By : Alva Agee (1858 - 1943)
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Natural Strength of Land.—Nearly all profitable farming in this country is based upon the fundamental fact that our lands are storehouses of fertility, and that this reserve of power is essential to a successful agriculture. Most soils, no matter how unproductive their condition to-day, have natural strength that we take into account, either consciously or unconsciously. Some good farm methods came into use thousands of years ago. Experience led to their acceptance. They were adequate only because there was natural strength in the land. Nature stored plant-food in more or less inert form and, as availability has been gained, plants have grown. Our dependence continues.
Plant Constituents.—There are a few technical terms whose use cannot be evaded in the few chapters on the use of lime and fertilizers. A plant will not come to maturity unless it can obtain for its use combinations of ten chemical elements. Agricultural land and the air provide all these elements. If they were in abundance in available forms, there would be no serious soil fertility problem. Some of their names may not interest us. Six or seven of these elements are in such abundance that we do not consider them. A farmer may say that when a dairy cow has luxuriant blue-grass in June, and an abundance of pure water, her wants are fully met. He omits mention of the air because it is never lacking in the field. In the same way the land-owner may forget the necessity of any kind of plant-food in the soil except nitrogen, phosphoric acid, potash, and lime. Probably the lime is very rarely deficient as a food for plants, and will be considered later only as a means of making soils friendly to plant life.
Nitrogen, phosphoric acid, and potash are the three substances that may not be in available form in sufficient amount for a growing crop. The lack may be in all three, or in any two, or in any one, of these plant constituents. The natural strength of the soil includes the small percentage of these materials that may be available, and the relatively large stores that nature has placed in the land in inert form as a provision against waste.
The thin covering of the earth that is known as the soil is disintegrated rock, combined with organic matter. The original rock "weathered," undergoing physical and chemical change. A long period of time was required for this work, and for the mixing and shifting from place to place that have occurred. Organic matter has been a factor in the making of soils, and is in high degree a controlling one in their production of food.
Organic Matter.—Nature is resourceful and is constantly alert to repair the wastes and mistakes of man. We may gain fundamental truth about soil fertility through observance of her methods in restoring land to a fertile condition. Our best success comes only when we work with her. When a soil has been robbed by man, and has been abandoned on account of inability to produce a profitable crop, the first thing nature does is to produce a growth of weeds, bushes, briers, or aught else of which the soil chances to have the seeds. It is nature's effort to restore some organic matter—some humus-making material—to the nearly helpless land. Vegetable matter, rotting on and in the soil, is the life-giving principle. It unlocks a bit of the great store of inert mineral plant-food during its growth and its decay. It is a solvent. The mulch it provides favors the holding of moisture in the soil, and it promotes friendly bacterial action. The productive power of most farming land is proportionate to the amount of organic matter in it. The casual observer, passing by farms, notes the presence or absence of humus-making material by the color and structure of the soil, and safely infers corresponding fertility or poverty. Organic matter is the life of the soil.
A great percentage of the food consumed by Europe and the Americas continues to come out of nature's own stores in the soil, organic and inorganic, without any assistance by man except in respect to selection of seeds, planting, and tillage. The percentage grows less as the store of original supplies grows less and population increases. Our science has broadened as the need has grown greater. We have relatively few acres remaining in the United States that do not require intelligent treatment to insure an adequate supply of available plant-food. The total area that has fallen below the line of profitable productiveness is large. Other areas that never were highly productive must supplement the lands originally fertile in order that human needs may be met.
When soils have been robbed through the greed of man, nature is handicapped in her effort to restore fertility by the absence of the best seeds. Man's intelligent assistance is a necessity. Successful farming involves such assistance of nature that the percentage of vegetable matter in the soil shall be made high and kept high. There must be such selection of plants for this purpose that the organic matter will be rich in fertility, and at the same time their growth must fit into a scheme of crop production that can yield profit to the farmer. Soils produce plants primarily for their own needs. It is a provision of nature to maintain and increase their productive power. The land's share of its products is that part which is necessary to this purpose. Skill in farming provides for this demand of the soil while permitting the removal of a large amount of animal food within the crop-rotation. Lack of skill is responsible for the depleted condition of soils on a majority of our farms. The land's share of the vegetation it has produced has been taken from it in large measure, and no other organic matter has been given it in return. Its mineral store is left inert, and the moisture supply is left uncontrolled. Helplessness results.
Drainage.—Productive soils are in a condition to admit air freely. The presence of air in the soil is as necessary to the changes producing availability of plant-food as it is to the changes essential to life in the human body. A water-logged soil is a worthless one in respect to the production of most valuable plants. The well-being of soil and plants requires that the level of dead water be a considerable distance below the surface.
