Best way to boost yields

Winter wheats sown early best way to lift average yield


On Farm
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Research suggests that winter wheat varieties with long coleoptiles (pointed protective cover that encases the emerging shoot) have the potential to raise average yields across southern Australia.

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Bonnie Flohr (CSIRO), author of a study, that shows average wheat yields could rise with winter wheat varieties that have long coleoptiles.

Bonnie Flohr (CSIRO), author of a study, that shows average wheat yields could rise with winter wheat varieties that have long coleoptiles.

Research suggests that winter wheat varieties with long coleoptiles (pointed protective cover that encases the emerging shoot) have the potential to raise average yields across southern Australia. For NSW this aligns with areas south of Coonabarabran. Two main reasons support these findings. Firstly, wheat plants with long coleoptiles can be sown much deeper, for example 12.5 cm compared to the current practice of around 5.0 cm depth.  

In seasons with dry late summers and autumns, deeper sowing enables germination using stored sub soil moisture that is accumulated during fallow periods. Current varieties that require shallower sowing are often unable to be sown early (March April, early May) due to dry conditions and dry topsoil. For many areas, 2017 and 2018 were typical of such years.

Secondly “winter habit” wheats (commonly referred to as having a vernalisation requirement) have a more flexible sowing window than fast developing spring habit types. In some regions, winter wheats with appropriate maturity can be sown from late February through to mid-May.

A further underlying premise of the study is that there is a significant amount of research supporting early sowing where possible, with appropriate varieties, on average leading to higher yield. This is particularly so if crop rotations are sound and a high standard of fallow management is practiced to conserve fallow moisture.

Thus, wheat with the combination of long coleoptile and winter habit has the potential to be sown into wet or dry topsoil across a wide window, providing growers with an opportunity to maximise yields, from early sowing, in a larger proportion of seasons. 

CSIRO journal Crop and Pasture Science details the study in the paper “Genotype management strategies to stabilise the flowering time of wheat in the south-eastern Australian wheatbelt”. Bonnie Flohr (CSIRO), senior author, James Hunt (La Trobe University), John Kirkegaard (CSIRO), John Evans (ANU), and Julianne Lilley (CSIRO) conducted the simulation study. Research was funded by the GRDC through a Grains Industry Research Scholarship.

Coleoptile lengths of modern semi dwarf wheats are shorter than those of older tall varieties with genes for shorter straw closely linked to shorter coleoptiles. However other CSIRO research has identified alternative dwarfing genes that can also reduce crop stature without reducing coleoptile length and early growth, as well as genes that promote longer coleoptiles. 

Lines with these longer coleoptile genes have been released to wheat breeders. For example Britt Kalmeier, Australian Grain Technologies winter wheat breeder, notes their potential and has them included in her program. Breeders like Ms Kalmeier emphasise it is going to be quite a challenge to incorporate these into winter wheats while retaining all the other important traits such as quality, high yield, resistance to diseases like the three rusts and good agronomic type including relatively short straw. 

In the simulation study, highest yielding strategies involved winter wheats with long coleoptiles established on stored subsoil moisture from the previous rotation and achieved on average a mean yield increase of 1200kg/ha or 42 percent relative to the baseline strategy. 

The study stresses that consistent, year on year benefits of early-established, slow-developing cultivars are unlikely to be realised until the release of cultivars with long coleoptiles that can be sown at a greater depth than existing cultivars. Stacking genetic traits (development type, long coleoptile) with sound management (fallow, early sowing) generally had an additive yield effect at most locations studied. Sites from NSW included in the study included Temora, Condobolin and Cootamundra. 

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