Those exports have been made possible by major increases in soybean yields in the U.S., Gianessi says. “Since 1976, herbicide use in the U.S. has been a key component of soybean yield increases, with 95 percent to 98 percent of all soybean acres now treated with herbicides.

“Each acre of cropland in the U.S. contains 50 million to 300 million buried weed seeds, which an be viable in the soil for 20 to 30 years or more. This is a buried menace. Without herbicides, we’d have massive carpets of weeds taking an enormous toll on soybean yields.”

For those who oppose agri-chemicals, he says, “There is a non-chemical alternative: cultivation. But research at

Michigan State University has shown that in too many cases, weather or other problems prevent timely weed control operations with cultivation alone. If the U.S. were to grow soybeans without herbicides, every third year we’d be losing, the amount of soybeans we sell to the Chinese. That’s unacceptable. The world’s counting on us. We can’t take this kind of risk.”

The U.S. has, over the years, faced many of the same issues with weeds and other crop pests that other countries are now coping with, Gianessi says.

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“The development and adoption of increasingly effective herbicides, insecticides, and fungicides allowed farmers to step up and meet the challenge, increasing output by a factor of five, at a time when population increased by only a factor of three. We had enough to feed not only our own people, but more that we could share with the rest of the world. We’re growing five times as much on our farms with far less labor, and we’re doing it across a broad spectrum of crops on 20 percent less land.”

Rice in the U.S. has been a major beneficiary of herbicides, he says. “From 1900 up until the 1950s, without weed control, yields were about 1 ton per acre. With herbicides, yields have more than doubled.”