Aim
Determine the value of managing nitrogen and seeding rates on yield and quality of wheat varieties.
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.
Trial details
| Property | Holt Rock |
|---|---|
| Soil type |
Depth: 0-10, 10-20, 20-30, 30-40 |
| Crop | Wheat varieties |
| Rotation |
2014 - canola, 2013 - barley, 2012 - wheat |
| Paddock details |
Nitrogen (kg/ha): Target plant populations (TPP): 60, 120, 180 plants/m2 Varieties: Corack, Emu Rock, Hydra, Mace, Magenta, Yitpi |
| Replicates | Three |
| Sowing date |
Dry sown 1 May Effective sowing 16 May following 20mm rain |
| Seeding rate | Various |
| Fertiliser |
120kg/ha Super CMZ drilled at seeding |
| Rainfall |
Holt Rock: 110mm (1 January to 22 June) |
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. Grain yield increased from 2.5-2.7t/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 76kg/hl. Grain protein was significantly higher at 50kg/ha of nitrogen compared to the nil treatment.
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.
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).
Response 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.
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.
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 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.