Rice Yield Doubled In Chinese Experiment 

Without Genetic Engineering or Pesticides

Carol Kaesuk Yoon / New York Times 28aug00

In a stunning new result from what has become one of the largest agricultural experiments undertaken, thousands of rice farmers in China have doubled the yields of their most valuable crop and nearly eliminated its most devastating disease without using chemical treatments or spending a single extra penny.

Under the direction of an international team of scientists, farmers in China's Yunnan Province implemented a simple change in their rice paddies. Instead of planting the large stands of a single type of rice, as they typically have done, the farmers planted a mixture of two different rices.

With this one change, growers were able to radically restrict the incidence of rice blast the most important disease of this most important staple in the world. Within just two years, farmers were able to abandon the chemical fungicides previously widely used to fight the disease.

"I wasn't surprised that the system worked, but I was surprised that it worked so well,'' said Christopher Mundt, population biologist at Oregon State University and the one author of the study based in America. The study was published in the current edition of the journal Nature.

"I'm excited about the possibilities. There is a lot of potential even beyond rice.''

In fact, many researchers have long argued that planting a diversity of crops should lead to benefits like greater productivity and the suppression of disease, compared with single variety plantings known as monocultures. Yet the use of diversity and other ecologically based cures for agricultural ills have tended to be viewed as more politically correct than economically viable.

Scientists say that this latest study shows that such environmentally friendly methods can be highly effective even more effective, in this case, than standard chemical pesticides.

Those studying natural ecosystems also welcomed the new work, saying it closely paralleled findings for the role of species diversity in reducing the incidence of disease in the wild.

"It's an important study,'' said David Tilman, ecologist at the University of Minnesota. "It's going to raise a great deal of interest.''

The scientific hypothesis behind the study, the latest in an increasing number examining the effects of biodiversity, is simple. If one variety of a crop is susceptible to a disease, the more concentrated those susceptible types are, the more easily disease can spread and the more victims it can claim.

The disease should be less likely to spread, however, if susceptible plants are separated from one another by other kinds of plants that do not succumb to the disease and can act as a barrier.

Rice blast fungus, which destroys millions of tons of rice and costs farmers several billion dollars in losses each year, moves from plant to plant as an airborne spore a method of transport that should easily be blocked by a row of disease-resistant plants.

Scientists tested the hypothesis by asking farmers to plant their farms in experimental plots using two kinds of rice: a standard rice that does not usually succumb to rice blast disease and a much more valuable sticky rice known to be highly susceptible. Farmers also planted control plots of monocultures, allowing scientists to rigorously test the importance of the mixtures in the health and productivity on these farms.

What scientists found was that farmers garnered even more benefit from the mixtures than expected. Resistant plants did block the airborne spores in a field, but as more and more farmers became involved in the study, these positive effects began to multiply across the region. Not only were disease spores not blowing in from the next row, they were no longer coming from the next farmer's field, either, or the next or the next, rapidly damping the spread of the disease on a grand scale.

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