Fertiliser sales generally, since this time last year, have been significantly down on the buoyant sales of the previous twelve months.
Dolomite sales have however bucked the trend, and even into November demand is steady, a tribute to its effectiveness and value.
Value in this case can be defined as the dollars saved and extra generated as a result of its use less the cost. This may be difficult to calculate with great accuracy however those that apply dolomite regularly often become devotees.
In pastoral farming dolomite is applied for its magnesium content. Soils vary in the amount of magnesium contained naturally in the root zone accessed by ryes and clovers. Soils high in organic matter often contain the most due to the large nutrient storage capacity compared to coarser textured soils.
The loss of magnesium from intensive dairy properties, as far back as the 1960’s, was calculated at 15kg/ha/year.
With markedly higher stocking rates, higher inputs of potassium, and regular inputs of nitrogenous fertiliser losses will now be considerably higher though probably not exceeding 25kg/ha/year. Irrigation may well increase leaching losses.
Soil and leaf testing will help quantify the need for magnesium however those that have neglected magnesium inputs to the point of low availability understand both the trauma involved with acute magnesium deficiencies in stock and the amount of money that can be lost with just the loss of one high producing animal, often its progeny of that season, and the loss of production.
The prevention of magnesium deficiencies is often as simple as applying 20 – 25kgMg/ha/year in the form of dolomite. With dolomite typically containing 11.5% magnesium the recommended application rate is 220kg/ha.
On the light pumice based soils of the North Island’s Central Plateau where dolomite is applied regularly to many hectares under intensive dairy 220kg/ha is sufficient to prevent all simple magnesium related metabolic disorders provided animals are fully fed on high quality pasture.
Where potassium inputs are withheld until November, animals are fully fed and rumens are functioning well, often the only extra magnesium needed is during prolonged spells of both cold and wet weather.
Dolomite also contains 24% calcium. Once lactating, the demand for calcium increases and dolomite provides a ready source, an attribute unique to dolomite.
One of the yet to be fully understood reasons for the marked improvement in animal health as a result of regular dolomite applications may be that magnesium is also a carrier for phosphorus. Phosphorus is an important growth element also essential for the formation of sugars in plants.
In spring the demand for energy by animals increases. Higher energy pasture is lower in crude protein and more energy is available for essential body functions including good rumen function ensuring more of the ingested magnesium is utilised.
Dolomite can be applied at any time of the year with the effect lasting a full twelve months.