Dolomite has never been called ineffective. My introduction to dolomite was during the first spring of my dairy farming career when helping with another cow down at calving the owner muttered, “we never had these problems when we used dolomite”.
The questions were, “what is dolomite” and “why don’t we still use it?” The answers were that dolomite was the most effective magnesium fertiliser available and when the cost of the freight was no longer subsidised it became too expensive.
That conversation took place in 1979. Dolomite remains the most effective magnesium fertiliser today and there is a commitment from the mine owners and those involved in transport, storage, marketing and selling, to mine it and transport to property as cost effectively as possible.
Too dear? The cost is measured against the benefits and it will differ for each.
Dolomite is similar to lime in that both contain calcium in the carbonate form. The analysis is 59% calcium carbonate and 39% magnesium carbonate, which convert to 24% calcium and 11.5% magnesium. Dolomite is only applied where there is a need for magnesium.
Being in the carbonate form provides much of the unique benefit. The rate of release of finely ground carbonate is in sync with demand. Whilst soil temperatures are low release is relatively slow increasing with temperature and peaking in spring when demand is highest.
The rate of application is usually around 220kg/ha providing 25kg Mg/ha. Even in the most demanding situation this is sufficient to minimise calcium/magnesium related metabolic situations in spring. Should it be applied a little heavier the effect will simply last a little longer.
A 28 tonne truck and trailer load provides sufficient magnesium for 127ha. If the area to which it is spread is less, a smaller quantity may be purchased from a local provider.
The price per tonne increases with distance from the mine at Golden Bay. Dolomite can be delivered to Central Canterbury properties in truck and trailer load lots for $151.20+GST/tonne. The price per hectare at a spreading rate of 220kg/ha is therefore $33.26+GST not including the cost of spreading.
For that price all animals well fed on dolomite dressed pasture are unlikely to suffer a severe calcium/magnesium imbalance. Our experience is that calcium/magnesium related metabolic disorders are few and when treated recovery is usually rapid.
The following, by John Ruskin is worth keeping in mind –
“It is unwise to pay too much, but it is worse to pay too little. When you pay too much you lose a little money – that is all. When you pay too little, you sometimes lose everything because the thing you bought was incapable of doing the thing it was bought to do. The common law of business balance prohibits paying a little and getting a lot – it cannot be done.”