Organic Gardener's Composting Part 15

Here's something I find very interesting. Temperate climates having seasons and winter, vary greatly in average temperature. Comparing annual decomposition loss from a hot soil carrying 2 percent humus with annual decomposition loss from a cooler soil carrying 5 percent, roughly the same amount of organic matter will decay out of each soil during the growing season. _This means that in temperate regions we have to replace about the same amount of organic matter no matter what the location._

Like other substantial colleges of agriculture, the University of Missouri ran some very valuable long-term studies in soil management. In 1888, a never-farmed field of native prairie gra.s.ses was converted into test plots. For fifty succeeding years each plot was managed in a different but consistent manner. The series of experiments that I find the most helpful recorded what happens to soil organic matter as a consequence of farming practices. The virgin prairie had sustained an organic matter content of about 3.5 percent. The lines on the graph show what happened to that organic matter over time.

Timothy gra.s.s is probably a slightly more efficient converter of solar energy into organic matter than was the original prairie.

After fifty years of feeding the hay cut from the field and returning all of the livestock's manure, the organic matter in the soil increased about 1/2 percent. Obviously, green manuring has very limited ability to increase soil humus above climax levels. Growing oats and returning enough manure to represent the straw and grain fed to livestock, the field held its organic matter relatively constant.

Growing small grain and removing everything but the stubble for fifty years greatly reduced the organic matter. Keep in mind that half the bioma.s.s production in a field happens below ground as roots. And keep in mind that the charts don't reveal the sad appearance the crops probably had once the organic matter declined significantly. Nor do they show that the seed produced on those degenerated fields probably would no longer sprout well enough to be used as seedgrain, so new seed would have been imported into the system each season, bringing with it new supplies of plant nutrients. Without importing that bushel or so of wheat seed on each acre each year, the curves would have been steeper and gone even lower.

Corn is the hardest of the cereals on soil humus. The reason is, wheat is closely broadcast in fall and makes a thick gra.s.sy overwintering stand that forms bioma.s.s out of most of the solar energy striking the field from spring until early summer when the seed forms. Leafy oats create a little more bioma.s.s than wheat.

Corn, on the other hand, is frost tender and can't be planted early.

It is also not closely planted but is sown in widely-s.p.a.ced rows.

Corn takes quite a while before it forms a leaf canopy that uses all available solar energy. In farming lingo, corn is a "row crop."

Vegetables are also row crops. Many types don't form dense canopies that soak up all solar energy for the entire growing season like a virgin prairie. As with corn, the ground is tilled bare, so for much of the best part of the growing season little or no organic matter is produced. Of all the crops that a person can grow, vegetables are the hardest on soil organic matter. There is no way that vegetables can maintain soil humus, even if all their residues are religiously composted and returned. Soil organic matter would decline markedly even in an experiment in which we raised some small animals exclusively on the vegetables and returned all of their manure and urine too.

When growing vegetables we have to restore organic matter beyond the amount the garden itself produces. The curves showing humus decline at the University of Missouri give us a good hint as to how much organic matter we are going to lose from vegetable gardening. Let's make the most pessimistic possible estimate and suppose that vegetable gardening is twice as hard on soil as was growing corn and removing everything but the stubble and root systems.

With corn, about 40 percent of the entire organic matter reserve is depleted in the first ten years. Let's suppose that vegetables might remove almost _all_ soil humus in ten years, or 10 percent each year for the first few years. This number is a crude. and for most places in America, a wildly pessimistic guess.

However, 10 percent loss per year may understate losses in some places. I have seen old row crop soils in California's central valley that look like white-colored blowing dust. Nor does a 10 percent per year estimate quite allow for the surprising durability I observe in the still black and rich-looking old vegetable seed fields of western Was.h.i.+ngton State's Skaget Valley. These cool-climate fields have suffered chemical farming for decades without having been completely destroyed--yet.

How much loss is 10 percent per year? Let's take my own garden for example. It started out as an old hay pasture that hadn't seen a plow for twenty-five or more years and where, for the five years I've owned the property, the annual gra.s.s production is not cut, baled, and sold but is cut and allowed to lie in place. Each year's acc.u.mulation of minerals and humus contributes to the better growth of the next year's gra.s.s. Initially, my gra.s.s had grown a little higher and a little thicker each year. But the steady increase in bioma.s.s production seems to have tapered off in the last couple of years. I suppose by now the soil's organic matter content probably has been restored and is about 5 percent.

