Sustainable Agriculture

Organic carbon is an important component of healthy soils and is essential for sustaining productive agricultural landscapes. Soil organic carbon (SOC) improves physical soil structure and stability, enables retention of soil moisture and nutrients and improves aeration essential for plant growth.

Tweed Shire Council conducted a three-year research project in collaboration with industry, local farmers, research agencies, NSW DPI and soil scientists to investigate the benefits of compost for soil carbon capture with financial support from the Australian Government under the Carbon Farming Initiative.

The purpose of the project was to trial innovative on-farm practices to increase sequestration of soil carbon through the use of organic amendments such as compost, and reduce nitrous oxide emissions using biochar. The project aimed to improve understanding of the processes that increase SOC and reduce emissions of nitrous oxide arising from application of nitrogen rich fertilisers. The project involved a total of 30 farms including sugar cane, banana, vegetable, perennial tree crops and livestock (dairy and beef) in the Tweed Local Government Area.

Whilst the addition of compost did not result in an overall increase in SOC, a number of factors were identified that lead to SOC decline in agricultural soils including excessive nitrogen use, overgrazing and tillage.

Increasing Soil Carbon in Tweed Valley Farmland Final Report (905kb)
Increasing Soil Carbon in Tweed Farmland Flier (1.55mb)
Poster presented at the joint conference of the New Zealand Society of Soil Science and Soil Science Australia, Queenstown, New Zealand, 12-16 December 2016

Tidal Floodgate, with Float Arm

The Tweed River is brackish (salty) as far upstream as Murwillumbah. Historically, floodgates were installed in creeks and drains to prevent high tides from flooding arable land with brackish water. This action inadvertently lead to a range of environmental issues such as acid sulfate soil pollutant export and reducing fish nursery habitiat.

In 2000 Council, in partnership with landholders and state government agencies, commenced a program to improve tidal flow and fish passage through floodgate modification in drains and creeks on the floodplain. Improving tidal flow in cane drains helps to buffer the impact of acid sulfate soil discharge, significantly reducing pollutant export to waterways.

Thirty-nine high priority floodgates have been modified so far, delivering significant environmental outcomes and even a few unexpected benefits to landholders, such as reducing the time and cost associated with controlling weeds in cane drains, which are reduced / displaced when drains are regularly flushed with brackish water.

Unvegetated Cane Drain Costly to Manage and Environmentally Damaging

Greenbanks Poster (5.76mB PDF)
Green bank projects on the Tweed floodplain flier (1.78mb)

Maintaining cane drains often requires soil disturbance to remove sedimentation and rectify bank slumping.

In 2007 Council, in partnership with state government agencies and local landholders commenced a program to plant out cane drains with native ground cover and small trees to stabilise the banks, discourage weeds and prevent topsoil runoff.

A Greenbank in Action

Known as ‘green banks’, vegetated drain banks require little maintenance and so the soil is not disturbed, drastically reducing acid sulfate soil impacts.

A Greenbank with Three Years of Growth

Nearly 30km of green banks have been planted on the floodplain in areas such as Johnsons Creek Condong, Blacks Drain South Murwillumbah, McLeods Creek Duranbah, Leddays Creek Tumbulgum and Mooball Creek Wooyung.

Cane farmers interested in participating in the program are encouraged to contact the Program Leader – Sustainable Agriculture on (02) 6670 2400.

For more than a decade Tweed Shire Council in partnership with state government agencies and local landholders have facilitated field levelling and drain in-filling programs to reduce acid sulfate soil runoff to local waterways.

Historically, cane paddocks have had varying degrees of inundation, requiring large numbers of field drains to export surface water to the adjacent river or creek. These drains require regular cleaning, which disturb the soil and generate sulfates and release heavy metal pollutants detrimental to aquatic life.

Levelling cane paddocks reduces the number of field drains required, as excess water can flow off the paddock naturally. This increases the amount of land available for production while reducing soil disturbance associated with drain maintenance. This in-turn reduces acid sulfate soil runoff to the waterways.

