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 quantities 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 quantities 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 grass 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 assumptions. 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 classic 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 assay." Evaluating soil fertility by biological assay 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 quantitative 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.