Gypsum

Gypsum (Calcium sulphate) is a very useful amendment to have on standby. 

Providing Calcium and  Sulphur, it delivers its payload without raising soil PH (if anything, it can have a very mild acidifying quality). This makes it a great choice for topping up Calcium in situations where you don't want to modify PH significantly, such as mid-season or when formulating mixes that are not inherently acidic (like Coco).

There are a variety of Gypsum sources sold in Australia, in different levels of purity. We stock White, graded Gypsum with an approx maximum particle size of 2-3mm, and most being a fine powder. 

Be wary of cheap gypsum as it can often be recycled from Gyprock particle boards, or sourced from low quality mines where seam wall ends up mixed with the Gypsum extract. Both of these we view as inferior sources due to potential contamination or lowered purity.