Development of an Adaptive Grid-Based Soil pH Mapping and Lime Recommendation System

Maintaining optimum soil pH for specific crops is essential for improved nutrient intake and maximum yield. Conventional soil testing method uses composite samples tested in laboratory, which fails to capture the spatial variability within the field. This paper presents an adaptive grid-based soil pH mapping and rule-based, zone specific lime recommendation system. The system incorporates an ESP-32 based pH sensing node and a cell phone for fetching GPS coordinates and displaying map. Bluetooth communication is established between microcontroller and cell phone. The pH sensor is calibrated using laboratory results for improved measurement accuracy. Median filtering with averaging is used to eliminate sensor noise. An adaptive grid sampling is implemented, so that greater number of samples are taken from regions having high pH variability and reduced number of samples in relatively homogenous area. The calibrated pH measurements are used to generate a spatial map with interpolation technique. Based on the soil pH and agricultural recommendations, the system estimates zone specific lime requirement for the field. This approach suggests a variable lime rate application for different zones of the field and reduces the unnecessary lime usage. The proposed system aims at providing a cost-effective alternative to the conventional technique, suitable for precision agricultural application.