Magnesium Carbonate

Magnesium Carbonate is a super cool mineral. It can raise PH in a similar way to Lime or oyster powder, but instead of supplying Calcium, it provides Magnesium. 

If you have ever used Dolomite, then you have, in effect, used something somewhat similar. Limestone is predominantly Calcium Carbonate, while Dolomite is Calcium Magnesium Carbonate. Magnesium Carbonate is just Magnesium and Carbon without Calcium piggybacking on the tail end. This allows you to more easily achieve better  Calcium and Magnesium ratios, as well as optimise soil PH. 

Magnesium Carbonate, or Magnesite, as it is sometimes known, is a great way to add a slow, long-term source of this important mineral in a non-sulphate (non-acidic) form, making it unique in its application from ingredients such as Kieserite or soluble Magnesium Sulphate. 

The ability to maintain regular access to Magnesium throughout the plants life cycle is imperative to good, strong, and healthy growth, and as important if not more so, the quality and quantity of flowers produced. Magnesium governs many enzymatic processes within the plant and so running out of this crucial mineral, will affect the overall plants performance drastically. 

Doses vary based on your soils magnesium, and PH requirements, doing some testing is a good idea to determine how to much to add. 

As a general rule, 1 cup (250ml) dug into soil is a good starting rate, along with your chosen buffering ingredients. 

For top dressing, it is best incorporated along with other ingredients, and makes a good addition to "craft blend" style fertilisers. A little goes a long way when top dressing, a teaspoon per 40L pot may be enough.

Keep in mind it is a non soluble mineral, and will take time for its results to show. its best to incorporate this ingredient as long before planting as possible.