Teagasc - Soil Fertility Trends
Soil fertility is a key component of sustainable agricultural production and is critical for low cost grass based livestock systems practiced on most Irish farms. Maintaining or increasing grass and crop yields through better soil fertility will help make Irish farms more resilient to commodity price volatility and to better compete in world markets.
The first step towards improving soil fertility is to test your soil. Teagasc Director Professor Gerry Boyle said: “A Teagasc study of dairy farmers has shown that those dairy farmers that test their soil regularly are younger, have larger farms and herd sizes and have higher farm gross margins and gross output compared to those who don’t regularly test their soil. Farmers with formal education are almost four times more likely to voluntarily test their soils.”
Over the last 10 years Teagasc have analysed approximately 38,500 soil samples annually for its farmer clients. These samples provide an insight to national soil fertility trends (soil pH, phosphorus (P) and potassium (K)) for each farming sector. Overall soil test results for 2015 show that approximately 90% of samples have sub-optimal fertility status (soil pH < 6.3, P & K index 1 or 2) a situation that has persisted for the last number of years. Mark Plunkett, Teagasc Soil and Plant Nutrition Specialist said: “This is a serious limitation to the production potential of our soils and limits our ability to maximise our most competitive advantage in the market place, which is our ability to grow high yields of quality grass.”
Currently 64% of grassland soils and 45% of tillage soils have below the optimum soil pH (i.e. pH 6.3 for efficient grassland production and pH 6.5 for tillage crops). According to Dr David Wall, leader of the Teagasc Soil Fertility Research Programme at Johnstown Castle: “Nationally we are applying less than half the quantity of lime that was applied in the 1970’s and early 1980’s. Applying lime to correct soil pH is the cornerstone for maintaining the productivity of our soils, something that has been largely overlooked in recent decades. Identifying fields that require lime for pH adjustment should be the first step towards correcting soil fertility.”
A major concern emerging from these soil test data is the continuous decline in soil P levels over the last decade with the majority of both grassland (61%) and tillage (59%) farms having suboptimal P fertility (i.e. P index 1 or 2). Although fertiliser P usage has recovered somewhat from its lowest level in 2008-09, it appears that the levels of current usage are not balanced with P off-takes on many farms. Approximately 50 % of grassland and tillage soils have low K fertility levels (54% and 47% respectively) however; soil K trends show a stabilization or gradual improvement over the last 5 years. This may be due to better distribution of manures on grassland farms and the targeting of higher K compound fertilisers on tillage farms.
This soil fertility information is summarised by county and by farming enterprise and can be found at http://www.teagasc.ie/soil/analysis/results.asp