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April 10, 2008

China experiments with aerobic rice as demand increases and water becomes scarce

In 2006, China suffered one of its worst droughts in half-a-century. Crops in the rice-growing provinces of Anhui, Hunan and Hubei were wiped out and water levels in lakes, rivers and reservoirs dropped to historic lows.

Extreme weather is becoming more frequent in China. As the world's most populous country, it urgently needs to find ways of living with water scarcity if it is to continue to feed its 1.3 billion people. Aerobic rice, bred to require significantly less water than ordinary lowland rice, promises to be a step in the right direction.

Two-thirds of Chinese people depend on rice as a staple food and as the world's top producer and consumer, the country plants nearly 30 million ha per year to this cereal grain, yielding over 180 million tonnes. But lowland or 'flood-irrigated' rice, is a notoriously thirsty crop, requiring around 2000 litres of water to produce 1 kg of grain - twice as much as wheat or maize. Rice production consumes 50 per cent of all China's freshwater resources at a time when water scarcity is becoming increasingly common. In short, the days of lowland rice may be numbered.

Developed by scientists at the International Rice Research Institute (IRRI), in collaboration with scientists in national research programs, aerobic rice combines the positive traits of hardy upland rice with those of high-yielding lowland rice. With its longer roots aiding water absorption and improving air circulation, aerobic rice needs 50-70 per cent less water than lowland rice. It also produces acceptable yields under flood conditions, if and when the floods hit.

Aerobic rice is also much less labour intensive - unlike transplanted lowland rice, aerobic varieties do not need to be raised as seedlings before being planted in the field; seeds can be broadcast or row-seeded. This is an important factor given that rapid urbanisation has drawn seasonal labour away from rural areas to the cities, reducing the supply of agricultural workers and forcing up wages. Importantly, aerobic rice also passes the taste test - farmers and their families enjoy eating it.

But development of aerobic rice is still in its early stages and the crop has received mixed responses from Chinese farmers who have trialled it. When there is no flooding or drought, yields are significantly lower than ordinary lowland rice - sometimes by up to 30 per cent. Also, in field experiments, yields of aerobic rice continue to fall sharply year-on-year to around 50 per cent by the seventh season. New diseases build up in the soil and attacks from insects, fungi and bacteria are common. Similarly, weeds such as nutsedge and barn yard grass thrive around aerobic rice and the soil gradually becomes exhausted.

Despite these drawbacks, aerobic rice safe bet for an acceptable yield when droughts or floods hit and all other crops can fail. Providing a way for farmers to hedge their bets against a bad harvest does not simply protect them against the vagaries of the weather, but also the increasing competition for water between farmers and industry as the affects on groundwater levels of urbanisation and rapid economic development take hold.

The simple fact is that China needs to produce 20 per cent more rice by 2020 in order to feed its population at a time when water is becoming increasingly scarce. Average lowland rice yields are falling due to unfavourable weather - down from 7.5 tonnes per ha to 6.6 tonnes, while aerobic rice yields 5-6 tonnes with current germplasm. Some scientists expect yields to converge somewhere in the middle, meaning more and more farmers could adopt the new technology.

ILRI's Dr Shaobing Peng has been involved in field trials of aerobic rice since 2001. He is a firm believer in the future of aerobic rice varieties, given the right institutional support. "Farmers are desperate for cultivars that give a good and stable yield", he says, "and breeding is a numbers game - you need more people to come up with new varieties."

"Therefore we need more resources and institutions to research aerobic rice. Once we have good cultivars, then aerobic rice should be a very attractive option."

New Agriculturalist

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