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 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60 Page 61 Page 62 Page 63 Page 64 Page 65 Page 66 Page 67 Page 68 Page 69 Page 70 Page 71 Page 72 Page 73 Page 74 Page 75 Page 7613 IREC Farmers' Newsletter No. 195 ­ – Rice R&D 2016 740 plant/m2 where a direct comparison between plant population and grain yield was measured in over 800 research plots (Figure 1). It is recommended that growers in the Murray and Murrumbidgee valleys aim to achieve a plant population between 100 and 300 plants/m2 for all sowing methods. This provides a buffer should establishment problems occur. High grain yields can still be achieved with plant populations less than 40 plants/m2 but there is a declining trend in yield with decreasing plant population (Figure 1). Uniformity in distribution of the plants becomes increasingly important in maintaining grain yield at plant populations less than 40 plants/m2 . As plant population decreased, the number of tillers each plant produced and the number of grains per panicle increased. Both of these factors combine to help to maintain grain yield at low plant populations. The varieties tested included Reiziq, Sherpa, Langi, Opus, Topaz and Koshihikari and they all responded similarly to changes in plant population. Lower plant population limit The lower plant population limit is dependent on the cost that a grower puts on the inputs used to grow the crop and if the crop is aerial or drill sown. Gross margin analysis using 2015 input costs and contractor rates reveal that yields of 4.8 t/ha for aerial rice and 3.7 t/ha for drill sown rice are required to cover the gross margin input cost of a crop (Table 3). A minimum plant population of 10 plants/m2 can achieve these critical yield levels provided the plants are uniformly distributed and best management practice is followed (Figure 2). At low plant populations the distribution of plants is often more important than the number of plants in maintaining grain yield. Therefore it is recommended that the rice ring (0.2 m2 ) be used to determine plant population and distribution. Ten plant counts, using the ring, should be obtained for each zone in the field with different plant population levels. When 10 plants/m2 is the minimum target population, an average of two plants per ring from the ten rings counted would be required. If more than three of the rings have only one plant or one ring has zero plants then re-sowing the poor establishment areas in the field is recommended. Upper plant population limit The upper plant population limit for aerial and drill sown rice and delayed permanent water is 300 plants/m2 . The results are not conclusive regarding any impact very high plant populations may have on cold induced sterility, but there is no yield advantage in having a plant population greater than 300 plants/m2 and seed costs will be higher. There is no practical or economic benefit in having very high plant populations. High sowing rates rarely result in improved plant populations when establishment problems occur. Sowing rates greater than 150 kg/ha are not recommended for any sowing method or any potential circumstances during the growing season. Row spacing Row spacing between 18 and 27 cm is recommended for drill sown rice. A row spacing wider than 27 cm is not recommended as missing rows or gaps in plants within rows cannot be compensated for by neighbouring plants and grain yield is reduced. There is no advantage in row spacing narrower than 18 cm and no potential for increased grain yield. The required sowing equipment is more expensive to purchase Table 1. Aerial sown plant population experiments conducted in the project. All experiments were located in commercial rice fields with the farmer managing field preparation, water management, nitrogen and pesticide applications. Season Site Variety Sowing rates (kg/ha) 2013–14 Mayrung Reiziq 25, 50, 75, & 150 Bunnaloo Sherpa 25, 50, 75, & 150 Morago Reiziq 25, 50, 75, & 150 Jerilderie Opus 25, 50, 75, & 150 2014–15 Mayrung Reiziq 25, 50, 150 & 450 Bunnaloo Opus 25, 50, 150 & 450 Morago Reiziq 25, 50, 150 & 450 Jerilderie Reiziq & Opus 25, 50, 150, 300 2015–16 Mayrung Sherpa 25, 50, 150 dry & 150, 450 pre-germinated Bunnaloo Reiziq 25, 50, 150 dry & 150, 450 pre-germinated Murrami Langi 25, 50, 150 dry & 150, 450 pre-germinated Table 2. Drill sown row spacing and plant population experiments conducted in the project. Season Site Variety Row spacing (cm) Sowing rates (kg/ha) Nitrogen rates (kg N/ha) 2013–14 YAI* Reiziq, Sherpa 18, 27, 36 25, 50, 150, 300 90, 150 Jerilderie Reiziq, Sherpa 18, 27, 36 25, 50, 150 90, 150 2014–15 YAI Reiziq, Topaz 18 25, 50, 150, 300 60–60, 120, 180 LFS Reiziq, Langi 18, 27, 36 25, 50, 150 180 Jerilderie Reiziq, Opus 18, 27, 36 25, 50, 150 180 2015–16 YAI Reiziq, Topaz 18 25, 50, 150, 300 90–60, 90, 150 Jerilderie Reiziq, Koshi 18 25, 50, 150, 300 90–60, 90, 150 LFS Reiziq, Langi 18, 27, 36 25, 50, 150 240 Jerilderie Reiziq, Opus 18, 27, 36 25, 50, 150 150 * Yanco Agricultural Institute