Nitrogen nutrition and use in horticultural crops
Résumé
The fertilization practice lays mainly on two concepts, maintenance of the rooting medium fertility and balancing of the crop nutrient demand. Both benefited from recent scientific advances which serve the purposes of diagnosis, crop modelling and optimization of fertilizer use. These would be most helpful to horticulture which makes the most intensive use of N amendments, but they seem challenged by its uttermost diversity of cultural techniques and cultivated plant species. For instance, fertility must be defined for plain soil as well as for hydroponically grown crops, while N demand may concern a very large range of time scales, from a few hours in the case of fertigation on inert media to weeks or months in the open field. This paper confronts the concepts of fertility and crop nutrient demand, mostly developed for field crops, to the needs of horticulture with particular reference to the constraints imposed by genetic and time scale diversities.