Nitrogen Management for Improved Use Efficiency.

World demand for N fertilizers has increased proportionately with increased world population over the past forty years. Increased demand for fertilizer N with expected increases in production costs (natural gas) will exacerbate the need for improving fertilizer use efficiency in cereal crops that is known to be near 33%. Although the need for spatially variable N rates at small scales has been apparent for years (e.g, fecal deposition in wheat pastures or corn fields creating small areas where N need was small), it was not until recently that sensors were capable of detecting these small scale differences, and able to treat each corn plant real-time, at 10 kph. These systems can treat every corn plant based on a projected yield potential and N removal. If improved nutrient use efficiency is expected at the by-plant resolution, on-board sensing/nozzling systems will be needed that operate independent of GPS driven maps. The use of annually applied nitrogen rich strips in farmer fields is one of the more simple yet promising practices available for improving NUE. Reference strips whether sensed visually, or with sensors serve as guides of whether or not to apply added N mid-season. Recognizing that the need for fertilizer N is dependent upon the environment and what the environment has supplied (N in rainfall and that mineralized from soil organic matter), has assisted agronomists in refining mid-season fertilizer N rates. Of all the emerging technologies that are currently available, this is the most affordable, practical, and useful for improving NUE and this methodology should be extended worldwide.