Bioactive compounds, total antioxidant capacity and yield of kiwiberry fruit under different nitrogen regimes in field conditions.

BACKGROUND Actinidia arguta known as the 'kiwiberry' or 'mini kiwi' is relatively new among the cultivated berry species. Recent studies indicate the kiwiberry fruit could be an important source of many health-promoting compounds. A knowledge-based fertilisation concept was evolved to define optimal strategies for feeding Actinidia with nitrogen (N) because a deficit and excess of N both have a negative impact on plants and the surrounding environment. RESULTS Kiwiberry yield and fruit internal quality significantly depended on soil N level, cultivar and growing season. A higher soil N led to an increase in carotenoid content and a decrease in phenolic content, whereas ascorbic acid and glutathione contents were not affected by soil N fertility. Under the highest N dose, enzymatic antioxidants were activated. Trolox equivalent antioxidant capacity clearly decreased with an increasing N level. CONCLUSIONS Competent and skilful fertilisation management should focus on balancing a high fruit yield and maintaining their high quality. Based on yield level and fruit antioxidant potential, the N guide values for A. arguta vary between 30 and 50 mg N per kg-1 of soil. The recommended N dose may depend on overall soil quality traits and cultivar N demand, as well as on weather conditions. © 2020 Society of Chemical Industry.