The quantities of ammonia thus absorbed, both in the laboratory and field experiments are small--from 0.7 to 1.3 _per cent._ The absorption is without doubt chiefly due to the organic matter of the peats, and in all the specimens on which these trials were made, the proportion of inorganic matter is large. The results therefore become a better expression of the power of _peat_, in general, to absorb ammonia, if we reckon them on the organic matter alone. Calculated in this way, the organic matter of the Beaver Pond peat (which constitutes but 68 _per cent._ of the dry peat) absorbs 1.4 _per cent._ of free ammonia, and 1.9 _per cent._ of ammonia out of the carbonate of ammonia.
Similar experiments, by Anderson, on a Scotch peat, showed it to possess, when wet, an absorptive power of 2 _per cent._, and, after drying in the air, it still retained 1.5 _per cent._--[Trans. Highland and Ag'l Soc'y.]
When we consider how small an ingredient of most manures nitrogen is, viz.: from one-half to three-quarters of one _per cent._ in case of stable manure, and how little of it, in the shape of guano for instance, is usually applied to crops--not more than 40 to 60 lbs. to the acre, (the usual dressings with guano are from 250 to 400 lbs. per acre, and nitrogen averages but 15 _per cent._ of the guano), we at once perceive that an absorptive power of one or even one-half _per cent._ is greatly more than adequate for every agricultural purpose.
III.--_Peat promotes the disintegration of the soil._
The soil is a storehouse of food for crops; the stores it contains are, however, only partly available for immediate use. In fact, by far the larger share is locked up, as it were, in insoluble combinations, and only by a slow and gradual change can it become accessible to the plant. This change is largely brought about by the united action of _water_ and _carbonic acid gas_. Nearly all the rocks and minerals out of which fertile soils are formed,--which therefore contain those inorganic matters that are essential to vegetable growth,--though very slowly acted on by pure water, are decomposed and dissolved to a much greater extent by water, charged with carbonic acid gas.
It is by these solvents that the formation of soil from broken rocks is to a great extent due. Clay is invariably a result of their direct action upon rocks. The efficiency of the soil depends greatly upon their chemical influence.