The Position of Mineral Nitrogen Fertilizer in Efficient Use of Nitrogen and Land: A Review

Our attitude towards mineral nitrogen (N) fertilizers is ambivalent. N fertilizers have on one hand increased our supply of food, feed and other bio-based raw materials tremendously and also improved the use efficiency of land and labor, but have on the other hand a negative impact on the quality of the environment and contributed to the depletion of fossil fuel reserves. This awareness has resulted in strong pleas to spend much more attention to the recycling of N containing downstream “wastes”. It is, however, naive to assume that even perfect recycling suffices to offer the same number of people the same diet without inputs of “new” N, as inevitable losses of N make compensations indispensable. “New” N can be derived from either biological N fixation (“legumes”) or from industrially fixed N (“fertilizer”). The existing literature provides no evidence that the use of N fertilizers is per se unsustainable, as these fertilizers can also be made from renewable forms of energy. Besides, soil health and human health appear sensitive for the dosage but not for the form of N. It is yet imperative to reduce the input of “new” N as much as possible, so as to minimize adverse environmental effects. Measures to this end are a more precise assessment of crop N requirements, a better timing and positioning of N inputs, and any measure supporting the acceptance of “wastes” by farmers. The present paper elaborates the above aspects.