Diversity caveat: don’t go chasing rainbows
GroundCover™ Issue: 125 Nov - Dec | Author: Brad Collis
Increasingly sophisticated grain and graze regimes are intensifying Tasmanian broadacre farming as growers and researchers find new ways to keep raising the productivity bar
There is one thing Tom Green will never be: bored. At least five and often six different crops, along with sheep and cattle, makes every day a juggling act – and that is before you start factoring in seasonal variability, multiple market movements, and keeping abreast of the latest research that on the one hand is consolidating cropping, but is also intensifying day-to-day management.
Tom is one of the new guard of Tasmanian grain growers, harvesting double-digit wheat yields, for example, that mainland growers do not even dream about. But the expansion in that state’s cropping comes with distinctive geographical limits – one of the reasons why growth has been more yield than acreage-based.
It is as fascinating as it is instructive to watch leading Tasmanian growers setting up their futures, based around enterprise diversity, management flexibility and ongoing research provided by the GRDC-supported Southern Farming Systems (SFS) group.
Tom farms 4000 hectares near Cressy in the state’s northern midlands. The property covers a wide range of topography and it is this, he says, that dictates what and how they farm.
“As much as we might wish, we simply are not in a position to just crop,” he says. “So we are running many more enterprises than we would like and it pushes us away from being able to just adopt the cropping or livestock models you have on the mainland.”
Because of the enterprise diversity, Tom says they are still wrestling with rotations because the best mix from an agronomy perspective might not be the best mix for the hip pocket.
“So we are benchmarking the whole farm each year to try to work out what rotations will provide the best gross margin long term. We don’t want to be chasing rainbows.”
The mix of markets, prices and factors such as climate and irrigation have made ryegrass the current principal crop: “We grow about 300ha for commercial pasture seed and all other enterprises revolve around this,” he says.
It might cause a grimace among mainland growers for whom the grass is a costly weed, but Tom is quick to point out that it makes weed control for him even more challenging.
Protecting ryegrass from ryegrass
“The ryegrass we are contracted to grow has to be the right ryegrass. We have to be able to guarantee seed purity, so that means a zero tolerance towards the wrong ryegrass getting in.”
Integral to the ryegrass rotation, therefore, is a two-year break, which can be filled by wheat, canola, poppies, oats, barley or canning peas. Another crop option becoming available is faba beans.
Tom says the target yield for ryegrass seed is two tonnes per hectare and the average price is about $1500/tonne.
This puts it on par with their Revenue feed wheat that, while earning only a comparatively modest $300/t, yields 10 to 12t/ha.
The key to both of these crops is irrigation, “especially ryegrass, which needs watering right up to being windrowed for harvest”.
Tom says the diverse enterprise mix has evolved following the changing fortunes for wool and the step-up in irrigation that was implemented to allow an expansion into cropping, particularly poppies.
The family’s main enterprise, traditionally, was wool, plus a self-replacing beef herd. Then poppies came into play and these became the crop around which everything revolved. The wheat grown at the time averaged just 3t/ha.
“When the profitability of poppies fell away, through disease and smaller production allocations from the buying companies, we turned to grass seed. Now, canola, with the advent of winter grazing varieties, is growing in importance, along with wheat. Other crops in the mix are green canning peas, oats and barley. And faba beans are looking promising in trials.”
Tom says that although the wheat, Revenue, is dual purpose, it is grown solely for grain for the local feed market.
The grazing crop of most interest is canola (Hyola® 970), which has been the focus of considerable SFS research because of the potential it offers both as a grain and as a basis for increasing livestock-carrying capacity.
“Grazing canola might just be the gross margin trigger for putting a lot more land under this crop,” Tom says.
“It’s good forage, and a good grain crop at the end. But there’s still work being done on getting the agronomy, and grazing rates, right.”
SFS project leader Heather Cosgriff has been running GRDC and NSW DPI-funded row-spacing trials to measure the effects on dry matter production and yield.
This follows successful earlier trials of spring-sown canola, which is grazed through summer until autumn, then allowed to recover for harvest up to 15 months after sowing.
Because of this benefit to diverse cropping/livestock enterprises, Ms Cosgriff decided to see if the crop could be further manipulated by widening the row spacing.
“The whole idea of the narrow rows was to achieve canopy closure to reduce the weed burden, but that was being achieved by the grazing … so my thinking was that wider rows would allow more stubble to be left in place, and later after grazing, wider rows would also provide a nice open space for a good weed kill.”
Ms Cosgriff ran the first trials in 2015, pushing well out from the conventional 20 to 25-centimetre rows to 78cm, and achieved a 1.1t/ha increase in grain yield without any loss of forage during the grazing stage.
“The plants on the wide rows were so much bigger and stronger. Perhaps because it was a dry year and there was less competition for soil moisture compared with the narrow rows.”
To further test the effects of row spacing, more trials in 2016 are measuring forage production and yield on 20cm, 40cm and 60cm row spacings.
The other innovation attracting grower attention is the use of strip-tillage between the previous season’s stubble.
The implement only tills a 10cm-wide strip so stubble rows remain undisturbed, as does most of the surrounding soil, keeping any moisture and nutrient loss to a minimum.
In recent trials, Ms Cosgriff says the tilled strip gets the new canola crop off to a strong start, maximising grazing and grain potential.
“Crops in Tasmania have to fit into a diverse enterprise and strip-tillage looks like enhancing this even further,” she says.
“It also opens up the option for bringing high-value vegetable crops, such as broccoli, into a cropping rotation, growing a broadacre vegetable crop in between the stubble rows of a previous season’s wheat or barley crop.”
Tom has been watching the strip-till trials keenly, seeing the opportunity for an early extra crop in the narrow, tilled strip: “It prepares a narrow seedbed without disturbing the rest of the soil, which means you’re not losing the nitrogen or moisture that would otherwise be released through conventional tillage,” he says.
Ms Cosgriff notes that the goal for many growers now is to get two crops off one paddock in a single land-use cycle of about 16 months.
The concept fits well with Tasmanian growers’ intensive approach to farming and the way everything needs to interconnect.
“It’s a systems approach,” Tom Green says. “For example, we graze sheep on the grass seed paddocks in September to encourage increased plant tillering, which increases the seed yield. So the sheep are actually a cropping tool … and to make sure we have enough stock for this, we utilise the grazing canola to keep numbers up through winter.”
Tom says that having a grower research group such as Southern Farming Systems on-hand has been critical in developing diverse cropping options within a whole-of-enterprise framework.
“We have had local research guiding us all the way, from nitrogen applications to choosing the most appropriate varieties.”
He says confidence is high among the state’s grain growers, with a long way still to go before local production makes Tasmania self-sufficient in grain, particularly feed grain.
“The market is there and the production potential is there, in fact our next goal is to lift wheat yields from 10 to 12t/ha to 20t/ha.”
Nothing in the rise and rise of Tasmanian cropping over the past decade gives anyone reason to doubt this possibility.
More information:Tom Green,
GRDC Project Code DAN00198, SFS00028
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