Ion-Selective Electrode Offers Accurate, Inexpensive Method for Analyzing Soil Solution Nitrate in Remote Regions

Abstract

Nitrogen (N) applied as fertilizer is subject to runoff and leaching. Nitrate (NO₃⁻-N) concentrations in soil solution reflect the impacts of farm management on N cycling. Some of the most remote regions in the world are undergoing rapid land-use change, yet there are major barriers to conducting research in these locations. Fortunately, new tools such as ion-selective electrodes (ISEs) provide low-cost and simple methods for conducting chemical analysis in the field. Researchers compared soil solution NO₃⁻-N concentrations measured using an ISE with concentrations measured on a colorimeter (cadmium reduction) and found good agreement (r² = 0.96, P < 0.0001) between the two methods. The ISE is also 66 times less expensive than in-country laboratory analysis or shipping and analyzing the samples in the United States. Thus, the ISE is an excellent tool for rapid analysis of N in soil solution, providing critical information on N dynamics in remote regions.

Keywords:

• Field methods
• ion-selective electrode
• leaching
• nitrate

Acknowledgments

We thank Wilson Ondiala, Stephen Ogendo, Kassim Masibuka, and Ismail Rashid for their support in the field, and Todd Rosenstock for encouraging us to publish these results.

Funding

This research was supported by the Bill and Melinda Gates Foundation and a Cross-Cutting Initiatives grant from Columbia University.