Spatial Variability of some fertility traits in rice cultivated soils using GIS

The study area was selected in the Abbasid district of Najaf Province, which is confined between two longitude 32° 06 42.8 ° to 32 ° 07 57.2 ° North and two latitude 44 ° 25 ° 16.4 ° to 44 ° 24 30.5° east. Coordinates of piedons study locations were determined by GPS. Eight piedons were detected for soils cultivated with rice, the piedons were described morphologically. Samples were obtained from each horizon interfaces samples was obtained randomly of four equal depths of 25-0 cm, 50-25 cm, 75-50 cm, 100-75 cm, for the study of spatial variability for the traits of those soils, then the necessary laboratory analyzes, statistical and geological analysis were conducted, and the samples number for each trait was calculated. When using geological statistics to describe the variability of fertility traits, the availability zinc was the most variability in the horizons C1 and C2, followed by the availability iron in the horizons Ap and C1 and the total zinc at horizon C3. The effective distance values ranged for these traits in those horizons between 208-653 m, and the appropriate statistical models to describe the variability of soil traits when the geological statistics uses, it was the spherical model and the Circular model by 50% for each. It found that the appropriate technology for obtaining soil samples be represented more efficiently, Depending on the effective range value with a strong spatial dependence of all the traits studied. As the number of samples that were calculated by the randomization law for fertility traits between 1-1586 samples, but when using geological statistics, the number of samples varied 4-12 sample. The soil of the study was classified under the rank of modern soil composition (Entisol), under the rank of river deposits (fluvents), the large group (Torrifluvents) and under the group (Typic Torrifluvents).

Keywords:

rice soils , fertility traits , spatial variability , variance function