Instead of the traditional precision agriculture method of making zone maps for the application of fertilizer, the technology is moving to in-field sensing where the health of the crop is being assessed just ahead of the tractor and the on-board computer varies the rate in real time.
The in-field sensor uses two light beams of red and near-infrared where the red light is absorbed and the near-infrared is reflected back. The sensor measures the ratio between the absorbed light and the light reflected back to develop a normalized difference vegetation index (NDVI), which provides details on plant density. The areas with lower density receive less fertilizer, saving the bulk of the fertilizer for the high-density areas where the yield can be most improved.
This new in-field sensing technology is pricey at the moment, but studies indicate that the application can significantly reduce the amount of nitrogen used without impacting crop yield, saving money as well as watersheds.
Read more about this technology in this feature in Farm and Ranch Guide.