STUDY OF SPATIOL VARIABILITY OF SOIL SALINITY BY USING REMOTE SENSING TECHNIQUES (RS) AND GIS TO SHAIKH SAAD PROJECT SOILS

Abstract

Shaikh Sa'ad project, in Wasit province, was chosen to conduct the current study, which located between. 15' 46˚ and 35' 46˚E, and . 30' 32˚ and 45' 32˚N, , Tigris river at the south, and Al-Jabbab river at the west. The project area was about 75000 ha. Auger holes samples were taken as a grid system of 100 m in terral between each two points in three transects set for two depths (0 – 25 and 25 – 50 cm) in a totel of 75 samples. Fifteen soil profiles were exposed for the the most extensive and freguented soil units .Fourteen locations were determined out of the chosen area to represent the rest of the soil units as the requirements of EM38 device across readings of the same points which were read for two depths, vertical and horizontal. Vegetation spectral indices of the saline soils were evaluated through evaluating non-vegetation indices of the saline soils. Soils Salinity mappings were according to Kriging and Cokriging for the laboratory measurements soil Salinity and the data from the satellite I mage Statistical Analysis 1-The statistical analysis were conducted to obtain correlation relationships between laboratory ECe and EM38 readings as well as predicting formula. 2- ArcGIS was used to conduct Geostatistico analysis to account estimate ranges of , spatial dependancy, and the number of representative samples. The study results indicated that pH of the study area ranged between 7.1 – 7.9, ECe with a mean of 69.4 dS.m-1 ranged between 2.7 – 100 dS.m-1 . Exchange Sodium Percentage (ESP) ranged between 8.1 – 14.1% with mean 12.1%. Total CaCO3 content ranged between 27 – 46 %, while the gypsum ranged between 0 – 25.5%. Organic Matter (OM) ranged between 0.1 – 1.1% for surface horizons. The results of statistical relationships were tasted between EM38 readings and salinity values, where the determination coefficient (R2 ) of the salinity values, measured in the laboratory of the surface horizons, and the vertical readings of EM38 were high significant of 72% while with the horizontal readings of 70%. High significant R 2 , of the laboratory salinity values for the sub-surface depth and EM38 vertical reading, was 66% while with the horizontal values was 70%. The results showed that the high significant R2 of the relationship between ESP, measured in the laboratory for the surface depth, and EM38 vertical readings of 62% while for the horizontal readings of 60%. For the sub-surface depth, the high significant R2 of 61% was between ESP and EM38 vertical readings while was high significant of 44% for the horizontal readings.The results showed the higher Salinity Index (SI) with high significant positive correlation of 0.68 followed by Normalized Difference Salinity Index (NDSI) with significant correlation which indicated that increasing soil salinity values led to increasing SI values between (0.34-0.52) The results of Kriging study explained the ESP value for the class E0 which occupied 2.22 ha 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 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%.Between ESP values and EM38 vertical readings, the results showed that class E0 had an area of 2.21 ha with a ratio of 0.002% while the class E3 had the highiest area of 52655.7 ha with a ratio of 54.16% of the project area .results between ESP values and NDVI showed that the class E0 had 0.008 area while the class E3 had the highiest 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%. Geostatistics The results showed that the Electrical Conductivity (EC) was a variable property from a horizon to anether where the Coefficient of Variation (C.V) value of Ap horizon was 93.5%. The spatial variability of EC 1.08 where the spherical model was the best to predict 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 was50.01%. Spatial Dependancy The required representative samples ranged between 4 – 20 samples, where the limited were for NDVI and the higher unit was for EC. NDVI had the 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 analysis was conducted, spherical model was appropriate for most of studied properties with ratio of 71.5% followed by circular model of 28.5%.