_Loss by heating or fermenting._
When barn manure is thrown into piles it soon heats and throws off more or less steam and gas. This heating of the manure is caused by fermentation or the breaking down of the materials composing the manure and the forming of new compounds. This fermentation is produced by very small or microscopic plants called bacteria.
The fermentation of the manure is influenced by the following conditions:
A certain amount of heat is necessary to start the work of the bacteria. After they have once started they keep up and increase the temperature of the pile until it gets so hot that sometimes a part of the manure is reduced to ashes. The higher the temperature the more rapid the fermentation. This can be seen particularly in piles of horse manure.
The bacteria which produce the most rapid fermentation in manure need plenty of air with its oxygen. Therefore fermentation will be more or less rapid according as the manure is piled loosely or in a close compact ma.s.s.
A certain amount of moisture is necessary for the fermentation to take place, but if the manure is made quite wet the temperature is lowered and the fermentation is checked. The water also checks the fermentation by limiting the supply of air that can enter the pile.
The composition of the manure influences the fermentation. The presence of considerable amounts of soluble nitrogen hastens the rapidity of the fermentation.
Now when the manure ferments a large part of the organic matter in it is broken down and changed into gases. The gas formed most abundantly by the fermentation is carbonic acid gas, which is produced by the union of oxygen with carbon of the organic matter. The formation of this gas means a loss of humus. This loss can be noticed by the fact that the pile gradually becomes smaller.
The next most abundant product of the fermentation is water vapor which can often be seen pa.s.sing off in clouds of steam.
When manure ferments rapidly the nitrogen in it is changed largely into ammonia. This ammonia combines with part of the carbonic acid gas and forms carbonate of ammonia, a very volatile salt which rapidly changes to a vapor and is lost in the atmosphere. This causes a great loss of nitrogen during the rapid decomposition of the manure. This loss can be detected by the well known odor of the ammonia which is particularly noticeable about horse stables and piles of horse manure.
Besides these gases a number of compounds of nitrogen, potash, etc., are formed which are soluble in water. It is these that form the dark brown liquid that sometimes oozes out from the base of the manure heap.
At the Cornell University Agricultural Experiment Station, the following experiment was carried out to find out how much loss would take place from a pile of manure:
"Four thousand pounds of manure from the horse stable were placed out of doors in a compact pile and left exposed from April 25th to September 22d. The results were as follows:"
----------------------------+-------------+--------------+---------- | April 25. | Sept. 22. | Loss | | | per cent.
----------------------------+-------------+--------------+---------- Gross weight | 4,000 lbs. | 1,730 lbs. | 57 Nitrogen | 19.6 " | 7.79 " | 60 Phos. acid | 14.8 " | 7.79 " | 47 Potash | 36 " | 8.65 " | 76 Value of plant food per ton | $2.30 | $1.06 | ----------------------------+-------------+--------------+----------
This shows a loss of more than half the bulk of the manure and more than half the plant food contained in it.
CHECKING THE LOSSES
The first step to be taken in preserving the manure or in checking losses is to provide sufficient bedding or litter in the stable to absorb and save all the liquid parts.
The losses from fermentation of hot manures like horse manure may be largely checked by mixing with the colder manure from the cow stable.
Losses from fermentation may also be checked.
By piling compactly, which keeps the air out.
By moistening the pile, which lowers the temperature and checks the access of oxygen.
The manure may be hauled directly to the field each day and spread on the surface or plowed in. This method is the best when practicable because fermentation of the manure will take place slowly in the soil and the gases produced will be absorbed and retained by the soil.
Gypsum or land plaster is often sprinkled on stable floors and about manure heaps to prevent the loss of ammonia.
Copperas or blue stone, kainite and superphosphate are sometimes used for the same purpose. There is, however, nothing better nor so good for this purpose as dry earth containing a large percentage of humus.
Losses from washing or leaching by rain may be prevented by piling the manure under cover or by hauling it to the field as soon as produced and spreading it on the surface or plowing it under.
APPLYING THE MANURE TO THE SOIL
From ten to twenty tons per acre is considered a sufficient application of barn manure for most farm crops. Larger amounts are sometimes applied to the soil for truck and market garden crops.
