Do our current wheat varieties need different
agronomy at Holt Rock 2015 trial report
Authors Christine Zaicou-Kunesch and Brenda Shackley
Do our current wheat varieties need different management to get the best
performance from them. A better understanding of how agronomy influences varietal
performance will assist growers to be confident in their in decisions at seeding and
throughout the season.
What we did
A series of small plot field experiments were conducted in 2015 to assess how
changing plant density of new and existing affected their nitrogen requirements.
The trials were at Yuna, East Koorda, Moorine Rock and Holt Rock in Western
Australia.
This is a report for the study at Holt Rock. Mace, Corack, Emu Rock, Hydra,
Magenta and Yitpi wheats were dry sown on the 1st May (effective sowing was 16th
May following 20mm of rain). For each variety and at each of these three target
plant densities (60, 120 and 180 plants/m2), and four target nitrogen treatments of 0,
10 kg/ha at seeding, 30 kg/ha (10kg/ha at seeding and 20 kg/ha on 11th June) and
50 kg/ha (10kg/ha at seeding and 40 kg/ha on 11th June) were applied.
What we found
Plant establishment was lower than expected. Mechanical issues at seeding
influenced establishment at Holt Rock however establishment was uniform. For
each of 60, 120 and 180 plants/m2, 40, 90 and 125 plants/m2 established.
At Holt Rock, the varieties Magenta and Yitpi were significantly lower yielding than
Mace wheat (Figure 1). Agronomy did influence grain yield but the responses were
similar for each variety.
Variety response to added nitrogen
Grain yield increased from 2.5 to 2.7t/ha with nitrogen added to 30kg/ha. This is a
7kg/ha increases in yield for each kilogram of added nitrogen. There was no further
yield increase with additional nitrogen. The hectolitre weights of all varieties were all
above industry standard of 76 kg/hl. Grain protein was significantly higher at
50kg/ha of nitrogen compared to the nil treatment.
Supporting your success
Figure 1 Effect of applied nitrogen (kg/ha) on adjusted grain yield of wheat varieties
in 2015 at Holt Rock (LSD: 0.05 averaged across varieties).
The grain protein of varieties was influenced by applied nitrogen. Mace wheat had
significantly lower grain proteins at Holt Rock compared to Emu Rock and Magenta
wheats.
Figure 2 Effect of applied nitrogen (kg/ha) on grain protein of selected wheat
varieties in 2015 at Holt Rock (LSD: 1.2 (across variety) and 0.7 (within variety)).
Yield components such as ear numbers and grain size were influenced by the main
effects of nitrogen applied and plant density however variety interactions with these
factors were not significant. The response of applied nitrogen on grain yield mirrors
the response of applied nitrogen on ear numbers/m2 (Figure 1). However, there was
a decline in grain weight, measured as 1000grwt, with increasing nitrogen applied at
Holt Rock (Figure 3)
Figure 3 Effect of applied nitrogen (kg/ha) on ears number/m2 and grain weight
(g/1000 seeds) measured as 1000grwt) (average for variety and density) in 2015 at
Holt Rock (LSD:10.3).
Variety responses to plant density
Plant establishment was lower than expected and influenced by either a drying seed
bed or mechanical issues at seeding. This will influence some of the responses to
increasing plant density.
There was a small yield benefit of 80kg/ha when plant density increased from low
(40 plants/m2) to medium (99 plants/m2) (Figure 4). This equates to 1.6 for each
additional plant per meter squared. A further increase to the high density (an
additional 60kg/ha of seed) did not significantly increase yield or account for the
additional seed sown at the high density. The higher density treatment only
established 125 plants/m2 and this will have influenced the response.
Figure 4 Effect of increasing plant density on grain yield (average for variety and
nitrogen) in 2015 at Holt Rock (LSD: 21kg/ha).
What does it mean?
The agronomy of wheat varieties will influence yield however the varieties did not
differ in their agronomy package. Nitrogen had the biggest influence on yield,
followed by variety choice. Density had a small effect on yield but there was no
influence on grain quality. These responses are similar to testing at other locations
and in 2015.
Yields increased with added nitrogen to 30kg/ha however there is no evidence that
varieties differed in their grain yield response to added nitrogen in 2015. Ear
numbers were a good indication of yield response to added nitrogen in the
experiments. However management did influence yield components and potential
yield compensation. For example while ear numbers increased with increasing
nitrogen, the individual grain weights of varieties declined.
Density and nitrogen did not influence small grain screenings. Small grain
screenings were within industry standards and not affected by the different plant
densities. Nitrogen treatments were increased to 50kg/ha and this did not
significantly affect grain screenings in 2015.
Plant establishment was lower than expected and influenced by either a drying seed
bed or mechanical issues at seeding. This will influence some of the responses to
increasing plant density.
Lower densities limited production however the responses were small with
increasing plant density. Increases in yield with increasing plant density from 40 to
99 plants/m2 accounted for additional seed sown. Hence it is concluded that lower
densities will limit grain yields compared to medium plant densities. Further
increases in density to 125 plants/m2 did not improve grain yields to account for the
additional seed sown.
Acknowledgements
The outputs of this project contribute to the Tactical wheat agronomy for the west
project (DAW00249) with is funded by GRDC and DAFWA. This funding is greatly
appreciated. This projects team are key to the its success and we wish to recognise
the contributions of our colleagues Jeremy Curry, Bob French, Dion Nicol, Rod
Bowey, Rachel Brunt, Bruce Haig, and Melaine Kupsch. Appreciation DAFWA’s
research support unit in Kataning for excellent trial management. Our appreciation
to the Grain Crop Agronomy Reference group (managed by GRDC), for their support
with research development.