HKB
can only be relied upon, when the plots are accurately measured, when the peat, etc., are applied in known quantities, and when the crops are separately harvested and carefully weighed.
If experiments are made upon grass or clover, the gravest errors may arise by drawing conclusions from the appearance of the standing crop. Experience has shown that two clover crops, gathered from contiguous plots differently manured, may strikingly differ in appearance, but yield the same amounts of hay.
The chemical examination of a peat may serve to inform us, without loss of time, upon a number of important points.
To test a peat for soluble iron salts which might render it deleterious, we soak and agitate a handful for some hours, with four or five times its bulk of warm soft water. From a good fresh-water peat we obtain, by this treatment, a yellow liquid, more or less deep in tint, the taste of which is very slight and scarcely definable.
From a vitriol peat we get a dark-brown or black solution, which has a bitter, astringent, metallic or inky taste, like that of copperas.
Salt peat will yield a solution having the taste of salt-brine, unless it contains iron, when the taste of the latter will prevail.
On evaporating the water-solution to dryness and heating strongly in a China cup, a vitriol peat gives off white choking fumes of sulphuric acid, and there remains, after burning, brown-red oxide of iron in the dish.
The above testings are easily conducted by any one, with the ordinary conveniences of the kitchen.
Those that follow, require, for the most part, the chemical laboratory, and the skill of the practised chemist, for satisfactory execution.
Besides testing for soluble iron compounds, as already indicated, the points to be regarded in the chemical examination, are:--
1st. Water or moisture.--This must be estimated, because it is so variable, and a knowledge of its quantity is needful, if we will compare together different samples. A weighed amount of the peat is dried for this purpose at 212 deg. F., as long as it suffers loss.
2d. The proportions of organic matter and ash are ascertained by carefully burning a weighed sample of the peat. By this trial we distinguish between peat with 2 to 10 per cent. of ash and peaty soil, or mud, containing but a few per cent. of organic matter.
This experiment may be made in a rough way, but with sufficient accuracy for common purposes, by burning a few lbs. or ozs. of peat upon a piece of sheet iron, or in a sauce pan, and noting the loss, which includes both water and organic matter.
3d. As further regards the organic matters, we ascertain the extent to which the peaty decomposition has taken place by boiling with dilute solution of carbonate of soda. This solvent separates the humic and ulmic acids from the undecomposed vegetable fibers.
For practical purposes this treatment with carbonate of soda may be dispensed with, since the amount of undecomposed fiber is gathered with sufficient accuracy from careful inspection of the peat.
Special examination of the organic acids is of no consequence in the present state of our knowledge.
4th. The proportion of nitrogen is of the first importance to be ascertained. In examinations of 30 samples of peat, I have found the content of nitrogen to range from 0.4 to 2.9 per cent., the richest containing seven times as much as the poorest. It is practically a matter of great moment whether, for example, a Peruvian guano contains 16 per cent. of nitrogen as it should, or but one-seventh that amount, as it may when grossly adulterated. In the same sense, it is important before making a heavy outlay in excavating and composting peat, to know whether (as regards nitrogen) it belongs to the poorer or richer sorts. This can only be done by the complicated methods known to the chemist.