The content of macroelements in white mulberry (Morus alba L.) leaves

Abstract

The aim of this study was to evaluate the agrochemical and biological quality indicators of soil and to determine the best harvest time to maximize the nutrient contents of white mulberry leaves (Morus alba L.) from two different cultivars. Mulberry leaves were analysed to determine the seasonal changes in the contents of Ca, K, P, Mg and S. The study was carried out on 7-year-old mulberry trees belonging to Morus alba L. cultivated in an organic farm in the Kaunas District of Lithuania in 2016 and 2017. The soil agrochemical and biological indicators and mulberry leave samples were analysed two times during the tree vegetation period. The soil samples were collected in May and September (in the 2nd ten-day period) and leaves in June and September (in the 2nd ten-day period). The study revealed that a decreasing tendency for soil agrochemical indicators was observed throughout the entire period of growth of mulberry trees. At the end of the vegetation period the contents of nitrogen, available phosphorus and available potassium significantly decreased by 7.93, 24.85 and 25%, respectively, compared with that taken in May. At the end of the mulberry tree vegetation period the microbial biomass and dehydrogenase activity in the soil significantly decreased, by 20.39 and 17.95%, respectively, compared with that taken in the beginning of the vegetation period. The study revealed that harvest months had a statistically significant impact on the levels of the examined elements among the two Morus cultivars. It was found that the main macroelement in the leaves of both cultivars was Ca followed by K, P, Mg and S. However, the highest Ca, Mg, P and S contents in ‘Turchanka’ leaves increased with maturity. Importantly, the amount of macronutrients in the mulberry leaves varied in accordance with the cultivar and the harvest time. These results can help farmers to select a cultivar and harvest time that would allow them to produce mulberry leaves with superior quality. Leaves collected from mulberry plants grown in Lithuania plantations may be used as a food supplement to help meet the recommended daily intakes of some macrominerals for adults.