Calcium nitrate supplies two nutrients: calcium and nitrate nitrogen. Calcium builds the walls of plant cells. When it runs short, the damage shows on fruit first, because calcium travels with the water stream and fruit draws less water than leaves.
Signs your crop is short of calcium
- Blossom end rot in tomato, chilli and capsicum: a dark, sunken patch at the bottom of the fruit.
- Tip burn on cabbage and lettuce.
- Soft fruit that does not keep after picking.
- Cracking in pomegranate and some other fruits, often together with irregular watering.
Uneven irrigation makes all of these worse, because calcium only moves when water moves. Steady watering matters as much as the fertilizer.
How to apply
Through drip, calcium nitrate is usually given from flowering through fruit development, in small, frequent doses. It can also be sprayed on leaves and fruit. Your dose depends on crop, soil and stage; ask us for a schedule.
The mixing rule
Never mix calcium nitrate in the same tank with phosphate or sulphate fertilizers, such as 12:61:0, 0:52:34, 19:19:19 or SOP. Calcium reacts with them and forms a solid that settles in the tank and blocks drippers. Run calcium nitrate on a separate day or from a separate tank.
A note on saline water
If you irrigate with salty water, calcium helps protect soil structure by pushing sodium off the clay. That is one more reason drip farmers in dry districts keep calcium nitrate in the schedule.
