This is because climate, crops and conditions vary in different parts of the country and on different farms. Therefore we should study carefully our conditions and the principles and make our practice so combine the two as to produce the best and most economical results under the circ.u.mstances.
If we can get manure out in the winter it will very much lessen the rush of spring work.
In some parts of the country on account of deep snows, heavy rainfall and hilly fields, it is not advisable to apply manure in the winter.
This will necessitate storing the manure.
If conditions are such that we can get the manure on to the land as soon as it is made, it should be applied to land on which a crop is growing or land which is soon to be planted. If land is not intended for an immediate crop, put a cover crop on it.
COMPOSTS
Composts are collections of farm trash or rubbish, as leaves, potato tops, weeds, road and ditch sc.r.a.pings, fish, slaughter-house refuse, etc., mixed in piles with lime, barn manure, woods-earth, swamp muck, peat and soil.
The object of composting these materials is to hasten their decay and render available the plant food in them.
There are certain disadvantages in composting, namely:
Expense of handling and carting on account of bulk.
Low composition.
Loss of organic matter by fermentation.
Compost heaps serve as homes for weed seeds, insects and plant diseases.
Nevertheless, all waste organic matter on the farm should be saved and made use of as manure. These materials when not too coa.r.s.e may be spread on the surface of the soil and plowed under; they should never be burned unless too coa.r.s.e and woody or foul with weed seeds, insects and disease.
[Ill.u.s.tration: FIG. 81.--SOY BEANS IN YOUNG ORCHARD.]
[Ill.u.s.tration: FIG. 82.--A YOUNG ALFALFA PLANT JUST COMING INTO FLOWER.]
CHAPTER XX
FARM MANURES--CONCLUDED
GREEN-CROP MANURES
Green-crop manures are crops grown and plowed under for the purpose of improving the fertility of the soil.
The main object of turning these crops under is to furnish the soil with humus. Any crop may be used for this purpose.
By growing any of the cla.s.s of crops called Legumes we may add to the soil not only humus but also nitrogen. Cowpeas, beans, clover, vetch and plants having foliage, flowers, seed pods and seeds like them are called Legumes.
Most of the farm plants take their nitrogen from the soil. This nitrogen is taken in the form of nitric acid and nitrogen salts dissolved in soil water. The legumes, however, are able to use the free nitrogen which forms four-fifths of the atmosphere. This they do not of their own power but through the aid of very minute plants called bacteria or nitrogen-fixing germs. These germs are so small that they cannot be seen without the use of a powerful microscope. It would take ten thousand average sized bacteria placed side by side to measure one inch.
These little germs make their homes in the roots of the legumes, causing the root to enlarge at certain points and form tubercles or nodules (Figs. 34 and 35).
Carefully dig up a root of clover, cowpea, soy bean or other legume and wash the soil from it. You will find numbers of the little tubercles or nodules. On the clover they will be about the size of a pin head or a little larger. On the soy bean they will be nearly as large as the beans. These nodules are filled with colonies or families of bacteria which take the free nitrogen from the air which penetrates the soil and give it over to the plant in return for house rent and starch or other food they may have taken from the plant.
In an experiment at Cornell University Agricultural Experiment Station, in 1896, clover seeds were sown August 1st, and the plants were dug November 4th, three months and four days after the seeds were sown. The clovers were then weighed and tested and the following results were obtained:
----------------+---------------------------------------------- | NITROGEN IN AN ACRE OF CLOVERS.
+---------------+----------------+------------- | Lbs. in tops. | Lbs. in roots. | Lbs., total.
----------------+---------------+----------------+------------- Crimson Clover | 125.28 | 30.66 | 155.94 Mammoth Clover | 67.57 | 78.39 | 145.96 Red Clover | 63.11 | 40.25 | 103.36 ----------------+---------------+----------------+-------------
A large part of the nitrogen found in these plants was undoubtedly taken by the roots from the soil air.
Besides adding humus and nitrogen to the soil the legumes, being mostly deep-rooted plants, are able to take from the subsoil food which is out of reach of other plants. This food is distributed throughout the plant and when the plant is plowed under the food is deposited in the upper soil for the use of shallow-rooted plants.
BENEFITS
The benefits derived from green crop manuring then are as follows:
We add to the soil organic matter or humus which is so helpful in bringing about the conditions necessary for root growth.
By using the legumes for our green manure crops we may supply the soil with nitrogen taken from the air.
We return to the surface soil not only the plant food taken from it but also plant food brought from the subsoil by the roots of the green manure plants.
CHARACTER OF BEST PLANTS FOR GREEN CROP MANURING
The plants best adapted to green crop manuring are deep-rooted, heavy-foliaged plants. Of these the legumes are by far the best, as they collect the free nitrogen from the air which other plants cannot do. This enables the farmer to grow nitrogen which is very expensive to buy.
THE TIME FOR GROWING GREEN MANURE CROPS
Green manure crops may be grown at any time that the soil is not occupied by other crops, provided other conditions are suitable. Land which is used for spring and summer crops often lies bare and idle during fall and winter. A hardy green manure crop planted after the summer crop is harvested will make considerable growth during the fall and early spring, and this can be plowed under for the use of the following summer crops. If there is a long interval of time during spring or summer when the land is bare, that is a good time for a green manure crop.
Green manure crops are often planted between the rows of other crops such as corn or cotton at the last working of the crop for the benefit of the crop which is to follow.
It is advisable to arrange for a green manure crop at least once in three or four years.
LEGUMINOUS GREEN MANURE CROPS
_Cowpea_. (Field pea, stock pea, black pea, black-eyed pea, clay pea, etc.) (Fig. 79.)
The cowpea is perhaps the most important leguminous plant grown for soil improvement in the South. It will grow anywhere south of the Ohio River and can be grown with fair success in many localities farther north.
It is a tender annual, that is, it is killed by frost and makes its entire growth from seed to seed in a single season. It should therefore be planted only during the spring and summer. This crop not only has power like the other legumes to take nitrogen from the air, but it is also a strong feeder, that is, it can feed upon mineral plant food in the soil that other plants are unable to make use of.
For this reason it will grow on some of the poorest soils, and is a good plant with which to begin the improvement of very poor land. It is a deep-rooted plant. On the farm of the Hampton Normal and Agricultural Inst.i.tute cowpea roots have been traced to the depth of sixty-one inches.
Cowpeas will grow on almost any land that is not too wet. From one and one-half to three bushels of seed are used per acre. These are sown broadcast and harrowed in or are planted in drills or furrows and cultivated a few times. Aside from its value as a green manure crop the cowpea is useful as food for man and the farm animals. The green pods are used as string beans or snaps. The ripened seeds are used as a food and the vines make good fodder for the farm animals.