Take cover
Let’s not lose our grip on nature’s genetic tools to help heal the earth.

By Genevieve Slocum

editor's NOTE:

Last season our interns took turns tracking their observations and sharing what they were learning as they helped out the various departments here at The Rodale Institute.

This next generation of farmers offered insights into what motivates them to go against the tide when so many farm families struggle to keep up-and-coming generations interested in farming.

As the season turned colder, most of our interns left us for greener pastures. Genevieve Slocum stayed on a little while longer and continued to share her experiences here in Intern Journals.

Now Genevieve is leaving and heading to 14 Acre Farm in Jim Thorpe, Pennsylvania, to make room for a new season of interns here at the Institute.

--NF Editors

Posted April 12, 2007: What the world needs now is cover crops (and love, yes). There is too much bare, eroded, over-exploited ground, and not enough stuff anchoring it and revitalizing it.

This is something not only farmers should care about (and I know that apathy is not difficult, because before I came to work as an intern at The Rodale Institute, the concept was meaningless to me as a non-farmer). There are cover crops for every soil type, climate and nutrient-deficient terrain. There are cover crops to satisfy even the most demanding and high-maintenance vegetable or field crops. There are some that are prepared to survive even the cruelest conditions, reclaim marginal land and begin to remedy today’s most pressing environmental concerns, from global warming to the depletion of finite resources like topsoil, soil nutrients and water (problems that non-farmers in the industrialized world are rarely confronted with).

Individuals who work directly with these resources have to face the effects of their scarcity. Sadly, as mere individuals, they are often ill-equipped and ill-informed to reach a solution.

The genetic resources of cover crops have vast and often untapped potential. Our agricultural industry seems bent on whittling down the crop gene pool to select for only the highest-yielding varieties that can be cropped intensively and homogenously, disregarding other attributes, and then solving the problems it has created through the artificial variation of genetically engineered crops and chemicals to match. We had everything we needed at our fingertips in the now-dwindling natural gene pool, and that genetic material was actually integral to its environment (with safe and predictable “side effects”).

One grim manifestation of this genetic consolidation and loss of biodiversity is that at least one-quarter of the food products sold today contain several ingredients derived from a single crop—corn. As Michael Pollan observes in his recent bestseller The Omnivore’s Dilemma (Penguin, 2006), “The food industry has done a good job of persuading us that the forty-five thousand different items or SKUs in the supermarket—
seventeen thousand new ones every year—represent genuine variety rather than so many clever rearrangements of molecules extracted from the same plant.”

Cultivar trials present us with an array of valuable traits that can be endlessly combined and recombined in polycultures or selection processes. Adaptability and versatility of the cover crop can be as important or more important than that of the main crop, since it is setting the stage by building up nutrients, soil structure and permeability (important for the more efficient use of water and nutrients).

After the rollercoaster ride of a winter we had this past year, the resilience of many of our overwintering crops was striking, as was the greatly varying levels of resilience among different cultivars of the same crop. Winter annual, biennial and perennial plants never cease to amaze me in their capacity to endure extremely harsh conditions. Even a brown, lifeless, crunchy mess can often belie a rich life-support system (concealed underground or in small nubs pushing from the base of the stem) of stored carbohydrates, ready to send up tender green shoots at the first blush of warm weather.

Many of our hairy vetch accessions that appeared to be winter-killed had, upon closer examination, new shoots with baby leaves beginning to unfold. Others simply had a deceptive brown top layer that sheltered surviving life just below. Our cover of ladino clover (a perennial clover) is at first glance just a dense brown mat of residue. Peel back this layer, however, and you find thick, green stems pushing out rows of unfolding leaves. The biennial clovers—tall, dead stalks—showed the first signs of regeneration with barely perceptible green buds next to the base.

A robust and extensive root system is the plant’s true engine for survival and growth. Too much aboveground biomass before temperatures drop below freezing can actually be a liability, especially in leguminous crops with vulnerable nitrogen-rich tissue. The root and crown (the interface between root and stem) have thick, hardy tissue with high carbon content, storing sugars and carbohydrates throughout periods of cold weather. Our greenhouse trials of hairy vetch from different seed tag origins illustrated that the hardier hairy vetch from Nebraska or Minnesota did not at first produce the most rapid growth, but tended to put out multiple stems more quickly, evidence that crowns had formed. Crowns are crucial because they will be responsible for generating the plant’s second-year growth after overwintering.

Hairy vetch turned out to have a high threshold for pain, and therefore is one of the most widely adaptable cover crops across many different climates. Our evaluation revealed that the majority of kill took place after temperatures dipped below 15°F and remained around 5°F-7°F for a period of time. If there had been snow cover during this time, the vetch probably would have survived. Even the insulation provided by a nurse crop of oats was sometimes enough shelter for the vetch, since the dense bent-over residue formed a tent under which we found perfectly green vetch in late March.

