In order to keep pace with the food needs of the world, application of nitrogen in chemical fertilizer must be and is being increased very rapidly, with a doubling time of about 10 years. The efficiency of use of fertilizer N by crop plants diminishes as rate of application is increased. The N not used by the growing plants may be stored in the rhizosphere, beneath it, percolate to groundwater, or principally, be volatilized to the atmosphere. Efficiency of crop plants in use of N and in its accumulation as nitrate varies widely. Genetic variation is notable; e.g., the chenopods — beets, spinach, and the like — are notable accumulators. Under drought conditions, oats, corn, and other crop plants may also accumulate NO2. Nitrate in well-water in some areas is presently high; unrelated to fertilizer use.
Research to provide systems for more efficient use of fertilizer N is needed both on grounds of economy and to minimize the accumulation of N from fertilizer in our waters and, as nitrate, in our feed, forage and food plants.