A Stand-Alone, In Situ, Soil Quality Sensing System for Precision Agriculture

The pressure on agricultural efficiency is nowadays greater than ever, hence there has been an abrupt technological involvement in this sector in the last decade. In this article, a stand-alone, in situ, soil quality sensing system is presented for the first time, capable of monitoring chemical parameters in the soil without any human intervention. The system is capable of measuring potassium and nitrate concentrations with a sensitivity of $\sim$ 0.6 $\mu$ A/mM (R $^{2}$ = 0.9775) and $\sim$ 2 $\mu$ A/mM (R $^{2}$ = 0.9708) in the range of 0.1–10 mM, pH with a sensitivity of $\sim$ −30 mV/pH (R $^{2}$ = 0.9068) in the range of 4–10, and temperature with a sensitivity of $\sim$ 1.6 $\Omega$ / $^{o}$ C (R $^{2}$ = 0.9999) in the range of −30 to 60 $^\circ$ C. It includes an impedance probe for impedance measurements up to 1 MHz. A unique packaging was also developed to protect the array from the soil while allowing enough time for the sensors to take precise measurements. The thick-film multisensor array was connected to a stand-alone, electronic node, while the complete system was deployed in the field, taking measurements every 30 min, showing the capability to track watering and fertilizing times.