Aerobic rice is now a possibility for North Coast growers, but in the Riverina, where the majority of rice is grown, the water-efficient practice is not yet a viable option.
NSW Department of Primary Industries researcher Brian Dunn and his team have been comparing the water use and yields of aerobic, delayed permanent water (DPW) and conventional drilling practices at the Yanco Agricultural Institute.
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"Traditionally, rice in southern Australia is ponded for most of the season, but when you're growing it aerobically you're just flush irrigating it when needed and not ponding at all," Mr Dunn said.
"Normal drill sown rice is ponded for 105 days, grown until it's 10cm tall and then ponded to maturity.
"Then we've been working for several years on DPW, where you don't pond it until it's getting close to the reproductive period, you might only pond it for 75 days.
"Aerobic is taking it to the next stage where you don't have any ponding at all, you just have continual water on and off to meet the plant's demand. Rice grown under pivots is one aerobic option."
Their trial found the aerobic water use was only 10.7ML/ha, DPW was 11.6ML/ha and drilled was 13.7ML/ha.
However, although the aerobic rice used the least water, its yields across all varieties in the trial were down by up to five tonnes per hectare compared to drilled rice.
Mr Dunn said the environment in the Riverina was problematic for aerobically grown rice because there was often cold nights and hot days during the reproductive period.
"Commercially, we have to pond water during the reproductive period to protect the crop from extreme temperatures."
DPW was found to be a viable option though, yields close to, or even better than, conventionally drilled rice.
"The actual water productivity, tonnes per megalitre, which is really dollars per megalitre, is higher with delayed permanent water," Mr Dunn said.
"We've seen an increasing number of Riverina growers using that method, of the growers drill sowing rice, around 30-40 per cent now use DPW, compared to around five per cent three years ago."
Mr Dunn explained DPW worked because the water was still ponded over the rice during the crucial reproductive period.
"This provides a buffer to protect against cold and heat, something you don't get with aerobic," Mr Dunn said.
He said they would still work to make aerobically grown rice an option in southern Australia.
"We're looking at nitrogen management, row spacing, what varieties that might be more tolerant to no ponding, more tolerant to the hot and cold," Mr Dunn said.
"Water productivity is the number one focus in our research and development so we can maintain the viability of the industry."
