Growers focus on protecting cropping soils after fire
Grain growers in South Australia’s fire-ravaged Lower North cropping region are being advised to develop and implement tailored and collaborative erosion control strategies based on soil type and drift susceptibility.
Minimising topsoil loss is a priority for growers in the region who are working together to reduce the impact of fire on their now bare cropping land and to protect their livelihoods.
A recent fire recovery and soil protection meeting organised by the Mallala Agricultural Bureau brought together around 150 local landowners and experts from numerous organisations to discuss soil-saving options and the immediate and longer-term agronomic repercussions of fire in terms of crop rotations, weed control and soil nutrition.
The meeting was facilitated by Grains Research and Development Corporation (GRDC) Southern Regional Panel member and Ardrossan-based agronomist Bill Long, who said that many growers in the region were well versed in treating deliberately-burnt paddocks, as practised in the past, but for younger generation farmers it was a new experience.
“Of course, dealing with a fire of this scale is going to be a challenge for everyone,” Mr Long said.
“In the immediate term, farmers will need to manage erosion to the best of their ability. They will need to observe what’s happening on their properties, share those observations with their neighbours and act if necessary. Because no-one is an expert in these situations and because soils are highly variable, there are no clean-cut and easy answers.
“Growers and their advisers will also need to think about next year’s cropping programs and those beyond because what they do now and over the coming months will have implications for their farming systems in the longer term.
“As many people said at the meeting, it will be very much a ‘suck it and see’ approach.”
Those attending the meeting, which involved inspections of the fire-hit properties of local growers Derek Tiller and Richard Konzag, discussed at length the merits of emergency cultivation and cover crops as soil protection measures.
Key messages regarding such activities – delivered to growers by personnel from the SA Research and Development Institute (SARDI), Primary Industries and Regions SA (PIRSA) and Rural Solutions SA, CSIRO, agronomists and others – included:
- Assess levels of topsoil drift and potential for wind erosion in individual paddocks before determining if emergency cultivation is necessary. If the soil is black and still holding ash, or if drifting is not occurring in windy conditions, cultivation may not be necessary. Stable areas should be left untouched.
- Deep sands are likely to require immediate attention. Sandy loams are also susceptible to drift.
- If cultivating, aim to produce clods big enough (fist-sized) to act as a wind barrier and hold topsoil in place. These clods, if in paddocks where stubble retention has been practised, are not expected to be an issue at seeding if prior rainfall, to break open the clods, has been received.
- If ground is to be worked up, it is preferable to cultivate the entire paddock, rather than doing it in skip rows. Leaving uncultivated patches will potentially cause drift into cultivated rows.
- Minimise soil disturbance by keeping stock off and avoiding vehicle traffic over the burnt land.
- Consider cover crops for stabilising sandhills, especially, if sufficient rainfall is likely. F3 barley could be an option but it must be sown at a sufficient depth to prevent loss. Sorghum, millet, buckwheat, cereal rye and sunflowers are other options, depending on adequate plant-available moisture and predicted rainfall.
- If sowing a cover crop, consider what is likely to follow in the rotation to avoid issues with winter crops.
- Clay delving and spreading, if practical and economically feasible, will prevent drift on sandy soils. Clay should be spread as soon as possible and then left on the surface until incorporation prior to next season’s opening rains.
- If planting legumes next season, sow into heavier soil types and sow later than normal to allow soils to stabilise. Poor early vigour and blasting are potential issues for legumes sown into bare paddocks. Variety choice will be critical.
- Group C chemicals Diuron and Simazine, used for broadleaf weed control in pulses and applied in front of the seeder, are likely to be more "active" than normal because there is no stubble to slow movement into soils, posing a crop safety issue in bare soils.
- Fire will have reduced the weed seed load, but not completely as seed banks can be at depth in the soil. Soils laid bare by fire are at risk of invasion of weeds from nearby non-burnt paddocks and roadsides.
- There may be a reduction in some soil-borne root diseases such as crown rot and take-all.
- The exposed land provides an opportunity to undertake soil mapping, paddock zoning and fencing reconfiguration.
Mr Long encourages growers to consult with local agronomists – many of whom contributed valuable insights and recommendations at the Mallala meeting – when considering erosion control strategies.
More information on the treatment of fire-affected cropping land is available in resources provided by PIRSA.
Bill Long, GRDC Southern Panel, 0417 803 034
Mark Stanley, GRDC Southern Panel, 0427 831151
Sharon Watt, Porter Novelli, 0409 675100