Study of soil shows importance of more nutrients

Researchers are beginning to unravel the mystery of why organic fields consistently out-yield conventional ones under extreme drought conditions, and the relevant management practices are largely transferrable.

Science is on the verge of discoveries about the mysteries living beneath our feet that may hold the key to a future agriculture that is both more productive and able to economically sequester massive amounts of greenhouse gas.

A substance that may account for a quarter or more of all the carbon in soil and is essential for being able to absorb and hold water and cycle nutrients, had not even been discovered a quarter century ago.

The beneficial mycorrhizae fungus, which can only survive in contact with host plants, secrets a substance called glomalin in order to protect itself, and to more efficiently bind the crop's roots to the soil.

"Glomalin was not even discovered until 1996," said Tom Willey, one of the pioneers of organic farming who operated T & D Willey Farms in Madera with his wife, Denesse, for decades. "Imagine what we could accomplish if the research community joined us."

The research community did join in late January as Washington State University regents professor John Reganold and longtime U.S. Department of Agriculture soil microbiologist Kris Nichols delivered keynote addresses during the 39th Annual Ecological Farming Conference at Asilomar.

Following her 10 years as a USDA soil microbiologist, Nichols served a four-year stint as the head scientist at the Rodale Institute for organic research but resigned because she said she believes the message of building agriculture from healthy soil on up is far broader than just organics.

"I left the Rodale Institute partially because I used to work with farmers who were not organic, and will never be organic, but are innovators," she said. "We can feed 15 to 20 billion people off the land we have if we do it right. We can solve having too much greenhouse gas in the atmosphere. We can move things forward."

If there is one message Nichols emphasized, it is that soil must always have living plants in it in order to restore and maintain health.

"The one problem we have in agriculture is we do not have enough carbon in our soil," Nichols said. "Carbon goes into the soil through a living plant by photosynthesis. We can't say that we can't grow in Manitoba because it is too cold, or California because it is too dry. The sun shines 365 days a year—grow plants and fix carbon."

Carbon is a shorthand for living microbes in the soil, and the most important may be mycorrhizae, a fungus that helps build soil aggregates and also sends out a network of filaments attaching the roots to the soil but can only survive in contact with plant material.

This symbiotic fungus plays a remarkable role in helping the soil absorb and hold more water, allowing the crops to mine for water and nutrients, but mycorrhizae cannot survive either extensive and frequent tillage or long periods without contact with living plant material.

"We have no idea how much water it takes to grow a plant because the studies we have done have been in soils that were degraded," Nichols said. "When we design our system, we should think in terms of how much fungi connects the soil to the plant."

Dozens of studies show that organic yields for rice, soy, corn and grass are typically 6 to 11% lower than conventional, according to Reganold, and as much as 27 or 28% lower for fruits or wheat.

He said he believes that breeding varieties specifically for organic production would do much to narrow the yield difference.

"When varieties are bred in organic systems, you close the gap," Reganold said. "Improvements with organic-specific breeding would make a difference."

But the real story may be what happens when both systems are managed under conditions of drought stress.

"The organic yields are equal or higher under severe drought," Reganold said. "If you look at conditions of drought, organic yields are equal or higher."

Rodale Institute began its side-by-side trial of organic and conventional agriculture 37 years ago in a 12-acre field at its headquarters in western Pennsylvania.

Following a five-year transition period under the watchful eyes of the Rodale experts, corn yields in manure-based organic plots, which trailed badly at the beginning, increased to be competitive with nearby conventional plots.

But the real story is that under drought stress conditions these organic plots produced 40% more corn than conventional plots a few feet away.

The resilience that lets the ground produce more with less water, while also holding far more carbon, depends less on organic materials than on a system of minimum tillage and constant plant ground cover that lets the soil live.

"You have to have something growing 365 days a year," Nichols said. "Have trees, shrubs, annuals or perennials. I don't care. We need to protect our soil surface with living plant, and if not living plant residues for a brief period. There is no reason for there to be bare ground with pools of water. Treat the soil like you want to be treated."

Nichols looks at world maps showing that the most degraded soil is almost always where we produce our food, and concludes we need to fundamentally change our systems.

"We have 900 million acres in agriculture in the U.S.," she said. "We need 400 million acres to be in regeneration yesterday, another 400 million on the way, and I'll give you 100 million you can treat any way you like."

Nichols frequently discusses this perspective with the many progressive ranchers she meets in her native upper Midwest.

"Ranchers tell me they don't raise livestock anymore, they grow grass," she said. "I tell them, no, you don't grow grass, you build soil."

(Bob Johnson is a reporter in Sacramento. He may be contacted at bjohn11135@gmail.com.)