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Spot-drop Biosensor-based Spatial Nitrogen Management
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: 2026 ASABE Annual International Meeting 2601229.(doi:10.13031/aim.202601229)Authors: Ahmed Abdalla, Ali Mirzakhani Nafchi
Keywords: Precision agriculture, Spot-drop Biosensor, Variable rate technology, Remote sensing, Biosensor.
Abstract. Rain-fed corn fields do not behave the same every year. The swing interactions can flip which parts of a field perform best, making nitrogen (N) decisions risky. To make N decisions more responsive to what the crop needs, we evaluated a Spot-drop biosensor approach that uses the crop as the “sensor.” With Spot-drop, small N-rich georeferenced spots are applied at planting. Remote sensing compares the crops inside these N-rich spots to the surrounding crop. That difference is used to generate zone-specific, in-season N rate recommendations, helping match N rates to within-field demand instead of relying only on pre-season expectations. We tested this approach in on-farm precision trials across 116 acres of rain-fed corn in SD, comparing Spot-drop recommendations to a flat-rate strategy and a conventional variable-rate prescription. Crop response in the N-rich spots varied across four field zones, with the strongest NDVI response in Zone 1 and the weakest in Zone 4, showing that N need and yield potential were not uniform across the field. Across zones, higher N rates generally increased grain yield, while lower N rates improved Nitrogen Use Efficiency (NUE). Spot-drop–guided variable-rate N improved corn yield by up to 20%, demonstrating strong potential to refine in-season N decisions, boost returns, and reduce unnecessary N losses.
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