The absence of livestock waste in streams means farmers did not spread slurry during the closed period, a Teagasc study suggests.
Research from the Teagasc Agricultural Catchments Programme found that there was little evidence of livestock slurry in streams following the end of the ‘closed period’ for slurry spreading from October 15 to mid to end-January, depending on the region.
Mairéad Shore, hydrochemist with the Teagasc Agricultural Catchments Programme, said: “This research finding is based on over four years of detailed data collected in the agricultural catchments during storms when surface runoff is expected, and shows, very precisely, the nutrient concentrations of water flowing out of the catchments.
“Less detailed sampling would likely be insufficient to pick up these patterns as surface runoff tends to be short-lived. The analysis specifically used the relationship between phosphorus and sediment in river outflows and also different forms of nitrogen.”
The study findings suggest farmers either weren’t spreading slurry during the closed period, or were spreading it on the parts of their farms where it was less likely to be washed off.
There were, however, some signals of livestock slurry in runoff at the start of the closed period, in some of the studied catchments. This occurred when early autumn storms quickly followed the last few days of the ‘open period’.
These signals were also found during the particularly wet summer of 2012, when soils were wet and storms coincided with normal summer slurry spreading.
There was also evidence of other nutrient losses during the closed period and the analysis suggested these were from residual soil sources rather than slurry.
This shows the potential for nutrients that were spread in earlier years, or even decades, to be lost to water now, and into the future.
Farmers can reduce nutrient losses in soils in wetter periods by managing livestock manures in the growing season, said Teagasc experts.
© Irish Examiner Ltd. All rights reserved