Cedar River Watershed Project: Healthy Soil
Written by Larry Stone
Please don't call it dirt!
“Soil is, in fact, a very vibrant, living community,” declared Frederick L. Kirschenmann, distinguished fellow at the Leopold Center for Sustainable Agriculture at Iowa State University.
“There are more living organisms beneath the surface of the soil than there are above the surface,” Kirschenmann explained. Estimates range from 50 million to four BILLION per teaspoonful of soil. “It isn't just all of the things that we can see – the earthworms and the beetles and the ants,” he said. “It is those micro-organisms which dominate all of our soil culture.”
“So this is a community of life,” Kirschenmann marveled. “And if we're going to have not only good food, but any food at all, we have to sustain that community of life in the soil.”
Healthy soil also can help hold water, thus reducing erosion and flooding, noted Dr. Doug Karlen, Research Leader for the U. S. Department of Agriculture's National Laboratory for Agriculture and Environment in Ames.
He lamented most farmers' reliance on just two crops: corn and soybeans. “We all have benefited by the advancements in corn and soybeans,” Karlen said, “but the mistake has been to put those two crops on every square inch of our landscape.”
“We have done that by putting in more drainage, bigger tile lines,” Karlen continued, “but all we're doing is short-circuiting the system and sending both water – and anything that's carried by that water – downstream.”
The problem is exacerbated by the fact that these are annual crops. “There is no vegetation growing from roughly the first of October to the middle part of April across much of our watershed,” Karlen said.
With nothing to hold the water, rain or snowmelt runs off the surface or through tile lines. “There's only one place for that water to go and that's right into the channels, which have been straightened, and scooting on down past our cities,” Karlen said. The water also carries nitrogen and phosphorus – nutrients which are lost to the farmer, but which contribute to the hypoxia (dead zone) in the Gulf of Mexico.
“Over the long term, we have to change our land use decisions,” Karlen declared. “What made our soils of the Midwest great was having a high percentage of deep-rooted, perennial plants. The carbon that was fixed from the atmosphere was put into the soil and cycled through the microbial processes and then had an impact on the physical, on the chemical, and on the biological properties and processes,” Karlen said, “which is really the essence of soil health and soil quality.”
A diversified plant community – perennial grasses and trees, pastures, and winter small grains – can take in, hold, and use the water, and transpire the excess back into the atmosphere, Karlen said. Soil scientists calculate that adding one per cent more organic matter to the soil could enable it to hold 19,000 more gallons of water per acre. Without those growing plants, however, water runs into streams and can contribute to flooding.
Growing deep-rooted perennials could help, Karlen said – but farmers are “up against a wall” because economics dictates that they plant corn and soybeans for the market.
Society must step in, Karlen said. “It has to be a community effort, as well as an individual farmer effort. (The community must make) decisions that we're going to create these opportunities and these markets so they can sell other materials.” Woody species and perennial species could be used in bioenergy production, or for other bioproducts – from baby diapers to food to chemicals.
Karlen envisions woody buffers along streams, wetland species in flood-prone river bottoms, and conventional crops on uplands. Entrepreneurs could harvest and process the alternative crops, while farmers focus on conventional species.
“It's a bigger, more holistic land management approach,” Karlen said.
Kirschenmann said that “holistic” approach looks at soil as “a web of relationships.” Unfortunately, some farmers regard soil as something to hold plants in place where they can be doused with chemical fertilizers and pesticides, he said.
That industrial model of agriculture is unsustainable, Kirschenmann fears. We're now dependent on dwindling supplies of three finite resources: fossil fuels, fertilizer, and irrigation water. When those artificial inputs become too scarce and expensive, we'll be forced to use our basic resources more judiciously.
To restore soil health, we should view the farm as an organism, Kirschenmann said. Plants and animals in the system should support each other and provide goods and services for each other. Then soil, water, and nutrients will stay on the land – and not clog our rivers.
Read other articles in this series.
Originally published by the Cedar River Watershed Project
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