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  • This is my compost bin. It's where I put used coffee grounds, melon rinds, corn husks;

  • pretty much anything that was a plant in its former life, along with shredded up newspapers,

  • junk mail and pizza boxes. If I wait long enough, something kind of amazing happens.

  • All that stuff is transformed into, well, what looks like ordinary dirt. But this dirt is

  • anything but ordinary. This dirt is alive. Yes, it's full of earthworms. We'll get

  • to them. But it's also full of millions of tiny creatures that you need a microscope

  • to see. You wouldn't know by looking at them, but these little guys hold the key to

  • human civilization. Without it, human life as we know it wouldn't be possible. Which makes

  • it all the more puzzling when you discover that its number one enemy is us.

  • So, not all dirt is created equal. It can have more or less of those little living creatures in it.

  • And there's an easy way to tell even if you don't have a microscope at home.

  • First, put about a handful of dirt in a clear glass jar. This is some soil I collected from the worm bin.

  • Don't worry, I took out the worms later. And this I dug up from my backyard.

  • Next, add some water. Screw the lids on nice and tight, and shake them up. And now, we wait.

  • OK, it's been a day, we're back, and we can see that both of our samples have separated

  • into distinct layers. You can see that they look really different.

  • Let's look closer at the dirt from the backyard. It has a bunch of stuff

  • on the bottom: gravel, sand, silt, and clay. This stuff floating at the top is called humus.

  • That's where all the microscopic creatures live. Scientists call them microfauna: micro

  • for small, fauna for animals. There are millions of different kinds. When old plants die, the

  • microfauna eat them and then, well, they poop. That waste is full of nutrients that

  • new baby plants need to grow. Grass, tomatoes, apple trees--- no matter the plant, the process

  • is the same. And the more microfauna there are in the soil; eating, pooping, doing their

  • thingthe bigger and healthier the plants. Over millions of years, the new plants would

  • use up nutrients in the soil, then the microfauna would replaced those nutrients by eating the

  • dead plants. In mild climates, the microfauna could build up about two and a half centimeters, or one inch

  • of humus every 500 years. Evolution continued and eventually produced a species who changed

  • this process forever.

  • Homo sapiens have been around for almost 200,000 years, but we didn't

  • start farming until about 12,000 years ago. Before then, we still depended on healthy

  • soil for food. The grass that fed the herd animals we hunted, the nut trees and berry

  • plants we foragedthese all grew from the rich humus that the microfauna created.

  • Farming developed at various points in time, in different regions of the world. And from

  • the beginning, some of those early farmers recognized the relationship between healthy

  • soil and healthy plants. Like the Iroquois in the eastern part of what is now the United

  • States. The first farmers there, women, by the way, planted corn atop mounds of

  • soil every spring. After they harvested the corn in the fall, they left the dead cornstalks

  • atop the mound. All winter long, the microfauna broke them down into nutrient-rich humus.

  • The next spring's new baby corn plants would use those nutrients and start the cycle again.

  • Iroquois farmers would also plant beans and squash in the same plot. Together, these three

  • crops were known as thethree sisters.” Not only did this combination make for a balanced

  • diet of protein, carbohydrates, and crucial vitamins for the Iroquois people, it also

  • kept the microfauna in the soil happy, healthy and pooping. Early farmers in other parts

  • of the world developed different ways to feed the soil. Like in the Amazon river basin.

  • Early farmers there used controlled fires to create patches of rich humus.

  • Today, if you dig deep into that soil, you can see that its much darker and healthier

  • than the regular tropical soil nearby.

  • All over the world, the earliest farmers found ways to care for the

  • soil so that it would produce healthy plants. But slowly, as European colonists descended

  • on various parts of the world, these ancient practices gave way to a new type of farming.

  • Machines like the steam engine and the power loom transformed life in Europe, and then in North

  • America, starting in the mid-1700s. The lure of factory wages drew people from the countryside

  • into cities, which meant the farmers who stayed on the land needed to produce more food to

  • be shipped to the cities. Farmers got stuck in a cycle of constant harvesting, without

  • giving the soil time to regenerate the nutrients it had built up over generations. The soil

  • quickly wore out, so they responded by cutting down forests and turning them into fields.

  • In North American, European settlers used violence to push the Iroquois and other indigenous people further west,

  • away from the three sisters fields that had sustained them for thousands of years. When

  • they stripped that soil of its life, the settlers kept moving west, seizing indigenous lands

  • along the way. New steel plows helped them break up the hard, heavy soils of the Great

  • Plains. But these new steel plows did something else. They turned up the soil over and over again, which killed

  • a lot of those microfauna that had been living in the soil making humus. And when gasoline-powered

  • tractors showed up in the early 1900s, their weight pressed down on the increasingly lifeless

  • soil, making it even harder for plants to grow. By the 1930s, the soil of the Great

  • Plains had lost so much of its microfauna, giant dust storms pummeled the region. Thousands

  • of families lost their farms. This new type of farming wasn't limited to Europe

  • and North America. The small farms that had sustained the indigenous peoples of Central

  • and South America for generations had been replaced by giant mega-farms, haciendas, run

  • by the Spanish and Portuguese settlers and worked by indigenous and enslaved people.

  • the crops didn't feed the people there. These fields were full of sugarcane and cotton to

  • be shipped out of the country to factories. And, just like in North America, the overworked

  • soil quickly crumbled and started to wash away. In response, farmers around the world

  • started to rely on chemical fertilizers, which help crops grow quickly, but can also pollute

  • drinking water and kill fish and other types of aquatic life. According to the United Nations,

  • practices like this are killing the humus so quickly, we may run out of healthy soil

  • in less than 60 years. That is, if we keep doing things the same way.

  • Remember the soil we tested, that these guys helped to make?

  • Look at it next to the jar of backyard soil. See how there's way more humus floating on the top? More of this stuff is exactly

  • what we need, all over the world, to replace the soil we've already destroyed.

  • And earthworms can help.

  • On farms where years of plowing has damaged the soil, a handful of farmers have stopped doing it.

  • Instead, they roll down the old crop then use a series of drills to plant the new seeds

  • underneath the old crop. Because this method doesn't disturb the soil, it gives earthworms

  • a chance to make humus, and to create tunnels that help water get to plant roots. It also

  • helps to loosen the soil so that plant roots can spread. But this method has been slow

  • to catch on. Just one in four American farmers use it. On many smaller farms, though, earthworms

  • are a big part of the operation. This is our worm bin. These are the hardest workers, these

  • are actually red wriggler worms. This is Marc White. He showed me around his urban farm,

  • right in the middle of Cleveland, Ohio.Here are the raspberries I talked about. Just pull

  • one off right there. Oh my gosh. Isn't that awesome? Everything is based on the soil. Everything that

  • we eat is a reflection of the soil.

  • This right here, this is the black gold.

  • On Marc's farm, that process starts here, in the compost

  • pile. Over time, wood chips and food waste break down with the help of earthworms and

  • microfauna.

  • So this is how the soil you saw inside, this is how it starts out.

  • In the next 10, 15, 20 years, this whole footprint will have been improved so much more for us

  • having been here.

  • We need healthy soil to grow healthy food, and we need healthy food

  • to grow healthy people. It's all connected.Dirt is so much more than the stuff beneath our

  • feet. It's the stuff of life. And the sooner we realize that, the better off we'll be.

This is my compost bin. It's where I put used coffee grounds, melon rinds, corn husks;

Subtitles and keywords

B1 INT soil dirt healthy plant indigenous farming

The secret history of dirt

  • 13 0
    林宜悉   posted on 2020/09/03
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