Increasing Productivity and Water Use Efficiency in Australia's Rice Industry through Nitrogen Management - Link (November 2009)

Subasinghe, R Angus, R

2009

This RIRDC report presents the finding of the project undertaken since 2002 investigating issues related to nitrogen management under different scenarios and developed nitrogen management options for newly released varieties and for different water management systems. This project aim was to enhance the rice yields by improving the nitrogen management practices in rice paddocks and to upgrade/update the maNage rice software based on findings of the project. Whilst also providing information on nitrogen management option for new varieties to the NSW rice industry, so that the maximum benefit of new varieties can be quickly obtained on farm. The method used was investigations carried out in farmers’ paddocks representing major rice growing soils and climatic zones for the area. The responses of key commercial rice varieties to rate and timing of nitrogen fertiliser application were evaluated in the investigations. Performances of new varieties released by rice breeders were also compared with their older counterparts. Investigations were carried out using local production standards under two water management systems currently practiced by farmers in the area. Many farmers keep the bays under continuous flooding whereas some practiced a midseason dry down where paddocks are kept without surface water for 12 – 14 days prior to panicle initiation. There were six key findings from the project that included indication that there are no significant differences in nitrogen responses among Australian rice varieties and optimum nitrogen requirement lies around 170–180 kg N ha-1 depending on the inherent soil nitrogen supply. It was also indicated that five years worth of results show that the best yields are obtained when nitrogen application is split between pre-flood and panicle initiation applications in continuously flooded bays. There were also indications that minimum pre-flood application of 90 kg N ha-1 is necessary to ensure adequate nitrogen supply during the vegetative growth stage of the crop to produce sufficient biomass to sustain a good yield Whilst a maintenance requirement of nitrogen at panicle initiation is necessary to ensure adequate nitrogen supply to the plant during the reproductive stages. The results also suggest that N uptake at PI beyond 150 kg N ha-1 is detrimental when plants are exposed to low temperature spell during young microspore stage. Mid-tillering nitrogen applications are warranted if an inadequate amount of pre-flood nitrogen was applied, early nitrogen application was not managed correctly, or the soil is inherently low in fertility. Finally Results indicated that it is better to carry out nitrogen topdressing just prior to re-irrigation in bay with midseason dry down.