I allocate about one acre of that old pasture to garden land. In any given year my s.h.i.+fting gardens occupy one-third of that acre. The other two-thirds are being regenerated in healing gra.s.s. I measure my garden in fractions of acres. Most city folks have little concept of an acre; its about 40,000 square feet, or a plot 200' x 200'.

Give or take some, the plow pan of an acre weighs about two million pounds. The plow pan is that seven inches of topsoil that is flipped over by a moldboard plow, the seven inches where most biological activity occurs, where virtually all of the soil's organic matter resides. Two million pounds equals one thousand tons of topsoil in the first seven inches of an acre. Five percent of that one thousand tons can be organic matter, up to fifty priceless tons of life that changes 950 tons of dead dust into a fertile, productive acre. If 10 percent of that fifty tons is lost as a consequence of one year's vegetable gardening, that amounts to five tons per acre per year lost or about 25 pounds lost per 100 square feet.

Patience, reader. There is a very blunt and soon to be a very obvious point to all of this arithmetic. Visualize this! Lime is spread at rates up to four tons per acre. Have you ever spread 1 T/A or 50 pounds of lime over a garden 33 x 33 feet? Mighty hard to accomplis.h.!.+ Even 200 pounds of lime would barely whiten the ground of a 1,000 square-foot garden. It is even harder to spread a mere 5 tons of compost over an acre or only 25 pounds on a 100-square-foot bed. It seems as though nothing has been accomplished, most of the soil still shows, there is no _layer _of compost, only a thin scattering.

But for the purpose of maintaining humus content of vegetable ground at a healthy level, a thin scattering once a year is a gracious plenty. Even if I were starting with a totally depleted, dusty, absolutely humusless, ruined old farm field that had no organic matter whatsoever and I wanted to convert it to a healthy vegetable garden, I would only have to make a one-time amendment of 50 tons of ripe compost per acre or 2,500 pounds per 1,000 square feet. Now 2,500 pounds of humus is a groaning, spring-sagging, long-bed pickup load of compost heaped up above the cab and dripping off the sides.

Spread on a small garden, that's enough to feel a sense of accomplishment about. Before I knew better I used to incorporate that much composted horse manure once or twice a year and when I did add a half-inch thick layer that's about what I was applying.

Fertilizing Vegetables with Compost

Will a five ton per acre addition of compost provide enough nutrition to grow great vegetables? Unfortunately, the answer usually is no. In most gardens, in most climates, with most of what pa.s.ses for "compost," it probably won't. That much compost might well grow decent wheat.

The factors involved in making this statement are numerous and too complex to fully a.n.a.lyze in a little book like this one. They include the intrinsic mineralization of the soil itself, the temperature of the soil during the growing season, and the high nutritional needs of the vegetables themselves. In my experience, a few alluvial soils that get regular, small additions of organic matter can grow good vegetable crops without additional help.

However, these sites are regularly flooded and replenished with highly mineralized rock particles. Additionally, they must become very warm during the growing season. But not all rock particles contain high levels of plant nutrients and not all soils get hot enough to rapidly break down soil particles.

Soil temperature has a great deal to do with how effectively compost can act as fertilizer. Sandy soils warm up much faster in spring and sand allows for a much freer movement of air, so humus decomposes much more rapidly in sand. Perhaps a sunny, sandy garden on a south-facing slope might grow pretty well with small amounts of strong compost. As a practical matter, if most people spread even the most potent compost over their gardens at only twenty-five pounds per 100 square feet, they would almost certainly be disappointed.

Well then, if five tons of quality compost to the acre isn't adequate for most vegetables, what about using ten or twenty tons of the best. Will that grow a good garden? Again, the answer must allow for a lot of factors but is generally more positive. If the compost has a low C/N and that compost, or the soil itself, isn't grossly deficient in some essential nutrient, and if the soil has a coa.r.s.e, airy texture that promotes decomposition, then somewhat heavier applications will grow a good-looking garden that yields a lot of food.

However, one question that is rarely asked and even more rarely answered satisfactorily in the holistic farming and gardening lore is: Precisely how much organic matter or humus is needed to maximize plant health and the nutritional qualities of the food we're growing? An almost equally important corollary of this is: Can there be too much organic matter?

This second question is not of practical consequence for biological grain/livestock farmers because it is almost financially impossible to raise organic matter levels on farm soils to extraordinary amounts. Large-scale holistic farmers must grow their own humus on their own farm. Their focus cannot be on buying and bringing in large quant.i.ties of organic matter; it must be on conserving and maximizing the value of the organic matter they produce themselves.

