Interpolation of Soil Nutrients (Nitrate and Phosphate), Organic Carbon, EC and pH in Agricultural Lands to the South of Tehran City

In this study, 83 sampling points were chosen in the study area. Sampling was conducted at two soil depths (0-30 cm and 30-60 cm) and the concentrations of nitrate, phosphate, EC, pH and organic carbon were determined. Interpolation maps were created using the IDW method. These showed that in the top soil, soil phosphorus, EC and OC have the maximum concentration in the northern part of the area and nitrate in the southern part of the area; in second depth soil, phosphorus has the maximum concentration in the North of the area and nitrate and EC in the South of the area, while OC has a uniform distribution over the whole area. Analysis of soil chemical properties showed high concentrations of nitrate and phosphate in the upper soil layer in the studied areas, mainly due to the use of untreated urban wastewater and chemical fertilizers by the farmers; in addition, results of organic carbon measurement showed that this area has a good condition in terms of organic matters. Soil pH in the area was alkaline and EC decreased at a lower depth. The results of Spearman correlation analysis showed that EC has a positive correlation with nitrate and a negative correlation with phosphate at both depths. Also, organic carbon has a positive correlation with soil phosphate in the top soil.