Plant density and N response of selected wheat varieties at Yuna 2015 trial report

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At Yuna, frost in September affected grain yield and quality of the short maturity varieties but not the longer maturing varieties Magenta and Calingiri.

Additional nitrogen increased grain yield of the longer maturity varieties at each plant density. These responses were not observed in the quicker maturing varieties because of the frost. Magenta was the highest yielding variety at the site.

Plant density did not influence the yield of the wheat varieties which were frosted in September.


The challenge in low rainfall regions is to understand the influence of management inputs on the expression of genetic difference between varieties. Growers in low rainfall environment are focusing on dry sowing technologies to enable timely seeding of a proportion of their cropping program. A better understanding of how tactical decisions influence varietal performance in low rainfall regions will build confidence in decision making at seeding and throughout the season.


To determine the value of managing nitrogen and seeding rates on the grain yield and quality of wheat varieties.

Trial details

Table 1 Trial details for Yuna wheat variety x nitrogen x plant density trial
Property Yuna
Soil type See Table 2

Total N to 90cm: 63kg/ha

Crop Wheat
Paddock rotation 2014 - canola
Treatments Six wheat cultivars (Mace, Calingiri, Magenta, Corack, Zen, Supreme) × four N rates (0, 10, 30, 50kg/ha) × three seeding rates (target densities 60, 120, 180plants/m2). N rates were applied as 10kg N/ha at seeding with an additional 20 or 40kg N/ha as Flexi-N at mid-tillering to give the appropriate rate. Seed rates were chosen to give the target densities on the basis of seed size and germination percentage, but approximately 30, 60, and 90kg/ha to give 60, 120 and 180plants/m2; respectively.
Replicates Three reps and plot size 8m x 1.54
Sowing date 12 May 2015
Seeding rate See treatment list
Fertiliser 120kg/ha Super CMZ drilled at seeding
Rainfall 371mm (107mm (Jan-Mar) and 243mm (Apr-Oct))
Table 2 Soil type
Depth (cm) 0-10 10-20 20-30 30-40
pH (CaCl2) 5.8 5.2 5.5 6
NH4 (ug/g) 1 <1 <1 <1
NO3 (ug/g) 9 5 3 4


The yield potential at this site in 2015 was 2.61t/ha, assuming 30% of summer rainfall is available for the crop, 80mm is lost by soil surface evaporation and a transpiration efficiency of 20kg/ha/mm. No variety achieved this yield potential.

Frost in September affected both grain yield and quality. The short-mid maturity varieties Corack, Mace and Supreme had significantly lower grain yields and lower hectolitre weights than longer maturity varieties. Screenings of these frosted varieties tended to increase with increasing plant density and additional nitrogen but this was not evident in Magenta and Calingiri.

Total nitrogen in the soil profile (to 90cm) was 63kg/ha (based on soil test). Both Magenta and Calingiri responded to additional nitrogen for each plant density treatment. These responses were not observed in the quicker maturing varieties because of the frost.

Plant density did not influence grain yield of Magenta or the varieties which were frosted. The yield of Zen and Calingiri were significantly higher at the lowest plant density (target plant density 60plants/m2) than the other two densities. Both these varieties has significantly lower head numbers.

Note: review attachments for more details on trial responses.


DAFWA colleagues Bob French and Brenda Shackley for trial development. The Grain Crop Agronomy Reference group, managed by Grains Research and Development Corporation (GRDC), for their support with research development in 2015. Larry Prosser at DAFWA for trial management and Melaine Kupsch at DAFWA for technical support with nitrogen application, data collection and management. The project; Tactical wheat agronomy for the west (DAW00249), is funded by GRDC and DAFWA.

Contact information


Christine Zaicou-Kunesch