Real-time monitoring of urea slow release through fiber Bragg grating sensors

This research aimed at using fiber Bragg grating (FBG) sensors for monitoring the slow release of urea. Urea granules were coated with ethyl cellulose for controlled-nitrogen release. The FBGs were fabricated using a 10 mm single-mode glass fiber optic, and silver nanoparticle coating was deposited on the partially removed cladding of the FBG using the electroless technique. The silver-coated FBGs at three operating wavelengths (FBG1: 1534 nm, FBG2: 1559 nm, and FBG3: 1565 nm) were used to monitor the slow release of urea in water and soil. The Bragg wavelength shift of FBG 1, 2, and 3 to the controlled-release rate in water was 0.028, 0.12, and 0.20 nm, respectively. In soil, the coated fertilizer responded to the FBG 1, 2, and 3 showing wavelength shifts of 0.028, 0.10, and 0.12 nm, respectively. This study demonstrates the potential of FBG sensors in agricultural applications. © 2023 Elsevier Ltd