Boron (B) in crops: role, deficiency signs and how to correct it

Boron is a micronutrient the crop needs to build cell walls, to grow at its tips, and above all for pollen to germinate and grow, so flowers set fruit and seed. A boron-short crop shows dying growing tips, thick brittle young leaves, flower and fruit drop, cracked or misshapen fruit and hollow stems. The gap between too little and too much boron is narrow, so it must be applied with care.

By Gafar Laiya and the Gujarat Bio Organics team. Updated November 2026.

What boron does in the plant

• Builds and holds cell walls together, especially in growing tips and young fruit.
• Needed for pollen to germinate and grow, so flowers set fruit and seed.
• Helps sugars move to flowers, fruit and roots.
• Works with calcium in cell walls; a boron shortage can look like a calcium problem.
• Supports root tip growth and nodulation in legumes.

How boron moves in the plant

In most crops boron moves little once inside the plant, so growing tips, flowers and fruit show the shortage first. A steady supply through the season matters more than one big dose.

Signs of boron deficiency

• Death of the growing tip, followed by many side shoots (a bushy top).
• Young leaves thick, brittle, curled or misshapen.
• Short internodes; hollow or cracked stems.
• Flowers and young fruit drop; poor fruit and seed set.
• Cracked, corky or misshapen fruit; uneven berry size in grapes.
• Hollow heart in groundnut kernels and some root crops.

Crop by crop

More crops and look-alikes: Boron deficiency symptoms crop by crop.

Where and why it happens

In India, an ICAR survey of more than two lakh soil samples found 44.7% of soils short of boron, counting hidden shortages.

• Sandy, light soils where boron washes out with rain.
• Calcareous and alkaline soils.
• Soils low in organic matter.
• Dry spells, because boron reaches the roots with soil water.
• High rainfall regions.
• Crops with a high need: cotton, groundnut, sunflower, cauliflower, mango, coconut, pomegranate.

How it works with other nutrients

• Boron and calcium work together in cell walls; a boron shortage stops calcium from doing its job, so fruit disorders can look like calcium shortage.
• Heavy liming and very high calcium can lower boron uptake.
• Dry soil reduces boron uptake even when the soil has enough.
• See nutrient interactions.

What happens if it is not managed

• Flower and young fruit drop, so fewer fruits even with heavy flowering.
• Cracked and misshapen fruit with low market value.
• Hollow kernels and poor seed fill.
• Weak root tips, so the crop uses water and nutrients less well.
• See the full picture of what unmanaged shortages cost.

How to confirm it

• Watch growing tips, flowers and young fruit, not only leaves.
• Check for hollow stems and cracked fruit.
• Ask for a hot-water soluble boron soil test; a leaf test confirms.
• Because the safe range is narrow, test before repeated applications.

How to correct it

• Apply boron where a soil test shows it is short, before flowering in fruit crops and at sowing in field crops.
• Foliar spray of a soluble boron product at the pre-flowering and flowering stage helps fruit set.
• Use only the dose on the label or advised by your agriculture officer; never double it 'to be safe'.
• Do not apply boron to every crop every season without testing.
• Keep soil moisture steady so boron can reach the roots.
• Organic matter helps hold boron in the root zone.

Too much boron

• Too much boron burns leaf edges and tips, starting on older leaves, then the leaf dies.
• The gap between enough and too much is narrow, especially for sensitive crops such as beans and some cereals.
• Irrigation water high in boron can also cause toxicity.

Doses depend on the crop, soil and product, so this page gives methods, not amounts. Take the dose from your soil test report, the product label or your local agriculture officer or KVK. Results differ from farm to farm with soil, weather, crop and management. Farmer experiences on this site are their own reports, not a promise of results.