More than 40km of field drains have been filled across the floodplain including farmland at Eviron, Bray Park, Christies Creek, Murwillumbah, Kynnumboon, Tygalgah and Chinderah with more field drains being filled every year.

For many years, Blacks Drain at South Murwillumbah has been identified as a major source of acid sulfate related pollutant (e.g. iron, aluminium, sulfuric acid) export to the Tweed River.

In 2008 Council was successful in obtaining $100,000 from the NSW Environmental Trust, Urban Sustainability Grant to reduce drain depth and increasing drain width to retain drainage capacity without disturbing the acid sulfate soil layer. These works have been very successful, improving a previously unusable pasture while preventing further oxidation and transport of sulfidic materials to the Tweed River.

Blacks Drain Photo Report (1.26mB PDF)

Paddock Remodelling to Reduce Soil Runoff During Rain

The Cudgen Plateau is famous for its fertile, volcanic soil and Cudgen Creek is famous for turning the colour of the soil after heavy rain.

Native Plants Help to Keep the Earth Berm Stable

Through the Sustainable Agriculture Program, Tweed Shire Council is working with local landholders to help keep the soil on the paddocks.

This has been achieved with minor modifications to the interface between paddocks and drainage lines along with revegetation works. Swales, or earth berms along drainage lines direct runoff into small settling ponds which slow the flow, giving the muddy water time to settle out. Farmers can then retrieve the soil that would have otherwise ended up in downstream waterways.

A two-year collaboration between Council, six local farmers and bush regeneration contractors has restored more than 1.5km of waterways along the Cudgen plateau. The project was funded by the NSW Environmental Trust and completed in December 2017, expanding on the Coastal 20 project area.

The project:

• planted more than 8000 natives to improve waterway health and biodiversity on State Significant Farmland
• led to the adoption of improved soil management practices to curb erosion
• increased landholders’ capacity to manage environmental weeds

In addition, famers and other community members volunteered their time at a planting day to plant over 1000 natives between an intensive cultivation area and a local waterway.

The project equipped landholders with improved practices to manage soil and erosion, improve biodiversity and reduce environmental impacts.

Cudgen Plateau Flyer (890kB PDF)

Council is also working with the local farmers to promote the adoption of better management practices (such as greater use of covercrops and biological farming practices) that improve the productive capacity of the soil whilst reducing erosion and the loss of soil and nutrients into the local waterway.

View the Coastal 20 Video

The University of NSW and Tweed Shire Council in partnership with NSW Cane Growers Association and NSW Sugar Milling Co‐operative undertook an Australian Research Council (ARC) Linkage project aimed at identifying and remediating acid sulfate soil hotspots in the Tweed Local Government Area. The project (LP110100480 ‘Exploiting Natural Processes to Effectively Remediate Acidified Coastal Environments’) commenced in 2011 with the aim of:

1. Identifying acid sulfate soil (ASS) hotspots within three catchments in the Tweed Shire and the most suitable remediation strategies to reduce ASS discharge on a catchment scale;
2. Conducting on‐ground remedial works; and
3. Determining the efficacy of the remedial works in reducing the discharge of problematic contaminants (particularly iron and aluminium) from the three catchments.

Acid Sulfate Soil Research by UNSW and Tweed Council

Between 2005 and 2008 Council co-hosted a research project by the Australian Research Council with the principal objective of developing innovative, scientifically-sound, practicable, floodplain management techniques to reduce the impacts on estuary and coastal water quality from Acid Sulfate Soils drainage products.

Acid Sulfate Soil Research by UNSW and Tweed Council

Investigations focused on three catchments, namely hotspots in the Clothiers Creek and Christies Creek catchments on the coastal floodplain and investigating the effectiveness of remediation works in Blacks Drain south of Murwillumbah. Remediation efforts are ongoing in the Clothiers Creek and Christies Creek catchments. More information is available in the Final Progress Report.

