Organic fertiliser nutrients - maximum use, minimum loss
By Mary Roache, Teagasc ASSAP advisor
THE diffuse loss of nutrients (N & P) to waters from organic fertiliser can occur at any time of the year. However, as we enter the last few weeks of the open period for spreading organic fertilisers, typical autumn weather of increased rainfall leading to wetter soils and lowering grass growth rates increases the risk of diffuse nutrient losses.
Careful management of organic fertilisers is required where these are applied in the run up to the closing date of October 15.
Farmers can play a significant role in preventing nutrient losses from organic fertilisers to waters in autumn by:
1. When applying organic fertilisers adhere to the 5m buffer zone from drains and watercourses. Remember that this increases to 10m between October 1 and October 15.
2. Apply slurry where ground conditions are suitable, i.e. apply to soils that are trafficable.
3. Umbilical slurry spreading systems should only be used where ground conditions are suitable. When using umbilical spreading systems ensure slurry is not over applied.
4. Slurry should not be spread if heavy rainfall is forecast. The high rainfall levels can lead to soils becoming saturated and water flowing over the surface of the fields, bringing with it the nutrients applied.
5. While soils temperatures are generally good in autumn, growth rates for grass declines so it is very important to match applications to grass growth rates to maximise nutrient uptake.
6. Where a contractor is spreading organic fertiliser for you take the time to show the tractor driver the locations of any drains, streams, wells, etc., and that they observe the relevant buffers.
7. Farmers are reminded to have all slurry tanks, FYM stores, etc., empty prior to the housing of cattle over the winter so as to avoid shortages of storage capacity later in the winter or early spring.
8. Apply slurry with Low Emission Slurry Spreading (LESS) equipment. This allows slurry to be spread on heavier grass covers which improves nutrient uptake and helps reduce the risk of diffuse nutrient and ammonia losses.
9. If abstracting water to use for agitating slurry tanks ensure that no nutrients are lost from the pipe to the water. Also practice utmost care to ensure no sediment from wheel tracks is entering waters.
10. Under no circumstances are slurry tankers to be washed out and liquid discharged back into the watercourse. This must be land spread according to regulation.
It also makes financial sense to maximise organic fertiliser use. They are a valuable source of nutrient for the farmer and can help reduce the overall farm fertiliser bill. For example the guide fertiliser value of 1,000gls of cattle slurry is €25, equivalent to 1 bag of 6.5.30 NPK (this value is dependent on Dry Matter content of slurry and timing of application).
Contact your local Teagasc office if you require any further advice on good practice for slurry spreading.