Lords of the dirt

All hail the soil scientist: the future of humanity is crumpled in their hands

Published April 26, 2007 5:28PM (EDT)

At the Swan Lake Research Farm in Morris, Minnesota, a group of USDA soil scientists are conducting research that could not possibly be more important. Their mission: "to develop agricultural systems in the Midwest that are environmentally, economically and socially sustainable by providing knowledge and technologies for proper land, crop and weed management to enhance the biological, chemical and physical properties of soils and to improve environmental quality."

This can mean investigating whether organic or non-organic agriculture sequesters more or less carbon dioxide from the atmosphere (so far, organic appears to be better), the sustainability of different cropping systems, and, perhaps most controversially, the question of how to maintain soil fertility while converting crop biomass to energy.

Their priorities are clear: as one of the scientists, Don Reicosky, wrote in a research report this month: "The soil is the fundamental foundation of our economy and our existence.... Society must be dedicated to investigating and protecting our global soil resources for the expanding population."

These are not venture capitalists looking to make a quick short term buck by exploiting corn-based ethanol government incentives. These are people who love dirt. And want to keep it healthy.

Reicosky continues:

Agricultural biomass for energy including ethanol can be part of the solution, together with other renewable energies (e.g., solar, wind) AND changing our high energy use habits. Sound research is needed to determine how much, when and where biomass can be removed without soil and/or environmental degradation. A balanced approach is critical to solving these related problems of global warming, limited fossil fuels and maintaining soil productivity.

It's all about how much organic carbon -- or "soil C," as these scientists abbreviate it -- remains after the harvest. After all the fossil fuels are burned away, soil C is all we're going to have left. We'd better take care of it.

A report today from the USDA summarizes research conducted by soil scientist Jane Johnson, who has been investigating how much "corn stover" (the stuff left over after harvesting the corn) can be removed from a field while maintaining acceptable soil organic matter. Her initial conclusions: "twice as many cornstalks have to be left in the field to maintain soil organic matter levels, compared to the amount of stalks needed only to prevent erosion." (Thanks to GreenCarCongress for the link.)

This doesn't mean harvesting cornstalks for cellulosic ethanol isn't feasible -- just that when you add soil organic matter concerns to erosion concerns, it slashes the amount of cornstalks available for conversion to ethanol. For example, 213-bushel-per-acre corn yields leave farmers an average four tons per acre of cornstalks after harvest. Farmers could then harvest about two tons of cornstalks per acre for conversion to ethanol -- but only from land with low erosion risks, using little or no tillage."

As a starting point to understanding the issues associated with proper soil management and the production of biofuels, you can't do better than "A Matter of Balance: Conservation and Renewable Energy," a paper co-authored by Johnson, Reicosky, and three other USDA scientists in July-August 2006 issue of the Journal of Soil and Water Conservation.

It is critical that we balance economic and energy opportunities with honest and complete assessments of environmental costs and identify who benefits from the economic return and who bears the environmental costs...

Economics and government policy will drive development of biomass for biofuel industries. However, we cannot afford to overlook the potential costs associated with wide-scale removal of crop residues from the land.These costs may not be readily apparent in the short term and economic impacts are not easily quantified. Thus far, farmers are not compensated based on the ecosystem services provided by agricultural watersheds. We suggest a cautious approach to harvesting crop biomass for energy until science-based research provides answers and guidance to the critical questions of how much, when, and where to harvest crop biomass.

Johnson's most recently announced results are part of that "science-based research." The work of the soil scientists at Swan Lake suggests that, under certain conditions crop biomass can be converted to energy without crippling soil productivity.

These conditions include what are known as "best management practices (BMP)."

Best management practices that have been proven to sequester soil C are crop residue management, conservation tillage practices like direct seeding systems, no till, conservation tillage, mulching, strip cropping, diverse crop rotations, cover crops, grassed waterways, elimination of summer fallow; perennial forage crops for hay or pasture; application of organic materials and manures; soil fertility optimization through improved fertilizer placement and site-specific management. In addition to promoting C sequestration, BMPs can also improve crop yields by reducing soil erosion and degradation while improving water quality by reducing silt and agricultural runoff into nearby waterways.

For your average Northern California organic farmer, such practices are holy writ. But how hard is it to see that they should be the law of the land? That no agribusiness or venture capitalist should even be allowed to start writing a business plan without demonstrating how a particular biofuel strategy conforms to the most stringent requirements for maintaining soil fertility? So far, it has been difficult to ascertain any "caution" in the current U.S. rush to pump up ethanol production. But there's no time like the present. Congress is about to start debating the nitty-gritty of a new Farm Bill. We'd all be a lot better off if the soil scientists at Swan Lake Research Farm had final say over its contents, instead of Archer-Daniels-Midland and Cargill.

By Andrew Leonard

Andrew Leonard is a staff writer at Salon. On Twitter, @koxinga21.

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