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.
|Soil type||See Table 2 |
Total N to 90cm: 63kg/ha
|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))|
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.