Pushing effluent up hill

FARM FORUM

The management of dairy effluent provides many opportunities for dairy businesses.

The Holman family has met the challenge of effluent application on a steeper property by expanding their application area through installing a mainline last year, and are starting to see the benefits of improved pasture growth.

The Holman property at Loch has some steep slopes across part of the farm which makes the pumping of effluent particularly challenging.

The dairy operation milks approximately 400 spring calving cows. Manure from the yards is collected into a solids trap and a 50,000 litre sump.

The sump is pumped daily to pasture using an effluent pump via a 1300 metre long mainline and a gun irrigator.

Expanding the effluent application area has enabled better use of the nutrients in the effluent, particularly potassium and nitrogen.

The gun irrigator is moved around every couple of days.

Andrew noted “I’m able to apply nutrients now to areas of the farm that were difficult to drive over and apply fertiliser to and we’re really able to see a response.”

The effluent was tested and in one megalitre (1,000,000 litres) contained 232kg of potassium, 95kg of phosphorus, 22kg of sulphur and 200kg of nitrogen.

This is equivalent to around 0.46 tonnes of potash and 0.43 tonnes of urea and 1 tonne of single superphosphate with an approximate value of $1,015 per megalitre (prices are a rough guide to illustrate value of effluent).

Each year approximately 7.4 megalitres is generated on the property with a fertiliser equivalence value of around $7511.

Reducing the on-going maintenance cost of the effluent system is also needed to gain the most value from the nutrients in the effluent.

Management challenges for the Holman’s effluent system include being able to generate enough pressure at the irrigator and managing solids so they don’t create blockages in the pipes.

Andrew used a plumber to size the mainline to ensure it was the right pressure rating for the steeper property to ensure pumping efficiency and reduce the risk of splitting pipes.

Solid material from the effluent is removed by a trap but some solid material does enter the sump which gets agitated and applied daily to pasture.

Andrew notes that having the ability to flush the mainline is important to remove solid material if it does get pumped through.

Placing hydrants at 50m intervals for the first 200m of the mainline then 100m after that is something Andrew would do differently next time to enable ease of flushing.

Andrew also removed the foot valve on the effluent pump (which is immersed on a pontoon) to allow effluent in the line to drain back to the sump when turned off to flush the pipe.

The mainline has also been buried to protect it from stock trampling, and to help reduce blockages by keeping the pipe cool over summer, reducing the baking of manure inside.

Two posts and horizontal rails have been placed around the hydrants to protect them from stock and machinery. Andrew prefers managing the effluent on a daily basis.

“At the end of each milking the effluent is gone; it’s not another job that I have to. There are no excavators, tankers or weeds on dams to deal with later.”

These are the benefits of a direct application system; however it can be difficult to manage these systems when conditions are wetter. It is therefore essential to have some back up storage capacity for these conditions.

The Holman’s have back up storage dam where effluent can go if conditions become too wet.

The Melbourne Water Rural Land program has supported the installation of the effluent mainline through a 50 per cent co-contribution financial incentive.