP values with Brightness Index (BI), showed that the class E0 had an area of 2.22 ha with a ratio of 0.002% while the class E3 had the higher area of 53562.03 ha with a ratio of 55.09%. The results showed that the Electrical Conductivity (EC) was a variable property from a horizon to other where the Coefficient of Variation (C.V) value of Ap horizon was 93.5%. The spatial reliability of EC 1.08 and the spherical model was the best to describe EC variation. In Ap horizon, ESP values ranged between 1 ? 81, the lowest value was in the pedon 5 and the higher was in the pedon 9 of the Ap horizon. C.V value was 50.01%. The required representative samples ranged between 4 ? 20 samples, the lower samples were for NDVI and the higher were for EC. NDVI had least variation, compared with EC, required a large number of samples ranged between 102 ? 296 samples according to random selection. The smaller number of samples was for BI and the larger was for ESP. The results showed that, when geostatics was used, spherical model was the appropriate for most of studied properties with ratio of 71.5% followed by circular model of 28.5%.