Assessing the Potential for Ion Selective Electrodes and Dual Wavelength UV Spectroscopy as a Rapid on-Farm Measurement of Soil Nitrate Concentration

Current fertiliser recommendations for nitrogen are limited in their accuracy and may be improved by the use of simple on-farm soil rapid tests. This paper investigates the potential for using nitrate (NO3) ion selective electrodes (ISEs) and dual wavelength UV spectroscopy as part of a rapid soil NO3 diagnostic test. Three soil types, representing the major soil types for agriculture in the western UK, were tested. For the three soils, the ISE rapid test procedure gave a near 1:1 response (r = 0.978, 0.968, 0.989) compared to the internationally-approved standard laboratory method. However, the accuracy of the ISE rapid test was reduced at low soil NO3 concentrations (<10 mg NO3 L). We also show that NO3 analysis of H2O soil extracts by dual wavelength UV spectroscopy was also highly correlated (r = 0.978, 0.983, 0.991) to the standard laboratory method. We conclude that both ISE and dual wavelength UV spectroscopy have clear potential to be used for the rapid on-farm determination of soil NO3 concentration. Barriers to use of these field-based assessment tools include, farmer perception of cost-benefit, general attitude to new technologies and the ability to generate useful fertiliser use strategies from soil NO3 measurements.