Calcium guide
Calcium is a secondary nutrient the crop needs to build strong cell walls, keep cell membranes healthy and grow new root and shoot tips. A...
Read the full guideBlossom-end rot, bitter pit and tip burn: when the soil has enough calcium
Why calcium disorders appear on calcium-rich soils, why calcium sprays alone often fail, and how water, potash, magnesium and boron decide the result.
Calcium travels in the plant only with the water stream to the leaves. Fruits lose little water, so they get little calcium, and any break in water supply cuts it further. Too much potash, magnesium or ammonium also crowds calcium out, and without boron calcium cannot do its job in the cell wall. That is why a field can show calcium problems on calcium-rich soil, and why calcium sprays alone often fail.
By Gafar Laiya and the Gujarat Bio Organics team. Updated November 2026.
The real causes
- Irregular watering: the biggest cause of blossom-end rot.
- Humid, still weather that slows water movement.
- Heavy potash, magnesium or ammonium nitrogen.
- Boron shortage, which stops calcium from building cell walls.
- Very fast growth from heavy nitrogen.
What fixes it
- Water little and often during fruit growth.
- Balance potash and nitrogen to the soil test.
- Check magnesium and boron along with calcium.
- Use calcium sprays at fruit development as a support, not the only fix.
- See how nutrients block each other.
Read more
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.
Read next
Calcium deficiency symptoms crop by crop
How calcium disorders look in tomato, chilli, apple, mango, groundnut, potato, cabbage and pomegranate, and why they appear even on calcium-rich soils.
Read the full guideHow Gujarat Bio Organics can help
Since 2006, lakhs of farmers from Kashmir to Kanyakumari have used Immunity products on almost every crop: from the mango farms around Somnath to the apple orchards of Himachal Pradesh and Kashmir, the tea estates of Assam and Darjeeling, and the banana, coconut and cardamom farms of Tamil Nadu, Karnataka and Kerala. Each Special is one formula made for one crop and its common problems. Tell us your crop, soil test and what you see, and our team will tell you what to check, whether a micronutrient correction is needed, and which Special fits your programme.
- Vegetables guide and Immunity Vegetable Special
- Apple guide and Immunity Apple Special
- Mango guide and Immunity Mango Special
- Groundnut (Mungfali) guide and Immunity Mungfali (Groundnut) Special
- Potato guide and Immunity Potato Special
- Pomegranate guide and Immunity Pomegranate Special
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.
Questions
Why did my calcium spray not fix the problem?
Because the cause was not a lack of calcium in the soil but water supply, nutrient imbalance or boron. Fix those and the calcium already in the soil reaches the fruit.
Is gypsum or lime better for calcium?
Gypsum supplies calcium without changing pH and suits most Indian soils. Lime is for acid soils that also need their pH raised.