Goal: Grow and maintain sustainable soil fertility

"The grandfather keeps sheep, the son keeps goats, the grandson keeps nothing."

—Richard St. Barbe Baker, My Life, My Trees

Sustainability means living in such a way that there are enough resources to live well in an alive, diverse, thriving environment—indefinitely.

Sustainability is possible—individual people, families, and communities accomplish this frequently all around the world. Yet most people find this challenging. Many of us are living on 6 times—or more—the resources that would be available to each person in the world, if the resources were divided up equally!

We often think of sustainability in terms of using nonrenewable resources carefully. More important, however, is using renewable resources well. If all the earth's agriculture became organic tomorrow, it would be wonderful and challenging. A more healthy resource-conserving, food-raising, and planetary ecosystem would be possible. However, the cost of purchasing the cured compost needed to grow food organically would be too high because the demand would exceed current supply. For that reason, we need to properly preserve, manage, and develop our renewable resources. Soil, for example, needs a given level of humus, or cured compost, in order to thrive. We each need to make sure we grow enough organic matter for our own needs.

For a garden or mini-farm to be sustainable, it must be able to produce sufficient crops to provide the gardener or farmer with what she or he needs over an indefinite period of time. This is possible only if the mini-farm's soil is kept fertile in a way that relies neither on nonrenewable resources, such as petroleum, nor on the nutrients or health of another soil. Most chemical fertilizers and pesticides are created in part from petroleum, which also fuels tractors, processing machinery, and transport vehicles. While organic fertilizers may seem to be a good alternative, their production relies on another farm's soil being able to produce the raw materials, such as alfalfa, cottonseed, and feed for animals that provide bone and blood meals. With these materials constantly taken away from the soil that produces them, these soils lose nutrients and eventually become depleted and infertile.

When our focus is on harvesting as much as we can from the soil, we forget to give the soil what it needs to remain fertile. We must grow soil in a way that is sustainable. Only then can it continue to provide us with abundant food. If we farm in a way that does not sustain soil fertility, the soil that is currently used to grow crops will soon be able to grow only fodder for sheep, later only scraggly weeds for goats, and then nothing at all.

The Loss of Soil Nutrients and Humus

When soil grows crops, it loses the nutrients the crops extract as well as the humus that the soil microorganisms consume. To maintain the soil's fertility, the nutrients and humus must be replenished. Both of these requirements can be met simultaneously when the crop and all other residues from those who consumed the edible portion of the crop are composted and returned to the soil. The cured compost will have almost all of the nutrients that the crop contained and, depending on the crops that are grown, enough humus to replenish the soil's supply. (Also, see Future Fertility.)

The carbon that left the soil in the form of carbon dioxide will be returned if plants that store a lot of carbon in their bodies (such as corn, amaranth, wheat, and rice) are grown and added to the soil as cured compost. These kinds of compost crops should optimally be grown on about 60% of the farm area over the course of a year in order to generate enough cured compost to maintain the soil's fertility.

Initially Adding Nutrients and Humus to the Soil

Not all soils naturally have all of the nutrients they need for their optimum health and crop productivity. Deep-rooted crops such as alfalfa and comfrey can be grown to bring up nutrients from below the range of most roots, then composted and added to the topsoil. However, if the needed nutrients are not in the deeper regions of the soil, they will not be present in the cured compost. On the other hand, when cured compost is added to the soil, nutrients that were previously unavailable in the soil may be made available by the biogeologic cycle.

In the biogeologic cycle, humic acid—which is produced from the decomposition process and is contained in the cured compost—along with the carbonic acid developed around the plant's roots, can increase soil microbial activity, decompose larger minerals, and possibly alter soil pH so that previously unavailable nutrients are made available. However, if the nutrients are not in the soil in the first place, even in an unavailable form, the cured compost made from plants grown on the nutrient-deficient soil will not contain the deficient nutrient, and the soil will still be unbalanced after the cured compost is added. Therefore, in some cases, you may need to bring nutrients in the form of organic fertilizers into the mini-farm from the outside, but probably only on a one-time basis, before the mini-farm can be maintained sustainably.

