Slow and steady wins the race

Planting slow maturing wheat varieties earlier in the year could be the answer to maintaining high yields in Southern Australia, despite its changing climate.
Nanjing Night Net

Research carried out with support from the Grains Research and Development Corporation (GRDC) shows slow maturing varieties planted earlier in the year have a better chance of delivering consistently high yields for growers in the Southern Cropping Region.

Dr James Hunt, a Commonwealth Scientific Industrial Research Organisation (CSIRO) researcher, said planting slow maturing varieties as early as mid April could let crops take advantage of precious stored soil moisture.

“It turned out that those slow maturing varieties planted early could take much better advantage of that stored soil water and had quite a significant advantage over main season varieties sown in May,” he said.

“What having a slow maturing variety in a wheat program allows you to do is open up your sowing window so you can take advantage of small rainfall events when they come.

You can start taking advantage of small events when they come as far back as April, or with winter wheats, back in March.

“In the last 17 years there’s been a marked decline in April and May rainfall.

“What that has meant is that we have less sowing opportunities in that main season period.

“There hasn’t been a decline in February/March rainfall – if anything it’s increased, and you can start to use that to replace our traditional autumn break.”

The research project monitored four wheat varieties planted across trial sites at Lake Bolac and Westmere (Victoria) in the high rainfall zone, Temora and Junee (NSW) in the medium rainfall zone, and Condoblin (NSW) in the low rainfall zone, with each variety planted between mid-April and late May. Results showed slow maturing variety EGA EagleHawk sown in mid-April outstripped the mid-fast variety Lincoln sown in mid-May by 0.8 tonnes/ha at Temora in 2011 and 2.1 tonnes/ha at Junee in 2012.

Although dry conditions late in winter at Condoblin meant all varieties sown mid-April to mid-May had roughly the same yields, low density plantings benefitted the yield of slow maturing varieties Eaglehawk and Bolac, but reduced yield in fast maturing wheats sown later.

Eaglehawk sown in mid-April at 30 plants/m² out-yielded Lincoln sown in mid-May at 90 plants/m² by 0.4 tonnes/ha in 2011 and 0.6 tonnes/ha in 2012.

High density plantings of Bolac at Lake Bolac yielded 7.0 tonnes/ha, compared to a mid maturing variety at 6.6 tonnes/ha and the fast maturing variety at 6.0 tonnes/ha, planted in late April, early May and late May respectively.

Bolac and mid-maturing variety Derrimut also performed well at Westmere when planted in early May.

Dr Hunt said early planting allowed slow maturing varieties to generally use stored soil moisture far better than faster maturing wheats.

“The main reason for the yield difference is that with slow maturing varieties, when you sow them early, they’re in the ground a lot longer, so their roots are able to use stored soil moisture much more efficiently,” he said. “They also lose less water to evaporation because they cover the soil surface faster because they’re developing at a time when the soil surface is warm and the air’s warm.

“They also have a longer stem elongation phase, which is when grain number is determined, so they grow a lot during that time and set a very large grain number, and thus yield.”

o CSIRO researcher, Dr James Hunt.

This story Administrator ready to work first appeared on Nanjing Night Net.

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