China's use of agricultural plastic mulch films, projected to 2024. Graphic: Bloomberg

5 September 2017 (Bloomberg News) – China will expand its agricultural use of environment-damaging plastic film to boost crop production even as authorities try to curb soil pollution, a government scientist said.

Some 1.45 million metric tons of polyethylene are spread in razor-thin sheets across 20 million hectares (49 million acres) — an area about half the size of California — of farmland in China. Use of the translucent material may exceed 2 million tons by 2024 and cover 22 million hectares, according to Yan Changrong, a researcher with the Chinese Academy of Agricultural Sciences in Beijing.

The plastic sheets, used as mulch over 12 percent of China’s farmland, are growing in popularity because they trap moisture and heat, and prevent weeds and pests. Those features can bolster cotton, maize and wheat yields, while enabling crops to be grown across a wider area.

“The technology can boost yields by 30 percent, so you can image how much extra production we can get — it can solve the problems of producing sufficient food and fiber,” Yan said in an interview at his office at the academy’s Institute of Environment and Sustainable Development in Agriculture.

The downside is that polypropylene film isn’t biodegradable and often not recycled. Potentially cancer-causing toxins can be released into the soil from the plastic residue, known locally as “white pollution,” which is present at levels of 60-to-300 kilograms (132-to-661 pounds) per hectare in some provinces.

While polyethylene contamination occurs worldwide, the threat is especially acute for China, where about a fifth of arable land contained levels of toxins exceeding national standards, according to 2014 government estimates.

Regrettably, there are no viable alternatives to polyethylene that possess the same agronomic advantages. That means farmers are compelled to keep using it to boost production and income, said Yan, as he flicked through slides showing pollution in the northwest region of Xinjiang.

Aerial view of farm land with plastic soil cover in Sichuan province. Photo: Jie Zhao / Corbis / Getty Images

The material enables crops to be grown in both drier and colder environments. In Xinjiang, which accounts for almost 70 percent of the country’s cotton output, plastic mulch is used on all cotton farms; and across 93 percent of the country’s tobacco fields, he said. The film reduces water demand by 20-to-30 percent.

To address mounting food-safety concerns amid worsening soil pollution, in May last year China’s State Council urged the recycling of used mulch films. The country’s top legislative body, the National People’s Congress, is also drafting the country’s first soil pollution law. [more]

Plastic Film Covering 12% of China's Farmland Pollutes Soil

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