Squeeze more out of effluent ponds
MANY dairy farmers are currently facing tight financial times but there may be a hidden, albeit small pot of gold in your effluent system that could be used to offset some fertiliser on some areas of the farm this year, or next autumn.
Admittedly some effluent systems may require an input of capital to fully utilise this pot of gold in the form of nutrients.
Effluent from the second pond in a two pond system is usually all liquid and contains many nutrients in high concentration and mostly in soluble form, that plants can use immediately once applied.
There may be some nutrients tied up in organic matter which has flowed from the first but the advantage here is that they are released over a longer time.
In one pond systems there will be a mixture of liquid overlaying various depths of solid, referred to as sludge.
Unfortunately many single or first ponds may also have a thick crust often with grasses and other plants happily living on the ready supply of nutrients in the ponds such as potassium (K), nitrogen (N) and phosphorous (P)
Can we make better use of these?
They are not actually ‘free’ as there is a cost to have the nutrients delivered to the paddock by a spray or flood irrigation, a manure tanker or the solids spread by a muck tanker.
Night paddocks and those receiving effluent regularly are usually high to very high in some nutrients.
The main offenders here are potassium (K), a precursor to Grass Tetany, nitrogen (N), which can be wasted if applied too heavily, and salt, which can increase substantially if bore water is use and especially if effluent is recycled.
Salinity in soils can result in reduced pasture production over time. Animal health problems such as Johnes Disease and Salmonella may be another issue of which to be aware.
However, all these problems can be overcome with the correct application rate, timing of application and lead time between application and grazing or ensiling.
On most farms there is nutrient drift to the front of the farm from the rear due to cows consuming pastures (including nutrients) and tending to soil a bit more at the dairy shed, feed troughs near the dairy, laneways and night paddocks.
Also silage and hay, both containing many nutrient, particularly K and N, is often made in the rear paddocks of the farm and often fed out in the night paddocks and feed troughs in laneways and feed pads, all near the dairy.
Another not so well known related issue is nutrient drift within paddocks. In larger paddocks cows tend to drop more poop and piddle towards the front half of most paddocks.
Even though the rear of these paddocks is grazed, cattle tend to move back towards the front for water, sometimes higher quality pasture and waiting to head home to the dairy for milking.
We can make better use of the nutrients sitting in the effluent pond but there will probably be a need to spend some money on infrastructure of some type.
This could be more and larger diameter delivery pipe, bigger effluent pump, increased cost of contractors to spread effluent further back up the farm than normal.
The gold is that you should now get a bigger bang for your buck because the nutrients are being spread where they are traditionally lowest.
Concentrate on the rear paddocks of the farm and areas regularly cut for silage and hay. Also spread more of the effluent or manure solids towards the rear half or third of all paddocks where pasture growth is less or poorer quality than at the front to increase soil nutrient status.
It is preferable to sample the ponds to obtain a nutrient and salt status so that the application rate can be determined. Stir the pond before sampling to get a more representative sample but if not possible, sample the surface.
The areas where effluent is applied should be soil sampled over time.
To further minimise the risk to stock: keep young stock under 12 months off any effluent-treated pasture and drains running from there to avoid Johne’s Disease; avoid grazing effluent-treated areas for at least three weeks; and graze the paddocks just before application to allow more sunlight penetration to kill bugs and extended rotation length before grazing again.
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