Organics, Erosion & Carbon

Posted by .

During a recent committee hearing at the capitol, a legislator offered up an anthoritative-sounding agronomic nugget of information: organic farming is bad for the environment. Specifically, the argument was made that organic cropping systems increase soil erosion and contribute more greenhouse gases to the atmosphere than their conventional counterparts. It’s the kind of clever, counter-intuitive statement that can stop a discussion about public funding of organic/sustainable ag research dead in its tracks. But, of course, there is much more to the story. In fact, there is mounting evidence that organic cropping systems provide more environmental benefits than first thought. It’s also becoming clear that a lot could be gained via some cross-pollination between “organic” and “conventional” agriculture. But those connection will not be made without a publicly-funded financial push.

At the core of the organic-ag-is-bad-for-the-environment argument is a simple thesis: since organic crop production doesn’t rely on chemicals to control weeds, it must utilize a lot of heavy tillage. Heavy tillage leaves the soil bare, leading to erosion and releasing greenhouse gases into the environment.

The backlash against organic agriculture’s use of tillage gained even more credibility as conservation tillage systems came into prominence in the 1980s and 1990s. At its most basic, conservation tillage is any cropping system that attempts to leave at least one-third of the field’s surface undistrurbed. Many variations of the system have evolved over the years. On the more mainstream end of the spectrum is “mulch tillage,” which uses a chisel plow to mix dead plants and soil, leaving approximately 30 percent of the soil surface covered with residue. “No-till,” on the other hand, leaves as much as 80 percent of the soil surface protected. The only tillage is the soil disturbance when a narrow slot is cut for the seed.

Soil conservation-wise, just about any breed of conservation tillage is a vast improvement over the conventional system of using moldboard plows, discs and various other pieces of heavy steel to turn, level and otherwise pulverize the soil into submission. “We’re stirring these soils up to the point where it’s like a sandbox,” a southwest Minnesota crop farmer once told me.

But conservation tillage systems rely on heavy dosages of herbicides to control weeds. In fact, USDA figures show than no-till acres consistently receive more herbicide applications than their conventionally-tilled counterparts. The Conservation Technology Information Center, a public-private partnership which is seen as a leader in providing conservation tillage information, has agrichemical heavy hitters like Monsanto and Syngenta represented on its board of directors. When soybeans that were genetically engineered to withstand applications of the herbicide glyphosate hit the market in the mid-1990s, no-till farmers were some of the first to buy them. By 1999, the volume of glyphosate (Monsanto’s Roundup is the most well-known namebrand glyphosate herbicide) used in the U.S. almost doubled.

Conservation tillage’s reliance on chemicals has left environmentalists feeling a little bit quesy—were we solving one environmental problem (erosion), by creating another (increased chemical use)? The issue became even more clouded on Sept. 15, 2000, when the respected journal Science published the results of a study that showed no-till agriculture sequestered more greenhouse gases than organic cropping systems.

As concerns about conservation tillage’s heavy reliance on chemicals have become more widespread, supporters of this type of farming defend it by pointing out its soil-saving and greenhouse gas-sequestering attributes. And in an era of high fuel prices, conservation tillage’s ability to reduce the number of times a farmer drives over a field has also become a major plus.
Oh the irony! All of a sudden organic cropping is being portrayed as not an eco-friendly system at all, but in fact an environmental disaster. And chemicals are being presented as the best friend our water, soil, air and wildlife ever had. At least that’s what apologists for the agrichemical and fertilizer industries, such as Dennis Avery, are arguing.

Indeed, I’ve seen firsthand how mimimum tillage systems that rely on heavy dosages of herbicides can provide some pretty good soil protection. Ever see a field of soybeans genetically engineered ro resist herbicide after they’ve been sprayed with Roundup? When the grasses and other weeds between the rows expire, they can form a nice soil-saving mulch. And I’ve also seen what happens when farmers convert highly-erosive Conservation Reserve Program acres into organic crops without any transition. All that chemical-free tillage can send soil downhill fast.

But these are examples of farming techniques being practiced in isolation of each other, rather than within a holistic system. Those Roundup-Ready soybeans may protect the soil, but how many petrochemicals went into producing the herbicide? And how much more herbicide will have to be sprayed to deal with the superweeds that inevitably evolve when so much of one chemical is used?

Yes, organic cropping systems that rely on heavy tillage rather than diverse crop rotations, cover crops, green manuring and a gradual build-up of organic matter can be bad for long-term soil health. But there’s a difference between an organic “system” and an organic “method.” Organic systems build up a field’s natural ability to ward off weed and insect pests while cooking up innate soil fertility. That takes time. A single organic “method,” such as simply replacing a post-emergence herbicide with mechanical weed control provides a short-term fix, but doesn’t give that field the ability to become organically self-reliant.

The inability of the conventional agriculture community to recognize the difference between methods and systems is having negative impacts out in the field. The USDA’s Conservation Security Program, which rewards farmers for using environmentally friendly methods, has done a poor job of recognizing the ecological benefits of resource-conserving crop rotations—alfalfa, small grains, etc.—in organic cropping systems. As a result, in many cases organic crop farmers have been bumped out of the program, or given lower payments, while their conventional counterparts who utilize conservation tillage (and chemicals) are rewarded by the government.

