A Field Method to Measure Symbiotic Nitrogen Fixation

Saliou Fall of the Institut Senegalais de Recherches Agricoles in Senegal will develop techniques to estimate biological nitrogen fixation (BNF) by legume crops to guide their use as alternatives to nitrogen fertilizers for more sustainable agriculture. They will assess BNF by estimating three underlying components. Crop biomass and the proportion that is nitrogen will be estimated by AI-based models, and the nitrogen fraction that comes from BNF will be estimated by measuring the levels of a stable isotope of nitrogen in the soil and in the plants. As test crops for data to train the AI models, they will grow groundnut and cowpea as staple legumes, with an adjacent non-nitrogen-fixing crop, and crotalaria as a cover crop. They will acquire images of the crops from drones or mobile phone applications, and perform laboratory analyses, including measuring biomass, analysis by near-infrared spectroscopy and wet chemistry, and measuring the natural isotope of nitrogen.