Investigation of the optimal number of soil moisture based on spatial variation of moisture for irrigation planning and soil and water resources conservation

The development of an accurate for monitoring the soil moisture is very important step in soil and water conservation activities and studies. The purpose of this study is to provide solutions to optimally determine the number of sensors required to monitor soil moisture bases on geostatistical approaches and intelligent monitoring of the water status in soil. In this research, 87 samples were taken as a regular network from the surface depth (0-30) cm. Three levels of the samples number were considered. By decreasing the samples number, the estimation accuracy decreases and the component effect increases, that indicates an increase in the random and non-structural part of the property. With the high sample number, the fitness of the model was 1.2% and 2.7% more than when the average and the minimum sample number. Reducing the samples has increased the radius of effect and decreased the ratio of structural to non-structural variance of properties. So the radius of effect of field capacity when the sensors number is at its maximum level is 36.8% and 38.4% less than the other two levels, respectively. As the samples number decreases, the estimation error increases sharply. Based on the findings, the use of between 20 and 30 sensors per 100 hectares produced the best results. The kriging method was an excellent estimator for moisture mediation. The proposed method can be used in determining the optimal sensors number for irrigation planning.