Where you do hear of an organic farmer (not vegetable grower but cereal/livestock farmer) building extraordinary fertility by spreading large quant.i.ties of compost, remember that this farmer must be located near an inexpensive source of quality material. If all the farmers wanted to do the same there would not be enough to go around at an economic price unless, perhaps, the entire country became a "closed system" like China. We would have to compost every bit of human excrement and organic matter and there still wouldn't be enough to meet the demand. Even if we became as efficient as China, keep in mind the degraded state of China's upland soils and the rapid desertification going on in their semi-arid west. China is robbing Peter to pay Paul and may not have a truly sustainable agriculture either.

I've frequently encountered a view among devotees of the organic gardening movement that if a little organic matter is a good thing, then more must be better and even more better still. In Organic Gardening magazine and Rodale garden books we read eulogies to soils that are so high in humus and so laced with earthworms that one can easily shove their arm into the soft earth elbow deep but must yank it out fast before all the hairs have been chewed off by worms, where one must jump away after planting corn seeds lest the stalk poke you in the eye, where the pumpkins average over 100 pounds each, where a single trellised tomato vine covers the entire south side of a house and yields bushels. All due to compost.

I call believers of the organic faith capital "O" organic gardeners.

These folks almost inevitably have a pickup truck used to gather in their neighborhood's leaves and gra.s.s clippings on trash day and to haul home loads from local stables and chicken ranches. Their large yards are ringed with compost bins and their annual spreadings of compost are measured in multiples of inches. I was one once, myself.

There are two vital and slightly disrespectful questions that should be asked about this extreme of gardening practice. Is this much humus the only way to grow big, high-yielding organic vegetable gardens and two, are vegetables raised on soils super-high in humus maximally nutritious. If the answer to the first question is no, then a person might avoid a lot of work by raising the nutrient level of their soil in some other manner acceptable to the organic gardener. If the answer to the second question is less nutritious, then serious gardeners and homesteaders who are making home-grown produce into a significant portion of their annual caloric intake had better reconsider their health a.s.sumptions. A lot of organic gardeners cherish ideas similar to the character Woody Allen played in his movie, Sleeper.

Do you recall that movie? It is about a contemporary American who, coming unexpectedly close to death, is frozen and then reanimated and healed 200 years in the future. However, our hero did not expect to die or be frozen when he became ill and upon awakening believes the explanation given to him is a put on and that his friends are conspiring to make him into a fool. The irritated doctor in charge tells Woody to snap out of it and be prepared to start a new life.

This is no joke, says the doctor, all of Woody's friends are long since dead. Woody's response is a cla.s.sic line that earns me a few chuckles from the audience every time I lecture: 'all my friends can't be dead! I owned a health food store and we all ate brown rice.'

Humus and the Nutritional Quality of Food

I believe that the purpose of food is not merely to fill the belly or to provide energy, but to create and maintain health. Ultimately, soil fertility should be evaluated not by humus content, nor microbial populations, nor earthworm numbers, but by the long-term health consequences of eating the food. If physical health degenerates, is maintained, or is improved we have measured the soil's true worth. The technical name for this idea is a "biological a.s.say." Evaluating soil fertility by biological a.s.say is a very radical step, for connecting long-term changes in health with the nutritional content of food and then with soil management practices invalidates a central tenet of industrial farming: that bulk yield is the ultimate measure of success or failure. As Newman Turner, an English dairy farmer and disciple of Sir Albert Howard, put it:

"The orthodox scientist normally measures the fertility of a soil by its bulk yield, with no relation to effect on the ultimate consumer.

I have seen cattle slowly lose condition and fall in milk yield when fed entirely on the abundant produce of an apparently fertile soil.

Though the soil was capable of yielding heavy crops, those crops were not adequate in themselves to maintain body weight and milk production in the cow, without supplements. That soil, though capable of above-average yields, and by the orthodox quant.i.tative measure regarded as fertile, could not, by the more complete measure of ultimate effect on the consumer, be regarded but anything but deficient in fertility.

Fertility therefore, is the ability to produce at the highest recognized level of yield, crops of quality which, when consumed over long periods by animals or man, enable them to sustain health, bodily condition and high level of production without evidence of disease or deficiency of any kind.

Fertility cannot be measured quant.i.tatively. Any measure of soil fertility must be related to the quality of its produce... . the most simple measure of soil fertility is its ability to transmit, through its produce, fertility to the ultimate consumer."

