Calcium Deficiency is caused by the immobile nature of calcium under either excessive temperatures or high humidity conditions.
It is often seen as Tip Burn in leafy plants such as lettuces and Blossom End Rot in tomatoes.
Under excessive temperature conditions the rate of transpiration is very high. The rapid uptake of water does not carry the Calcium molecule up into the plant which means it does not reach the edges of the leaves where it is most required for cell structure. A lack of calcium in the edges of the leaves results in Tip Burn.
Under high humidity conditions the movement of water within the plant is very slow, which leaves the calcium molecule at the bottom of the root system. Root infections with Pythium and Phytophthora also reduce the ability of the plants to translocate calcium.
Calcium is carried into the plant most effectively at a low E.C level. Some growers are able to reduce the problem of Tip Burn or Blossom End Rot by lowering the E.C during the daytime and increasing it at night so the plants are able to feed.
In the past Ca-EDTA (Calcium Chelate) at 1-1.5g/L + Surfactant applied weekly has prevented problems of tip burn but recent formulations of Ca-EDTA are causing leaf burn.
There is now a new product that is not phytotoxic and is doing a better job than the EDTA.
It is available as a micro-granule called Brexil™ Ca containing 14.82% Ca and 0.5% B and used as a wet spray at 2.5-3.0g/L. Surfactant is included.
Brexil Ca is based on the very large ammonium lignin sulphonate molecule (also known as the LSA-Complex molecule) that gains entry into the plant and cells by mimicking the DNA molecule. Foliar Spray Solutions must remain under pH6.5.
Brexil Ca is available form Pure Hydroponics in a 5kg pack for NZ$105.00 + GST
Please see article link below for further notes on Tip Burn Prevention.