INFLUENCE OF CLIMATIC CONDITIONS ON YIELDS, N UPTAKE AND EFFICIENCY IN SUNFLOWER

The Mediterranean area is often characterised by variable and unpredictable climatic conditions that strongly influence plant development and yield. In this matter, the right choice of the genotypes and of the agronomic practices could be im-portant features to obtain high crops performance. Therefore, the aim of this work was to study the effects of air tempera-tures, annual and seasonal rainfall on yield, oil production, N uptake and N utilisation efficiency of sunflower genotypes grown in a semiarid conditions. To accomplish this goal, a four-year field experiment was carried out at Foggia (Southern Italy) on five different genotypes cropped with three N fertilisation levels. The research was conducted in a “accentuated thermomediterranean ” environment, as classified by UNESCO-FAO, and on a soil defined by Soil Taxonomy-USDA as “fine mesic, Typic Chromoxerert”. During the field experiment, the minimum and the maximum air temperatures and the rains were daily recorded, whereas at the end of the each cropping year, yields, quality, plant dry weight, N content of the different parts of plant were determined, allowing the calculation of oil production, N uptake and N efficiency parameters. The results of this work indicated, trough the trial years, high rainfall variations during the first vegetative phases of sun-flower. This amount of rain was correlated with sunflower performance, confirming that environmental conditions clearly affected both yields and N uptake. In particular, in the year characterised by the lowest total rain the oil production de