What it does

Alkalinity impairs plant growth by restricting water supply to the roots, thus obstructing root development. It results to phosphorus and zinc deficiencies, and possibly iron deficiency and boron toxicity.

Why and where it occurs

Alkalinity is relatively rare especially in irrigated rice systems. It occurs in semiarid region soils and is often associated with salinity.

Alkaline soils have high levels of exchangeable sodium, usually more than 15%.

The high percentage of sodium usually causes soil structural problems, which can affect aerobic or upland crop systems. It can also have a direct effect on some varieties.

How to identify

Check leaves for discoloration and leaf rolling.

Symptoms show discolored leaves ranging from white to reddish brown, starting from the leaf tips. Leaves can also have senescence or natural drying.

In severe alkaline conditions, discoloration spreads down the leaf giving the plant a scorched appearance.

Strong alkaline soils also inhibit growth and tillering, causing plants to stunt, and leaves to roll.

Alkalinity can also delay flowering and cause whiteheads.

Its symptoms can be confused with Nitrogen deficiency. To confirm alkalinity, bring soil and plant sample to a laboratory for testing.

How to manage

There is currently no practical field management options for alkalinity. Alkaline soils need to be rehabilitated, and this is a long-term process.

Learn more

View full fact sheet:
Alkalinity on IRRI Rice Knowledge Bank