Western Victorian cooperative DemoDAIRY looks almost certain to liquidate its assets after failing to attract the tenant needed to save its dairy precinct.
Research scientist from the Department of Primary Industries Warrnambool, Graeme Ward, says dairy second pond effluent is best applied during the drier months to established pasture at rates of up to 100kg of Nitrogen per hectare (100kgN/ha), which he says is comparatively safe to the environment, pasture herbage and soils.
A 200kgN/ha rate was found to run increased risks and a 400kgN/ha rate was initially very productive but had unacceptable effects on the environment.
Over time, pasture production on the 400kgN/ha rate declined due to the detrimental effects the high rate of effluent has on soil health.
“Due to build up over time effluent should not be repeatedly applied to the same area of land every year,” Ward says.
In the trial, second pond effluent is irrigated onto established perennial pasture every summer for six successive years at rates of 0, 100, 200 and 400kg of nitrogen per hectare.
The project monitored the long-term effect of these applications on the pasture plots, the soils and on the environment.
Ward says effluent applications are very effective in boosting the total amount of pasture grown each year, with growth higher as more effluent was applied, but these responses declined over time.
He says effluent application increased the crude protein content of the pasture from summer through to mid winter.
“This is particularly valuable in summer and early autumn when protein is usually in short supply.”
It also helps correct potassium deficiencies and maintain phosphorous levels.
Ward says there are detrimental effects when too much second pond effluent is applied to land, which meant farmers should limit the rate and frequency of application on a particular area.
Negative impacts from a high level of effluent application include turning the soils magnesic, creating a high soil salt content, changes to the mineral content and balance of pasture and potentially polluting groundwater under the pasture.
Therefore, he recommends application be best applied at rates of 100kgN/ha or lower for optimum results.
The project was funded by the Gardiner Foundation, Dairy Australia and supported by DemoDAIRY.
A fact sheet detailing results is at www.demodairy.org.au