Building and maintaining soil fertility is one of the most important tasks of any farmer. Organic farmers in particular face new challenges in finding a good source of fertility. Since the new federal organic standards were passed, the use of both compost and manure has become more tightly regulated. With the new restrictions on using the old classics, many farmers have moved to using processed fish fertilizers such as Bio-gro as their main fertility source. This type of fertility is reliable and easy to apply, but it can hardly be called sustainable.

Chi Scherer and his wife Michelle, who farm about 10 acres in Williams, Oregon, have found their source of fertility much closer to home. They build their soil right where it is, in the field, through an intensive program of annual and perennial cover cropping. Chi has turned to cover cropping as the most ecological, sustainable, and self-reliant way to build soil. Their farm exemplifies what can be done, with minimum outside inputs, to manage fertility biologically and naturally. Chi and Michelle have been farming for more than 20 years in California and Southern Oregon. For the past 13 years they have worked and lived at Bluebird Farm in the foothills of the Siskiyous, where their major cash crops are carrots and beets. They also grow a full complement of other vegetables and have several hundred fruit trees and table grapes. They also grow a substantial amount of seed for Seeds of Change.

“The key to organic farming is organic matter,” says Chi, and cover cropping is the most economical, healthful way to get that needed organic matter into the soil. The nutrient-rich organic matter feeds microorganisms and earthworms and builds soil structure, what’s called “tilth.” Leguminous cover crops also add fertility by fixing nitrogen, and deep-rooted covers such as clovers mine nutrients from deep in the earth and recycle them into the top layers of soil. At the same time, cover cropping prevents erosion, crowds out weeds, and provides habitat for beneficial insects—and, as Chi’s farm proves, can be downright beautiful.

Through rigorous annual cover cropping, Chi all but returns the same fertility to the fields that he removes when he harvests production crops. The only additional fertility he finds it necessary to add is a minimal amount of composted chicken manure: one 5-gallon bucket per 75-foot, 48-inch bed.

Cover crops for field edges
According to Chi, however, cover cropping is not just for production areas. One of the most unique features of Chi’s farm is his attention to perennial cover crops in non-production areas. His farm is divided into permanent blocks of row crops, which are surrounded by a ground cover of grasses and clovers. The blocks are about 40 feet wide, which is the distance he needs between sprinkler rows. Any other area of the farm that is not in production (such as roads, ditch banks, and areas too sloped or too wet for cultivation) are also kept in perennial cover. Chi’s field is on a slight slope, and the grassy interludes divide the field into a series of terraces.

The result is a farmscape that is not only functional, but also possesses a harmonic order that borders on the beauty of a French garden. And the fruits and vegetables he produces are well worthy of the beauty of his farm.

Annual cover crops
One of the first steps in maintaining soil fertility and tilth is never to leave it bare. “Plants are the skin of the earth,” says Chi. “So whenever you uncover it, you’ve created a wound.” He quickly heals the “wounds” that he makes when he turns the soil by planting either a cover crop or a production crop. Harvest isn’t considered complete until the ground has been seeded to a cover crop; and he waits until the last possible moment in the spring to till in his cover and prepare the beds for production.

Incorporating organic matter fluffs the soil up like a sponge: It makes the soil more capable of both absorbing and retaining water. The soil drains more slowly and evenly without puddling. It becomes more stable and less susceptible to erosion. It doesn’t compact under winter rains and is still fluffy in the spring when the cover crop is tilled under.

Cover crops also add another dimension to crop rotation: Chi rotates his blocks between fruiting crops such as tomatoes and peppers, vegetative crops such as greens and lettuce, root crops such as carrot and beets, and grain crop such as corn and amaranth—but in addition, between each of these production crops he grows at least one soil-building cover crop.

Cover cropping prevents weeds from becoming established and, in the process of increasing the fertility of the soil, speeds up the evolution of weed species from noxious pioneer weeds (which can be heavily rooted and hard to pull) to fertile-soil weeds, such as purslane and chickweed, which are more easily eradicated.

Chi emphasizes that maintaining the right carbon-to-nitrogen ratio in your soil is just as important as it is in your compost pile. The correct balance can be achieved by cover cropping with a grass-legume combination. Legumes provide some carbon, but most importantly fix atmospheric nitrogen into a form usable by plants. Grasses, on the other hand, provide some nitrogen, but most importantly provide carbonaceous biomass to balance the nitrogen provided by the legume.

Grasses are also rich in in phosphorous and calcium. They “recycle” these minerals by taking them from the soil and incorporating them until they break down into nutrient-rich organic matter. In this way the minerals are made more available for the next production crop.
Grasses and legumes complement each other in other ways as well. Grasses are hardier than legumes and establish themselves more quickly in the fall. They provide a good ground cover through the cooler, wetter months of winter, while sheltering the younger legumes. As spring progresses, the legumes begin to dominate, until the field blocks are rich with the waist-high, broad-leaf beans.

