Cover Story JUNE 2018 www.irishfarmersmonthly.com The great soil fertility deficit The levels of infertility in our soils are astounding, writes Matt O’Kee e The fertility deficit has been confirmed by the fertiliser industry and by Teagasc, as shown in their soil sampling results. Peter Ging, president of the The Fertilizer Association of Ireland sums up the situation: “Lime status on Irish soils is far below what is required for optimum productivity. If you don't have the soil pH correct then all the other inputs, including nitrogen, phosphate and potash, will not deliver their full value. The farmer will find himself in a position where he is only utilising three quarters of the fertiliser applied.” Lime application halved in 40 years annual lime application was running at around 1.7 million tonnes per annum. By the mid-1980s, however, that figure had halved, with only in the region of 800,000 tonnes applied on average each year. That’s reckoned to be about half of what is needed to maintain soil pH levels. While there has been some increase in lime spreading in recent years, the tonnages go nowhere near what is required. Soil samples analysed by Teagasc show that, on average, up to 60 per cent of grassland and tillage soils are below the optimum pH. In some regions, up to 80 per cent of soils are lime deficient. Unless these deficiencies are remedied in the years ahead, the ambition to lift our grassland productivity will not be achieved. Irish soils at suboptimal fertility 14 Lime has been applied to Irish soils for generations. The hundreds of disused lime kilns scattered across the Irish landscape bear testimony to a deep understanding of the value of lime application by previous generations of farmers. In recent decades, however, lime application has decreased to the extent that the majority of Irish soils are at suboptimal pH levels. Forty years ago, the average There have been some limited improvements in the past couple of years. However, at the current rate of improvement it will take decades to bring the majority of soils up to optimum levels of fertility. Right now, as verified by Teagasc, 12 per cent of soils have optimum soil pH, P and K levels. That means soils with pH greater than 6.2, and soil phosphorus (P) and potassium (K) indexes of 3 or 4. To put those figures in stark context,