Advanced In Situ Nitrate Sensing and Wireless Data Transmission Prototype for Precision Soil Fertility Monitoring

Excessive fertilizer application leads to inefficient resource utilization, increased costs, and environmental pollution, while reduced fertilizer application can lower crop yield and productivity. Yet, farmers lack real-time soil nitrate monitoring tools, as existing field detection methods compromise sensitivity, stability, deployment simplicity, or real-time data transmission, hindering sustainable nutrient management. This study presents a comprehensive solution that tackles these challenges by integrating an in situ potentiometric nitrate sensor with a dual-band wireless data link for communication from underground-to-aboveground (UG2AG). The potentiometric nitrate sensor, featuring a poly(3-octylthiophene) and molybdenum disulfide nanocomposite transducer layer, demonstrates high sensitivity of −82.2 mV $/$ dec, a detection limit of 6.34 ppm, and stable operation at soil depths of 5, 10, and 30 cm for ten continuous days. Its resilience to even low soil moisture levels (10%, 20%, and 30%) ensures reliable performance across diverse field conditions. To facilitate efficient UG2AG data transmission, a custom dual-band antenna operates at 850 MHz and 2.45 GHz, achieving realized gains of 2.03 and 2.38 dBi, respectively. The lower frequency band ensures robust signal penetration, while the higher band provides faster data transmission for real-time monitoring. Experimental results validate reliable wireless data transfer with less than 1% error at distances of 2 and 4 m. This system integrates advanced sensing and communication technologies, offering scalable, energy-efficient solutions to enhance agricultural productivity and resource sustainability.