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Limiting rice's role in global warming.

Cultivation of rice, the only major grain used almost exclusively for food, results in the emission of some 14 percent of the methane - a major greenhouse gas - caused by human activities (SN: 5/18/91, p.310). If the planet's population grows to 8 billion, as some demographers predict may occur within 30 years, the number of rice consumers might exceed 5 billion, says Heinz-Ulrich Neue of the International Rice Research Institute in Manila, the Philippines.

But the soil chemist says rice farmers should be able to feed the masses without upsetting the climate if agronomists apply themselves to refining the methane-mitigation strategies he outlines in the July/August BIOSCIENCE.

Though farmers can grow rice on relatively dry uplands, the highest yields - of grain and methane - result from its cultivation under water. Neue therefore focuses on methane-minimization techniques applicable to wetlands, such as managing precisely when farmers flood - or drain - their fields. Similarly, though resource-poor farmers tend to fertilize their fields with fresh organic matter, such as straw and green manure, Neue points to new research indicating that composted organic material could dramatically reduce a rice field's methane emissions. So too might a switch to other specific types of chemical fertilizers - ones broken down by soil microbes that compete with the bacteria that produce methane.

Many poorer parts of the world rely on rice as a dietary staple. Even if rising incomes allow some rice-based societies to diversify their diet, Neue predicts annual rice production must still climb 47 percent by 2020. That estimate is conservative, he adds, since this would merely maintain the "already inadequate" nutrition for hundreds of millions of people.
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Title Annotation:methane production resulting from rice growing can be minimized
Publication:Science News
Article Type:Brief Article
Date:Jul 10, 1993
Previous Article:Polluted air, low protein = infertility.
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