Soil testing survey reveals important grassland fertility trends
The end of March this year was marked by the successful completion of the European Exceptional Adjustment Aid (EAA) funded Soil Sampling and Analysis Scheme.
The scheme was delivered by the Agri-Food and Biosciences Institute (AFBI) to farm businesses across Northern Ireland.
Almost 20,000 fields were soil sampled across the whole of Northern Ireland over the recent autumn/winter season using Global Positioning Satellite (GPS) technology to record field locations and sampling transects.
The second component, the ‘Catchment Scheme’, was targeted at farmers within specific geographical areas of the upper River Bann catchment.
Over 1000 farm businesses who were successful in applying to the scheme received their soil sample analysis reports by the first week in April 2018.
The analysis reports contained detailed information about soils (i.e. pH, phosphorous and potash status) which will enable participating farmers to target the application of slurry, manure and chemical fertiliser more accurately.
The reports also contained recommendations for liming.
A preliminary analysis of the results from the scheme indicates that 43% of farmed grassland (excluding rough grazing) across Northern Ireland is under-limed with a total lime requirement of 1.2 million tonnes, requiring an expenditure of £30 million (€34.4 million).
Taking a typical 100 acre (40ha) grassland farm, lime application costing £1,440 (€1,655) would result in an increased grass yield of 86t DM (i.e. an extra 1t DM/ha/year for five years on 43% of the grassland area, i.e. 17ha).
As expected, grassland used by the dairy sector has a major phosphorus (P) over-supply problem with 50% of fields at soil P indices greater than 2+. But grassland used for beef and sheep production also has a significant P over-supply problem.
Over-use of P, and particularly of chemical fertiliser P, where not required, not only is detracting from farm profits; but, is exacerbating water quality problems.
Results of these soil tests demonstrate opportunities to save on fertiliser P inputs and to make better use of slurry P – another major benefit of the programme.