Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 4417 IREC Farmers' Newsletter No. 197 — Autumn 2017 As part of the project, an irrigated wheat experiment was conducted at Coleambally in 2016 to assess the effect of variety and plant population interactions on grain yield, grain quality (protein content) and crop lodging (tables 1 and 2). The experiment site was on a medium grey clay soil with soybeans as the previous crop. The plots were sown on 4 May 2016 on permanent beds with six rows per plot and a row spacing of 25 cm. There was a total of 457 mm of rain during the growing season and the crop was harvested by a small plot harvester on 2 December 2016. The experiment aimed for maximum grain yield potential with the nitrogen budget calculated on achieving 10 t/ha. Soil testing showed that the starting nitrogen level of the site was 109 kg N/ha and an estimated 50 kg N/ha became available with in- crop mineralisation during the growing season. At sowing, 200 kg/ha of MAP was applied under the seed and nitrogen was topdressed at the two leaf, first node and booting stages. The nitrogen topdressing treatments were hand applied on the surface as urea. The total nitrogen applied as fertiliser was 230 kg N/ha. Crop performance Grain yield The average grain yield across all varieties and plant populations was 8.02 t/ha. The highest yielding variety was LongReach Cobra with 9.52 t/ha, which was significantly higher than all other varieties. The second highest was LongReach Trojan (9.12 t/ha), also significantly higher than all remaining varieties. The durum line 280913 had a significantly lower yield (6.36 t/ha) than all other varieties. EGA Gregory was the lowest yielding bread wheat variety (7.06 t/ha) and was significantly lower yielding than all other bread wheat varieties (Figure 1). Protein content Grain protein content averaged 12.29% across all varieties and plant populations. The highest average protein content was achieved from the high nitrogen rate that included topdressing at the first node and booting growth stages. Grain protein content decreased as grain yield increased. The durum line 280913 had the highest grain protein (13.50%) but it was statistically similar to the other durum variety, EGA Bellaroi (13.25%). Table 1. Wheat varieties evaluated in the irrigated wheat experiment at Coleambally in 2016. Wheat variety evaluated under irrigation, Coleambally 2016 CorackA LongReach CobraA KioraA SuntopA EGA GregoryA LongReach LancerA WallupA LongReach TrojanA EGA BellaroiA MaceA CharaA 280913 (unreleased durum) Table 2. Plant populations evaluated in the irrigated wheat experiment at Coleambally in 2016. Treatment Target plant density (plants/m2) Actual plant density (plants/m2) Very low 80 81 Low 120 115 Medium 160 151 High 200 178 Based on trial results, the optimum plant population for irrigated wheat differs between varieties but overall should not exceed 160 plants/m2.