Less is More: The Influence of Nitrogen Fertiliser Application on Anthocyanins in Sweet Cherries

Sweet cherries are a rich source of anthocyanins, which are associated with fruit colour and human health benefits. The cherry variety determines the profile of anthocyanins which accumulate during ripening. However, the impact of orchard management practices including nitrogen (N) fertiliser application on anthocyanin content of cherries is unknown. A field trial in a commercial cherry orchard over two seasons assessed the impact of pre-harvest N fertiliser rates of 0, 23.5 and 45 kg N ha^-1 on the anthocyanin content of sweet cherries (“Lapins”). Anthocyanin profiles were determined by UPLC-MS/MS and contents by UVvisible spectroscopy (pH-differential method). Descriptive statistics were performed. Results indicate that cyanidin-3-rutinoside was the most abundant anthocyanin (82%), followed by peonidin-3-rutinoside (14%). Mean inter-seasonal differences in anthocyanin content were high (330 ± 154 and 48 ± 29 mg 100 g^-1 , respectively). In the second season, with the accumulative effect of treatments on cherry trees, cherries with increasing rates of nitrogen application showed decreased anthocyanin contents (60, 50, 33 mg 100 g^-1 , respectively). These results highlight for the first time that high pre-harvest N application reduces the anthocyanin content of cherries. This knowledge can inform orchard management decisions to regulate fruit colour and anthocyanin content of sweet cherries.