To monitor the health of agricultural soil, lead (Pb^{2 +} ) ion measurement is essential. The various sensors for lead ion detection reported in the literature earlier are either expensive or have complicated designs. This inspired us to propose a fiber optic sensor that is simple in design, less expensive, and more efficient. A photonic crystal fiber (PCF)-unclad single mode fiber (SMF)-PCF hybrid configuration makes up the suggested sensor, and the sensing mechanism is based on a synergistic application of surface plasmon resonance and interferometry. It is shown that the suggested structure is easy to use for Pb^{2 +} ion detection, in addition to other advantages in limit of detection (LOD) and sensitivity. The proposed structure is optimized to attain a LOD of 8.32 mg / kg, which is much less than the permissible limit of Pb^{2 +} ions permitted in healthy agricultural soil, i.e., 100 to 400 mg / kg. Additionally, a polymer that is attached atop the gold layer and to which only Pb^{2 +} ions can adhere ensures the sensor’s specificity. To the best of our knowledge, our proposed optical fiber-based sensor design and approach adopted to detect lead ions in agricultural soil are the first of their kind.