A Low-Profile Self-Similar Geometry-Based Microwave Planar Sensor for Assessing the Impact of Organic Matter Content on Soil Field Capacity

Field capacity (F.C.) is a crucial parameter in soil analysis, defining the limits of plant-available moisture content (M.C.). Integrating this concept into sensing technology provides valuable information for optimizing irrigation scheduling by determining the appropriate timing and quantity of irrigation, thereby preventing crop damage. This article presents a fractal-based microwave planar sensor (MPS) designed to estimate soil-moisture characteristics related to F.C. The proposed sensor utilizes a self-similar fractal (SSF) approach, operating in the ISM frequency band at 2.4 GHz, achieving high return losses of approximately −47.94 dB and enhanced sensitivity in material characterization. The sensor’s performance is evaluated by varying F.C. values from 0% to 100% for similar textured soils with organic matter content (OMC) variations. The results demonstrate that variations in OMC significantly impact the dielectric properties of soil with moisture variations. Specifically, Sample-1, which has a low OMC, exhibits a lower $\epsilon _{r}$ values than Sample-2 at all F.C. levels. The data suggest that the proposed sensor is sensitive to detect the impact of OMC variations on soil-moisture characteristics concerning F.C. A mathematical model has been formulated as a second-order polynomial equation, exhibiting coefficient of determination ( ${R} ^{{2}}$ ) value of 0.9771. This model has been developed specifically to evaluate F.C. values, demonstrating a strong correlation with the observed data. The performance of the proposed sensor confirms its potential application in agricultural fields for efficient irrigation scheduling and water resource conservation.