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Fishing for Better Ways to Protect the Paddies
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China's 5,000-year rice-growing history has inspired scientists to develop new ecological rice planting methods. China is the world's largest rice producer with an output of more than 180 million tons each year. That's 37 percent of the world's rice supply. Its rice planting area accounts for 22.8 percent of the world's total.


Despite the achievement, China's rice growers suffer various problems. The increased use of chemical pesticides, herbicides and fertilizers has caused environmental pollution, increased farming costs and left high pesticide residue in the rice.


This should not be the future picture in the world's largest rice farming country, said Ma Tianjie, rice project manager of Greenpeace China.


Ma said ecological rice farming would reduce the use of pesticides and fertilizers, environmental pollution and the residue in rice.


Disease prevention


The Greenpeace report, which was released earlier this month, lists ways of ecological rice planting, such as combining ancient experience with modern science in pest and disease prevention while avoiding overusing chemicals.


In Yunnan Province, Zhu Youyong and his team from Yunnan Agricultural University are using a biodiversity tactic to prevent rice blast, a major rice disease caused by fungi infection.


They plant different varieties of rice in certain proportions and in certain distance from one another. Some varieties can resist rice blast, but may not have high outputs. However, planting them together with the high-output varieties may reduce the rate of rice blast and at the same time maintain the output.


Similar methods have been used to prevent rice bacterial leaf blight, another rice disease caused by bacteria.


According to Zhu, the rate of rice blast among conventional rice is between 20 percent and 45 percent, while the biodiversity-based rice planting only has 0.05 percent to 5 percent of blast rice rate.


"Many of the rice blast-resistant varieties are traditional species that only farmers in the remote mountainous areas in Yunnan have kept," said Zhou Jianghong, an associate professor at Yunnan Agricultural University and a member of Zhu's research team.


"Tapping their traditional techniques and interbreeding the traditional varieties with modern high-output breeds, we are able to find ways of not using fungicides," Zhou said.


Zhou said the biodiversity-based rice planting has been expanded in Yunnan and Sichuan provinces in the past eight years. So far, it has been adopted in 102 counties in Yunnan.


Organic ducks


Ducks and frogs were also being raised in paddy fields in China in the past centuries.


After the rice seedlings grow about one week, young ducks are driven into the paddy fields and then they will live there until rice begins to grow ears.


According to Zhang Jia'en, a professor of agricultural ecology at Guangzhou-based South China Agricultural University, rice-ducks can control most weeds, reduce insect pests, and help stop several kinds of rice diseases.


The consistent activities of ducks also help rice grow stronger, and promote it to bear fruits more quickly.


"In our studies, in a rice-duck growth period, each duck need only to be fed 0.5 kilograms of fodders. It can get enough food by eating weeds, pests and other planktons," Zhang told China Daily.


Duck excrement is an ideal fertilizer. Zhang's studies show that each duck can produce up to 10 kilograms of excrement. If a duck is grown in every 50 square meters, its excrement can meet rice's most nutritional demands.


The ecological rice from Zhang's experimental fields now sells at a higher price in the market, with a bright future in profit making.


"Our researches are mainly focused on rice, but sometimes, restaurant chefs come to us to buy ducks, because our ducks can sell with a higher price. You cannot imagine how delicious the rice duck meat is," Zhang said.


Zhang's field experiment also yields an unexpected result. The activities of duck in the paddy field can reduce the emission of methane, the secondary greenhouse gas in terms of contributing to global warming.


Asian rice field is a major source of methane and China is the world's largest emitter of the gas, emitted from the rice soil due to microorganism activities.


"But the activities of ducks break the cycle of soil microorganisms and reduce the amount of methane they emitted," said Zhang, adding his team will soon publish such a paper in leading international science journals.


In Zhejiang, Jiangsu and Hubei provinces, farmers have been developing rice fish farming, an environmentally friendly technique. 


A farmer in East China demonstrates how his fish work together with his rice crop to produce a better harvest. The fish eat pests that destroy the rice. Fish-breeding rice farmers use 50 per cent less pesticides.


When rice seedlings are grown, farmers put fries into the paddy fields, which will then grow in the water in the fields.


The fish in the paddy fields feed on insects and their eggs, such as rice borers, plant hoppers and leaf rollers. By adjusting water levels, fish can jump to catch the pests feeding on the rice plant. They also feed on the nucleus of the bacteria which causes sheath and culm (stem) blight.


The fish excrement also acts as a rich fertilizer. Breeding fish in rice fields also helps eliminate mosquitoes because the fish eat the larvae.


The Greenpeace report indicates that in some paddy fields with fish, 89.6 per cent of weeds can be eliminated and the density of mosquito larvae decreased by 50 per cent.


Economically, rice fish farmers use 50 per cent less pesticides.


(China Daily August 23, 2006)

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