Manures kept in cellars without being mixed with refuse matter are subject to the same losses.

When kept in the yard, they are still liable to be lost by evaporation.

They are here often saturated with water, and this water in its evaporation carries away the ammonia, and carbonic acid which it has obtained from the rotting ma.s.s. The evaporation of the water is rapidly carried on, on account of the great extent of surface. The whole ma.s.s is spongy, and soaks the liquids up from below (through hollow straws, etc.), to be evaporated at the surface on the same principle as causes the wick of a lamp to draw up the oil to supply fuel for the flame.

LIQUID MANURE containing large quant.i.ties of nitrogen, and forming much ammonia, is also liable to lose all of its organic part from evaporation (and fermentation), so that it is rendered as much less valuable as is the solid dung.[X]

[When does the waste of exposed manure commence?

What does economy of manure require?

What is the effect of leaching?

Give an ill.u.s.tration of leaching.]

From these remarks, it may be justly inferred that a very large portion of the _value_ of solid and liquid manure as ordinarily kept is lost by evaporation in a sufficient length of time, depending on circ.u.mstances, whether it be three months or several years. The wasting commences as soon as the manure is dropped, and continues, except in very cold weather, until the destruction is complete. Hence we see that true economy requires that the manures of the stable, stye, and poultry-house, should be protected from evaporation (as will be hereafter described), as soon as possible after they are made.

LEACHING.

The subject of _leaching_ is as important in considering the _inorganic_ parts of manures as evaporation is to the organic, while leaching also affects the organic gases, they being absorbed by water in a great degree.

A good ill.u.s.tration of leaching is found in the manufacture of potash.

When water is poured over wood-ashes, it dissolves their potash which it carries through in solution, making ley. If ley is boiled to dryness, it leaves the potash in a solid form, proving that this substance had been dissolved by the water and removed from the insoluble parts of the ashes.

[How does water affect decomposing manures?

Does continued decomposition continue to prepare material to be leached away?

How far from the surface of the soil may organic const.i.tuents be carried by water?]

In the same way water in pa.s.sing through manures takes up the soluble portions of the ash as fast as liberated by decomposition, and carries them into the soil below; or, if the water runs off from the surface, they accompany it. In either case they are lost to the manure. There is but a small quant.i.ty of ash exposed for leaching in recent manures; but, as the decomposition of the organic part proceeds, it continues to develope it more and more (in the same manner as burning would do, only slower), thus preparing fresh supplies to be carried off with each shower. In this way, while manures are largely injured by evaporation, the soluble inorganic parts are removed by water until but a small remnant of its original fertilizing properties remains.

[What arrests their farther progress?

What would be the effect of allowing these matters to filter downwards?

What does evaporation remove from manure? Leaching?]

It is a singular fact concerning leaching, that water is able to carry no part of the organic const.i.tuents of vegetables more than about thirty-four inches below the surface in a fertile soil. They would probably be carried to an unlimited distance in pure sand, as it contains nothing which is capable of arresting them; but, in most soils, the clay and carbon which they contain retain all of the ammonia; also nearly all of the matters which go to form the inorganic const.i.tuents of plants within about the above named distance from the surface of the soil. If such were not the case, the fertility of the earth must soon be destroyed, as all of those elements which the soil must supply to growing plants would be carried down out of the reach of roots, and leave the world a barren waste, its surface having lost its elements of fertility, while the downward filtration of these would render the water of wells unfit for our use. Now, however, they are all retained near the surface of the soil, and the water issues from springs comparatively pure.

EVAPORATION removes from manure--

Carbon, in the form of carbonic acid.

Hydrogen and oxygen, in the form of water.

Nitrogen, in the form of ammonia.

LEACHING removes from manure--

The soluble and most valuable parts of the ash in solution in water, besides carrying away some of the named above forms of organic matter.

FOOTNOTES:

[X] It should be recollected that every bent straw may act as a syphon, and occasion much loss of liquid manure.

CHAPTER IV.

ABSORBENTS.

[What substances are called absorbents?

What is the most important of these?

What substances are called charcoal in agriculture?

How is vegetable matter rendered useful as charcoal?]

Before considering farther the subject of animal excrement, it is necessary to examine a cla.s.s of manures known as _absorbents_. These comprise all matters which have the power of absorbing, or soaking up, as it were, the gases which arise from the evaporation of solid and liquid manures, and retaining them until required by plants.

The most important of these is undoubtedly _carbon_ or charcoal.

CHARCOAL.

_Charcoal_, in an agricultural sense, means all forms of carbon, whether as peat, muck, charcoal dust from the spark-catchers of locomotives, charcoal hearths, river and swamp deposits, leaf mould, decomposed spent tanbark or sawdust, etc. In short, if any vegetable matter is decomposed with the partial exclusion of air (so that there shall not be oxygen enough supplied to unite with all of the carbon), a portion of its carbon remains in the exact condition to serve the purposes of charcoal.

[What is the first-named effect of charcoal? The second?

Third? Fourth?

Explain the first action.]

The offices performed in the soil by carbonaceous matter were fully explained in a former section (p. 79, Sect. 2), and we will now examine merely its action with regard to manures. When properly applied to manures, in compost, it has the following effects:

1. It absorbs and retains the fertilizing gases evaporating from decomposing matters.

2. It acts as a _divisor_, thereby reducing the strength (or intensity) of powerful manures--thus rendering them less likely to injure the roots of plants; and also increases their bulk, so as to prevent _fire fanging_ in composts.

3. It in part prevents the leaching out of the soluble parts of the ash.

4. It keeps the compost moist.

The first-named office of charcoal, _i. e._, absorbing and retaining gases, is one of the utmost importance. It is this quality that gives to it so high a position in the opinion of all who have used it. As was stated in the section on soils, carbonaceous matter seems to be capable of absorbing every thing which may be of use to vegetation. It is a grand purifier, and while it prevents offensive odors from escaping, it is at the same time storing its pores with food for the nourishment of plants.