The effect of the combined use of zinc, boron and magnesium on the growth and development of tea plants on the Black Sea coast of Russia

Given the limited resources of suitable soil and climatic conditions for tea cultivation in Russia, as well as various degradation and erosion changes, special attention is paid to creating balanced nutrition systems that enhance plant resistance to diseases and adverse weather conditions. The purpose of the research is to study the growth and development of tea plants grown on a new mineral nutrition system, including macro-(NPK) and microelements (Zn, B, Mg) in the humid subtropics of the Black Sea coast of Russia. The object of the study is a zoned tea variety Kolkhida. In the field experiment, it was found that the amount of precipitation for the period July–August less than 100 mm is critical for tea plants, the tea shoot СJС increased to 16.3% and severe stress was noted. The quantitative content of chlorophyll a (1.33–1.89 mg/g) was higher than the content of chlorophyll b (0.87–1.35 mg/g), and the carotenoid content was 3.8–5.0 times lower than the total amount of chlorophylls (2.55–3.08 mg/g). In the studied variant (Zn+B+Mg) under conditions of summer drought, a tendency was revealed to increase the proportion of photosynthetically active chlorophyll a in the total of chlorophylls by 0.07–0.09 c.u. compared with the control variant, which shows the restructuring of the photosynthetic apparatus under conditions of abiotic stress. At the same time, the recovery period in autumn also demonstrates a significant increase in the content of chlorophyll a – by 0.23–0.59 c.u. in the studied variant compared with the control. The study of chlorophyll fluorescence parameters during prolonged drought also showed a significant increase in the viability index by 0.59 units in comparison with the control. The root application of the elements (Zn+B+Mg) enhanced the shoot-forming ability of tea plants by 106% of tea, which increased the yield.