Positive lessons from the blackest day
GroundCover™ Issue: 121 | Author: Rebecca Jennings
South Australia’s Zwar family has built a productive cropping system founded on soil health, minimal disturbance, ground cover, diverse rotations, timeliness and consistency – ingredients that helped them rebuild after a devastating fire
South Australian Southern Flinders Ranges grower Russell Zwar stands in a paddock of wheat stubble, overlooking his house and sheds. He points across the farm to the neighbouring Wirrabara State Forest, recalling how two years earlier a bushfire from there swept across the paddocks.
In less than one hour on 17 January 2014, most of the 1200 hectares Russell and his wife Davina farm in partnership with his parents, Don and Annette, was burnt.
They lost three sheds, 1000 tonnes of hay, a tractor, a tubulator conveyor and a mother bin, but the biggest blow came from losing the bank of ground cover nurtured for decades.
Russell recalls initially thinking the sun would never come up again, but two years on he can see the fire’s impact in a more positive light.
Russell credits the burn with reducing their burden of snails, millipedes and resistant ryegrass, and the family took a strategic approach to rebuild burnt infrastructure by consolidating sheds, repositioning their workshop and realigning fences.
The family had not burned or tilled their land for more than 20 years, to retain stubble to preserve moisture and encourage soil microbiology. After the fire, they were concerned about erosion, without ground cover to stabilise their undulating country, so rebuilding their stubble bank was a top priority.
The Zwars changed their rotation following the fire and on sloping country planted barley instead of beans (which prefer heavy residue) to cover the soil surface more quickly. Without the moisture-preserving benefits of ground cover, they also sowed deeper.
“We are passionate about our farming system and the weeks after the fire were very difficult,” Russell says. “We were fortunate to receive good opening rains in April and had a good year after the fire to start rebuilding ground cover, and now we are back on track. The experience really reinforced the value of stubble retention in our system.”
The Zwars have a measured, long-term approach to developing soil condition and productivity. Russell’s grandfather Reg experimented with minimum till and direct drilling in the 1960s and 1970s to repair erosion and ‘wheat sick’ paddocks. He filled in washouts, added dryland lucerne to stabilise and rebuild soils, and designed a narrow point system to prevent digging up lucerne during cultivation.
Discs made to work
Don started direct seeding in the mid-1980s and by the early 1990s the system was no-till. Don and Russell stopped grazing stubbles in 2006. When their tyne and press-wheel seeder could no longer handle the residue they bought a John Deere 1890 single-disc implement in 2010.
“We did a lot of research and talked to a lot of growers who were running discs,” Russell says. “It was a big change but we are confident we now have the machine set up for our environment.”
Initial challenges of the disc system included increased slugs, waterlogging after a wet summer and winter, and some run-off without the ‘mini contour banks’ created by press-wheel furrows.
However, on the back of one of their best years ever, Russell is confident they are on the right track. He is understandably reluctant to divulge his 2015 yields when many other SA growers had to cope with a dry finish, late heavy rains, frost and fire, but he is happy to talk long-term averages.
“We have definitely seen our wheat and barley averages increase as a result of moving to our current system. Our long-term wheat average is 3.87t/ha, but our average for the past six years is 4.7t/ha.
“Last year was a near-perfect season until mid-September, when our crops went without reasonable rain for 46 days and suffered from severe heat during grain-fill. Yet we still produced some of our best wheat and barley yields with no screening issues. This gives us confidence our soils are improving.”
The Zwars introduced controlled traffic when they bought the disc seeder, to further repair soils. They cut and extended the boomspray axle to take it to three times the seeder width and put wheel spacers on the tractor, and now operate 9.14-metre machinery widths (or multiples of) on 3.05m wheel centres.
Maintaining cover on tracks is a priority to prevent run-off and erosion, so Russell uses real-time kinematic (RTK) guidance to locate and sow all wheel tracks.
Other strategies to optimise disc performance included:
- adding weight to the seeder frame to create more down force to cut through the residue burden;
- replacing discs every 1200ha to combat abrasive soils;
- lifting the header front to 400 millimetres to improve disc movement through residue;
- introducing 19-centimetre row spacing for cereals; and
- aiming to complete seeding by 20 May (historically seeding could extend to early June) to avoid hair-pinning and achieve optimal disc performance in warm, dry conditions.
Although the disc system emphasised the need for timely sowing, the Zwars balance a calendar-based program with agility to respond to seasonal conditions. They retain more seed than is necessary, so they have several varieties on hand to suit early or late starts.
Russell introduced EGA Wedgetail wheat in 2014 and last year sowed it on 8 April to capitalise on an early break. It was a solid performer at 5.4t/ha. However, with spring wheats (LongReach Trojan and LongReach Cobra) sown in the first week of May still the best performers, he sees EGA Wedgetail as being of use in early or wet starts, in paddocks that are prone to waterlogging.
“In the past few years, we’ve had some good early breaks and finished seeding between 15 and 18 May, which resulted in some of the best crops we have ever had, so although I want to have varieties that allow us to be flexible, I still want to see our seeding program done in a timely manner,” Russell says.
“Hopefully, in the near future there will be some new winter wheats released with higher yield potential for SA conditions.”
The Zwars use summer crops such as sunflowers – an unusual sight in this region of SA – to provide diversity and help with waterlogging; however, Russell is still evaluating their fit in the system.
He is also reassessing the role of canola – yields have stagnated while cereals have gone ahead, so he has increased the area planted to beans. Hay also compromises the system by causing compaction and removing residue, but the gross margins and its value as a non-herbicide weed control are hard to ignore.
Mapping the way ahead
The Zwars use Topcon CropSpec normalised difference vegetation index (NDVI) cameras for on-the-go variable-rate (VR) nitrogen applications and are motivated by optimising, rather than reducing, this input.
“We have increased our total nitrogen use over recent years with better seasons and as we gain confidence in our system, to bring the lower-yielding areas up while not over-applying on better soils.”
In an area characterised by cold and wet July/August months and unpredictable winter rainfall, fertiliser decisions can be difficult.
There is a fine line between timely applications and minimising losses to run-off or denitrification, and the Zwars find multiple applications are the best approach. They give wheat a small blanket rate in June to prepare it for winter, with the main VR application in August at GS32, followed by a top-up blanket rate in September if conditions allow.
They are pH mapping the farm, taking two tests per hectare to paint a picture of their variable soils, which range from a pH of 4.5 in lower areas up to 7.5 on rises. The pH maps will guide targeted lime application.
Russell is also investigating radiometric mapping as a tool to identify any soil potassium deficiencies.
“Soil health and nutrition is what is going to drive us forward, continuing on with minimal disturbance, ground cover and diverse rotations,” he says.
He runs on-farm trials to test ideas in his own environment, such as assessing different in-furrow treatments and seeding rates for faba beans in 2015. Halving seeding rates produced as good (if not higher) yields in better soils but decreased yield in poor soils, so Russell is considering VR seeding beans to improve canopy management.
Another on-farm trial also reinforced the Zwars’ decision to use 19cm row spacings for cereals, as narrower rows delivered a 10 per cent yield increase and reduced ryegrass populations compared with 38cm rows.
As a former chair of the SA No-Till Farmers Association, Russell keeps his finger on the pulse of research and stays in touch with growers, researchers and advisers around the country.
He blends advice from his local agronomist (for region-specific issues), an adviser in the high-rainfall zone of SA (for varieties), and a consultant in Western Australia (for an ‘out-of-the-box’ perspective).
Region South, West