Plant density and N response of selected wheat varieties at Ogilvie 2016 trial report

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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 2016 to assess how changing plant density of new and existing wheat varieties affected their nitrogen requirements. The trials were at Ogilvie, East Koorda, Lake Varley and Grass patch in Western Australia.

This is a report for the study at Ogilvie. Emu Rock, Hydra, Mace, Magenta, Scepter and Zen wheats were sown on 2 May on a sandy earth soil. For each variety and at each of these three target plant densities (60, 120 and 240 plants/m2 ), nitrogen was applied at seeding at 0, 10, 30 and 50kg/ha.

What we found

Yield

Magenta, Scepter and Zen wheat yields were not statistically different to Hydra and Mace wheat but they were significantly better than Emu Rock wheat (Table 1). Emu Rock wheat is a short maturing wheat variety and it was also the lowest yielding variety at the site. It was at least 300kg/ha lower yielding than the Magenta, Scepter and Zen which yielded between 3.0-3.2t/ha.

Varieties differed in how yield was achieved. The harvest index is an indication of a crops ability to convert biomass into yield. This was measured by sampling the crop prior to harvest. Both Emu Rock and Scepter had harvest indexes of 0.51 which was significantly higher than Mace and Magenta which had harvest indexes of 0.47. This is reflected in the differences in ear production between varieties. The ears produced by the varieties differed (Table 1). Scepter had significantly fewer heads than the other varieties. However the higher yields of Scepter are achieved through a larger grain size than the other varieties (Table 1) and potentially increased grain per head. A larger grain size can influence grain protein and this will be one factor affecting the lower grain protein of Scepter.

Table 1 Grain yield, ears/m2 and 1000 grain wt of wheat varieties sown at Ogivlie in 2016 (averaged across nitrogen and plant density)
  Yield (t/ha) Ears/m2 1000 grain wt (g)
Magenta 3.28 209 48
Scepter 3.14 189 52
Zen 3.01 209 46
Hydra 2.96 214 46
Mace 2.96 207 45
Emu Rock 2.65 226 47
LSD 0.32 16 1

The response to changing nitrogen was similar for each variety. With increasing nitrogen from 0-50kg/ha (top dressed at seeding), yields (averaged across variety and density), increased by 600kg/ha. A change in density did not have such a large effect on yield.

Table 2 Grain yield of wheat varieties at increasing nitrogen rates when sown at Ogilvie in 2016 (averaged across plant density) (LSD: 0.06t/ha for N and 0.31t/ha for variety)
Nitrogen units applied (kg/ha) Emu Rock Hydra Mace Magenta Scepter Zen
0 2.29 2.57 2.66 2.96 2.77 2.60
10 2.47 2.80 2.73 3.11 2.93 2.77
30 2.82 3.10 3.22 3.39 3.25 3.22
50 3.04 3.35 3.22 3.66 3.59 3.46

Increasing density is a technique to provide competition for weeds.  The target plant densities of 60, 120 and 240 plants/m2 resulted in actual plant establishment of 55, 100 and 166 plants/m2 respectively. The yields of Emu Rock, Magenta and Zen did not change with increasing plant density.

Scepter and Mace yields were similar with changing density. Their yields at 55 and 100 plants/m2 were similar however they declined by about 150kg/ha at the higher density of 166 plants/m2. In the case of Hydra, yields increases slightly at the higher density. The influence of density on yields were not large at the site and there was no effect on grain quality.

Table 3 Grain yield (t/ha) of wheat varieties at three plant densities when sown at Ogivlie in 2016 (averaged across nitrogen)
Actual plant density 55 plants/m2 100 plants/m2 166 plants/m2
Emu Rock 2.62 2.65 2.69
Hydra 2.87 2.96 3.04
Mace 3.04 2.97 2.85
Magenta 3.24 3.33 3.27
Scepter 3.11 3.24 3.06
Zen 3.02 3.02 3.00
LSD 0.33 between variety 0.14 within variety  

Quality

Grain proteins in this trial, as was experienced by growers in 2016, were significantly lower than experienced in the region. The site mean grain protein was 8.8% and density and nitrogen did not influence protein levels. However, there were differences in the grain protein of the varieties. Scepter and Magenta had the lowest protein levels (averaged across density and nitrogen applied) of 8.3 and 8.4% respectively. This corresponds with the higher yields of these varieties. Emu Rock's grain protein was 10% when averaged across density and nitrogen applied and this corresponds to the low grain yield of this variety. The grain protein of Mace, Zen and Hydra were about 8.6-8.7%.

The hectolitre and screenings of the varieties were within industry standards and would not affect price received at delivery to markets.

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.

Grain quality was not influenced by plant density or nitrogen at seeding. Temperatures were mild during grain fill in 2016, and this may have influenced the grain screenings.

Varieties differ in how yield is achieved. Scepter's yields are achieved with lower ear numbers but larger grain size (and potentially larger head size but this was not measured) and this will influence this varieties grain protein. Site selection and nitrogen will be important to manage the yield and quality of this variety.

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 research team are key to the project’s success and I wish to recognise the contributions of my colleagues Jeremy Curry, Bob French, Dion Nicol, Brenda Shackley, Rod Bowey, Rachel Brunt, Bruce Haig, and Melaine Kupsch. Thanks to Steve Cosh who leads DAFWA’s research support unit in Geraldton for their excellent trial management. My appreciation is given to the Grain Crop Agronomy Reference group (managed by GRDC), for their support with research development. The support of the Northern Agri Group and their growers is highly appreciated; they have provided a location for the research and an avenue for extension.

Author

Christine Zaicou-Kunesch