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Profits from farming depend more largely upon the productive capacity of the soil, than upon any other single factor. Unless the soil is in condition to grow large crops, but little profit can be made from tilling it. Schemes of cropping should be arranged that provide for the maintenance of soil fertility and large production. the farm manager should so plan his farm and organize his cropping system, that as much fertility will be put back on the land as has been taken from it in producing the crops. Just how to do this is one of the most intricate problems the farmer has to meet. to solve the problem successfully he must understand the nature of the soil and how plants grow.
Soil is composed of disintegrated rock particles called inorganic or mineral matter, and organic or vegetable matter formed from decaying plants. Sand is an example of the former, and peat and leaf mold are examples of the latter. Upon the proportion of the mixture of mineral and vegetable matter the producing power of the soil largely depends.
The farmer's chief concern lies in keeping up the supply of vegetable matter. This can be accomplished by the growth of green crops which may be plowed under; by returning the straw of grain crops to the land; and by feeding the crops to live stock and hauling the manure back to the land. When the plants and manures decay in the soil, they form certain dilute acids which act upon the rock particles causing them to more rapidly break up and liberate the mineral elements required for plant growth.
The mineral elements of plant food, as nitrogen, phosphorus, potassium, calcium, are taken up by the plants only in soluble forms, in the vehicle known as the soil solution.
[Illustration: Fig. 42.--The soil particles are portions of rocks that have been broken up by weathering.]
This soil solution is formed of water and the
elements which
have been liberated by the chemical re-actions that have taken place
between the rock particles and the decaying plant material.
The
larger part of all growing plants is composed of materials which are
taken up in the soil solutions by the roots, and from the carbon
dioxide secured from the air by the plants, through their leaves.
Not more than 5 per cent of the materials required by the
plants
comes directly from the soil. So essential are these
materials,
however, that no crop of plants can be matured without them.
They
must be taken up in solution through the roots of the plants.
It
is for this reason that the farm manager must give close attention to
the cropping of the land, the tilling of the land, and the feeding of
the soil.
Plant food is made soluble largely by the decomposition of rotting vegetable matter. A pile of rotting manure gives a good illustration of this fact. Streams of water running from it will be noticed to be highly colored. This is because plant food has been dissolved from the pile by the water and is being carried
104 Farm Management
off in solution. Land over which this highly colored solution is distributed is greatly enriched and grows large crops.
When vegetable matter, as green clover or manure from the barnyard, is placed on the soil and allowed to decompose, the plant material breaks down and portions become soluble. These are taken up in the soil solution.
[Illustration: Fig. 43.--Organic matter being decomposed before being applied to the land.]
In decomposing, the vegetable matter generates heat.
In the re-action, a weak acid is formed which acts on the
soil particles, thus aiding in the liberation of the mineral elements
of plant food. The heat and the acid, both generated by the
decomposition of vegetable matter, cause the soil water to act more
strongly on the soil particles, portions of which become soluble.
The materials composing the vegetable matter and small
amounts of soil particles are thus converted into forms that can again
be used in building up plant structures.
In order that plants may be liberally supplied with food, the conditions for plant decomposition and soil disintegration must be favorable. Vegetable matter cannot decay unless air and moisture com in contact with it in the right proportions. Heat also is necessary. Hay, straw, grain and other farm products are preserved by drying and keeping them under cover. No attempt is made to keep the air away so long as the product can be kept dry. Silage is prevented from decaying in the silo by excluding the air, though moisture is plentifully included. These examples illustrate how necessary it is to have air and moisture both present in the proper proportions in the soil to bring about the
Soil Management 105
liberation of plant food. The soil must contain vegetable matter, air, heat and moisture before decomposition can take place. Particles of vegetable matter mixed between soil particles help to maintain passages for the free circulation of air, from which oxygen, the active agent in causing decomposition, must come. The vegetable matter being porous absorbs large quantities of moisture. Therefore, in a soil well supplied with vegetable matter, there is likely to be also a plentiful
[Illustration: Fig. 44.--Much of the fertilizing value of the manure leaches out and is lost when manure is left in heaps to rot.]
supply of air and moisture. Decomposition goes on rapidly in such a soil and plants grow well on it.
There are three ways of supplying vegetable matter, (1) By raising green crops which can be plowed under. Such crops as rye, wheat, barley, or oats may be used for the purpose. Even a rank growth of weeds can be satisfactorily used though it is not advisable to grow them. The annual grain crops, however, develop small root systems and do not penetrate so deeply as the alfalfa and clovers. For this reason, they are not so satisfactory for
106 Farm Management
green manure crops. Dwarf Essex rape, cow peas, soy beans, Canada field peas, and other annual crops are successfully used.