Chi’s winter cover crop of choice is a mix of bell beans (a type of fava) and oats. Chi has found that in his bioregion favas create the most biomass, and that since oats are more broad-leaved and faster growing than rye, they also create a little more biomass.
Other grass-legume combinations may work just as well or better in other bioregions. Annual rye is a more cold-hardy substitute for oats and makes a good combination with Austrian peas or vetch (both legumes). When grown together, the peas and vetch can climb on the scaffolding provided by the sturdy rye stalks instead of matting on the ground.

Chi usually plants his winter cover crop from September 15 to October 15. Once in a while, if he has an especially late crop, such as a carrot harvest just finishing up around Thanksgiving, he won’t have time to get a cover crop established before the weather turns too wet and rainy. In that case, he will let the weeds grow at the end of the carrot cycle so that he’ll have at least some sort of protective covering over the ground through the winter.

For summer cover cropping, Chi uses a combination of buckwheat and beans (cowpeas, or any summer bean he has leftover seed for), or sometimes just buckwheat. Once in a while Chi will grow two production crops successively in the same block; for instance, an early onion crop and a late greens crop. But if space allows that late greens crop to go elsewhere, he will plant the ground to buckwheat and beans. Since it only takes 30 days for buckwheat to flower, he can often get a quick rotation in before it’s time to plant the winter cover. Sometimes he will also plant a quick spring rotation of buckwheat after the winter cover has been worked in and before summer crops are set out.

Buckwheat is also good for acidic soils, since it raises the pH in the same way lime does. Buckwheat is also rich in calcium and magnesium.

Perennial cover crops
Before Chi moved to his current land 13 years ago, it had been heavily pastured. In traditional pastures, there is generally too much grass in relation to broad-leaved plants and clovers. The grasses are generally non-native, relatively invasive grasses that were brought in by cattle ranchers, as opposed to the native bunch grasses. The non-native grasses generally overwhelm any beneficial broad-leaved plants.
In other words, most ground covers have too much carbon with respect to the available nitrogen—just as in a compost pile that has too much straw with respect to manure. Decomposition is stifled, the population of microorganisms decreases, and the soil’s fertility gradually degrades.

In land that is not to be used for annual crops, the way to remedy the carbon-nitorgen imbalance is to establish perennial clovers among the grasses. Just as the oats and bell beans balance each other in Chi’s annual cover, orchard grass and clovers balance each other in his perennial cover.

In the cycle of the season, grasses predominate in the colder weather of early fall and winter. This is good because the clover alone couldn’t provide enough protection for the soil, since in the colder months it dies back close to its crown. With the onset of warmer weather in the spring, the clover kicks in and becomes a stronger presence Frequent mowing also favors the clover, since it grows back faster than grass after being cut. Clover also provides a good nectar source for beneficial insects.

When Chi initially broke the sod on his farm, he started broadcasting clover and orchard grass seed anywhere not in annual production. He broadcasts three types of clover: ladino clover which does better in full sun, New Zealand white clover which prefers the shade, and red clover which pushes the deepest roots to mine nutrients from where they would otherwise be inaccessible.

Of course many of the pasture grasses have re-established themselves in his ground cover. But he has also seen a notable increase in native broad-leaf species such as plantain, dock, and dandelion—medicinal herbs which Chi and Michelle have used at home and for sale. Chi re-broadcasts clover seed about every three years, to make sure the grasses don’t encroach too much.

The benefit of the perennial ground cover can be seen clearly in Chi’s orchard. In the first three years after Chi planted his fruit trees and grapes, he fed them with compost. He grew annuals between the orchard rows while the trees were still small, but now that the trees are grown and he has planted the rows of annuals to perennial cover, he finds it unnecessary to feed his trees or vines with any type of additional fertilizer. They are fed only with the mulch that is spread after each mowing of the cover crop. And his trees and vines continue to bear more and more fruit for him each year.

The steady feed of green manure echoes the way the earth feeds itself. Leaves steadily drop to the ground, grasses grow up and die, providing a slow, steady supply of organic matter to the soil and its host of microorganisms, earthworms and beneficial insects.
Chi mows half the farm each week. That way, any given part of the farm is mowed every two weeks. Frequent mowing ensures that the plants are cut back before they put energy into seed. The grasses and clover are turned into a nourishing mulch when they are at their most succulent, vegetative stage. Mowing also allows light and air circulation around the production crops, and provides habitat for beneficial insects, without creating harbor for too many insect pests. Chi spends a lot of time mowing, but as he says, “You have to be diligent to get the full benefit out of the program. . . . Some people think I just like having nice lawns, but this is my fertility program right here.”

Rachel Airmet farms in southern Oregon with her partner Mark Bassik. She is also a free-lance writer on small-farm issues. She most recently wrote about her experiences as an intern in the April issue of Growing for Market. She can be reached at rairmet@yahool.com