An increasing number of studies are showing that organic cropping systems are in fact not only saving soil, but offer great potential for reducing greenhouse gases, particularly when one takes into account the fact that they don’t rely on energy-intensive chemical pesticides and fertilizers. In a study published in the journal Nature. scientists compared similar soils that were under conventional and organic cropping systems. They found that the organically-farmed soil had significantly higher organic matter content and was less erosive than the conventionally farmed soil.

The researchers concluded that organic cropping systems are much more effective at maintaining a soil’s long-term productivity. In fact, excessive use of commercial fertilizers such as urea nitrogen is aging our soil well beyond its natural life-cycle. The application of agricultural inputs over a three-decade period has aged soil at one Wisconsin research plot the equivalent of 5,000 years. When one considers that the soil is “only” 10,000 years old to begin with, that’s alarming. “The change is irreversible,” says Phillip Barak, a University of Wisconsin associate professor of soil chemistry and plant nutrition.

Some of the most interesting research on organic cropping and its overall environmental impacts has been done at the Rodale Institute in Pennsylvania. The Farming Systems Trial study has shown that organic soils “scrub” the atmosphere of greenhouse gases by capturing carbon dioxide and converting it to soil material. The study has found that over a 23-year period, soil carbon increased 15 percent to 28 percent in the organic systems studied. The organic soils, on average, sequestered about 3,500 pounds of carbon dioxide per acre-foot annually. Such results caught the attention of the Pennsylvania Departments of Agriculture and Environmental Protection, which agreed to support further research in this area.

It turns out the conventional wisdom that no-till farming systems automatically sequester more carbon is based on some pretty shaky science, say people like John Baker, who is research leader with the USDA’s Agriculture Research Service, and is based at the U of M. In a commentary published in Agriculture, Ecosystems and Environment, Baker and other researchers make a good argument that reducing tillage alone won’t trap a significant amount of carbon in the soil. Their analysis concluded that rather than sequestering carbon, conservation tillage just redistributes organic carbon in the soil profile. The authors conclude: “Though there are other good reasons to use conservation tillage, evidence that it promotes C sequestration is not compelling.” Now there’s a heartburn-inducing statement for all those coal-burning utilities forking over greenbacks to no-till farmers via “emissions-trading” arrangements.

Other research Baker has been involved with shows that cover crops such as rye hold great potential for helping a corn-soybean system sequester carbon in places like Minnesota. Cover crops such as winter rye are planted in the fall, providing important ground cover and the kind of biological activity that ties up carbon during those times of the year—late fall and early spring—when corn and soybean fields are usually bare. As an added benefit, cover crops cut erosion and can help preseve soil moisture.

A recent paper co-authored by Edward Nater, head of the U of M’s Department of Soil, Water and Climate, concludes that, “Although only limited data are currently available, they strongly suggest that cover crops have the potential to dramatically increase the potential of the corn-soybean system to sequester carbon in Minnesota.”

That news needs to get out to those USDA Natural Resources Conservation Service staffers that are failing to recognize the benefits of resource-conserving crop rotations when writing up Conservation Security Program contracts.

The kind of research being done by the likes of Rodale and John Baker is exciting, precisely because it points to an important truth: there is no one farming method, or farming system for that matter, that offers the silver bullet solution to our many environmental problems. But systems that blend all of these various elements hold tremendous potential.

I’m reminded of a study involving Minnesota test plots that evaluated a two-year corn-soybean rotation and a four-year corn-soybean-oat/alfalfa-alfalfa rotation under conventional and organic management production strategies. The researchers found that adding alfalfa and small grains like oats to a crop rotation builds soil quality while naturally breaking up weed and insect cycles, thus eliminating, or at least reducing significantly, the need for chemical fertilizers and pesticides.

On the face of it, the results are only relevant to farmers seeking to go organic. But the study had positive implications for producers who decide to stick with chemicals but are willing to expand the rotation beyond the typical corn one year, soybeans the next, routine. The researchers found that conventional soybeans grown in a four-year rotation yielded 3 percent to 6 percent more than their counterparts grown in a two-year rotation.

What if we combined the best of no-till (reduced soil disturbance, fewer trips across the field) with the most positive elements of organic production (diverse crop rotations that build soils, cover crops, sequestering of carbon, cutting nasty chemicals)? There are scientists and farmers doing that right now. Pursuing Conservation Tillage Systems for Organic Crop Production offers a nice summary of what can be done to reduce soil erosion while protecting the general environment in an organic system. Published by ATTRA, the publication describes how farmers raising everything from small grains to corn to vegetables are showing that organic production can be done without intense tillage. One prime example is the Dick and Sharon Thompson farm in Boone, Iowa, where a hybrid conservation tillage system called “ridge till” has been used to produce row crops organically. Farmers like the Thompsons would not fit the strict definition of “no-till,” because they do use mechanical cultivation to control weeds. However, research on the farm shows their soil is staying in place and is building up its own organic matter.

But a lot more research must be done before chemical-free conservation tillage becomes the norm. It’s not an easy system to master, and farmers can’t afford to experiment on their own. The majority of conservation tillage has been built around chemical use because major chemical companies are funding a lot of research in this area. Little private sector funding is available to investigate organic conservation tillage because it doesn’t rely on a lucrative input farmers can buy.

If such a system were to become widespread, it would create a public good environmentally and economically, and thus research in this area needs to be publicly funded. And that’s where the Minnesota Legislature comes in.

Comments are closed.