ABSTRACT
The productivity of natural ecosystems and cultivated swards is generally limited by nitrogen availability. Integration of recent pysiological knowledge at the level of the whole plant in swards is a necessary step in agronomy to not only understand the relationship between nitrogen nutrition and plant productivity, but also in finding diagnostic tools for evaluation of the nitrogen nutritional status (N) of a sward. This knowledge enables adjusting the supply of nitrogen to precisely sustain the nitrogen reguirement of plants, depending on the potentialities of the environment and the objectives of production.
