New South Wales

Cereal Stubble Management

Harden is located approximately 130 kilometres north east of Wagga Wagga in the south west slopes region of NSW, and is generally classed as a mixed farming area. Most farms crop between 40% and 60% of total farm area. Winter cereals occupy around 60% of the total cropping area and are rotated with canola and various legumes. Wheat is the major cereal crop grown with small areas of both oats and triticale.

With support and funding from Murrumbidgee CMAs National Landcare Program project the Harden Murrumburrah Landcare Group (HMLG) investigated methods of cereal stubble management.

The natural resource issueHistorically, stubble burning has been a quick and economical means of removing stubble to enable easy sowing of the following crop. However, for a number of years farmers in the Harden district have been trying to move away from stubble burning for a number of reasons.

The burning of cereal stubbles is still common practice for many producers in southern NSW for reasons such as weed and disease control, but mostly to aid the sowing of subsequent crops. Although new and improved sowing equipment is available and enables farmers to retain stubble with some success, stubble burning is still required in years with heavy stubble loads.

Burning of stubble can potentially result in changes in a whole range of soil physical, chemical and biological properties, including pH, soil organic carbon, nutrient availability, infiltration and microbial activities, with long term implications on sustainability (Walker et al., 1986). Research has shown that while no effect is evident in the short term (e.g. 5 years), a long history of stubble burning can significantly reduce soil carbon levels (Yin Chan & Heenan, 2004). This management practice is also time consuming, labour hungry and impacts on the timeliness of sowing.

The standard practice at present in the Harden area is to reduce the stubble load as much as possible over the summer period by mechanical means and/or grazing, then burn the remaining stubble (if necessary) as late as possible prior to sowing. Many growers are uncertain as to what impact this practice has on soil health and subsequent crop yields.

What the group has doneIn 2004, the HMLG established a cereal stubble management project which set out to compare and identify practical, cost-effective stubble management options that would reduce the need to burn cereal stubbles.

Many growers in the HMLG have been trying various stubble management methods since the early 1990s with various degrees of success. Thus the group set up the cereal stubble management trial to examine some of the newer methods of improving stubble decomposition and hence stubble load at sowing.

Project focus: Managing cereal stubble

Location: Harden, 130km north-east of Wagga Wagga

Group: Harden Murrumburrah Landcare Group

Enterprises: Winter cereals, canola, legumes

C a s e s T u d y

www.murrumbidgee.cma.nsw.gov.au

Wagga Wagga

Harden

Hay Murrumbidgee River

Cooma

Rob McColl ‘Bobbara Station’

Galong in canola crop

C a s e s T u d y

The trials examined and compared a range of cereal stubble management options, including:

Table 1. Cereal stubble management options

Mechanical Nitrogen and Biological treatments

Prickle chain Nutri-Life Stubble Tech® – 10L/ha

Harpers Stubble Cruncher

BioAg Digest It® (4L/ha)

Low harvest height Nitro Humus – 40L/ha plus sugar (2kg/ha)

Coolamon Harrows Nutri Soil – 5L/ha

Grazing

Some of the above were used in combination (e.g. stubble cruncher and Nutri-Life Stubble Tech®).

What the group foundThere was no significant difference in the stubble loads under any of the applied treatments, with the Harpers Stubble Cruncher and Coolamon harrows resulting in increased stubble contact with the ground. Grazing had no significant effect on stubble loads.

The breakdown or decomposition of stubble is determined to a large extent by two factors: moisture and temperature (Singer & Munns, 1992). During the trial period, there was below average rainfall and above average temperature, hence conditions were not ideal for increased cereal stubble breakdown.

The lack of clear-cut differences in the trial means that no perfect solution exists and farmers will continue to adapt their stubble management with their circumstances. The ‘best’ stubble management option is largely farm-specific and will be determined by how the technique fits in with the overall farming system.

Cost/BenefitTo quantify the impact of stubble burning is difficult due to many compounding factors that come into play when soil is involved. However, stubble burning has costs that are often not recognised. Considerable time is required to organise permits, as well as costs associated with equipment and labour to conduct the burn.

One member of the HMLG believes it costs $25/ha to burn cereal stubble, hence there are clear financial and other benefits from not burning. One key benefit comes from the ability to sow canola on time and often into conserved moisture. There are often time delays waiting for suitable weather conditions to burn cereal stubble which results in the late sowing of crops and potential negative impact on crop yields.

Assuming a 5% yield penalty for every week the canola crop is not sown on time, yield would decline from 2.0t/ha to 1.9t/ha if planted one week late, impacting on gross

margins (Figure 1).

Figure 1. Gross margins

Benefits and challengesMembers of the HMLG recognise the following key benefits of retaining cereal stubble:

• Improved organic matter content, soil carbon levels and nutrient cycling

• Improved water use efficiency– through better water infiltration and utilisation of summer rainfall

• Increased yield through timeliness of sowing

• Decreased soil erosion as a result of ground cover all year round.

Messages for other land managersMembers of the HMLG see stubble retention as playing a major role in increasing profitability of cropping systems through greater resource utilisation. The efficient use of resources (inputs, time, soil) is important, as is capitalising on every drop of rainfall (converting mm of rainfall into grain). Planning and flexibility within the plans are important factors when adopting a

cereal stubble retention farming system.

For more informationMurrumbidgee Catchment Management Authority www.murrumbidgee.cma.nsw.gov.au

Murrumbidgee Catchment Management Authority (2005). ‘Harden Murrumburrah Cereal Stubble Management Project – Summer of 2004/2005’.

Murrumbidgee Catchment Management Authority (2006). ‘Harden Murrumburrah Landcare Group Cereal Stubble Management Project – Summer of 2005/2006’. http://www.murrumbidgee.cma.nsw.gov.au/uploads/media/HMLG_Cereal_Stubble_Managment_Project.PDF

Pritchard, F, Ballinger, D and Potter, T (2007). Growing dryland canola in 2007, Irrigated Cropping Forum 2007. http://www.icf.org.au/proj_f/pdf/Irrigated canola in 2007.pdf

Singer, M.J. & Munns, D.N. (1992). Microbial Processes. In SOILS- An introduction, MacMillan: New York.

Walker, J., Raison, R.J. and Khanna, P.K. (1986). In ‘Australian Soils-The Human Impact.’ (Eds. J.S. Russell and R.F. Isbell) pp.185-216, University of Queensland Press, Brisbane.

Yin Chan, K & Heenan, D (2004). ‘Long term effect of stubble burning on soil carbon levels and wheat yield in southern New South Wales’, 4th International Crop Science Congress.

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Harden stubble management site

Photo courtesy of Industry and Investment NSW

Cootamundra

acknowledgements: The Murrumbidgee CMA wishes to acknowledge land managers Rob McColl, Peter Holding, and I&I NSW for their time and input in assisting with the creation of this case study.