28 May 2012

Africa: How to Grow Rice With Less Water

Around 700 million of the world's poor live in rice-growing areas in Asia.

Rice is the staple food in Asia and 95 percent of the world's rice is produced there. Mostly grown in soils submerged under water, irrigated lowland (or 'paddy') rice accounts for nearly 80 percent of the world's rice production and receives close to half of the fresh water diverted to agriculture in Asia.

Increasing scarcity and rising cost of water threatens the sustainability of irrigated lowland rice. It is expected that by 2025, 13 million hectares of Asia's wet season rice and two million hectares of its irrigated dry season rice will experience physical water scarcity due to overuse of water, exacerbated by unpredictable rainfall caused by a changing climate.

Most of the approximately 22 million hectares of irrigated dry season rice in South and Southeast Asia will experience water scarcity and farmers will not be able to afford to irrigate their rice fields.

Since 2000, the International Rice research Institute (IRRI) and its partners in China and in the Philippines have pioneered a new production system aimed at drastically reducing water use in rice production, called "aerobic rice".

Unlike in conventional lowland rice, aerobic rice does not grow in submerged soils but, like other crops such as wheat or maize, in well-drained, nonflooded and nonsatured soils. Initial results demonstrated that aerobic rice uses only half the water required by lowland rice, with only 20 to 30 percent less yield. Hence, the amount of rice per unit water input is higher under aerobic than under lowland rice production.


Aerobic rice holds promise for farmers in areas where water available at the farm level is too scarce or too expensive to grow flooded lowland rice.

A CGIAR Challenge Program for Water and Food (CPWF) project led by IRRI further builds upon this promising research to develop and disseminate aerobic rice systems for environments where there is not enough water to grow conventional lowland rice.

Called the System of Temperate and Tropical Aerobic Rice in Asia (STAR) project, it has expanded the network of partners collaborating on the breeding and selection of aerobic rice varieties and developed appropriate crop management practices that address environmental and sustainability issues.

In China the project has attained a maximum yield of 6 tons per hectare using only half of the water normally used to grow lowland rice.

Yield potentials of 6 tons per hectare were also demonstrated in the Philippines, although actual yields in farmers' fields there ranged from 2.9 to 3.8 tons per hectare in the dry season, and up to 4.5 tons per hectare in the wet season. In Central India, selected varieties produced similar yields.

Cultivating aerobic rice in China is already economically viable at yields of only 3.5 tons per hectare.

Farmers in China appreciate the fact that aerobic rice is both resistant to drought and water-logging.

Aerobic rice is a profitable alternative to maize and soybean crops, which are badly affected by water-logging in the summer season. In addition, the reduced labor involved in aerobic rice cultivation is another feature beneficial to farmers.

Specially adapted varieties have been identified and released in China, India, and the Philippines. The potential positive impacts are substantial as the aerobic rice provides a viable response to temperature and water stress from increased climate variability, and economic water scarcity.

Bas Bouman is the lead scientist at the International Rice Research Institute (IRRI), which is part of the Consultative Group on International Agricultural Research (CGIAR). CGIAR is co-organising Agriculture and Rural Development Day on June 18, 2012, ahead of the Rio+20 summit.

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