Contents of nitrogen compounds during bud break and peach tree performance in response to budburst-inducing products.

• Relationship between nitrogen compounds and chemical induction of bud break. • Budburst, flowering and fruit set were correlated with higher nitrogen and spermidine. • The main challenges to evaluate possible replacements to hydrogen cyanamide (HC). • HC and nitrogen fertilizer + calcium nitrate improved crop performance. The growth of peach orchards in subtropical regions depends on the minimal requirements for chilling accumulation, and crop loading requires sprays of chemical compounds to overcome dormancy, induce bud break, and allow adequate flowering and fruiting. The ability of hydrogen cyanamide, nitrogen fertilizer and calcium nitrate to break the dormancy of 'BRS Kampai' peach trees and their effects on nitrogen, tryptophan, and polyamine contents in buds were evaluated. Furthermore, budburst, flowering, fruit set percentage, flowering period, tree performance, and bioactive compound content in the fruits were assessed. The study was undertaken in São Paulo state, a subtropical region of southeast Brazil, and the field experiment was carried out in two crop seasons. Short flowering duration and higher percentages of budburst, flowering, and fruit setting were correlated with higher nitrogen content in vegetative buds and spermidine contents in flower buds. The better performance of hydrogen cynamide, compared with other treatments, was confirmed by the anticipation, patterning, and increase in budburst, flowering, and fruit setting, associated with high levels of spermidine in the flower buds. Hydrogen cyanamide also increases the concentration of antioxidant compounds in fruits. Hydrogen cyanamide and the combination of nitrogen fertilizer and calcium nitrate enhanced yield and production efficiency and are recommended for inducing budburst in subtropical regions. [Display omitted] [ABSTRACT FROM AUTHOR]