Iron chlorosis in calcareous soil: why iron sulphate in the soil often fails

Calcareous soils hold plenty of iron, but the high pH and bicarbonate lock it into forms roots cannot use. Ferrous sulphate added to such soil is often locked up in the same way within days. Foliar sprays, iron chelates made for high pH soils, better drainage and more organic matter work better than adding more plain iron to the soil.

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

Why the soil iron is locked

• At high pH, iron turns into insoluble forms.
• Bicarbonate in soil and irrigation water makes it harder for roots to take up iron.
• Waterlogging and compaction make it worse.

What works better

• Avoid over-irrigation and improve drainage.
• Spray iron on the leaves, repeating as new leaves appear.
• Use iron chelates designed to stay available at high pH for soil or drip use.
• Add compost and organic manure to support root health and iron availability.
• Ask your agriculture officer about varieties that tolerate calcareous soil.

What not to do

• Do not keep adding plain ferrous sulphate to calcareous soil if it has not worked before.
• Do not treat yellowing with more urea; nitrogen does not fix iron chlorosis.
• See why more urea does not fix yellow leaves.

Read more

• The full iron guide.
• Iron deficiency symptoms crop by crop.

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.