How to Save and Build Soil
Well, there’s a little more to it than that.
Centuries ago in the Amazon Basin of South America, natives used a mix of charcoal, bone, and manure to build a soil called terra petra. This soil -- still productive -- makes soil scientists salivate more than puppies in a pile of pork chops.
The Amazon natives basically built this soil out of an unproductive one. Terra petra literally means black earth or black land in Portuguese; it's a rich, black soil oozing in productivity.
Terra petra soils seem a long way away from today. Over the last 40 years, soil erosion and degradation caused farmers to abandon about 430 million hectares (1.062 billion acres) of arable land. That’s according to David Montgomery, a Washington State University geologist.
Montgomery spoke at this week’s 6th World Congress on Conservation Agriculture in Winnipeg, Manitoba. Montgomery also authored the book Dirt: The Erosion of Civilizations. The book traces how abuse of soils negatively impacted nations and empires ranging from Rome to Central America to the U.S. Dust Bowl of the 1930s.
Commercial fertilizer outlook cloudy
The future of maintaining soil quality based on commercial fertilizers is also questionable. Commercial fertilizer fueled 20th century crop production advances.
That will be difficult to continue going forward, says Montgomery. With worldwide oil production on a downward slope, the tighter supply will likely raise petroleum costs. This will translate into higher fertilizer prices, since commercial fertilizer is derived from petroleum. This will make it economically more difficult to build soils via commercial fertilizers.
“Doing so and maintaining it with decreasing energy costs is a challenge,” says Montgomery.
The news isn’t all bad
Montgomery sees ways that modern-day farmers can mimic the Amazon natives in building soil quality and conserving what topsoil we have.
“We can build soils surprisingly fast,” he says. “It takes (building) organic matter, labor, and biological assistance (from microbes).”
Gardeners do it all the time, via aggressive composting and mulching programs.
It’s the labor portion of this equation that’s a challenge for farmers. Farmers don’t have time to pore over each foot of their fields the way gardeners do. Still, steps like no-till and cover crops can play a part in boosting soil quality. It’s also a way to retain carbon in soils, rather than having it escape into the atmosphere.
Some of the methods farmers now use to increase soil fertility over the long-term, like no-till, can increase organic matter, says Montgomery. In turn, this can increase the soil holding moisture over time and decrease water runoff.
Livestock also can play a vital role in revitalizing soils.
“One of the things that led us down the path to where agriculture is today is the divorce of livestock husbandry from cropping,” he says.
It’s a challenge to distribute manure evenly when cattle are concentrated in small areas, he notes. A way to more easily disperse manure is to integrate more livestock back into on-farm cropping systems. Although dispersing livestock won’t work in all areas of the world, there are places where it may, says Montgomery.
Stop treating soil like dirt
Back in 1937, President Franklin Roosevelt said, “A nation that destroys its soils destroys itself. “
“Those words are as prophetic now as they were then,” says Montgomery.
It is not a question of organic vs. conventional agriculture, or GMO vs. non-GMOs, he says.
“The question is how to apply an understanding of soil ecology to the applied problem of increasing -- and sustaining -- crop yields in a post-oil environment,” he says. “First and foremost, soil restoration means having to stop treating soils like dirt.”