Soil structure and pasture improvement using soil biological cultures


Year of trial: 2012-3

Project ownership:

South Gippsland Landcare Network, (SGLN) David Hall (Landholder), Kevin Hughes (Soilwise Farm Services)


Jenny O’Sullivan (SGLN)


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Project details

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This demonstration seeks to see if soil structure and pasture species palatability can be improved by addressing soil chemistry in combination with a culture of soil biology. It is hoped that the addition of biological cultures will

  • improve soil structure, root penetration and pasture resilience.
  • increase numbers of desirable pasture species, such as rye, and clover and
  • increase palatability of species such as cocksfoot.

Application of Petrik Digestor™ and Green Manure™ claims to rapidly initiate the creation of stable humus.


Adding a culture of soil biology to pasture in combination with magnesium, lime, potash and sulphur will improve soil profile and pasture quality to a greater level than magnesium, lime, potash and sulphur alone.

Basis of trial:

Plants exude between 10 and 25 % of the photosynthates they produce into the rhizosphere to support beneficial microbes (Walker 2003.) Microbial decomposition of organic residues leads to nutrient release and the formation of stable humic compounds. A stable humic soil structure glues soil particles together, gives the soil porosity allowing air and water movement, acts as a reservoir for nutrients and creates conditions ideally suited to further proliferation of microbes.

Management history

Fertilizer history of the test site:

2011 (200kg 3 and 1 Super/Potash +70 kg Urea/ha)

2010 (2 tonne Calcimo 50/50 Lime/ha + 1tonne /ha of Pig Manure )

2009-1999 (An average of 300kg 3 and 1/ha +70kg Urea/ha )

2005 (Copper/Molybdenum) 2002 (2.5 tonne Darriman Lime/ha )

Grazing history

Beef cattle property grazed rotationally.

Location details

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Farm: Amey’s Track Foster.

Elevation: 200 metres

Aspect: Ridge on Strzelecki ranges

Soil Type: Dermasol – grey brown clay over siltstone

Pasture Species: Rye Grass (Lolium sp), Clover (Trifolium sp), Bent Grass (Agrostis sp), Cocksfoot ( Dactylis glomerata), Brome

Rainfall: 1008mm

pH CaCl2: North test area– 4.9

South test area– 5.1


Trial site details:

All parts of the paddock have compacted soil with shallow root development in the pasture.

The eastern boundary of demonstration site used to have a cypress hedge (in photo) which was removed 3 years ago and the plants burned in the paddock. Some charcoal residue can be seen in the soil profile.

The paddock has a large concrete water tank in approx the centre of the paddock, which, for the purposes of this project was considered to be the division between the north and south areas. The north area of the paddock is the wettest area. The western side is steepest and in both north and south test areas, contains cocksfoot and plantain. The landholder has observed that grazing stock find some of the grasses (cocksfoot) unpalatable and tend to selectively graze.

Pasture transect results to the 30/6/2013 found here

Solvita Biological test results

The gel on the paddles releases CO2 when removed from the jar so the colour change in the sealed jars is most accurate. As can be seen the south part of the trial has the most CO2 released with a colour reading of 4, the north has a colour reading of 3.5 and the control a colour reading of 1. (The jars were labelled in pen which did not show up in the photo, so were overwritten before the lower photo was taken).

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Pasture root response:

This soil from the trial paddock shows the root growth before treatment. Some roots penetrate the soil with some growing horizontally in the first five centimetres of soil. This sample is from the northern trial area of the paddock—the Petriks trial zone 1.

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 Brix test :

Measured by David Hall at 1pm July 12,  2013
Brix test         Soil temp

Nth             3                       9.1

Control       2                       9.0

South          2                       8.8

Sun was a factor according to David but he has never got a 3 before.

Pasture plant response

In the first six months, Cocksfoot in both biologically treated areas were grazed lower by cattle than cocksfoot in the control, suggesting that the palatability of the plants in the biologically treated areas may have increased.

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Experimental Design

Addition of microbes to the north and south of the paddock. 30 metre control strip across the middle of the paddock to provide a comparison area to both biology application areas. Soil and plant measurements taken on an east – west transect across the centre of each area.