Final Progress Report for the Australian Research Council Linkage Project (2.97mb)

A 2015 project successfully engaged 16 commercial livestock farmers through an education program highlighting the economic, environmental and social benefits of managing their grazing systems using more sustainable practices. The project was funded by the NSW Environmental Trust with significant in-kind contributions from North Coast Local Land Services. The project raised awareness and appreciation for the value of soil health, effective pasture management, the importance of on-farm biodiversity and practical farm planning. Participants identified production limiting factors in their soils through mineral testing and physical assessment and were given strategies for improving soil health based on biological farming principles that will lead to more productive pastures, less erosion and runoff and ultimately healthier livestock and a healthier environment.

Sustainable grazing in the Tweed (3.20mb)

Tweed Shire Council has been assisting a number of commercial sweetpotato growers on the Cudgen Plateau to trial and adopt more sustainable farming practices resulting in less reliance on synthetic inputs and healthier soils for growing crops. Farmers were trained in biological farming practices and a soil improvement plan was developed to address a number of soil health and production issues with financial support from the North Coast Local Land Services. The Tweed Fruit and Vegetable Growers’ Association then trialled the soil improvement plan with support from the Australian Government’s 25th Anniversary National Landcare Grant Program.

The trial determined that biologically-farmed sweetpotato is achievable in a commercial setting, and can result in acceptable, quality yields at similar or lesser costs than existing practices without the need for interventions with synthetic pesticides and fertilisers.

Biological farming on the Cudgen Plateau (1.80mb)

Minimising the loss of valuable topsoils is a significant and ongoing challenge for Cudgen farmers especially where steep slopes, erodible soils, high intensity rainfall and intensive cultivation are involved. However, a two year project funded by the NSW Environmental Trust has helped make a difference by revegetating and restoring the local waterway with native species.

Restoring the Waterways of the Cudgen Plateau (2.69mb)

Dung beetles play a critical role in sustainable livestock production systems, transporting dung below ground and digesting its contents, these beetles can improve soil structure and pasture productivity and significantly reducing nutrient and soil runoff into waterways. Healthy beetle populations also benefit animal welfare by reducing pest fly populations and reducing costs and exposure to chemical controls. Beetles are however adversely affected by many cattle parasite controls. Tweed’s farmers have been learning how to optimise their beetle populations through a number projects.

Dung beetles of the Tweed (1.16mb)

Tweed Shire Council Shire Profile page.

For further information about acid sulfate soils and approval requirements for disturbance, please visit the Tweed Shire Council Acid Sulfate Soils page.

Acid sulfate soil is the common name given to soils and sediments containing iron sulfides, the most common being pyrite. When exposed to air due to drainage or disturbance, these soils produce sulfuric acid, often releasing toxic quantities of iron, aluminium and heavy metals.

In the Tweed, acid sulfate soils are common throughout the coastal floodplain, much of which has been disturbed by human activities, particularly agriculture. Tweed Shire Council, state government and local landholders have been working together for a number of years to manage the impacts of acid sulfate soils. Refer to the projects list for more information.

For more information about acid sulfate soils visit:
QLD Government - Acid Sulfate Soils
NSW Department of Primary Industries - Restoring the Balance – Guidelines for Managing Floodgates and Drainage Systems

Are you a primary producer who needs help accessing landholder resources, grants and incentives?

A good place to start is Council’s Program Leader – Sustainable Agriculture (02) 6670 2400 or Tweed Landcare on (02) 6670 2199 or
tli@tweedlandcare.org.au

Stock and Waterways (5.16mB PDF)
Making Compost (86kB PDF)
Climate Change Impacts – Northern Rivers (800kB PDF)
Northern Rivers Floodplain Network (200kB PDF)

NSW Department of Primary Industries
QLD Department of Agriculture, Fisheries and Forestry
North Coast Local Land Services
Tweed Landcare Inc.
Adapt NSW
SoilCare Inc.