Real time soil monitoring provides efficient and timely information of crop and soil for precise decision making in the crop production and yield improvement. The high cost, time consuming soil chemical analysis, and laborious collection of soil samples are significant problems in soil monitoring. In an attempt to solve these problems, different types of soil sensing systems have been developed with applications in site-specific nutrient management in precision agriculture. Most of these "on-the-go" soil sensors are based on electrical or electromagnetic sensing. These "on-the-go" soil sensors might be less accurate than conventional laboratory methods, but are still advantageous due to their high-resolution spatial information. Optical and radiometric sensors also require a higher initial equipment cost compared to the other sensors.