Boron Deficiency in Cotton and Sunflower: Symptoms and Correction
Boron deficiency is easy to overlook because the plant often looks broadly healthy — the main symptom is poor flower and boll retention in cotton, or reduced seed set in the sunflower head, rather than dramatic leaf discoloration.
In cotton, deficient plants may show thickened, brittle stems and shortened internodes near the growing tip, along with shedding of small bolls shortly after flowering — losses that are frequently misattributed to heat stress or pest damage rather than a nutrient shortfall.
Sunflower is particularly sensitive to boron during head formation and flowering; deficiency at this stage can result in incomplete seed fill across the head, visibly reducing the harvestable yield even when the plant otherwise appeared normal through vegetative growth.
A foliar spray of liquid boron, such as Bukhara (5% B), timed to just before flowering is the standard correction, and growers in fields with a known history of boron shortfall often build a preventive spray into their flowering-stage program rather than waiting for symptoms to confirm the deficiency.