OPTIMIZATION OF NITROGEN-FERTILIZATION - RELATIONSHIP BETWEEN PRECIPITATION AND EXPECTED YIELDS

The optimisation of nitrogen fertilisation for cereals in Mediterranea n regions is very difficult, because yields and leaching losses are de pending on winter rainfall. In this article five years of nitrogen fer tilisation trials are analysed in order to get a model which relates w inter rainfall, nitrogen fertilisation and wheat yields. A highly sign ificant model obtained, in which soil type and the cultivar were taken into account. In order to improve nitrogen use efficiency and to avoi d unnecessary nitrogen fertilisation, information on the minimum amoun t of nitrogen at seeding time and for how long the first top dressing can be delayed without yield losses will be necessary.