(2) The grass crops, such as timothy, orchard grass, bromus, and the legumes, particularly the clovers and alfalfa used for hay and pasture crops, are very satisfactory for plowing under to enrich the soil. The clovers and alfalfa especially, develop large root systems and penetrate deeply. When properly inoculated with nitrifying bacteria, the plants are enabled to use the nitrogen of the air in building plant tissue. When
[Illustration: Fig. 45.--A green manure crop being plowed
under
to increase the production of other crops. The decaying
plants
help to form an abundance of plant food.]
the roots of the plants decay in the soil, it is consequently enriched.
A soil which grows frequently such crops as medium red
clover,
alsike clover, or alfalfa, is likely to be well supplied with vegetable
matter and when sown or planted to other crops, will give large yields.
Soil Management 107
(3) The third source of vegetable matter lies in feeding the crops to live stock and returning the barnyard manure to the soil. The straw of the grain crops, the stalks of corn, peas and other crops, can successfully be used as bedding for littering the yards, thus absorbing large quantities of the liquid manures which go easily into solution when applied to the soil. Through the use of barnyard manures it is possible to enrich the soil greatly, and largely increase its producing power. The use of the grass, grain, and cultivated crops in rotation combined with liberal applications of barnyard manure, will maintain the producing power of most soils. Even the arrangement of crops in rotation has a desirable effect in this respect.
The benefits from crop rotation are well illustrated by the results of investigations at the Minnesota Experiment Station. These experiments began in 1894. On some of the plots continuous cropping without manure has been followed. A plot of land which has been continuously cropped to wheat since 1894, yielded from 1902 to 1911, an average of 19.3 bushels per acre. On a plot beside it, which had also been continuously cropped to wheat but in which was sown six pounds of red clover each spring and plowed under in October of each year, the average yield for the same period was 22.1 bushels per acre. This increase of 2.8 bushels per acre is due to the effect of the clover plowed under each year. On a plot that has grown corn continuously for the same time, the yield is 27.5 bushels per acre. In a three year rotation of wheat, clover, and corn, the yield of corn is 46.3 bushels. No manure is used in either case. The increase in the yield of corn on the land where the crops are rotated, is due to the effect of clover roots and wheat stubble which are plowed under and mixed with the soil. The results from two two-year rotations also point to the value of vegetable matter in building up the producing power of the soil. In one of these rotations, wheat and mangles are alternated. The yield of wheat is 23.4 bushels per acre. In the other rotation
108 Farm Management
wheat is alternated with annual pasture. The annual pasture crops are composed of peas in the early season and corn during the late season. The yield on this latter rotation is 27 bushels of wheat per acre. The difference in yield is unquestionably due to the vegetable matter returned in the roots of the pasture crops and in the droppings from the animals pasturing on the land.
To illustrate the value of manure in rotation, the results are given from a three year rotation of wheat, clover, and corn without manure, and a five year rotation of wheat, meadow, pasture, oats, and corn with eight tons of manure per acre once in five years. In the three year rotation, wheat has yielded 20.6 bushels per acre. In the five year rotation with manure, the yield has been 27.4 bushels per acre, or 6.8 bushels more. In the three year rotation, corn has yielded 46.3 bushels per acre; in the five year rotation, 61.3 bushels, an increase of 15 bushels per acre. The comparison between the three year rotation and the continuous cropping plots emphasizes the importance of providing vegetable matter through the use of green manure crops and the roots of plants.
Rotations at the Minnesota Experiment Station and Average Yields Secured for Ten Years 1902-1911
| Systems of Cropping | Wheat Bu. | Corn Bu. | Oats Bu. | Hay Tons | Mangles Tons |
| Wheat, continuously | 19.3 | ||||
| Corn, continuously | a27.5 | ||||
| Hay, continuously | b1.7 | ||||
| Mangles, continuously | 3.8 | ||||
| c Wheat, continuously, 6lb red clover | 22.1 | ||||
| 2 yr. rotation, wheat and mangles | 23.4 | 9.2 | |||
| 2 yr. rotation, and annual pasture | 27 | ||||
| 3 yr. rotation, wheat, clover, and corn | 20.6 | 46.3 | a2.7 | ||
| 5 yr. rotation, wheat, meadow, pasture, oats, corn | 27.4 | 61.3 | 58.6 | b3.6 |
a 9 year average. b 8 year average. c Clover plowed under in fall.
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No manure is used in any of the above plats except 8 tons applied to the corn crop in the five-year rotation.
Land is fall plowed for all grain and corn crops except where grain follows corn, when land is thoroughly disced.
On rolling land, particularly in the South, thee is much loss of fertility through the erosion or washing away of the land. This loss must be guarded against by the farm manager. Crops can be so arranged as to keep the rough land covered with crops possessing large root systems. The roots of the plants will prevent washing to a large extent and the addition of manures and the frequent tillage of the land will keep the soil open or porous, so that rainfall may be absorbed. when so absorbed, erosion is prevented to a large extent. In working land that is subject to erosion, great care must be used. Plowing sidewise of the hills, working the sidehills in terraces, and keeping hate land covered with mulch or keeping it in crops that will bind the soil through extensive root systems, will avoid the loss to a large extent.
