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4. The Fertility Chain and Soil Balance
THE fertility chain, as stated in the previous chapter, is that series of factors which Nature employs in maintaining the richness in her primeval prairies and on the forest floor. Some of these fertility factors have already been discussed. Fiber is one link vitally necessary as a source of food and warmth for the other links, the bacteria and insects and worms, each of which performs its own specific tasks. Fiber is also important in the regulation of the soil's moisture, particularly in building up and maintaining a reservoir in the lower soil zones.
The earthworms, the tunnel makers, not only build air passages but add to the soil's fertility through their own manure deposits. Earthworms form a link in the fertility chain the value of which would be hard to measure. A weak earthworm population is a good indication that several things are wrong in the soil world.
Nature's constructive wild plants are the most condemned, yet are among the most valuable of all the fertility links. With their strong root systems these "weeds" reach down into the subsoils, open them up, and fiberize such soils so the other agents of fertility can move down and broaden their fields of operation. Sol Benson and his pusley again! Some of the links of the fertility chain are outside the scope of this book: certain soil-improving molds, for instance. There are many links, no doubt, which have not yet been discovered.
That weed cove which meant so much to me as a boy was very close to an ideal example of a soil-fertility chain with no links missing. I have since studied many rich soils in many parts of the world, but rarely have I encountered a soil where there seemed such a uniformity of action among the several workers or chain links. The horseweeds,, never seriously disturbed during their growing periods, year after year had developed, seeded, then died and passed through the various stages of disintegration and decay until the erstwhile weeds were turned into velvety mold. Here other workers took over; the mellow mold was further processed until it became finally plant-food elements ready to be dissolved in the soil moisture so the feeding roots could absorb them. As I see it now, that horseweed cove was an exception to some of Nature's universal laws: save for a border around the outside of the cove, the horseweeds were alone masters of the area; there were no unrelated root systems at work in the cove itself.
Even to one unlearned in the technical science pertaining to the fertility chain, it was both thrilling and instructive to handle and study that living soil which the horseweeds had formed without any external assistance other than that given by the sunlight and rain. If the soil at our pioneer well was constantly moving, the soil in the cove was really bouncing with life. Working my hands into the cove soil, I could unmistakably feel the life of the soil itself.
That cove held on in its sheltered spot and continued to build velvety soil until the land on the slope back of the cove had become seriously eroded because of improper farming methods, and the holding vegetation along the brink of the ravine had been destroyed. Then the runoff, no longer with any sponge structure to hold it back and absorb it, swept across the slope and poured into the small canyon. From there it roared on to the creek, carrying the surface soil with it. The cove, now deprived of the seepage which it had previously received from the slope water, gradually succumbed. The horseweeds gave way to more hardy species. Common annual ragweeds and thistles took over -- another law of Nature in manifestation: the blanket of vegetation must not remain broken for long. Nature abhors barren land.
Then years later man moved out and the almost ruined slope was handed back to Nature. But when I last visited the slope (I couldn't even recognize the spot where my cove had been) I found a grand awakening. The holding vegetation had come back wonderfully along the edge of the ravine; lush grass was creeping over the field that not long ago was spread with soil-building weeds of many kinds. There was still plenty of evidence that the weeds had first taken over and done some constructive work before the grass could move in.
And there was still going on one of the grandest battles of grass versus weeds that I have yet come across. The prairie grass was well on its way to final victory, but the struggle was still tenacious in spots. Invariably where the ground was still hard and lacking in fiber, the grass was unable to push the weeds out. Scattered through every sizable area of weeds were clumps of bluestem grass -- spots where the weeds had built up the soil to the point where it was suitable for the grass roots. There were areas of common annual ragweeds spotted with many grass clumps. Three or four sunflower spots along two sides of the slope were slowly giving way to the grass as were the ragweeds. The blackeyed Susans seemed to be better fighters than the other weeds, probably because they were fiberizing their soil more slowly.
Of all the operations involved in a successful agriculture, maintaining an unbroken fertility chain in farmlands is decidedly the most important. But the farmer's soil-maintenance problems are quite different from those of Nature. Whereas Nature in her virgin fields produces and then turns her production back into the soil almost entirely, the farmer produces and harvests, and thus is forced to weaken his soil-fertility chain -- unless he carries on permanently constructive soil-maintenance operations at the same time. Most of our food-producing lands have sunk below their primitive strength because farmers have failed to play fair with Nature. Even where quantity production has held up fairly well, quality of produce, compared with what came from our lands several decades ago, is much lower than what producers and consumers realize. The soil-fertility chain has vital links missing!
