Improving Parramatta grass dominated pastures and increasing soil pH

Lead Organisers and Collaborators:

Maffra & Districts Landcare Network

Contact:

Malmo Street Maffra

PO Box 727

Maffra – Vic – 3860

ABN: 88 065 838 078

Phone: 1300 094 262

E: maffralandcareoffice@gmail.com

Web: www.landcarevic.net.au

 

 

Context:

In 2010, the West Gippsland Catchment Management Authority commenced a project titled; Healthy Soils Sustainable Farms – building carbon and managing pH in West Gippsland.

The project has been supported by the three years of funding from the Australian Government‘s Caring for our Country program with the five Landcare Network’s that operate within the West Gippsland region engaged to deliver soil health information to their respective communities.

As part of the project delivery approach, the Maffra and District Landcare Network instigated a series of farmer workshops focussed around the basics of soil health management and production related issues. Based on a group learning model, the establishment of paddock demonstration sites was identified as being a critical learning component to assist farmers in following up on their theory based workshop learning.

More importantly, it was recognised that conducting on farm demonstrations would provide the most effective way of positioning those farmers involved in the project with the best information to make realistic on farm management decisions and to adopt new soil management techniques relevant to their own farm enterprises. This case study provides some background to the property ‘Redbank’ one of the three properties in the Maffra and District Landcare area where a paddock focussed demonstration site has been established.

The case study outlines the soil and pasture constraints identified within the focus paddock on ‘Redbank’ and provides a summary of the remedial techniques that are now being tested and trialled.

Consideration of the treatments undertaken during the first year of the demonstration and the related observations are also provided.

It is envisaged that this on farm demonstration site story will be updated as the various treatments and their results continue.

Project details

Objectives:

Based on the paddocks identified constraints, the purpose of the demonstration site at ‘Redbank’ and the various treatments chosen have been undertaken to test, observe and make considerations to the on farm management actions that should;

  • Encourage preferred perennial grass species establishment and growth (Focussed toward reducing the dominance of the Parramatta grass)
  • Encourage more vigorous and deeper plant root growth
  • Increase seasonal ground cover %
  • Increase soil fertility (pH)
  • Increase soil carbon levels

Management considerations:

  • Increasing the grazing pressure should encourage stock to graze less selectively assisting to create more desirable growing conditions for preferred perennial plant species to survive and thrive.
  • Extended grazing management should encourage preferred perennial grass populations to recover and aid deeper & more vigorous plant root growth.
  • The strategic use of lime should improve soil growing conditions (pH) to better support plant growth.
  • The introduction of an additional summer active C4 perennial grass (Premier Digit) should assist to further compete with and reduce the dominance of Parramatta grass whilst providing an alternate and more palatable summer feed source.
  • The combination of above actions would collectively help to improve pasture quality, pH and soil carbon levels.

Location details

‘Redbank’ is a historic property located on Redbank road near the township of Stratford. The property being situated adjacent to the Avon River.

The current custodians of ‘Redbank’ purchased the historic 260 acre property in 1990. They have since purchased a further 260 acres of adjoining land and currently lease a neighbouring block of 230 acres.

‘Redbank’ is operated as a beef breeding property based primarily on a July calving pattern. The female herd is comprised of 160 (approx) Angus/Black Baldy females.

Steer calves are typically sold off at 10 to 11 months of age with heifers calves typically being carried over until the following autumn where they are either kept as herd replacements or sold on.

‘Redbank’ is grazed under Beefcheque grazing principles with the owners being active members of the local Stratford Farmcheque Group.

The standard grazing regime aims to achieve and retain 12 – 13 tonne’s of dry matter per hectare (DM/ha) post grazing as the desirable amount of ground cover (Seasonal conditions being taken into consideration).

Grazing pressure is typically managed with electric tapes, with tapes also used to restrict back grazing.

Rainfall at ‘Redbank’ nominally averages 620mm per annum but consistent with East Gippsland’s rainfall, is inconsistent in its pattern.

The soil characteristics of ‘Redbank’ and in particular the demonstration paddock can be described as being dark/ greyish brown, gritty sandy loam over yellowish/brown/grey medium clay.

