In 2022 I gave a presentation where I showed that sensor Normalized Difference Vegetative Index (NDVI) values could result in an erroneous diagnosis of the causal nutrient deficiency. In early September of 2023 I was contacted by Darrin Malone, certified crop advisor/marketing specialist with AMVAC Corp. Mr. Malone had received a photo of one of my slides and was interested in a succinct explanation of the point. When I explained that the NDVI sensor sensed canopy color and extent, but could not distinguish amongst any nutrient deficiency (nitrogen, phosphorus, sulfur) that could cause either color or extent to be insufficient without ground-truthing, he immediately understood the agronomy behind my position. He no longer recommends NDVI sensing for nutrient deficiency diagnosis/fertilizer recommendation without independent corroboration by plant tissue analysis.