21 IREC Farmers' Newsletter No. 198 — Spring 2017 Figure 1. Grain yield and lodging score for nitrogen timing and rate treatments on YRK5. Nitrogen was applied before permanent water and/or at PI, at total rates ranging from 0 to 260 kg/ha of urea. 0 2 4 6 8 10 12 0 130-0 200-0 260-0 0-260 65-200 130-130 Pre-permanent water ─ PI nitrogen (kg/ha urea) n Grain yield (t/ha) n Lodging score (1=Standing, 10=Flat) A nitrogen rate and timing experiment conducted on drill sown YRK5 at Finley in 2016–17 highlighted the impact that high rates of nitrogen applied before permanent water can have on increasing lodging in susceptible rice varieties (Figure 1). Increasing nitrogen applications before permanent water significantly increased lodging potential compared with nitrogen applied at panicle initiation. For varieties that are very susceptible to lodging (e.g. Koshihikari and YRK5), it is important to reduce the rate of nitrogen applied before permanent water by up to 50% of the normal application that would be applied to a Reiziq crop grown in the same field. The crop’s nitrogen uptake should be measured at panicle initiation, and then if required, nitrogen top dressed. When applying nitrogen to crops, growers need to be aware of not only the nitrogen rate applied but also the evenness of spreading patterns. Areas or strips that receive heavier application rates often lodge, sometimes also bringing down surrounding areas of crop. Water depth during establishment The need for the seedling to emerge from the water and intercept sunlight for photosynthesis combined with the buoyancy provided by the water result in taller weaker plants in deeper water. It is important to keep water depth shallow during establishment and through to mid-tillering so plant height is not increased, which will increase crop lodging potential. Draining When to drain the water from a rice crop for harvest is a very important and difficult decision. If the field is drained too early, and sufficient soil moisture is not available to take the plants through to physiological maturity, the crop will “hay off”. Haying off makes the stem very weak resulting in considerable lodging, which reduces grain yield and whole grain millout. Weather A high yielding crop is often finely balanced as it nears maturity, so anything that upsets the balance, such as heavy rain or strong winds, can cause it to lodge. You cannot control the weather but harvesting as soon as the crop is mature helps reduce the chance of lodging and also ensures good grain quality. Acknowledgements This research was co-funded by the NSW Department of Primary Industries and the Rural Industries Research and Development Corporation. Further information Brian Dunn Research Agronomist (Irrigation) T: 02 6951 2621 E: [email protected] Extensive lodging in an aerial sown rice crop.