Distribution of foliar applied labelled nitrogen in grapevines (Vitis vinifera L., cv. Riesling)
2002
Schreiber, A.T. | Merkt, N. | Blaich, R. | Fox, R.
The spread of foliar applied 15N (10.74 atom% 15N access) in the overall grapevine and the effects of this application on the development of amino acids in must and wine were examined. The study was carried out in a vineyard with 12-year-old Riesling vines grafted on Binova in the growing region of Württemberg, Germany. The soil had been fertilized since 1995 with different quantities of N (0 kg N ha-1 and 60 kg N ha-1 per year). In 1999 15NH415NO3 (total amount of 20 kg N/ha) was applied to the leaves of both variants every two weeks during berry development including one additional application after harvest in order to study the remobilization of N without grapes for replenishing the reserves of the grapevine. All the grapevines were dug out at 5 set dates to analyse the N content. Each treatment was repeated four times. Due to the foliar fertilization the relative nitrogen contents of the must increased by approximately 30%, the absolute N contents increased by almost 40%. As a result of the foliar fertilization the content of yeast utilisable amino acids was increased by 100% in plants receiving 0 kg N/ha and by more than 30% in those receiving 60 kg N/ha, a fact positively affecting the fermentation speed. Due to low contents of glutamine and arginine in the must the fermentation period was extended by up to 33 days. On the first sensory evaluation of the wines the “unpleasant” wine flavours were found to be reduced by the foliar fertilization. The second sensory test did not reveal any differences in taste. The aminoacetophenone contents of foliar fertilized and non foliar fertilized variants were the same.
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