Chapter 23

FARM MANURES

FUNCTIONS OF MANURES AND FERTILIZERS

In Chapter II we learned that the roots of plants for their growth and development need a soil that is firm yet mellow, moist, warm, ventilated and supplied with plant food. We also learned that of the plant foods there is often not enough available nitrogen, phosphoric acid, potash and lime for the needs of the growing plants.

Manures and fertilizers are applied to the soil for their beneficial effects on these necessary conditions for root growth and therefore to assist in maintaining soil fertility.

CLASSIFICATION OF MANURES AND FERTILIZERS

Manures may be classified as follows:

{ Barn or stable manures, Farm manures. { Green-crop manures, { Composts.

Commercial { Materials furnishing nitrogen, fertilizers { " " phosphoric acid, or artificial { " " potash, manures. { " " lime.

IMPORTANCE OF FARM MANURES

Of these two classes of manures the farmer should rely chiefly on the farm manures letting the commercial fertilizers take a secondary place because:

Farm manures are complete manures; that is they contain all the necessary elements of plant food.

Farm manures add to the soil large amounts of organic matter or humus.

The decay of organic matter produces carbonic acid which hastens the decay of mineral matter in the soil and so increases the amount of available plant food.

The organic matter changes the texture of the soil.

It makes sandy soils more compact and therefore more powerful to hold water and plant food.

It makes heavy clay soils more open and porous, giving them greater power to absorb moisture and plant food. This admits also of better circulation of the air in the soil, and prevents baking in dry weather.

Farm manures influence all of the conditions necessary for root growth while the commercial fertilizers influence mainly the plant food conditions.

The farm manures are good for all soils and crops.

They are lasting in their effects on the soil.

BARN OR STABLE MANURE

Barn or stable manure consists of the solid and liquid excrement of any of the farm animals mixed with the straw or other materials used as bedding for the comfort of the animals and to absorb the liquid parts.

The liquid parts should be saved, as they contain more than half of the nitrogen and potash in the manure.

The value of barn manure for improving the soil conditions necessary for root growth depends in a measure upon the plant food in it, but chiefly upon the very large proportion of organic matter which it contains when it is applied to the soil.

These factors are influenced somewhat: by the kind of animal that produces the manure; by the kind of food the animal receives; by the kind and amount of litter or bedding used; but they depend particularly on the way the manure is cared for after it is produced.

LOSS OF VALUE

Improper care of the manure may cause it to diminish in value very much.

_Loss by leaching._

If the manure is piled against the side of the stable where water from the roof can drip on it, as is often the case, or if it is piled in an exposed place where heavy rain can beat on it, the rain water in leaching through the manure washes out of it nitrogen and potash, which pass off in the dark brown liquid that oozes from the base of the pile.

_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 mass.

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 passing 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, coarse weeds.