Chinese scientists have developed a smart pesticide that, once in the soil, is controllable and recyclable.

A team led by Wu Zhengyan, professor with the Technical Biology Institute, under Hefei Institute of Physical Science, Chinese Academy of Sciences, used diatomite, iron magnesium oxide and chitosan to make a compound that can be activated by changes to pH levels in the soil.

"The release of the pesticide mixed with the additive can be easily adjusted by pH changes. The additive wraps up the drug and acts like a gatekeeper. It opens the gate and dissolves in acidic conditions," Wu said.

He said the research showed that a single-season crop only needed the pesticide spray once. During the growth of the plant, growers simply spray a weak-acid agent to activate and control the pesticide's effect. Conventional farming needs several rounds of pesticide spray.

The report on the research was published in the latest issue of the Chemical Engineering Journal, an international research journal.

Wu said China's agriculture relied heavily on the use of pesticide, which was estimated at over 1 million tonnes a year. However, less than 40 percent of such pesticide actually had an effect on crops and the rest simply washed off, contaminating soil and water.

He said the additive had magnetism, which made it feasible to recover the pesticide from soil and water.

"The recycling effect during our tests shows 30 percent of pesticide residue can be recovered," Wu said.

According to the research, sponsored by the National Natural Science Foundation and the Chinese Academy of Sciences, the nano-pesticide showed a high adhesion ability on weak surfaces and pest epidermis.

Wu said that it was still too early to put the results into commercial use as the cost of nano-material and recycling was too high for farmers.

"We take it as a stage one success and will continue to upgrade to make it more efficient and economical," he said. (Xinhua)