Soil nutrients mapping and monitoring are of great importance in order to reach the goals of sustainable agriculture in all over the world. In developing countries, neglecting soil test before adding fertilizers results in unbalanced fertilization of soils, nutrient deficiency or toxicity in plants and also soil and water pollution. Soil phosphor (P) is one of the essential elements in plant life cycle which is low soluble in calcareous soils of arid and semi-arid regions. The common concept of soil P unavailability to plants along with low price- high availability of fertilizers to farmers sometimes results in over use of P in agricultural lands. The aim of this research was to investigate P and some other nutrients availability and soil P mapping in soils of Urmia Plain, northwest Iran. 277 soil samples from an area of 900 km2 of agricultural lands were taken. Soil samples were gathered from the depth 0-30 cm on a grid of 0.7-1 km. Samples were sieved and analyzed for macro and micro nutrients, organic carbon (O.C), calcium carbonate equivalent (T.N.V) and clay. According to the findings, soil available phosphor (Pav) varied from 1.9 to 346 ppm. In order to map the soil Pav, logarithmic transferred values were used to develop variogram. Then spatial prediction of soil salinity was done on a grid of 500 m using ordinary kriging (OK). Results showed that although soil Pav had large variations through study area with S.D of 33.64, soil samples commonly had P deficiency based on Olsen critical level of 15 ppm. However, small area at the center of the study area had high values of Pav. Correlation analysis revealed that there were significant correlations (1% probability level) between soils Pav with O.M, potassium (K) and copper (Cu). The application of the organic fertilizers from sewage slug sources could result in local increase of soil P up to 100 mg/kg or more, while in other parts of the area soil available P is normally below 30 mg/kg. According to the findings
