To compare the effect of delayed seeding and seeding rates on the yield and quality performance of wheat varieties.

• Crop establishment was good for both sowing times due to good rainfall after seeding in 2011. Seed rates of 40 kg/ha achieved the target plant population of 100 plants/m2 on all sites. With each additional 40kg/ha of seed, plants numbers increased by approximately 50 plants/m2 at Badgingarra.   Ears/m2 increased from 219 to 320 with increasing seeding rate from 40 to 120kg/ha.   Averaged across all seeding rates, the ear numbers of Mace (227 ear/m2) were significantly lower than the other varieties (approx 275 ears/m2).
• At Badgingarra, increasing the seeding rate from 40 to 120 kg/ha increased the mean grain yield of King Rock, Mace, and Wyalkatchem at both sowing times. The mean yields of Fortune and Calingiri were not influenced by seeding rate at the May sowing time, but did increase from 40 to 120 kg/ha at the second sowing time in June (Fig. 1).   Magenta mean yields were higher at the 120 kg/ha than 40 kg/ha seeding rate at the second sowing time, but were highest with the 80 kg/ha seeding rate at the first sowing time in May.   Fungal staining of Mace and Wyalkatchem (data not presented) was greater than 5% at all seeding rates when sown on May 18th at Badgingarra.  

Seeding rate did not influence the level of screenings at Badgingarra of the varieties sown on May 18th.   The screenings of Magenta and Fortune declined when seeding was increased from 40 to 120 kg/ha at the June sowing (Figure 2).

Fungal staining of Magenta was greater than 5% for Magenta when sown at the second sowing time.  This influenced the gross income of this varieties (Table 2).   Lower yields and downgrading due to hectoliter weight (<74HLW) influenced the economic returns of Calingiri and Fortune in the first sowing time.

In a season like 2011 with good winter rainfall across all sites and stored moisture at seeding, higher seeding rates either improved maintained high grain yields when sown in May and June in a range of environments in Western Australia.   There was no evidence that increased seeding rate increased screenings risk in a season with good winter and spring rainfall.