#Malyukova L

#Malyukova L.S. , Kozlova N.V. , Velikiy A.V. Effect of boron and zinc-containing fertilizers on yield of tea leaf on Russian Black Sea Coast

Сельское хозяйство / 3. Земледелие, грунтоведение и агрохимия

L.S. Malyukova, N.V. Kozlova, A.V. Velikiy

The All–Russian Scientific and Research Institute of Floriculture and Subtropical Crops, 354002, Krasnodar region, Sochi, Yana Fabritsiusa str. 2/28

Effect of boron and zinc-containing fertilizers on yield of tea leaf on Russian Black Sea Coast

Industrial cultivation of tea on the Black Sea coast of Russia, accompanied by the prolonged use of mineral fertilizers, has led (due to the increased soil acidity) to the increase in the mobility of some elements (Ca, Mg, Mn, Fe, Al, Cu, Zn), changed the balance of nutrition elements in soil-absorbing complex and some other soil properties [2, 5-8]. In this regard, the task is to develop the most effective agrochemical methods of increasing yield, quality of tea leaves as well as to preserve fertility in unique soils [1, 7, 10]. Multicomponent mineral nutrition of tea plants is considered as one of the most promising areas, including the use of micronutrients. The most significant role in ensuring high productivity and quality of tea raw material is experimentally proved by many tea-producing regions and belongs to such micronutrients as boron and zinc [1, 3, 9, 11]. Boron and zinc play an important role in the physiological and biochemical processes concerning plant growth, particularly in phenolic and carbohydrate metabolisms, respiration and plant resistance to abiotic stress factors [4, 9]. The aim of this research was to study the effect from soil fertilizers containing boron and zinc on yield of tea raw material, in conditions of Russian Black Sea coast.

The studies were conducted during 2008-2013 based on the field experiment, which was pledged on a tea plantation in 2003 and included a regionalized cultivar called Colkhida (planted in 1983) on the Russian Black Sea coast. Zinc sulfate (Zn - 4,3 kg/ha of active substance) and boric acid (B - 6 kg/ha of active substance) were added to the soil surface on the background nitrogen rate (240 kg N·ha), phosphorus (70 kg P₂O₅·ha) and potassium rates (90 kg K₂O ha). As a control, there was an option with the introduction of macrofertilizers nitrogen rate (240 kg N·ha), phosphorus (70 kg P₂O₅·ha) and potassium rates (90 kg K₂O ha). The size of experimental plots was 10 m². The frequency - 3-fold. The soil is brown forest acidic with low humus content and powerful, on eluvium-deluvium of mudstone. Before setting the experiment, the soil was characterized by acidic reaction of medium of the soil solution ( pH 3,2-3,3 ), average supply with hydrolyzable nitrogen ( 80-100 mg/kg), mobile phosphorus (300-400 mg/kg) and potassium (200 - 300 mg / kg). Уield was considered as an integral indicator of plants growth and was recorded from May to October (6-10 harvests) on the test options during the periods of complete formation of 3-leaf tea fleches. In order to assess photosynthetic activity in tea plants, the content of photosynthetic pigments (chlorophyll a, b and carotenoids) in green tea leaves was determined after extraction with with acetone (100%) by Shlyk method using computational formulas of Tsingler and Egle [12].

On average, the studied years were characterized by relatively favorable weather conditions for cultivating tea culture in Russia (no return of winter cold in spring, sufficient rainfall during the vegetation season - on average - 800 mm), which contributed to high yield of tea leaves for a given zone (Table).

Table - Effect of boron and zinc-containing fertilizers

on the yield from tea cultivar Colkhida, kg/ha

Option	Observation years				On average for 2008-2013 yy.	Addition to the control, %
Option	2008	2010	2011	2013	On average for 2008-2013 yy.	Addition to the control, %
control	4150	4720	5900	9200	5993	–
B	4680	5940	9200	11600	7855	34
Zn	3530	5090	7700	10000	6580	10
LSD _0,05	346	541	623	755	–	–

However, the optimal hydrothermal conditions in 2011 and 2013, including the summer period, contributed to the formation of a higher yield from tea leaves, approaching potentially possible (maximum) for the cultivar called Colkhida (10 000-12 000 kg/ha). The most significant increase in their harvest during the analyzed period was marked on the option with the introducing boron into the soil on the background of macrofertilizers (Table ), due to its element’s ability to intensify shoots-formation in tea plants (fig.1). The option with applying zinc-containing fertilizers also exceeded the control, but was a bit worse in productivity growth than that with boron. Analysis on the content of photosynthetic pigments (chlorophyll a, b) in mature leaves showed minor differences in absolute values for the test variants, with a tendency to reduce their content if boron and zinc were applied to the soil (2,01-2,85 and 2,24-2 99 mg/g of chlorophyll a and b, respectively) compared with the control (2,42-3,02 mg/g amount of chlorophylls a and b), which is probably due to the more intensive use of these pigments in the options with higher yields. However, these options had a stronger process of accumulation of chlorophyll a, b and carotenoids in physiologically mature leaves from July till September; their content was significantly increased in 1,3-1,4 times (1,2 times when in the control), indicating more intensive activity of plants photosynthetic apparatus.

Figure 1. The effect of boron and zinc on the shoot-forming ability of tea plants during the growing season, pcs. / m².

Shoot-forming ability in this embodiment may also be activated due to the increased synthesis of growth stimulants, such as auxin and cytokinin, and due to the speed of their movement within a body or on the boundary of different organs. Zinc also intensified shoot-forming activity of tea plant, thereby increasing productivity. There is some data on the effectiveness of this type of fertilizers, associated with its influence on the complex redox processes, including enzymatic defining an adequate defensive response and, therefore, resistance to stress of different nature.

The research has shown that soil fertilization with boron and zinc (6 and 4,3 kg/ha of active substance, respectively) on the Black Sea coast of Russia provided tea plantation productivity to 34 and 10%, respectively, increasing shoot-forming and photosynthetic activity.

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