Effect of boric acid solutions in organic solvents on productivity and chemical composition of meadow clover herbage

A comparative study of the effectiveness of boron in various forms (aqueous solution / chelated form) on the yield and quality indicators of Martum variety meadow clover herbage was carried out. Chelated forms were solutions of boric acid in organic liquids: monoethanolamine, diethanolamine, triethanolamine, glycerol, ethylene glycol. The plants fertilized with solutions of boric acid in organic solvents were bulkier and their biomass grew more intensively. The use of an aqueous solution of boric acid (the traditional form of boron microfertilizers) increased the plant growth by only 6.2 % compared to the variant without fertilization. The use of organic solvents led to more significant increase in the height of red clover: its increase compared to control test varied from 5.5 to 19.6 cm. The tallest plants were observed in the variant with the use of boric acid dissolved in ethylene glycol, which exceeded the control value by 1.3 times. Foliar top dressing with boric micronutrient fertilizers allowed increasing the herbage of the experimental crop by 7.4-78.5 %, in relation to the control test. The use of triethanolamine, glycerol, and ethylene glycol as solvents contributed to the maximum significant growth of the vegetative mass of clover, which was 8.1, 7.7 and 9.5 t/ha higher, respectively, compared to the unfertilized variant. The collection of dry matter in the experimental variants increased by 0.1-1.1 t/ha. The highest value of this indicator was noted during foliar treatment of clover with the solution of boric acid based on ethylene glycol, which exceeded the value of the control test by 73.3 %, as well as the variant with an aqueous solution of boric acid by 62.5 %. In addition to taking into account the total content of organic or mineral compounds in the clover phytomass, the content of the main nutrients - nitrogen, phosphorus, and potassium - was determined. The highest concentration of nitrogen was observed after adding a mixture of boric acid and glycerol, which is 24.2 % higher than the value in the control test, as well as 33.1 % higher than the variant after the aqueous solution of boric acid. The content of phosphorus in the clover herbage was maximal in the variant using a solution of boric acid in glycerol; it exceeded the control test by 15.4 %. The dissolution of boric acid in water and ethylene glycol, on the contrary, significantly reduced the concentration of this element by 11.5 % compared to the control test. The content of potassium in the clover herbage in the control test was 1.95 %, while the use of solutions of boric acid in organic solvents for foliar feeding led to an increase in this indicator by an average of 1.04 times. At the same time, the maximal increase in the indicator under consideration in the variant where a solution based on diethanolamine was used equaled 7.7 % to the corresponding value of the unfertilized variant and 8.2 % to the variant using an aqueous solution of boric acid. The use of boric acid contributed to a slight decrease in the content of nitrates, and the options with the use of di- and triethanolamine were characterized by the greatest effect in this case.