Tarago Soil Biological Health Trial

Year of study:


Lead organisation & collaborators:

Neerim and District Landcare Group

Tarago Catchment Sustainable Farms Project

Department of Primary Industries



Jessie Horton, DPI

Nicole Driessen, Tarago Project Officer

Best available science assessment:


Conceptual model

Study design

Soil analysis

Production & financial

Method reporting

Data analysis

Results reporting











Project details


The trial was intended to test the effect of fertiliser use on pasture growth in a trial using conventional fertilisers and compost tea application. The trial was conducted in the Tarago water supply catchment and sought to find ways of maintaining production, while using less fertiliser and reducing fertiliser loading into the Tarago reservoir.


Compare pasture yield through the use of conventional fertiliser and compost heap.

Basis of trial:

Reduced fertiliser use can have positive impacts on water quality and improve soil health.

Location details

Trial site details:

2009-2010 financial year

The trial was undertaken during a period of drought and the seasonal conditions varied over the timeframe of the trial.

Neerim- 1110.9 (NOOJEE (SLIVAR) BoM station)

Red soils (medium clay- Ferrosol) on east sections

Black soil (grey sandy loam- Devonian granite and granodiorite) on west section

Located on a hill, lower slope with waterways either side.

Management practices tested:

Application of compost tea vs the application of conventional fertilisers

Pre-trial management:

Goats/cattle since 2006

Trial management:

Burnt during February 2009- but seeds and biological matter was not sterilised.

Summary of key findings of trial

Compost tea treated area showed an improvement in compaction and fewer broadleaf weeds.

Trial results showed little difference in production across the site.

Variation in soil C with time and management influence:

Can’t compare given no baseline sample was taken, but organic carbon increased over each trial site.

Variation in soil pH with time and management influence:

Can’t compare given no baseline sample was taken, but pH was measured. pH decreased on red soil sites, remained the same on the biological black soil site and increased on the traditional black soils site.

Other soil treatments:

Compaction (measured using a Penetrometer) improved across entire trial site during the trial period.

Bacterial and fungal biomass increased over trial.

Variation in productivity/profitability with time & management influence:

The same production of silage bales were identified as the traditional practices.


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Experimental design


Biological trial Compost tea (200L) applied via spraying, applied seven times. Fish meal (such as fish hydrolsate- food source for fungi). Sprayed onto site with compost tea (6 weeks withholding period for stock grazing)

Organic molasses applied (as food source for bacteria) at 50L/2.5 hectare site (1 part molasses:4 parts water).

Conventional trial- 27/6/2009, 100kg urea and 100kg DAP applied (80kg/ha)

Cattle grazing (Jan/Feb 2010)

Goat grazing (Feb-August 2010)

Oats and rye crop sown by direct drill (May 2009) after disc and power harrow was used.

Silage harvested October 2009.

Trial design/layout:

2.5 hectare plot. – biological practices on north side, conventional practices on south side.

Soil sampling

0-10cm samples, a combination of 20 soil cores taken along transects along each section of the trial site. Cores (no baseline sampling taken)

Testing by Farmright Technical Services for:

Olsen P, PBl, K, S, pH (CaCl2), organic carbon, Ca, Mg, K, CEC, Na%, Al%

Cost and value of production:

Soil Foodweb Grower Program + preparation, seed, compost, fertiliser, molasses, fish meal, soil tests, consultant and silage testing = $21,830
How results have been reported:

Technical report

How a copy of any relevant reports can be obtained:

Jessie Horton, DPI

Level of review of results:

Internal review

Next steps

The landholders will continue to use biological farming practices on their farm and aim to completely eliminate the use of inorganic fertilisers. They intend to brew their own compost tea from litter gathered from the adjacent forest. They will continue to soil test.

Planning soil analyses prior to the trial, as well as crop density and pasture production. Undertake before, during and after trial.

Need to have a clearer understanding of objectives from start and more information on appropriate monitoring/measuring techniques.

Check and double check advice given from external parties

The ongoing need for biological testing – learn how to use microscope

Molasses is difficult to use (use an alternative)

Make compost tea on site

Larger spray tank (labour intensive)