Winter-hardiness is just one genetic dimension to consider for cover crops in a rotation. Sweetclovers are another highly adaptable cover crop that can tolerate a wide range of conditions and whose uses range from green manure to forage to bee pasture to mine reclamation solution. Our 2006 crop of annual sweetclover (also known as Hubam clover) was a prolific nectar producer and was a constant hum of insect life. Each of its racemes may contain as many as 100 flowers, with up to 1,500 flowers on a single plant. They most commonly draw honeybees, tachinid flies and large predatory wasps, which will keep harmful pests in check for the following crop and can help to break up existing pest life cycles. Irregularity of flowering times ensures an inflorescent season of several months.

Sweetclovers can grow in almost any ground that is not acidic—infertile, eroded soils, poorly drained soil, overly-drained soil, soil with too much organic matter such as peat, or clay soil with hardly any organic matter. It tolerates environments from sea level up to 4,000 feet in altitude. Its one major requirement is calcium. It improves any soil it grows in with its penetrating root structure that reaches several meters deep, breaking up compacted soil, improving drainage and soil tilth, and bringing leached nutrients from the subsoil up into more easily accessible regions of the soil profile. This makes it extremely valuable not only in a rotation or as a forage, but in restoring marginal or depleted land. It self-maintains with the vigor of a weed in these demanding conditions, reseeding itself every other year (or every year if it is an annual variety). Its high proportion of hard seed (about 50 percent), frustrating to seed producers and farmers, becomes a major survival asset, staggering the onset of germination and even delaying it for up to 20 years.

As a warm-season crop, sweetclover was widely used in the South before the advent of chemical fertilizers in the 1950s, especially in Texas. It grows more quickly in hot weather than any other crop, exceeding even alfalfa in its summer biomass production, and has no problem with drought. Annual sweetclovers are especially suited to hot weather. Prior to World War II, 500,000 to 600,000 acres were planted with sweetclover annually in Texas, and research from half a century ago on improving its forage quality and its use as ground cover is now being rediscovered at Texas agricultural experiment stations, especially as the price of oil—and synthetic nitrogen—skyrockets.

Legume cover crops, and cover crops in general, have fallen out of favor since World War II. When chemicals are readily available, and are quick and easy, who cares about planting an extra crop? The benefits to soil, the environment and even yield are not immediately apparent, and we want an input that “pays off” right away, a quick return on investment. Too often, techniques we have come to call “organic practices” are isolated, maintaining a distinct set of associations. We only turn to them when in sustainability mode; otherwise, they can stay up on their shelf. It is still a relatively niche market for a particular niche pattern of thinking, and we fail to see the big picture or the possible unexpected applications of organic cultural practices.

Environmentalists and farmers worry about preserving soil and defending the land against erosion, but they seldom choose cover crops as an immediate solution. Instead, overworked land is simply prescribed a “rest period” and taken out of production and commission. No-till methods are often claimed as the farmer’s panacea—just don’t break up the soil, and preserve its integrity, they are told. This is certainly a huge step in the right direction, but conventional no-till methods are typically used in monoculture or very short corn-soybean rotations and are still heavily dependent on herbicide applications for weed control, insecticides for control of such common pests as corn root worm, and synthetic nitrogen for fertility.

Cover crops add the crucial element of biodiversity, mixing in different combinations of rhizospheres (the plant’s root-zone environment and the most active microbial site in the soil) to the rotation, different nutrients and different pest cycles. No-till is indeed a positive step, but it too often fails to go far enough and ends up preserving the status quo of continuous corn or two-crop rotations with no true rejuvenation of the soil.

Planting cover crops is the proactive step to take, instead of falling into complacency or helplessness, believing the only way to protect endangered topsoil is simply to stop using it, or to disturb it a little less. Cover crops do have the potential to enhance tillage, no-tillage and minimum-tillage systems. They sequester carbon from the atmosphere and store it in the soil in the form of organic matter. They scavenge leached nutrients and enable the soil to better retain them in an available form, and they impede the lateral flow of water across the soil surface. They can survive unimaginable conditions and regenerate the ground into a habitable and fertile place for other species. There is a cover crop to fit almost any situation, and we can still reclaim this valuable gene pool and tap into its potential to rebuild eroded rangelands, grasslands, cultivated land and many other seemingly dead or abandoned corners of the earth.

On a personal note: The Rodale Institute is one of the few research stations in this country where it is possible to test crucial and groundbreaking organic practices on a long-term basis. Even the most basic organic management techniques are relatively dead to the mainstream agricultural consciousness, as the ag-chemical industry gains a deeper toehold in our institutions of higher learning, warping and corrupting our most trusted sources of knowledge and innovation. I feel extremely privileged to have had the opportunity to work as an intern at The Rodale Institute and to learn from its passionate researchers and staff. They are independent thinkers willing to run against the grain, and to put to the test what conventional agronomists say can’t be done. I want to thank them for their inspirational leadership, and for the support and vision of Ardath Rodale, without whom none of the Institute’s work would be possible.