Soil fertility is essential for optimum production, but is one of the most neglected aspects of Irish farming.
Teagasc tests of almost 40,000 soil samples annually indicate we are applying less than half the amount of lime we applied in the 1970s. As a result, farmers get very much reduced value from fertilisers.
Teagasc figures from 2015 showed sub-optimal fertility in up to 90% of soil samples.
There has been continuous decline in soil P (phosphorus) in the past decade. Coupled with low pH, which reduces the availability of P and N, this is a very serious situation.
It prevents Irish farmers from availing of their natural grass growing advantage.
Currently 64% of soil samples are sub-optimal for P. There has been a 50% reduction in the use of P fertilisers in the past decade, partly due to the Nitrate Directive, and partly due to a rapid rise in the cost of fertiliser.
Apart from reduced grass production, low soil P can also seriously affect animal health. Cows suffering from P deficiency can usually be seen eating stones, sticks, and other non-nutritional objects. Milk production and fertility will be severely reduced.
Even if cows show no obvious signs of P deficiency, they may suffer from sub-clinical P deficiency.
When the pH of soil drops to 5.5, two thirds of the applied P and one third of the applied N is tied up in the soil, unavailable to the growing plants.
Money spent on lime should return three times its cost in terms of extra grass and less purchased feed.
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