Maximising wheat yields while managing risk
With northern region growers facing climate data pointing towards the possibility of shorter winter periods, but with frosts still a significant risk to crops, how do they maximise the potential of wheat varieties to improve yields, while developing risk management strategies?
It is a complex challenge being addressed by the GRDC-funded ‘Variety Specific Agronomy Packages’ project in Queensland. The project is examining the effect agronomic practices such as time of sowing, nutrition rates and populations can have on wheat varieties planted in different geographic locations.
While the project has been run by NSW’s Department of Primary Industries for several years across a range of crops, it has now been extended into Queensland for wheat, with research being undertaken by the Queensland Department of Agriculture and Fisheries’ (DAF) Regional Research Agronomy Network.
Research started in 2015 with more than 2000 trial plots planted across six sites in Queensland. This year, 2500 plots have been planted across six sites, with core sites at Emerald in Central Queensland, and Goondiwindi and Hermitage in southern Queensland.
Emerald-based Queensland DAF senior research agronomist Darren Aisthorpe, who is leading the research work in Queensland, says that by manipulating triggers such as time of sowing (TOS), different varieties can and will perform differently.
“By understanding these differences we can better manage risk and maximise production for a given region,” Mr Aisthorpe says.
“The research sets out to answer a number of questions, such as what effect does time of sowing have on different wheat varieties across geographic locations, what’s the population effect on yield, does a maturity group perform better or worse for a given time of planting, and is this consistent across the times of sowing?”
Mr Aisthorpe says while it is difficult to draw conclusions based on a year’s worth of data, early analysis of the 2015 and 2016 trials has shown three key trends.
“Data has shown so far that TOS had a significant effect on yield, that varietal maturity is important, and there is significant yield compensation despite low populations,” Mr Aisthorpe says.
“Frost, or rather timing flowering so the probability of frost is as low as possible, has always been the biggest driver of when growers decide to plant a variety.
“What we’ve done with the TOS trials is to look at what happens if we mix it up and plant in an earlier period of mid-April, compared to a traditional planting period in mid-May.
“The 2015 trials had early (mid-April), main (mid-May) and late-season (mid-June) plantings, and this year we’ve added a fourth planting period in late March.
“Our first lot of data examined flowering dates based on TOS. It shows that early-maturing varieties like LongReach Dart, Sunmate, Condo and LongReach Spitfire generally seemed to beat the frost when planted early.
“They were flowering within just over 60 days of planting in Central Queensland, which is exceptionally quick when you compare the southern sites, which could take 90 to 110 days. They were planted in mid-April and flowering in early to mid-June, which was just before the peak frost period for that region.
“There was a spread of about 10 days between those varieties, with LongReach DartA being the fastest and SuntopA the slowest.
“The same varieties planted at the traditional planting time of mid-May took longer to flower, with a spread of 10 days, but with most varieties flowering in peak frost-risk time, which is what the long-term research reinforces about selecting flowering dates and variety selection.
“Late planting in mid-June showed days to flowering was similar to the May plant, but flowering time would be considered past peak-frost periods, and once again reinforces traditional planting logic which aims to have flowering occurring as soon as possible after frosts are over.
“In 2015, when you compare the geographic spread of trials across Queensland, we saw differences of up to 20 days in the time to flowering of a single variety planted at different locations at about the same time.”
Based on 2015 data, once populations in the Central Queensland trials exceeded 500,000 plants per hectare, there was minimal effect on yield across varieties.
“However, we strongly recommend growers still target one million plants per hectare. Previous research indicates this is an ideal population which will allow growers to maximise yields in optimum conditions,” Mr Aisthorpe says.
However, he says data suggests not all varieties react the same way to population density within a row.
“An early-maturing variety such as LongReach Dart still relies heavily on population to maximise yield, however longer-season varieties such as EGA Gregory appear to have a greater ability to compensate in Central Queensland conditions when planted early enough,” Mr Aisthorpe says.
He says there is a difference in the way maturity groups performed based on TOS, but understanding this difference could help maximise yields.
“For example, in the April planted trials, the mid-season varieties such as Mitch performed the best,” Mr Aisthorpe says.
“In 2015 in the May and June-planted varieties, the early-maturing varieties like Condo and LongReach Spitfire outperformed the medium and long-season varieties.
“A data summary from the Emerald site in 2015 showed an almost one tonne per hectare difference in average yield between TOS 1 (mid-April) to TOS 2 (mid-May) and again to TOS 3 (mid-June).
“TOS 1 performed the best in 2015, but it’s crucial to remember this is just one year’s data, from one site.
“Growers also need to be very mindful that frost risk must still be their number one concern if they’re considering planting earlier than they traditionally have and need to understand their local frost risk.”
0427 015 600,
‘Time of Sowing’ Fact Sheet
‘Sowing early in 2014 – how did it work?’ GRDC Research Update paper
GRDC Project Code DAN00167