密歇根新闻广播 农耕产生了大量温室气体（在线收听）

We know that burning fossil fuels releases a lot of greenhouse gases. But there are other human-caused sources that contribute to climate change. As Lester Graham with the Environment Report found, one of them is how farmers plant crops.

All agriculture accounts for 23% of human greenhouse gas emissions, according to the International Panel on Climate Change. We’re going to look at a smaller, but still significant portion of that.

When we think just about cropping systems, we're looking at somewhere on the order of eight to 12 percent of total greenhouse gas loading. And eight to 12 percent is a lot when we think about what we need to do to rein in greenhouse gases, said Phil Robertson, a Michigan State University professor who works at the Kellogg Biological Station near Battle Creek.

When he says cropping systems, think row crops such as corn, wheat, and soy beans. Conventional tilling, that is plowing up the dirt, encourages microbial action. That can lead to CO2 emissions and the more potent greenhouse gases methane and nitrous oxide.

And therefore the microbes go to town. And so we end up with a lot more CO2 being emitted than we would in a natural system, for example, or in a system that's no till, Robertson said.

That’s why Michigan State University researchers have been studying no-till and similar techniques.

No-till is a way of farming without plowing the soil, Robertson explained.

No-till can mitigate the greenhouse gases that contribute to climate change.

When it's time to plant the next crop, they'll use a planter that cuts a slit in the soil and the seeds go into that to let the plants come up and are just as happy as when they're being put into plowed ground, Robertson said.

That keeps the carbon in the soil.

About 50 percent of corn, wheat, and soybean are planted using no-till. Each year the soil is not plowed up, more carbon is stored.

But, it can all be lost. Let’s say a farmer used no-till for four years. If that field is then conventionally plowed, that carbon stored over the years is released.

Farmers say it’s sometimes not practical to use no-till. They say they need to plow the field when it’s too wet to plant. It can help dry things out.

I don't agree with that statement, Blaine Baker said.

He was working on his combine at his family's farm in Lenawee County. He's been using no-till for 23 years. He says there are years he's actually planting earlier than other farmers.

I mean, I'm not saying no-till is a cure-all for everything, but we planted days when other people weren't running and we didn't hinder our yields, Baker said.

He thinks the real barriers to no-till are these: first, is the idea that this is the way we’ve always done it; second is money.

There’s costs associated with it, and especially when you're sitting there and you got the full line of other equipment to go out and do it like you've always done. Why do you want to invest another, you know, 50, 60, 70 thousand dollars when I've got the equipment sitting there ready to go, he said.

There is a third factor: politics. Despite the preponderance of scientific evidence, climate change is still political. Some farmers simply dismiss climate change as fake science.

Baker says there are other benefits from no-till. One is preventing the erosion of rich topsoil.

And particularly now that we've gone to cover crops, we've got something growing out there all the time. So our erosion is pretty much nil, he said.

Despite the benefits, few farmers use no-till consistently. Baker says that's a shame.

Huge, huge amount of carbon that is sequestered, but every time you open it up, you're releasing it, he said.

A four year survey by the U.S. Department of Agriculture shows only about 20% of cropland was in no-till or similar techniques all four years.

Until more farmers commit to using no-till every year, planting crops will continue be a significant contributor to climate change.