Barn manures are applied to the soil by these methods:
The manure is sometimes hauled out from the barn and placed in a large pile in the field or in many small piles where it remains for some time before being spread and plowed or harrowed in.
Some farmers spread it on the field and allow it to lie some time before plowing it in.
It is sometimes spread as soon as hauled to the field and is immediately plowed in or mixed with the soil. This last is the safest and most economical method so far as the manure alone is concerned.
When the manure is left in a large pile it suffers losses due to fermentation and leaching.
At the Cornell University Agricultural Experiment Station, five tons of manure from the cow stable, including three hundred pounds of gypsum which was mixed with it, were exposed in a compact pile out of doors from April 25th to September 22d. The result was as follows:
----------------------------+-------------+-------------+---------- | April 25 | Sept 22 | Loss | | | per cent.
----------------------------+-------------+-------------+---------- Gross weight | 10,000 lbs. | 5,125 lbs. | 49 Nitrogen | 47 " | 28 " | 41 Phos. acid | 32 " | 26 " | 19 Potash | 48 " | 44 " | 8 Value of plant food per ton | $2.29 | $1.60 | ----------------------------+-------------+-------------+----------
When distributed over the field in small piles and allowed to remain so for some time, losses from fermentation take place, and the rain washes plant food from the pile into the soil under and immediately about it. This results in an uneven distribution of plant food over the field, for when the manure is finally scattered and plowed in, part of the field is fertilized with washed out manure while the soil under and immediately about the location of the various piles is often so strongly fertilized that nothing can grow there unless it be rank, coa.r.s.e weeds.
[Ill.u.s.tration: FIG. 79.--A CROP OF COWPEAS.]
[Ill.u.s.tration: FIG. 80.--RED CLOVER.]
When the manure is spread on the surface and allowed to lie for some time it is apt to become dry and hard, and when finally plowed in, decays very slowly.
When the manure is plowed in or mixed with the soil as soon as applied to the field there results an even distribution of plant food in the soil, fermentation takes place gradually and all gases formed are absorbed by the soil, there is very little loss of valuable nitrogen and organic matter, and the fermentation taking place in the soil also aids in breaking down the mineral const.i.tuents of the soil and making available the plant food held by them.
Therefore it seems best to spread the manure and plow it in or mix it with the soil as soon as it is hauled to the field, when not prevented by bad weather and other more pressing work.
PROPER CONDITION OF MANURE WHEN APPLIED
A large part of the value of barn manure lies in the fact that it consists largely of organic matter, and therefore has an important influence on soil texture, and during its decay in the soil produces favorable chemical changes in the soil const.i.tuents. Therefore it will produce its greatest effect on the soil when applied fresh. For this reason it is generally best to haul the manure to the field and mix it with the soil as soon after it is produced as possible.
If coa.r.s.e manures are mixed with light, sandy soils it is best to follow with the roller, otherwise the coa.r.s.e manure may cause the soil to lie so loose and open that both soil and manure will lose moisture so rapidly that fermentation of the manure will be stopped and the soil will be unfit for planting.
If it is desired to apply manure directly to delicate rooted truck and vegetable crops it is best to let it stand for some time until the first rank fermentation has taken place and the manure has become rotten.
A good practice is to apply the manure in its fresh condition to coa.r.s.e feeding crops like corn, and then follow the corn by a more delicate rooted crop which requires the manure to be in a more decomposed condition than is necessary for the corn. In this case the corn is satisfied and the remaining manure is in proper condition for the following crop when it is planted.
Another practice is to broadcast the coa.r.s.e manure on gra.s.s land and then when the hay is harvested the sod and remaining manure are plowed under for the following crop.
A study of root development in Chapter II. tells us that most of the manure used for cultivated crops should be broadcasted and thoroughly mixed with the soil. A small amount may be placed in the drill or hill and thoroughly mixed with the soil for crops that are planted in rows or furrows in order to give the young plant a rapid start. For the vegetable garden and flower garden and lawns, it is best to apply only manure that has been piled for some time and has been turned over several times so that it is well rotted and broken up.
There may not be a single farm where it will be possible to carry out to the letter these principles applying to the treatment and application of barn manures.