When a soil has recently grown trees, the rotting stump roots leave cavities in the subsoil that permit the removal of some surplus water, and the rotted wood and leaves that give distinctive character to new land are absorbents of such water. As land becomes older, losing natural means of drainage and the excellent physical condition due to vegetable matter in it, the need of drainage grows greater. The tramping of horses in the bottoms of furrows made by breaking-plows often makes matters worse. The prompt removal of excessive moisture by drains, and preferably by underdrains, is essential to profitable farming in the case of most wet lands. The only exception is the land on which may be grown the grasses that thrive fairly well under moist conditions.
Lime.—The stores of lime in the soil are not stable. The tendency of lime in most of the states between the Missouri River and the Atlantic seaboard is to get out of the soil. There is no evidence that lime is not in sufficient quantity in most soils to feed crops adequately, but within recent years we have learned that vast areas do not contain enough lime in available form to keep the soil from becoming acid. Some soils never were rich in lime, and these are the first to show evidence of acidity. In our limestone areas, however, acid soil conditions are developing year by year, limiting the growth of clover and affecting the yields of other crops.
The situation is a serious one just in so far as men refuse to recognize the facts as they exist, and permit the limiting of crop yields, and consequently of incomes, through the presence of harmful acids. The natural corrective is lime, which combines with the acid and leaves the soil friendly to all plant life and especially to the clovers and other legumes that are necessary to profitable farming. Nature is largely dependent upon man's assistance in the correction of soil acidity.
Crop-rotation.—A good crop-rotation favors high productiveness. One kind of crop paves the way nicely for some other one. The land can be occupied by living plants without any long intermissions. Organic matter can be supplied without the use of an undue portion of the time. The stores of plant-food throughout all the soil are more surely reached by a variety of plants, differing in their habits of root-growth. The injury from disease and insects is kept down to a minimum. There is better distribution of the labor required by the farm, and neglect of crops at critical times is escaped. The maintenance of fertility is dependent much upon the use of a legume that will furnish nitrogen from the air. A permanently successful agriculture in our country must be based upon the use of legumes, and crop-rotations would be demanded for this reason alone if none other existed.
Fertilizers.—When a crop is fed to livestock, and all the manure is returned to the land that produced the crop without loss by leaching or fermentation, there is a return to the land of four fifths of the fertility, and a good form of organic matter is supplied. A portion of the crops cannot be fed upon the farm, or otherwise the human race would have only animal products for food. The welfare of the people demands that a vast amount of the soil's crops be sold from the farms producing them. This brings about a dependence upon the natural stores of plant-food in the soil, which become available slowly, and upon commercial fertilizers.
There has been a disposition on the part of many farmers to regard fertilizers only as stimulants, due to the irrational use of certain materials, but a good commercial fertilizer is a carrier of some or all of the necessary elements that we find in stable manures. They may carry nitrogen, phosphoric acid, or potash,—any one or two or the three,—and the three are the constituents that usually are lacking in available forms in our soils. Examples of the best modern skill in farming may be found in the rational selection and use of commercial fertilizers.
Tillage.—Man's ability to assist nature in the work of production finds a notable illustration in the matter of tillage. Its purpose is to provide right physical condition of the soil for the particular class of plants that should be produced, while destroying the competition of other plants that are for the time only weeds. Most soils become too compact when left unstirred. The air cannot enter freely, plant-roots cannot extend in every direction for food, the water from rains cannot enter easily, there is escape of the moisture in the ground, and weathering of the soil proceeds too slowly. The methods used in plowing, harrowing, and later cultivations fix the productive power of a soil for the season in large measure.
Control of Soil Moisture.—The water in the soil is a consideration that has priority over plant-food in the case of agricultural land. The natural strength of the soil is sufficient to give some return to the farmer in crops if the moisture content is right throughout the season. The plant cannot feed unless water is present; the process of growth ceases in the absence of moisture. One purpose of plowing is to separate the particles of soil to a good depth so that water-holding capacity may be increased. When the soil is compact, it will absorb and hold only a very limited amount of moisture. We harrow deeply to complete the work of the plow, and the roller is used to destroy all cavities of undue size that would admit air too freely and thus rob the land of its water. Later cultivations may be given to continue the effect of the plow in preventing the soil from becoming too compact, but usually should be required only to make a loose mulch that will hold moisture in the ground, and to destroy the weeds that would compete with the planted crop for water, food, and sunshine.
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