Contaminated soil imminent threat to food supply

(Ecns.cn) -- Pollution and deterioration of arable soil are two pressing issues that China must tackle now, because they are already jeopardizing the country's grain security, the Economic Information Daily reports.

Since 2008, there have been over 100 major pollution incidents across the nation, and many have posed severe threats to food production, the business journal says.

According to Century Weekly magazine, about one-tenth of China's rice yield carries harmful levels of heavy metals, which are detrimental to liver function and bone health. The problem may be even more serious in the south, where hybrid rice is more commonly used.

In northeastern China, soil deterioration has become a major concern for grain production. Over the decades, the fertile black soil layer has thinned dramatically, causing a continuous decline in the regions' grain output.

Contamination

Rapid industrialization and urbanization have introduced toxic chemicals and heavy metals into rural areas, polluting arable land. When the pollutants enter crops, they are inevitably consumed by humans.

The situation is getting worse, making control measures for soil degradation urgent, says Zhang Weili, a researcher with the Chinese Academy of Agricultural Sciences.

Zhang, who is also deputy director general of the Soil Science Society of China, has been keeping a close eye on the problem. He says China's soil pollution is much worse than any other country, and it will continue to worsen in the next 30 years.

Statistics released by the Ministry of Land and Resources show that more than 10 percent of China's arable land has been contaminated by heavy metals such as cadmium, arsenic and mercury, scattered mainly in the southern parts of the country.

Since 2008, many people have suffered from food tainted by heavy metals. The Liuyang cadmium pollution incident in Hunan Province was a typical case; it claimed two lives and sickened more than 500 local residents.

Zhang is equally worried about pesticide residue. The annual amount of pesticides used in China is about 1.3 million tons, 2.5 times the global average, yet vast amounts of it are misused and wind up cycling into the ecosystem.

Soil degradation

In northeastern China, black soil suitable for growing grain is mainly distributed in the upper reaches of the Songliao Basin in Heilongjiang and Jilin provinces. But because of human interference, the black soil layer is becoming thinner.

One of the world's top three black soil regions, northeast China has 3,523.3 hectares of the fertile substance. About one-fifth of the country's grain is grown there, including rice and maize.

However, according to research conducted by experts from Northeast Agricultural University, the Chinese Academy of Sciences and the Jilin Academy of Agricultural Sciences, the thickness of the black soil layer usually shrinks from about 80 centimeters to 20 centimeters after seven to eight decades.

In the 1950s the thickness of the soil layer in Heilongjiang was over one meter, but is now less than 50 centimeters and has turned from black to brown or yellow, according to a local official in charge of soil conditions.

Some experts warn that nearly 1 million hectares of black soil in northeast China will disappear in the next 50 years, based on current annual soil erosion rates.

Grain output dropping

Soil pollution and deterioration will cause a decline of beneficial bacteria in arable land, and the soil will gradually be deprived of its production capability, says Pan Genxing, professor at Nanjing Agricultural University.

When the pollution is beyond the soil's ability to self-clean, and there is no controlling intervention, anything grown in it will contain harmful elements to our health, adds Pan.

According to a rough estimate made by environmental authorities, every year up to 12 million tons of grain is contaminated by heavy metals in China, causing annual financial losses of over 20 billion yuan (US$3.14 billion).

The country's grain output has been greatly affected, posing the threat of a food crisis. Chen Zhiqun, from the Ministry of Agriculture, says that China's grain output is reduced by 10 billion kilograms every year.

Currently the biggest problem is the implementation of laws concerning the protection of arable land, says Zhang Weili, who adds that most farmers know little about how to maintain the quality of soil.

Although China has more than 50 environmental pollution regulations, the country remains at the forefront of all types of contamination problems, Zhang says.

He adds that in northeast China, some farmers continue to plant the same crops on the same land and apply fertilizers in an unscientific way. With time, the arable layer is reduced.

Zhang hopes China will do more to avoid land takeovers and stop further soil degradation, and advises the government to offer training for farmers to help them understand healthier soil cultivation methods.