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Boron Fertilizers

Boron fertilisers are micronutrient inputs used to correct boron deficiency, one of the most widespread micronutrient deficiencies in Indian arable soils. Approximately 45% of Indian arable soils are reported to be boron-deficient, with the problem particularly severe in light-textured soils, red soils, and soils with high pH or low organic matter.

Composition

The major boron sources used in Indian agriculture include:

  • Borax decahydrate (Na2B4O7.10H2O): 11% B, the cheapest soil-applied source
  • Boric acid (H3BO3): 16.5% B, used in foliar sprays
  • Disodium octaborate tetrahydrate (Solubor, DOT): 20-20.5% B, fully water soluble, used for foliar and fertigation
  • Colemanite (Ca2B6O11.5H2O): slow-release calcium borate

Widely available Indian products include Tata Rallis Solubor (20% B) and IFFCO Boron 20%.

Mode of action

Boron is essential for pollen viability, pollen tube growth, fertilisation, cell-wall biosynthesis (pectin cross-linking), sugar transport through phloem, and meristem function. Symptoms of deficiency include hollow stems in cole crops, sterile flowers and poor fruit set in mango and pomegranate, and brown rot in cauliflower curds.

Target use and dose

  • Soil application: 5-10 kg borax per acre, broadcast at land preparation and incorporated, gives season-long supply for most field crops.
  • Foliar application: 1-2 g Solubor per litre, sprayed at pre-flowering and early fruit-set stages on pulses, oilseeds, cotton and fruit crops.

In paddy and chilli, foliar boron is commonly tank-mixed with calcium nitrate for fruit set; see Input Boron Foliar for foliar-specific dose details.

Safety and regulatory status

Borax and boric acid are FCO-notified micronutrient fertilisers. The margin between deficiency and toxicity is narrow: soil B above 5 ppm causes leaf-margin scorch and yield loss in sensitive crops, and overdosing must be avoided.

See also: Zinc Sulphate, Edta Chelated Zinc, Calcium Magnesium Foliar, Multi Nutrient Fertilizer Blends, Input Boron Foliar.

References

  1. Tata Solubor Boron 20% Micronutrient Fertilizer. Tata Rallis / Agriplex India.
  2. Solutions for India's Fortified Fertilizer Market. U.S. Borax India report.