5.--_The Examination of Peat (muck and marsh-mud) with reference to its Agricultural Value._
Since, as we are forced to conclude, the variations in the composition of peat stand in no recognizable relations to differences of appearance, it is only possible to ascertain the value of any given specimen by actual trial or by chemical investigation.
The method _by practical trial_ is usually the cheaper and more satisfactory of the two, though a half year or more is needful to gain the desired information.
It is sufficient to apply to small measured plots of ground, each say two rods square, known quantities of the fresh, the weathered, and the composted peat in order, by comparison of the growth and _weight_ of the crop, to decide the question of their value.
Peat and its composts are usually applied at rates ranging from 20 to 40 wagon or cart loads per acre. There being 160 square rods in the acre, the quantity proper to a plot of two rods square (= four square rods,) would be one half to one load.
The composts with stable manure and lime, or salt and lime mixture, are those which, in general, it would be best to experiment with. From the effects of the stable manure compost, could be inferred with safety the value of any compost, of which animal manure is an essential ingredient.
One great advantage of the practical trial on the small scale is, that the adaptation of the peat or of the compost to the _peculiarities of the soil_, is decided beyond a question.
It must be borne in mind, however, that the results of experiments 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.