Agriculture.com published an excellent article reviewing different techniques for gauging crop nitrogen requirements. While drone-based NDVI imagery was not explicitly addressed, the message was overwhelming. Farmers can significantly increase their profits by applying fertilizer only when needed. One farmer interviewed said that the technology he used allowed him to avoid fertilizing at all one season, saving him tens of thousands of dollars. NDVI images collected by Agribotix drones provide a farm-scale overview of nitrogen requirements and enable substantially reduced nitrogen and other inputs.
Give it a read at: http://www.agriculture.com/machinery/precision-agriculture/nutrient-management/crop-senss_239-ar42583?