Estimation and mapping of some soil characteristics of the Hiranregion of Northern Iraq using geostatistical andspectroradiometric techniques

Soil properties are important indicators for soil health and productivity. The aim of this study is to determine and map the spatial distribution of soil properties and make a correlation with reflectance spectroscopy in Hiran region of Erbil governorate in the north of Iraq. The study area was divided into 500 m x 500 m square grids 65 soil samples were collected in the sampling sites at 0 – 30 cm depth in December 2021. The coordinates of each location were recorded by geographic position system (GPS). Soil samples were analyzed for soil organic matter (SOM), Sand %, Silt %, Clay%, Soil reaction (pH), Electric Conductivity (EC) and Calcium Carbonate (CaCO3), Visible-near Infrared Reflectance Spectroscopy (VNIR) and geostatistical techniques were used for assessment of diverse soil properties. Geostatistical methods were used to determine spatial structure for each of soil properties. Interpolation methods ordinary kriging (OK) and inverse distance weighting (IDW) were used to estimate the spatial analyze of each soil properties. As a result the amount of Sand %, Clay %, Silt % and CaCO3 were significantly affected with soil reflectance. Strong and moderate spatial dependence in soil parameters might be explained using an exponential model as a best fit in semivariogram. Interpolation methods indicated that OK is more accurate than the IDW for interpolating of SOM %, Sand %, Silt %, Clay %, pH and CaCO3 and IDW was better than the ordinary kriging in estimating of EC. However, Estimation of soil properties by using VNIR spectroscopy in Hiran region is better technique than geostatistical analysis.