Have you spread any slurry yet?
Gareth Gormley, Countryside Management Branch, Department of Agriculture and Rural Department (DARD)
Did you take the opportunity to spread slurry over the past few months when ground conditions were suitable? If you did, what happened to the nutrients in the slurry?
The reality is that with essentially no growth, grass cannot use the nutrients in the slurry, and some of the nutrients will be washed out - over the surface or into the drainage system.
The extent to which drainage water could be contaminated following application of slurry to grassland was investigated at the College of Agriculture, Food and Rural Enterprise (CAFRE), Greenmount Campus over 25 years ago. Using a vacuum tanker, three rates of slurry equivalent to 23 m3/ha (2,000 gal/acre), 45 m3/ha (4,000 gal/acre) and 68 m3/ha (6,000 gal/acre) were applied on six separate occasions to four different sites. At all times the ground was sufficiently firm to carry the tractor and tanker without undue damage to the soil surface. There were 27 cases of contamination out of a total of 72 applications over all sites. These results highlighted the risk of nutrient loss to watercourses from application of slurry to grassland during the winter months.
Chemical analysis indicated that contamination generally appeared within a few hours of slurry spreading. The period over which drainage water samples were contaminated was greatly influenced by the amount of rainfall following slurry application and in one particular case it was 11 days before the drain was running clean again.
The Nitrates Directive aims to protect water quality, and one of the requirements of the Action Plan will be a closed period for spreading slurry. In addition there will be a requirement to make better use of the nutrients in slurry. It is therefore essential not only to spread slurry when ground conditions are suitable but when grass can use the nutrients.
You wouldn't spread chemical fertilizer at £160 tonne during the winter months so why spread liquid slurry fertilizer?
For further information contact Countryside Management Staff at your local DARD office.