Howard also tells of creating a super-healthy herd of work oxen on his research farm at Indore, India. After a few years of meticulous composting and restoration of soil life, Howard's oxen glowed with well-being. As a demonstration he intentionally allowed his animals to rub noses across the fence with neighboring oxen known to be infected with hoof and mouth and other cattle plagues. His animals remained healthy. I have read so many similar accounts in the literature of the organic farming movement that in my mind there is no denying the relations.h.i.+p between the nutritional quality of plants and the presence of organic matter in soil. Many other organic gardeners reach the same conclusion. But most gardeners do not understand one critical difference between farming and gardening: most agricultural radicals start farming on run-down land grossly deficient in organic matter. The plant and animal health improvements they describe come from restoration of soil balance, from approaching a climax humus level much like I've done in my pasture by no longer removing the gra.s.s.

But home gardeners and market gardeners near cities are able to get their hands on virtually unlimited quant.i.ties of organic matter.

Encouraged by a mistaken belief that the more organic matter the healthier, they enrich their soil far beyond any natural capacity.

Often this is called "building up the soil." But increasing organic matter in gardens well above a climax ecology level does not further increase the nutritional value of vegetables and in many circ.u.mstances will decrease their value markedly.

For many years I have lectured on organic gardening to the Extension Service's master gardener cla.s.ses. Part of the master gardener training includes interpreting soil test results. In the early 1980s when Oregon State government had more money, all master gardener trainees were given a free soil test of their own garden.

Inevitably, an older gentlemen would come up after my lecture and ask my interpretation of his puzzling soil test.

Ladies, please excuse me. Lecturing in this era of women's lib I've broken my politically incorrect habit of saying "the gardener, he ..."

but in this case it _was _always a man, an organic gardener who had been building up his soil for years.

The average soils in our region test moderately-to strongly acid; are low in nitrogen, phosphorus, calcium, and magnesium; quite adequate in pota.s.sium; and have 3-4 percent organic matter. Mr.

Organic's soil test showed an organic matter content of 15 to 20 percent with more than adequate nitrogen and a pH of 7.2. However there was virtually no phosphorus, calcium or magnesium and four times the amount of pota.s.sium that any farm agent would ever recommend. On the bottom of the test, always written in red ink, underlined, with three exclamation points, "No more wood ashes for five years!!!" Because so many people in the Maritime northwest heat with firewood, the soil tester had mistakenly a.s.sumed that the soil became alkaline and developed such a pota.s.sium imbalance from heavy applications of wood ashes.

This puzzled gardener couldn't grasp two things about his soil test report. One, he did not use wood ashes and had no wood stove and two, although he had been "building up his soil for six or seven years," the garden did not grow as well as he had imagined it would.

Perhaps you see why this questioner was always a man. Mr. Organic owned a pickup and loved to haul organic matter and to make and spread compost. His soil was full of worms and had a remarkably high humus level but still did not grow great crops.

It was actually worse than he understood. Plants uptake as much pota.s.sium as there is available in the soil, and concentrate that pota.s.sium in their top growth. So when vegetation is hauled in and composted or when animal manure is imported, large quant.i.ties of pota.s.sium come along with them. As will be explained shortly, vegetation from forested regions like western Oregon is even more pota.s.sium-rich and contains less of other vital nutrients than vegetation from other areas. By covering his soil several inches thick with manure and compost every year he had totally saturated the earth with pota.s.sium. Its cation exchange capacity or in non-technical language, the soil's ability to hold other nutrients had been overwhelmed with pota.s.sium and all phosphorus, calcium, magnesium, and other nutrients had largely been washed away by rain.

It was even worse than that! The nutritional quality of the vegetables grown on that superhumusy soil was very, very low and would have been far higher had he used tiny amounts of compost and, horror of all horrors, chemical fertilizer.

Climate and the Nutritional Quality of Food

Over geologic time spans, water pa.s.sing through soil leaches or removes plant nutrients. In climates where there is barely enough rain to grow cereal crops, soils retain their minerals and the food produced there tends to be highly nutritious. In verdant, rainy climates the soil is leached of plant nutrients and the food grown there is much less nutritious. That's why the great healthy herds of animals were found on scrubby, semi-arid gra.s.slands like the American prairies; in comparison, lush forests carry far lower quant.i.ties of animal bioma.s.s.

Some plant nutrients are much more easily leached out than others.