The Benefits of Slurry to the Farmer
Livestock slurry and manures have a real cash value in terms of nutrient content, but this can be variable so its worth getting them analysed.
The amount of nutrients that applied to land in slurry and manures will also depend on the volume applied; Table 1 indicates the amount of nutrient applied at various application rates:
Table 1: Nutrients applied at various application rates
| Cattle Slurry Application Rate | Applied Nutrient (kg/ha) | |||||
| Litres per hectare | Gallons per acre | Total N | Readily Available N | Phosphate (P2O5) | Potash (K2O) | Sulphate (SO3) |
| 15,000 | 3,300 | 39.0 | 18.0 | 18.0 | 48.0 | 10.5 |
| 25,000 | 5,499 | 65.0 | 30.0 | 30.0 | 80.0 | 17.5 |
| 35,000 | 7,699 | 91.0 | 42.0 | 42.0 | 112.0 | 24.5 |
However not all the nutrients are available in the year of application, with only around 50% of the Phosphate and 90% of the Potash being accessible. Depending on timing and method of application, between 10% and 65% of the Total Nitrogen is available to the following crop.
The best time to apply slurry is during the spring and summer to obtain the maximum amount of Nitrogen for the following crop. Band spreading or shallow injection methods of application maximise the amount of Nitrogen for plant growth compared to surface spreading.
The value of an application of slurry at the correct time and using the best equipment can be seen in Table 2. The values have been calculated using current costs for Ammonium Nitrate (£243/T), Triple Super Phosphate (£305/T) and Muriate of Potash (£280/T).
Table 1: Nutrients applied at various application rates
| Cattle Slurry Application Rate | Applied Nutrient (£/ha) | ||||
| Litres per hectare | Gallons per acre | Total N | Phosphate (P2O5) | Potash (K2O) | Sulphate (SO3) |
| 15,000 | 3,300 | £16.48 | £5.97 | £20.16 | £42.61 |
| 25,000 | 5,499 | £27.47 | £9.95 | £33.60 | £71.02 |
| 35,000 | 7,699 | £38.46 | £13.92 | £47.04 | £99.42 |
As the value of the Sulphate has not been included, the total benefit to the farm could be slightly higher than the value in the table above.
"Technical Note (TN736): Optimising the application of livestock farmyard manures and slurries" (which replaces SRUC “TN650 Optimising the application of bulky organic fertilisers”) provides additional information, including typical nutrient content of various slurry and manures. The Technical Note is available via the Farm Advisory Service (FAS) at www.fas.scot
Gavin Elrick, SAC Consulting
This article from Farming for a Better Climate was funded by the Scottish Government as part of its Climate Change Advisory Activiey and first published in the Farming Scotland Magazine during June 2016.
