Summer planting scenarios
GroundCover™ Issue: 138 January - February 2019 | Author: Rebecca Thyer
Across the northern region, summer-cropping paddocks may be left to fallow if subsoil moisture calculations do not add up
Growing a crop in any given year is a gamble, but the odds of a successful return can be calculated to some degree, says Tony Lockrey, a consultant agronomist with northern NSW research and merchandise business AMPS Moree.
“It all comes down to this: how do I get the best dollar return from my soil moisture? Although the background to this answer has to include rotation considerations with respect to disease, herbicide management, nutrition and other aspects, the key driver is profitability derived from soil moisture,” Mr Lockrey says.
It is a question being asked around Moree and other northern regions affected by the continuing dry, as growers decide whether to plant a summer crop.
Mr Lockrey’s region around Moree usually receives 575 to 675 millimetres annually, but by mid-November 2018 had only received 150 to 300mm. “As a consequence, our winter crop was close to a clean miss and the summer cropping season is hobbling off to a start with adequate planting moisture in places, but without ideal subsoil moisture levels,” he says.
In a bid to make these decisions simpler, Mr Lockrey and a local AMPS research committee, including key growers and private consultants, in August came up with key soil moisture and timing triggers – in conjunction with current gross margin numbers – to help decide on a ‘go or no go’ answer for summer cropping. In each case the question was asked: ‘Is a summer crop viable or does a long fallow into winter wheat make more economic sense?’
“We created a Christmas Day scenario – what is possible if we received enough rain, say 100mm?”
With the cotton-planting window closed by then and sorghum nearly done, the scenario saw three summer crops assessed: maize, sunflowers and mungbeans.
Mr Lockrey says maize and sunflowers need a full profile – one metre of stored soil moisture (180 to 250mm of plant-available water) – to be successful. Both need to be planted before the end of January.
Mungbeans could be planted on paddocks with 60 to 70-centimetre depth of stored soil moisture (140 to 180mm of plant-available water). “Growers could take the risk with these because they do not always extract moisture down to a metre and are more dependent on in-crop rain at flowering. The same planting window applies.”
The alternative option considered was to long-fallow paddocks for winter wheat.
“Return per millimetre of stored soil moisture is a key driver here. If a crop is planted on a shallow moisture profile, we are still committing to the planting and growing costs but may not see adequate income to cover them, let alone make a profit. The money is in the bottom foot of moisture in the profile, which may not be there at the moment. It takes time and multiple rainfall events to get moisture down there.
“We’ve got to ask: how will I get the best return from my moisture? And the answer could be to wait and plant a wheat crop.”
In calculations made for the areas of Bellata, Garah and Pallamallawa, NSW, the average costs per hectare of growing a long-fallow wheat crop are higher (at $450/ha) than sunflowers, mungbeans and maize (which range from $370 to $446/ha).
However, the returns on winter wheat are higher, at $451 to $1051/ha, than the more variable and lower average returns ($30 to $1300/ha) for late-summer crops.
In some of its long-term research work AMPS has also been bringing forward planting dates for early-sown wheat, finding that it can be successfully planted one to two weeks earlier than the traditional Anzac Day starting date, in areas of lower frost risk. “We are bringing the planting date forward a bit and with that frost and heat interactions need to be thought through and have been measured.”
Mr Lockrey explains the ‘sweet spot’ for grain filling is the 10 to 15 days around the end of August and early September. “If wheat flowers before that, there is a higher frost damage risk.” On the flip side, later-sown wheat risks losing more yield to heat.
The risk of heat damage can often seem less traumatic, he says. “It can take a bit off every year and you don’t notice it as much, whereas a bad frost can hit you hard and wipe out the whole crop.”
He says whatever summer decision is made, while paddocks are fallow the usual fallowing rules apply: “Keep it clean and don’t lock out possible options with residual herbicides. Once the intended crop type is known, more specific and residual herbicide options can be explored to help control key hard-to-beat weeds such as fleabane and summer grasses.”
0428 529 001
Was this page helpful?