 

Soil and production constraints:

As part of the healthy soils project, each participating farm identified what they considered to be their ‘worst’ paddock in terms of soil health and production constraints.

  • A 13ha paddock was selected on ‘Redbank’ as a result of the following attributes:
  • A developing dominance of the C4 perennial plant Parramatta grass (Sporobolus africanus)
  • A higher than desired % of summer active species 64.25% across both control & treatment plots (May 2012)
  • Low pH – 4.6 CaCl (acidic)

Paddock history

In 2005 the paddock selected for the demonstration trial was sprayed out with Glyphosate with the intention to sow down to Tecapo Cocksfoot.

After sowing the paddock, it then suffered the affects of a dry seasonal conditions and poor germination and survival of the Cocksfoot resulted.

Since this time there has been minimal establishment of desirable species and the paddock has become increasingly dominated by Parramatta grass (Sporobolus africanus).

The increase in prevalence of Parramatta grass is hypothesised to be a combination of grazing through dry seasonal conditions allowing the Parramatta Grass to benefit from its inherent competitive and survival characteristics.

The survival attributes of Parramatta grass, being drought tolerant and of low palatability along with a large seeding and seed spread capacity also support its dominance.

The paddock is situated on a sloping rise with part of the trial area having a slight southerly aspect.

The paddock also displays a low pH in association with deficiencies in Potassium and Calcium.

Applied Treatments and Management Actions:

Demonstration plots were established within selected the 13ha paddock on May 29th 2012.

To develop baseline evidence, transect quadrat assessments were recorded and soil samples taken for independently laboratory testing.

On August 2nd 2012 the 1200m2 treatment area was grazed by 150 (approx. 320kg) steers. The steers entered the site at 2pm and were left until the following morning. (i.e.) The are was grazed for a duration of 18 hrs approx.

The stock pressure applied to the treatment area represented approximately 20 times the farms standard grazing density.

The remaining of the site including the control was grazed according to the farms standard grazing practice. At the time this involved providing the mob with an area up to 2.5ha to provide the stock with a desired intake of 1t DM/ day.

Lime (Buchan Ag Lime) was applied to the treatment area on the 22nd August 2012 at the rate of 2t/ha.

On September 28th 2012, 1kg/ha of Premier Digit seed was hand broadcast across the treatment area with sand used as a carrier.

This low cost establishment method used on the basis of introducing an additional summer active species with the intent to become further established within the paddock over time through stock and other natural dispersion methods.

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Year 1 – observations/results

Over the initial 10 month trial treatment and monitoring period, ground cover for both the control and treatment areas changed significantly. This change considered to be largely due to the well below average rainfall experienced over the spring and summer period of 2012/2013.

The higher density grazing did result in a visual difference of the pasture in the following months post grazing.

In this instance the pasture was 1):- less selectively and more severely grazed removing oxidizing plant material and 2):- higher concentrations of manure and urine were achieved and the pasture appeared greener and more vigorous as a result.

Premier Digit germination/establishment was detected on the back of summer rainfall during February 2013.

In addition to plants being identified within the treatment area where seed was broadcast, seedlings were also surprisingly found to have geminated and established in the control area.

Earlier germination is believed to have be delayed by the dry conditions experienced during spring.

Soil pH has increased in both the control and treatment areas. The most notable change across the soil tests is the increase in calcium levels in the treatment areas that received the application of 2t/ha lime with levels increasing in excess of 200ppm in both treatments areas. Further increases are likely to occur over time, impacting further on pH and in particular, Aluminium levels.

Total average Soil Carbon levels determined at commencement of the demonstration in May 2012 were 45t/ha for the controls and 42.3 t/ha for the treatments.

In March 2013, these levels jumped substantially to 67.9t/ha in the controls and 67.4 in the treatments. The increase in carbon does appear to be significant and dramatic with one possible explanation being the accumulation of organic matter (and its carbon content) due to the dry conditions experienced over the spring/summer period, combined with a subsequent halt in breakdown of the organic matter; also due to the dry conditions.