Removing substances from the soil in order to support life is of course the aim of agriculture; neglecting to keep, up the fertility chain while doing it is poor farm management. It is invariable law that the farmer must put back quantity and quality into his surface soil for quantity and quality removed. That alone will maintain the soil-fertility chain. Rare is the farmer who does not have at his command the very materials that Nature herself uses in maintaining her primeval fertility, and usually in abundance: animal manures, compost materials, legumes and other green crops -- and deep-diving weeds.
But comes the objection: "Those weeds you're talking about will steal the soil moisture! They'll rob the crops!" To which I agree -- in a measure. If the soil is weak and the rainfall light, all of those deep-rooted annuals with which every farmer has to deal are going to demand their share of the upper moisture and food elements for a while. But a farmer rebuilding weak land should always keep in mind that the important things he is after are to strengthen his surface soil and enlarge his crop's feeding zone. That rich stuff which his deep-foraging pigweeds and lamb's quarter and sunflowers and all of the rest of them can bring to the surface from below, is exactly what he needs in the rebuilding. Those minerals and that nitrogen which the weeds are able to pump up will be worth far more than the support the weeds require while they are developing to the stage where their roots are ready to do the pumping. Thereafter the weeds will get most of their support in the lower soils.
"Yes, but why weeds instead of farm legumes or some other cultivated crop?" Here again is the answer to that one: because few cultivated crops have root systems that forage extensively through the subsoil -- Nature's cellar storehouse.
Of course, if there is no subsoil from which to pump materials -- better dispense with the weeds; unless the weeds are grown as a green manure. There is not much one can do in the rebuilding of one's land without some sort of a foundation upon which to build.
In improving land with weeds, every sprig of the weed growth should go back into the soil. When weeds are grown alone as a green manure, or when left thinly distributed through a cultivated crop, they should remain on the field as long as possible, but not until they become dry. The weeds should go under while green, yet be given the maximum time to store up materials that have been gathered in the lower soil zones. In this way man is able to improve on Nature's excellent practices. In the wild, the weeds normally can go back into the soil only after they have decayed above ground.
It is quite possible to have a complete fertility chain so far as the number of links is concerned, and yet have a soil that is not functioning satisfactorily, though the physical condition may be good. Such a condition may obtain when some of the links in the chain are weak while one or more are overly strong. This results in an unbalanced soil. Occasionally a farmer will throw his soil out of balance by pursuing the wrong course in an effort to strengthen the fertility of his land; by overbuilding one or more links to the neglect of the others.
Several years ago I ran onto a case of this kind while checking California orchards for suitable budwood for the various nurseries. The orchard in question had long been an excellent producer. Then it just gave up without any apparent reason. However, when I visited the orchard it was a picture of health and vigor. But it hadn't been that way a great while, and the orchard's owner assured me he had learned a valuable lesson in soil management through a serious mistake.
What had happened was that this man had been fertilizing heavily with a certain commercial product, and had neglected his organic fertilizer. Since he was getting good crops of high-class fruits with his system, he increased his concentrates, hoping to raise his production still more. He had promised himself, he told me, that he would get his legumes going the following spring. He felt that would be soon enough. But Nature follows her own laws, not man's whims. She soon showed this orchardist how the breaking of her soil-fertility laws doesn't pay.
One day this man noticed that something was happening to some of his trees. The trees appeared anemic. A branch here and there, he told me; then the whole tree. The trees didn't appear to be actually diseased; just weak and hungry looking, and that right when he was stuffing them with expensive fertilizer.
In less than one season more than half of his trees were affected. All of the trees produced fruit, but only a small percentage of the fruit was marketable. And by the end of the year practically all of the trees were "sick." He sought advice and relief from every available source, but received no encouragement. All he learned was that his orchard was apparently done for and that his only choice was to build him a new orchard -- but not on the same land.
So he finally concluded to pull out his trees, but decided to wait a year before doing it. Not that he had any hope of saving his orchard; only that he believed he could by then give up his trees with greater peace of mind. And he did nothing whatever to his orchard that year except to flood the area occasionally. There was no pruning, no spraying, no cultivating. He turned the orchard over to anything that wanted to grow in it -- which meant a grand array of California weeds.
