One of the challenges of writing a monthly article related to dolomite is isolating a single aspect of the effect of dolomite on pasture when its influence is so far reaching.
Ultimately it is the most effective magnesium fertiliser available although not always the cheapest per kilogram of nutrient applied. We regularly receive phone calls from farmers and growers who applied in the past, have no apparent magnesium requirement, but recall that many of the animal, pasture, or crop health issues they are now faced with were not a problem at that time.
History is a great teacher provided we take the time to read or listen to those whose experience goes back a good deal further than our own.
Over the years I have collected information and trial work on dolomite and when time permits it gets revisited, usually when a piece of information or observation triggers a vague memory.
Some years ago a farming family in the Waikato provided me with a 12 page letter on dolomite and its positive effect on animal health they had received from Les Hawill in 1994.
I had heard of Les, but did not meet him which was unfortunate as he obviously had a great deal of valuable knowledge and wisdom, only a small part of which is contained in the letter.
The second to last paragraph is worthy of reprinting “There are 98,000,000 tonnes of dolomite in the Nelson deposit near Collingwood that can supply all of the country with the right soil and magnesium compounds for agriculture and horticulture. What the movement needs is somebody with some common sense and the economy could bloom like never before.”
A bold claim perhaps, however the improvements in general animal health, and increases in milk yield in particular he details in the letter certainly support his contention that dolomite used sensibly can have a marked effect not only for the farming community but the New Zealand economy as a whole.
Other information from the letter also helps with perspective. The recommended rate of application was 2cwt/acre, which equates to 250kg/ha or 29kg Mg/ha, very similar to that recommended today.
The price of Dolomite today is only about 20% dearer than in 1994, reflecting increases in mining, handling, and transport efficiencies since then.
The letter also contains the following information that remains relevant today.
The ideal Calcium:Phosphorus (Ca:P) ratio of grazed pasture should be 1.5 of calcium to 1.0 of phosphorus.
The ideal Ca:Mg ratio should be 3.0 of calcium to 1.0 magnesium.
These ratios are the basis of high levels of milk production and animal weight gain. Typically our pastures contain approx. 0.42% of phosphorus, which means that calcium levels need to exceed 0.6% and magnesium 0.2% – 0.25%.
The analysis of pasture to which dolomite is applied annually at a rate of 220- 250kg/ha typically contain calcium levels of 0.6% – 1.0% (depending on clover content) and magnesium levels of 0.22% – 0.25%, hence the outstanding performance of well fed and managed stock on these properties.
For more information call 0800 436 566 (0800 4 dolomite) we look forward to hearing from you.