Mapping and spatial analysis of soil chemical effective properties to manage precise nutrition and environment protection

Soil fertility and plant nutrition management have received much attention in order to increase efficiency, improve plant productivity and also reduce environmental hazards. Soil cation exchange capacity (CEC) is a critical indicator of soil fertility quality and pollutant separation capacity. Plants such as rice need to provide their nutrients using fertilisers for maximum production, so it is essential to know the content of the major elements such as nitrogen, phosphorus and potassium in the soil and to prepare their ideal maps. To evaluate the factors affecting soil fertility and preparation of their maps, a total of 255 soil samples were collected from the study area located in northern Iran. The soil CEC, total nitrogen, available potassium and phosphorus were analysed using standard methods. Spatial variability maps of soil fertility properties were prepared using Ordinary Kriging method. The results obtained from field data show that the amounts of total nitrogen, available potassium and phosphorus are more than optimal limit in many parts of the study area. Evaluation criteria values including normalised root mean square error (NRMSE), normalised mean absolute error (NMAE) and coefficient of determination (R-2) were derived for CEC 0.164, 0.135 and 77.65, total nitrogen 0.232, 0.298 and 71.59, available phosphorus 0.214, 0.215 and 70.11 and available potassium 0.197, 0.146 and 78.15, respectively, in the test data group. NRMSE, NMAE and R(2)values showed that the accuracy of prepared maps was ideal. The spatial distribution maps can be used as an appropriate guide for precise and specific management of NPK nutrients application to protect the environment and stop the contamination of groundwater resources within the study area.