How Chinese Farmers Are Reducing Pesticide Use

BRIDGE NEWS September 15, 2000

CHURCHVILLE, Va. – The Chinese are reporting a new way to increase crop yields and use less pesticide. Their farmers plant lots of different modern high-yield varieties of rice together, both in the fields and across whole provinces.

As reported in Nature magazine, the technique has produced significantly higher yields and so frustrated the spores of rice blast disease (caused by a fungus and characterized by the appearance of lesions) that the farmers were able to quit spraying fungicides.

A British agriculturist, Martin Wolfe of Wakelyns Agroforestry in Suffolk, says he's had similar results from planting lots of wheat varieties together.

In recent years, most high-yield farmers have planted only one variety of grain in each field, to get uniform ripening and more consistent quality. It also helps them track the varieties that produce the highest-yields with their particular soils and climate.

But these results from China should make both researchers and farmers think about bundles of varieties instead of just a single seed stock for each field.

The Chinese experiment was by far the biggest test yet of the "many varieties" strategy. Thousands of participating farmers across Yunnan province planted a mix of modern blast-resistant rice varieties.

They even mixed in rows of the tall, lower-yielding "sticky" rice varieties, used for confections, with the short-stalked hybrid high-yield rices that produce most of China's grain crop.

The incidence of severe rice blast on the more susceptible glutinous rice dropped from about 20 percent to around 1 percent. On the hybrid rice, it dropped from about 2.3 percent to 1 percent.

Yunnan farmers typically spray fungicides several times on each crop, but with the reduced spread of the blast in mixed-variety fields, they were able to skip the fungicides completely during the second year of the experiment.

Planting a group of varieties frustrates many of the pests, in part because of the physical differences in the plants, such as different heights and leaf structures. In addition, there is an immunization factor, as unsuccessful pest attacks trigger the plants' disease-resistance mechanisms, strengthening their barriers against infection. Both factors help slow the development of pest epidemics.

Planting many varieties should also slow down the adaptation of the pests, so each crop variety will remain useful longer. Less pesticide should be needed, and each pesticide should have a longer useful life. Costs will go down for both farmers and consumers. Total rice yields from the Chinese fields increased a substantial 18 percent, and their total value rose 14 percent.

At least one organic farming advocate was quick to announce the Chinese results as "proof" organic farming is better than high-tech agriculture. George Monbiot wrote in Britain's The Guardian newspaper that the farming systems being "imposed" on the world by "big business" are "actually less productive than some of the methods developed by traditional farmers over the past 10,000 years," based on the Chinese reports.

Wrong, George. These farmers aren't planting low-yield, pest- susceptible seeds but the latest, most potent products of the breeding stations.

Secondly, the Chinese farmers are supporting those seeds with the same levels of chemical fertilizer use in the known world. China learned its lesson on organic farming 40 years ago. China then was already famous for using every scrap of organic waste from its people, animals and crops to support its rice yields.

But Chairman Mao didn't want to use scarce capital to build fertilizer plants, which take nitrogen from the air, to feed the country's rising population.

Mao told his peasants to cut vegetation from the hillsides and use it to mulch the rice paddies. The mulching failed to provide much nitrogen, millions of Chinese starved and the country suffered the worst soil erosion in its history.

When Deng Xiao-Ping took the reins of Chinese political power in 1978, he built the fertilizer plants and saved what remained of China's forests from being plowed for low-yield organic crops.

Nor have the Chinese farmers sworn off pesticides. They know there will inevitably be cooler, wetter years that will favor the rice blast, and then China will need to spray fungicides.

The Chinese people cannot take a year off from eating just to maintain their organic purity. Still, it's good to use as little pesticide as possible, which lowers farmer and consumer costs and minimizes health effects.

China harvests its rice by hand, so it can interplant two types of rice without much cost. That won't work for the First World, with its high labor costs and big combines.

However, the Chinese experiment strongly suggests doing more research on bundles of varieties that would work well together in the same field. The concept of mixed varieties may stimulate the continuing trend toward still-higher yields.

Even though the Soil and Water Conservation Society of America says high-yield farming with conservation tillage is the most sustainable in history, we should keep striving for still higher levels of sustainability and yields in the future, for the sake of both people and wildlands.