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With flower buds appearing very early this year, some farmers are wondering about the impact of late nitrogen application in the form of a nitrogen solution.  

The burns observed are mainly due to a contact effect: fertilizer droplets deposited on the plant parts become concentrated as the water evaporates. The increase in salt concentration can then cause dehydration and tissue necrosis. Recent leaves and especially flower buds, whose tissues are young and poorly protected by a cuticle, are particularly sensitive. In addition, the microcavities present in the buds can retain the droplets and prolong contact with the solution.

The risk increases when the buds are clearly visible and exposed on the inflorescences (progression from stage D1 to E), and as soon as the first flowers appear (stage F1). Sensitivity increases with the proportion of buds exposed to the droplets. Weather conditions also play an important role: hot, sunny, dry, or windy weather promotes rapid evaporation and increases the concentration of the solution.

In most situations, the impact on yield remains limited, unless the crop is already very fragile. Rapeseed has a strong compensatory capacity, thanks to the gradual development of its yield components (seeds/m² and TGW).

In practice, if no other form of fertilizer is available, it is preferable to apply nitrogen, even in liquid form, at a stage close to E-F1, rather than not applying any at all. Nitrogen solution should preferably be applied during rainfall, which will limit burning.

Jean Lieven - j.lieven@terresinovia.fr
Elodie Tourton - e.tourton@terresinovia.fr
Julien Charbonnaud - j.charbonnaud@terresinovia.fr
Thomas Mear - t.mear@terresinovia.fr