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Soil Treatment:

14/11/ 2012

Across both treatments and control.

Darriman Lime; 800kg per ha

Magnesium Oxide; 100kg per ha

Potassium Sulphate 100kg per ha

Debenham’s Copper, 2 Litres

Debenhams Cobalt/Selenium. 2 Litres

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Application to both treatment sites

Petriks Digestor™- – 2 litres per hectare

Petriks Green Manure™ – 1 litre per hectare

Approximately 20mm of rain fell before and after application Conditions were reasonably windy at the time, so there was some spray drift in a SE direction.


Application to both treatment sites

Petriks Digestor™- – 2 litres per hectare

Petriks Green Manure™ – 2 litres per hectare


October 2013

Urea across both treatments and control – 70kg p/ha


Soil Measurements

Soil carbon:

Benchmark test as part of National Soil Carbon Research Program (CSIRO) 25m square grid in South area Sample date: 15-Dec-2011 Region: Strzelecki Ranges Soil Type: Dermosol

Depth(cm) TOC (Mg/ha) POC (Mg/ha) HOC (Mg/ha) ROC (Mg/ha) TOC(%) IC (Mg/ha) TN (Mg/ha)
0-10 50.1 10.7 19.7 11.6 5.5 0.0 4.0
10-20 36.0 6.1 17.7 10.6 3.5 0.0 3.0
20-30 25.0 2.5 13.6 8.4 2.3 0.0 2.0
0-30 111.1 19.2 51.0 30.5 3.8 0.0 9.1

TOC = Total organic carbon (expressed as t/ha and as %)

POC = Particulate organic carbon

HOC = Humic organic carbon

ROC = Resistant organic carbon

IC = Inorganic carbon


Soil Chemical Analysis

30 cores to 10cm collected by Landcare Project Officer and bulked to one sample Olsen P, Colwell K, Sulphur, Organic Carbon, Nitrate Nitrogen, Ammonium Nitrogen, Electrical Conductivity, pH (Water and CaCl2), DTPA (Cu, Zn, Mn, Fe), Exchangeable Cations (Ca, Mg, Na, K, Al), Boron and Total Nitrogen.

30 August 2012

AREA North area South area North area South area
Ammonium Nitrogen mg/Kg 7 12 Manganese mg/Kg 14.52 4.4
Nitrate Nitrogen mg/Kg 6 7 Zinc mg/Kg 5.3 3.53
Phosphorus Colwell mg/Kg 108 47 Exc. Sodium meq/L 0.71 0.58
Potassium Colwell mg/Kg 336 205 Exc. Calcium meq/L 1.13 1.05
Sulphur mg/Kg 6.7 4.4 Exc. Magnesium meq/L 0.43 0.34
Organic Carbon % 4.05 3.30 Exc. Potassium meq/L 0.34 0.18
Conductivity dS/m 0.250 0.220 Boron mg/Kg 0.93 0.69
pH Level (CaCl2) pH 4.9 5.1
pH Level (H2O) pH 5.7 5.8 Cation Exchange capacitymeq/100g 16.1 13.6
Copper mg/Kg 0.95 1.08 Calcium Magnesium ratio 5.1 6.8
Iron mg/Kg 561.16 390.9


August 2013 – 2 tests (1 control, Zone 1 and 2 treatments combined)

Solvita Biological Respiration

(measures C02 respiration from soil sample indicating biological activity) One test after first application to determine biological activity in the soil

Visual Soil, Root development and pasture assessments

Observations taken by David Hall and Landcare monitoring staff.

Methodology – click here

August 2012

Production measurements

Pasture species composition

Pasture species by percentage, measured in a one metre by one metre frame placed 5 times every 5 metres across each of the test and control areas. Control and 2 test area results combined and averaged. August 2012

Cost of application

Annual application of

Evergreen at 2l/ha =$25.50

Greenmanure at 1l/ha – $22.00

Total costs $47/ha

Plus application costs


Case Study on SGLN web page, which contains an overview of the study.