What it does

Boron toxicity inhibits the formation of starch from sugars and affects the formation of B-carbohydrate complexes.

Why and where it occurs

Boron toxicity is a rare condition, especially in irrigated rice systems, that usually occurs during dry season when there is high boron content in groundwater.

B toxicity is most common in arid and semiarid regions, but has also been reported in rice in other areas. Soils prone to B toxicity include the following types:

soils formed on volcanic parent material, usually associated with the use of irrigation water pumped from deep wells containing a large B concentration (e.g., IRRI farm, Los Baños, and Albay, Philippines)
some coastal saline soils

How to identify

Plants affected by B toxicity exhibits

Chlorosis of tips and margins of older leaves as initial symptoms
Dark brown elliptical spots on discolored areas two to three weeks later followed by browning and drying up
Necrotic spots prominent at panicle initiation
Brownish leaf tips and dark brown elliptical spots on leaves
Vegetative growth is not markedly depressed

To confirm B toxicity damage, bring soil and plant sample to the laboratory for testing.

Click on images to enlarge

Infected plants have yellowish and discolored leaf tips

Field damage caused by boron toxicity

Large brown elliptical spots are visible on boron toxicity infected leaves

How to manage

Plant B-toxicity tolerant varieties (e.g., IR42, IR46, IR48, IR54, IR9884-54). B-toxicity tolerant varieties can yield up to 2 t ha-1 more than susceptible varieties.
Use surface water with a low B content for irrigation. Groundwater must be monitored regularly if used for irrigation.
Plow when the soil is dry so that B accumulates in the topsoil. Leach with water containing a small amount of B.

Learn more

View full fact sheet:
Boron toxicity on IRRI Rice Knowledge Bank