You may also need to bring carbonaceous materials into the garden or mini-farm in the beginning so sufficient humus can be added to the soil. Humus is the food of soil microorganisms that are responsible for creating good soil structure and soil fertility. It also helps hold the nutrients in the soil. If there is not enough humus (about 4% to 6% organic matter in temperate regions; about 3% organic matter in tropical ones), nutrients that are returned to the soil in the form of cured compost may leach out.

Losses = Gains?

Some nutrients will escape from the garden or mini-farm, whether from leaching, from rainfall runoff, or from the wind picking them up and carrying them away (although water and wind erosion are usually not a problem when the soil's humus supply is maintained and all of the grow biointensive techniques are used). At the same time, however, nutrients are added naturally to the mini-farm through rainfall, wind, the breakdown of the soil's parental rock material, and the upsoak-ing of groundwater. With grow biointensive sustainable gardening and mini-farming, the gain in nutrients may eventually be approximately equal to the loss of nutrients, and the soil's nutrient balance may be maintained if all nutrients are recycled.

100% Sustainability Impossible

According to the Second Law of Thermodynamics, all systems proceed toward a state of entropy or disorder. Therefore, no system, including agriculture, can be sustained indefinitely. At the extreme, all mini-farms will cease, as will all life as we know it, when the sun burns out millions of years from now. However, until this happens, we can maintain our soils at a level close to complete sustainability (instead of close to complete insustainability, as is now the situation with most agricultural systems). Within a garden or mini-farm, some soil nutrients may not be replenished by natural forces, or the same natural forces may add soil nutrients in excess. In both situations, if proper soil nutrient maintenance is not pursued, the soil may cease to be able to grow significant amounts of crops in a very short period of time.

The Need for up to "99%" Sustainability

At Ecology Action, we are looking for the quickest, most effective, most resource-conserving, and most ecologically sound ways to replenish and balance soil nutrients. Once the soil's nutrient base has been properly built and balanced, we need to learn how best to maintain those nutrients in our gardens and mini-farms. One promising approach is to grow all of our own compost materials in sufficient quantities so that the cured compost we add to the soil contains as many of the nutrients the crops removed from the soil as possible, as well as enough humus to feed the soil microbes and prevent nutrient leaching. In this way, our food-raising area becomes a source—rather than a sink—of carbon, nutrients, and fertility. (The net loss of carbon dioxide, or "leakage," from the system is a key concern. Worldwide, the loss of carbon from our soils—and plants in the form of harvested trees and their use for fuel—is a situation causing increasing problems.)

Keeping the nutrients within the mini-farm, as well as learning how to minimize the amount of nutrients we need to bring in from the outside, are important tasks if we are to grow all of our food, clothing, and building materials on the 9,000 square feet (or about V5 of an acre) that may soon be all that is available to each man, woman, and child living in developing nations (see "A Perspective for the Future"). Soon we simply will not have the luxury of taking nutrients from one soil to feed another.

With about 42 to 84 years' worth of topsoil remaining in the world, learning how to enrich, improve, and maintain soil— in a way that is sustainable—is of vital importance if we, as a species, are to survive. If they can only provide food for about a century before they deplete the soil, the agricultural systems that have brought us to where we are now are clearly not sustainable. Ancient civilizations sustained their soils to feed large populations for lengthy periods of time. China's soils, for example, remained productive for 4,000 years or more until the adoption of mechanized chemical agricultural techniques that have been responsible, in part, for the destruction of 15% to 33% of China's agricultural soil since the late 1950s. Many of the world's great civilizations have disappeared when their soil's fertility was not maintained. Northern Africa, for example, used to be the granary for Rome until overfarming converted it into a desert, and much of the Sahara Desert was forested until it was overcut.

