If ensuring adequate nutrient supply to plants were as simple as just applying more fertiliser, recommendations would be a great deal simpler.
Much of the advice given when fertiliser was more affordable than it is today appears to have been based on the philosophy that if a little was good then a lot was better.
With fertiliser prices as they are presently, and there is no sign that they may decline markedly, farmers need to shop carefully and increase their knowledge of what nutrients best meet their requirements in both the short and longer term.
The cost of the normally recommended phosphorus input for intensive dairy farms is now in excess of $200.00+GST per hectare annually. Then there is the cost of calcium, magnesium, potassium, and additional sulphur if required.
Phosphorus is an essential element that provides a range of essential functions however the generally accepted amount of plant available phosphorus required in the topsoil for maximum pasture production is in the range of 25 – 40kg/ha, often about 1 – 2% of the total phosphorus.
With this ‘reserve’ the question is how can maximum pasture growth be ensured at lesser fertiliser input rates.
Magnesium acts as a carrier for phosphorus increasing efficiency of plant uptake. Dolomite from Golden Bay is a highly effective magnesium fertiliser and when applied at 250kg/ha sufficient magnesium is applied to meet the maintenance requirements of the most intensive dairy situation.
During winter the nutrient requirements of pasture is modest due to slow growth. As soils warm in spring there is likely to be sufficient quantities of all essential elements to meet initial growth demand.
Biology plays an important role in the availability of both major and minor nutrients. Air is an essential component of biologically active humus producing soil, ideally comprising 25% of total soil volume. Some compaction and pugging is inevitable during wet winter conditions particularly in combination with a concentration of heavy feet.
Dolomite is a proven soil conditioner that helps restore physical structures allowing water to drain more freely.
For maximum phosphorus uptake plant roots need to work in conjunction with mycorrhizal fungi. Mycorrhizal fungi extend the root zone harvesting phosphorus for plant use, stimulating rye grass growth. A friable soil with good crumb structure allows plant roots to extend to 0.5metre deep harvesting nutrient not normally accessible.
The major benefit often associated with an annual dressing of dolomite is the reduction in calcium/magnesium related metabolic disorders during calving and lambing. Carrying animals through winter is expensive. Ensuring optimum health over winter and spring starts with a single application of dolomite.