Boron micronutrients: properties and applications
Boron micronutrients are a group of substances that provide plants with available boron — one of the most important trace elements necessary for normal growth and development. Despite the fact that boron is required by plants in extremely small quantities, its deficiency leads to serious physiological disorders: death of growth points, deformation of leaves and fruits, reduced fruit set and crop quality. Boron fertilizers are widely used in agriculture for pre-sowing seed treatment, foliar feeding and basic soil application.
Chemical Nature and Range
The main representatives of boron micronutrients are boric acid (H₃BO₃), containing 17.3% boron, and borax (sodium tetraborate, Na₂B₄O₇·10H₂O), containing about 11% boron. Boric acid is a fine crystalline white powder, readily soluble in hot water. Borax is also readily soluble in water and is often used to prepare solutions. In addition to these simple compounds, complex forms are used in agriculture: boron superphosphate (contains 0.2–0.4% boron), boron-magnesium fertilizer (about 13% H₃BO₃ and 14% MgO), as well as liquid concentrates based on organo-mineral boron complexes.
Modern industry produces boron fertilizers in various forms: powder, crystalline and liquid. Liquid concentrates are convenient for precise dosing during foliar feeding, while crystalline and powder products are more often used for pre-sowing seed treatment and basic application. Chelated forms of boron, although less common than metal chelates, are also used in intensive vegetable production and greenhouse operations.
Regulatory Framework
Requirements for boric acid as a fertilizer and technical product in Russia and CIS countries are regulated by GOST 9656-75 (boric acid) and GOST 18704-78 (technical boric acid). For borax, GOST 8429-77 applies. Depending on the application and purity, products are produced in various grades and classes. For agricultural use, it is important that the fertilizer does not contain heavy metal impurities and complies with sanitary and hygienic standards.
Agronomic Value and Applications
Boron plays a key role in carbohydrate and protein metabolism of plants. It is necessary for the formation of cell walls, cell division, pollen germination and fertilization, as well as for sugar transport. With boron deficiency, plants exhibit death of apical buds, "hollowness" of root crops, browning and deformation of fruits, and poor seed set. Boron fertilizers allow these disorders to be eliminated and increase yield and product quality.
Main methods of applying boron fertilizers:
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Pre-sowing seed treatment. Soaking seeds in boric acid solutions (typically 0.05–0.1% concentration) or dusting with boron-containing powders. This improves germination and initial growth.
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Foliar feeding. Spraying plants with boric acid or borax solutions during the growing season. The working solution concentration is typically 0.05–0.1% (150–200 mg boron per liter of water). Feeding is carried out in the budding and flowering phases, as well as after fruit set.
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Basic soil application. Boron superphosphate or boron-magnesium fertilizer is applied before digging or cultivation. Application rates range from 4 g per hundred square meters for boric acid to several centners per hectare for complex forms.
The most responsive crops to boron are sugar beet, legumes, fruit and berry crops (pome and stone fruits), grapes, citrus fruits, vegetables (tomatoes, cucumbers, peppers), and flower crops (roses, carnations, gerberas). Boron fertilizers are especially effective on soils with neutral and alkaline reactions, where boron is less available to plants.
Safety and Storage
Boric acid and borax belong to substances of moderate hazard. When working with them, personal protective equipment (respirator, safety goggles, gloves) is recommended to prevent irritation of mucous membranes and skin. Storage is carried out in dry, well-ventilated areas, in hermetically sealed containers, away from food products and feed. The shelf life of boron fertilizers under proper storage conditions is unlimited.
Conclusion
Boron micronutrients remain an indispensable tool in the agronomist's arsenal for the prevention and correction of boron deficiency. A wide range of forms — from simple boric acid to complex organo-mineral concentrates — allows the optimal product to be selected for any crop cultivation technology. Organising supplies of boron fertilizers, including the selection of form and concentration for a specific crop, requires an individual approach.