Good tillage will make the soil more productive. As has been pointed out, plant food is made available by the disintegration of rock or mineral particles, and by the decomposition of vegetable matter. Plowing, discing, and harrowing loosens the soil, thus allowing free entrance of air and moisture which results in a more rapid breaking up of the soil particles. The oxygen of the air is combined with the carbon of the decaying plants and forms carbonic acid which acts as a solvent of some of the compounds of the soil. the breaking up of these compounds makes possible the formation of more soluble compounds and aids in liberating plant food. More food thus becomes available for the plants. The pulverizing process of turning the land with a plow breaks up the soil particles and brings new surfaces in contact. More surface is exposed for the plants to feed upon and they thrive better in a plowed field than on hard
110 Farm Management
land. Tillage mixes the soil grains and hastens chemical reactions. The better aeration of the soil on tilled land is more favorable to bacterial life, also resulting in better conditions for the growth of crops. Tillage alone will not keep the soil fertile. Manures or green crops must be returned to the soil to keep up the supply of vegetable matter or the soil will become "worn out". Tillage serves a useful purpose in mixing the vegetable matter with the soil particles so that the decomposition takes place rapidly enough to supply abundant available food for the growth of the crop.
The same kind of tillage will not do for all land, and the farmer should study the effect of each tillage operation on his land. A sandy soil may be plowed when wet without injuring the texture. A clay soil deficient in vegetable matter is almost sure to puddle and "bake" if handled when wet. When "baked" the plant food is locked up closely and plant growth is made but slowly. In addition, it is lumpy and hard to work. A clay soil is seldom injured by tilling when dry. Some soils must be plowed deeply to get the best results; other soils are seriously injured by deep plowing. The pulverization of the soil, by discing, harrowing and cultivating, only completes the process begun in plowing. A thorough knowledge of the soil and its qualities is essential to successful soil management.
1. Have the pupils bring to class samples of pure sand and of leaf mold or other forms of vegetable matter.
2. Weigh four quarts of each and compare weights.
3. From the samples furnished, make soils composed of 7 parts sand to 1 part vegetable matter; 3 parts sand to 1 part vegetable matter; 2 parts sand to 1 part vegetable matter. Sow some wheat in each and note the growth made.
4. Find some clay soil devoid of humus and wet thoroughly. Work when wet, with the hands and lay away to dry. Wet some of the sand and treat in the same way. When dry, note which breaks up more easily.
Soil Management 111
1. Analyses show that about 70% of the nitrogen in the red clover plant is in the top and 30% in the roots and stubble, also that there are about 40lb. of nitrogen in a ton of air-dried clover hay. What amount of nitrogen will be in the clover roots of an acre which yields 3500 lbs. of air-dried hay?
2. If the clover plant received two-thirds of the required nitrogen from the air through bacteria, what will be the actual loss or gain in pounds of nitrogen an acre in the above problem if the hay is all removed?
3. A field of corn produces 10 tons of corn silage an acre and each 100 lbs. removes .3 lb of nitrogen, .12 lb. of phosphoric acid, and .35 lb. of potash. What will be the value of the plant food removed if nitrogen is worth 16¢ per pound, phosphoric acid 4¢, and potash 4¢?
4. What will be the value of the plant food left on an acre of corn yielding 50 bushels if only the ears are removed? One and on-third pounds of stover are produced for each pound of shelled corn, and corn stover averages 1% nitrogen, 3% phosphoric acid, and 1.4% potash. Nitrogen is worth 17¢, phosphoric acid 4¢, and potash 4½¢ per pound.
5. If there is .35 lb. nitrogen, 15 lbs. phosphoric acid, and .50 lb. potash in each 100 lbs. of potatoes, what will be the amounts of these plant foods required if a yield of 200 bushels per acre is secured?
6. If 5 tons of manure per acre is available for the above potato crop, how many more pounds of nitrogen, potash, and phosphoric acid, if any, will the operator need to apply in order to return all that was removed? The manure contains .5% nitrogen, .28% phosphoric acid, and .60% potash.
7. A 50-bushel crop of oats with the straw will take from the soil 50 pounds of nitrogen, 18 pounds of phosphoric acid, and 45 pounds of potash. Average fresh mixed horse and cow manure will contain about .50% nitrogen, .28% phosphorus, and .60% potash. How much manure must be supplied to replace the elements removed from an acre?
Snyder's "Soils and Fertilizers."
Fletcher's "Soils."
Minnesota Experiment Station Bulletins, Nos. 53, 70, 89, 109.
Soil Fertility and Permanent Agriculture.--C. G. Hopkins.
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