And those weeds took hold with a vengeance. In places, he said, the weeds grew so tall they almost hid the trees. In early autumn of the second year he happened to notice that the trees along the outer edge, instead of dying completely as they were supposed to do, had done just the opposite. They were now green and healthy looking. And that discovery sent him exploring in his weed jungle. What he found there brought him more and greater surprises. The trees inside the weed patch were thriving even better than those in the outer rows.
It was easy to see what had taken place in this man's orchard: the orchard soil had been thrown completely out of balance through a too-heavy application of the rich mineral fertilizer. The trees were overfed in one direction. They were not getting enough other food to go along with the strong mineral. At the critical moment the weeds had come forward and with their vigorous roots opened up the lower soil so the concentrates could be distributed by the irrigation water throughout the larger soil zone. The weed growth had probably been too dense to permit a large amount of deep diving; but there had been enough fiberization of the subsoil to save the day. Of course, the weeds themselves made use of great quantities of the minerals, but by the time the fruit grower was ready to roll the weeds down and work them into the soil, the soil zone was sufficiently enlarged to prevent further concentration when the decayed plants released their minerals.
When I last saw this orchard it was very much of a weed patch. Weeds were growing with legumes. I do not recall whether or not the legumes had been inoculated, but I do remember that the weeds and legumes were doing wll together. Which is to say, the weeds were being controlled to a certain degree now. "And my fertilizer from now on is going to be legumes combined with weeds," this man assured me -- "and with plenty of emphasis on the weeds!"
In short, in maintaining the soil-fertility chain, or in keeping up soil balance, watch the fertility chain as a whole. Don't emphasize some links to the neglect of others that are just as important. It is actually true that a soil is no stronger than its weakest fertility link. Keeping a balance in the fertility chain is practical agriculture at its best.
Mr. E. G. Cambell, discussing weed values in the magazine of the American Society of Agronomy (February, 1924), makes some terse observations which agree with my own findings as to the natural place of our common weeds in building and maintaining balance in the soil-fertility chain. Mr. Cambell evaluates weeds highly for their ability to pump the nitrogen back to the surface after it has dropped into the lower soil zones beyond the reach of ordinary crops, and their ability to hold this element in reserve. According to this author, heavy growths of summer annuals are especially valuable as nitrogen retainers.
Farmers are familiar with the weeds that spread over their fields after small grains have been harvested: common ragweeds, wild lettuce, thistles, sunflowers, nightshades, etc. Such weeds through the work of their roots actually fertilize the soil for the next crop. This is an excellent illustration of how Nature's soil builders play a sound part in maintaining soil balance.
Mr. Cambell hands the weeds along the highway and country roads some deserving commendation. Those weeds, he says, are an asset in a community's agriculture rather than a detriment. Mostly without the farmer's knowledge, the roadside weeds check erosion in numerous ways and thus save many acres that would otherwise be lost. And certainly they protect the highway itself -- but not when they are slaughtered the way they are in so many places.
Any farmer who wishes to learn the true habits of the weeds in his locality can find no better source of information than those strips and clumps of wild plants that border most roads. There he will find growing most of our soil improvers. Using his shovel when the ground is soaked and the weeds near full size, he can discover a great deal about the root growth of the annuals he has in his fields. Usually the roadside will reveal how these weeds grow under adverse conditions, and in what types of soil they seem to do best: whether in the tight clays, the sands, or the coarse gravels.
It will be worthwhile to learn how the weeds thrive in the spots that are very much like that field or two on the farm that may be badly in need of improvement. The roadside patch will show at what season of the year any particular weed makes its best growt -- -and when and how it produces its seed, in case a harvest of seed may be desired. Mr. Cambell emphasizes the value of weeds that grow during the winter. Winter weeds are usually deep feeders. Such weeds should be encouraged for they do their land improving during the off season for cultivated crops.
But -- weeds are not mushroom soil builders. Keep mind that weeds, aside from pumping much valuable material from the lower soils up to the surface, also do very constructive work by fiberizing the lower soils. Often it may require several weed crops before any noticeable benefit appears in the cultivated crop above ground. But in due course the weeds, if kept on the job, will re-establish land balance.
Next: 5. Plant Roots
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