Managing the Root Zone to Increase Pasture Yields

Year of study:


Lead organisation & collaborators:

Agriculture Victoria

Dairy Research & Development Corporation


Cameron Gourley

Anne Crawford

Jeff Hirth

Best available science assessment:

Overall score: 32

Overall rating: Very high


Conceptual model

Study design

Soil analysis

Production & financial

Method reporting

Data analysis

Results reporting











Project details


This trial investigates the effect of modifying the physical and chemical properties of soil on perennial pasture production and root distribution at two sites. A range of soil modification treatments were applied at different soil depths and monitored over 2 years.


Root distribution is strongly correlated with nutrient deficiencies and chemical toxicities. These nutrient deficiencies in sub-soils are a key restriction to root growth and function, as well as accumulated organic matter in the surface soils concentrate organic forms of nutrients. Acid soils induce toxic levels of Al, H and Mn ions, whilst resulting in deficiencies in P, N, Ca and Mo which all contribute to root growth. This trial considers how these properties may be altered to improve crop yields.

Basis of trial:

Nutrient deficiencies in sub-soils restrict root growth and function.

Location details

Trial site details:

1994 Lower than average rainfall

1995 Above average rainfall

Site Soil type Rainfall
Ellinbank Krasnozem 1100mm/a
Curdievale Hard setting duplex soil 897mm/a

 Pre-trial management:

Not specified.

Trial management:

Not specified.



How results have been reported:

Technical report

How copies of relevant reports can be obtained:

Anna Crawford, Cameron Gourley DPI

Level of review of results:

Internal peer review

Summary of key findings of trial:

The application of lime resulted in higher pH and lower exchangeable Al (the effect on soil depth being more dramatic at Curdievale than Ellinbank).

The incorporation of organic matter did not result in a measured increase in organic carbon at any depth or site. Further, no organic matter residue was noted 7 months after placement.

Treatment results

Variations in soil C with time and management influence:

Organic carbon

Graphical data is provided in the report

Site Carbon outcomes Depth Pre trial
Ellinbank There were no significant differences in organic carbon across any of the treatments or sampling times. 0-10 6.3%
10-20 5.2%
20-30 3.8%
30-40 3.0%
40-50 2.4%
Curdievale There were no significant differences in organic carbon across any of the treatments or sampling times. 0-10 5.0%
10-20 1.9%
20-30 1.7%
30-40 0.6%
40-50 0.3%

Variations in soil pH with time and management influence:

pH (CaCI2)

Graphical data is provided in the report

Site pH outcomes Depth Pre-trial
Ellinbank Significant differences in the pH (CaCl2) and exchangeable Al at most depths and sampling times. This reflects the effect of lime. Where lime was applied at 10t/ha pH was significantly greater than those without lime treatment. 0-10 4.34
10-20 4.29
20-30 4.4
30-40 4.46
40-50 4.53
Curdievale Significant differences in pH at all depths except 40-50cm. Where lime was applied, pH increased across all depths. 0-10 4.76
10-20 4.67
20-30 4.64
30-40 4.94
40-50 4.89

Other soil treatments:

The application of superphosphate and potash increased available P,K,S and EC at both sites.

Variation in productivity/ profitability with time & management influence:

Only two treatments at Ellinbank recorded increases in pasture yield, but were not maintained throughout the experiment.

Other measures of treatment response (e.g. water quality):

The abundance of earthworms at Ellinbank was low.

Experimental design


Site Treatments
Ellinbank (10 treatments to 5,25 and 50cm depth applied March 1994, replicated 4 times) SuperphosphatePotash

Trace elements


Organic Matter

Soil disturbance

Curdievale (7 treatments t0 5 and 50cm depth, applied March 1995, replicated 3 times) SuperphosphatePotash

Trace elements


Organic Matter

Soil disturbance

Ellinbank- sowed with clover in April 1994

Curdievale- sown with clover in April 1995.


Trial design/layout:

Site Layout
Ellinbank 8m x 4m plots. Replicated 4 times, randomised block design
Curdievale 6m x 1.5m plots. Replicated 3 times, randomised block design.

Soil sampling method:

4.25cm cores were sampled to 50cm depth for chemical analysis. Samples were sectioned into 10cm segments and bulked.

Ellinbank- 11/94, 5/95, 5/96

Curdievale- 11/95 and 4/96

Oven dried at 40 degrees for 48 hours, ground and sieved through a 2mm sieve.

Tested for (at Ellinbank):

Oxidisable carbon (Walkley)

Available P (Olsen)

Available K (HCl extraction)

Exchangeable Al (spectrometry)


Soil pH (H20 and CaCl2)


Plant and/or animal production measurements:

Earthworm numbers were also measured.

Next steps

Very high rates of lime and nutrients were required to alter soil chemical properties significantly, but these did not necessarily result in corresponding pasture yields. It appears that white clover and ryegrass pastures in high rainfall dairy regions can be maintained at high productivity levels with localised nutrient and water supply.

High rates of treatment application are required.