Mr Kuma Ranathungamage1, Emeritus Professor Shu Fukai1, Dr Vijaya Singh1, Dr Jaya Basnayake2, Associate Professor Jaquie Mitchell1
1University Of Queensland, Brisbane, Australia, 2Sugar Research Australia, Brandon, Australia
Biography:
Kuma Ranathungamage, PhD student at the School of Agriculture and Food Sustainability, Faculty of Science, University of Queensland, is conducting research entitled “Determination of varietal difference in grain yield and grain protein content in response to nitrogen under aerobic rice conditions’’. The project aims to explore the genotypic variation in grain yield and grain protein content in rice in response to nitrogen dynamics under aerobic conditions and contributing mechanisms for such variations under high and low nitrogen conditions.
Abstract:
The Australian rice industry faces challenges due to limitations and costs associated with irrigation, prompting a consideration of adopting water-saving production methods. One such method is aerobic rice production (AP). Increased GPC potentially compromises the culinary and cooking qualities of rice, necessitating genotypes with higher grain yield (GY) and lower grain protein content (GPC). However, the genotypic variation in GY and GPC in response to nitrogen (N) application in high-yielding AP conditions is unknown. Therefore, this study assessed the variation in GY and GPC of twenty-four rice genotypes under low-N (0 kg N/ha) and high-N (240 kg N/ha) application conditions. The zero N treatment was incorporated to determine the contribution of indigenous soil N to GY. The GY increased significantly (86%) with N application, while it varied significantly among genotypes, with mean GY ranging from 7.4- 10.6 t/ha. Notably, a significant (r = -0.48*, n = 24) inverse relationship was explored between GY and GPC, while GPC ranged from 4.7%-6.1% under low-N and 6.8% – 8.9% under high-N conditions. Additionally, higher-yielding genotypes were attributed to higher stomatal conductance (gs) and SPAD to secure assimilate production, higher allocation of N to grain and lower GPC, under high-N conditions. In contrast, under zero N fertiliser application conditions, high-yielding genotypes extracted a substantial amount of indigenous soil N for GY production. The varietal difference in GY and GPC can be utilised to obtain higher GY and lower GPC in AP systems when high-N is applied, and appropriate varieties are selected.