Sunflower family – Russell and Davina Zwar with their three sons (from left) Noah (nearly 2), Patrick (4) and Henry (6).
PHOTO: Rebecca Jennings
In southern Australia, stored moisture and summer weed control are vital, so summer crops can seem incongruous. However, Wirrabara grower Russell Zwar believes they are an opportunistic fit in his no-till continuous cropping system. The Zwar family farms 1200 hectares in the upper north of South Australia, with a disc-seeding system focused on building healthy soils through minimal disturbance, ground cover and diverse rotations.
They match sowing to seasonal conditions, retaining more seed than required from a range of varieties so they can respond promptly to early or late seasonal breaks.
It is not just an important strategy for cereal production. Their proactive, agile approach equips the Zwars with the ability to capitalise on late-spring and summer rainfall by planting cash crops.
Russell runs on-farm trials to test ideas in his own environment. He has trialled sorghum as a summer crop but, as optimal soil temperature for planting (16°C) is not achieved at Wirrabara until late October, the crop does not complement a winter cropping program.
He found maize and sunflowers can be planted a month earlier, when the soil is 12°C. However, maize is sensitive to heat stress during pollination in January, while sunflowers have proven to be a robust and economic summer crop.
Russell planted 40ha of sunflowers on 9 October 2015 into a mixed-species cover crop that was sprayed out in August. He will harvest in March to supply the birdseed market in Adelaide. “We need to harvest at least one tonne/ha to be worthwhile,” he says. “We do achieve this, but it is early days and the viability of these crops in our area is still uncertain.”
Russell says the future of summer crops in their system depends on what benefits they see in subsequent years. “Our best wheat crop was where we had maize three years ago, but we don’t know how much of an influence it had … we are keen to keep experimenting.”
Cover crops also add diversity to the Zwars’ system but are dependent on timing of rain, the paddock and the cropping sequence. The Zwars took advantage of 100 millimetres of rain in early November and sowed a mix of millet, sunflowers and cowpea on 80ha of hay stubble in a paddock prone to waterlogging. They will spray it out before seeding to act as a brown manure and hopefully remove excess soil water for barley.
Russell would like to see further research into the role of cover crops in southern farming systems: “It’s hard to put a number on what the benefit is from the diversity in our system – I’d be interested to see how the numbers stack up over a 10-year period. Is it like a brown-manure phase, where it won’t provide a financial benefit in the first year but will pay off through the following rotations?”
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