Haslestad said Yara tries to show farmers how to apply fertilizer intelligently to avoid over-fertilization, which gradually strips the land of growing power. "We don't want to oversell to destroy the planet," he said.

"We are convinced there will be a need for our products into the future." Why? The Chinese, he said, "are desperately afraid of not being able to produce enough food".

Although China's leaders are exploring alternative fertilization approaches to increase yields without wearing out the land, changing practices in the country is a huge challenge, Haslestad said.

"When you have set off something in one direction, it's difficult also to shift it and to modify and to bring it into another direction," he said. "The ideal situation would be to merge quite a few farms to get more efficient, larger farms.

"But the people who are living off the small farms, they have to have an income, then they have to move to the cities. The politicians don't want to force that to happen even faster than it is happening now," he said.

He was referring to China's effort to urbanize a quarter of a billion rural residents to boost domestic consumption and revive a slowing economy.

What about the oft-repeated claim that China's centralized government allows it to implement policy changes, such as those that would affect fertilization practices, quickly? "That's the framework," Haslestad said.

"But in China there are several layers below the central government. At the provincial layer, they interpret the policies in ways which they feel will benefit local activity. That can be good for the local population, but probably not good for China as a whole."

Highlighting an example from his own industry, he said the government could say that a small local fertilizer factory needs to be closed for environmental reasons. "That particular plant in that region could employ 2,000 people. Then the question is, is it better for the local community to have the plant polluting a bit, than not to have work?

"We have a tendency to say to the Chinese that they have to fix that, and fix that. It's not so easy to fix it. It takes some time."