Development of a Portable Automated Detector of Soil Nitrate for Mapping Using Nitrate Ion-Selective Electrodes

Abstract

Management of plant nutrients to suit soil conditions in each specific sub-area of a plot (Site-Specific Management, SSM) is crucial for efficient crop production. Excessive fertilizer application not only increases production costs for farmers but also leads to soil degradation and contamination of groundwater sources. Soil analysis using sensors is suitable for analyzing a large number of soil samples due to its low cost, quick operation, and applicability in agricultural fields. The main objective of this research is to develop a tool for measuring nitrate concentration in soil using a Nitrate Ion-Selective Electrode (Nitrate-ISE) along with a GPS system for automatic data recording on a secure digital card (SD card). The system is controlled by an Embedded Board (Arduino mega 2560) and consists of five main operations: 1. Soil extraction, 2. Measurement, 3. Cleaning, 4. Satellite coordinate detection, and 5. Controller and data logger. The analysis requires approximately 0.5 liters of clean water, and the time for each sample is around 5 minutes. The optimal soil-water ratio is 1:10, and the measurement time is 30 seconds. The average accuracy of the measurements is more than 80%, with an R² = 0.80 and RMSE = 1.44 compared to laboratory methods. This prototype reduces soil analysis costs by 5-6 times, providing reliable data for creating soil maps. This information can be used to support farmers in making decisions for nitrogen fertilizer management in subsequent crop cultivation.