On-the-go soil nitrate sensor for real-time precision nitrogen fertilizer management

Overview

N-Sense has developed a low-cost, robust mid-infrared spectrometer-based soil sensor system designed to be attached to fertilizer applicators. The sensor continuously measures soil nitrate concentrations as the applicator moves through a field, enabling real-time modulation of nitrogen fertilizer application rates. This precision agriculture approach addresses a critical inefficiency: only 40 to 50% of the approximately 13 million tons of synthetic nitrogen fertilizer applied annually to U.S. agricultural soils is actually used by crops. The remainder is lost to leaching or atmospheric volatilization, largely because farmers lack the ability to rapidly and accurately measure plant nitrogen requirements. By replacing traditional, time-consuming soil sampling protocols with automated, on-the-go sensing, N-Sense helps row-crop operations improve yields and profitability while reducing the environmental impacts of over-fertilization, including nutrient runoff into local water sources.

Technical specifications

Core technology:

• Mid-infrared (mid-IR) Fourier Transform Infrared (FTIR) spectroscopy-based soil nitrate sensor
• Proprietary calibration algorithm predicting soil nitrate concentrations from mid-IR spectra with accuracy of 8 to 10 mg/kg NO3-N
• Field-mobile prototype designed for attachment to fertilizer applicators
• Real-time data acquisition enabling variable-rate nitrogen application

Key features:

• Continuous, on-the-go soil nitrate measurement during fertilizer application
• Calibration data set exceeding one thousand data points
• Integration with landscape and soil analytics to generate high-resolution maps of soil composition, elevation, and predicted crop yields
• Web-based analytics platform supporting farmland evaluation
• Compatibility with existing fertilizer applicator control systems for automated rate modulation

Technology readiness level

N-Sense's current prototype is undergoing field-condition testing. Completed development milestones include expanding the calibration data set beyond one thousand data points, developing the proprietary calibration algorithm, and designing and building a new field-mobile prototype. Future work focuses on commercializing the technology: redesigning the prototype into a commercial product, developing user interface software, collaborating with an optical engineering company to optimize the mid-IR spectrometer design and improve signal-to-noise ratio, conducting additional field testing, and expanding the calibration algorithm to account for differences in soil textures. The technology has been supported by state and federal funding, including the National Science Foundation, and originated from research conducted at Iowa State University.