Ecology Action's Pursuit of Sustainability

When Ecology Action began the Common Ground MiniFarm in Willits, California, the soil was so infertile that many carbonaceous compost crops did not grow well. In an effort to improve the soil so it could grow all of the carbonaceous compost material needed to provide the mini-farm with sufficient cured compost, carbonaceous compost material (straw) and nutrient-containing horse manure were imported to the mini-farm. This approach eventually did not feel appropriate because we were importing a significant amount of carbon. Consequently, we limited our compost building to include materials produced by the mini-farm whenever possible. However, because many crops we were testing did not contain much carbon, the mini-farm produced significantly less carbonaceous compost material than was needed to increase and maintain the soil's fertility. Without sufficient cured compost, the soil began losing the humus it had, and its ability to grow sufficient organic matter declined.

While we still chose to grow some experimental crops that did not produce a significant amount of carbonaceous compost material, we grew more of our own compost material than before and supplemented our supply of carbonaceous compost material with purchased straw, goat litter (primarily from outside fodder inputs), and/or straw from noncrop areas.

We have been getting closer to achieving closed-system soil humus sustainability within the limits of the mini-farm and are now working toward closed-system soil humus sustainability by using compost materials grown primarily within the limits of the growing beds that receive cured compost. In the future, we will be emphasizing the growing of an even larger percentage of the carbonaceous compost material we need each year, and will continue to do so until we are growing all of this material ourselves in our own growing beds. In addition, we are exploring different levels of maintaining sustainable soil fertility. These methods involve using different amounts of cured compost (depending on its availability), with different corresponding crop yield levels resulting.

Current Goals of Understanding and Achieving "99%" Sustainability

Our goals are to understand how a garden or mini-farm can

  • produce all of its own compost material initially without having to import any straw, manure, or other carbonaceous material for the soil's humus sustainability,
  • maintain nutrient sustainability.

Because we are not currently returning the nutrients in our human urine and manure to the mini-farm's soil, we need to import some organic fertilizers to maintain the nutrient levels and balance in the soil. However, for the future, we are exploring ways to safely, effectively, and legally return the nutrients in our waste to the soil from which they came.

How to Better Sustain Your Soil's Fertility

In order to more easily sustain the fertility of your soil, you should divide your growing area as follows:

  • approximately 60% in carbon-and-calorie crops that produce large amounts of carbon for compost and that also produce food in the form of significant amounts of calories (To grow the nitrogen needed to make a good compost, legumes will need to be interplanted with these crops; for example, fava beans among wheat in winter and bush beans with corn in summer. See The Complete 21-Bed Biointensive Mini-Farm and One Basic Mexican Diet for more details.)
  • approximately 30% in special root diet crops that produce large amounts of calories
  • a maximum of 10% in vegetable crops for additional vitamins and minerals (Up to 3/4 of this area may be planted in income crops if the missing needed vitamins and minerals are provided by V4 of the area.)

See the information on pages 28 and 29 for details. We hope these guidelines will make your path to sustainability easier.

In order to mini-farm sustainably, the following goals should be taken into account as you grow compost crops and apply compost:

GOALS* FOR COMPOST AND SUSTAINABLE SOIL FERTILITY** Per 100 sq ft per 4- to 6-month growing season

Mature Immature Potential

Material Material Compost Application c to Grow to Grow (including 50% soil) Y. ,, lb/100 sq ft lb/100 sq ft grow biointensive amount 15 lb for a beginning level of and up sustainable soil fertility**

for Biosphere II*

grow biointensive amount 30 lb for an intermediate level of and up sustainable soil fertility

One expert's "good" amount —

of compost for soil fertility and productivity grow biointensive amount for 60 lb a high level of sustainable soil and up fertility

90 lb and up

180 lb and up

360 lb and up

2 cu ft

4 cu ft

3 1/4 inch 5gB

4.2 5gB

6 5gB

1/3 inch

1/2 inch

*including approximately 50% soil

Organic Gardeners Composting

Organic Gardeners Composting

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  • peter
    How to make my soil fertile?
    8 years ago
  • Louise
    What is sustainability grown vegetables?
    8 years ago
  • estella labingi
    Is GROW BIOINTENSIVE good for humus production?
    7 years ago

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