An Act was passed, and came into operation in January 1894, for the purpose of compelling every vendor of manure manufactured in this country or imported from abroad to give to the purchaser "an invoice stating the name of the article, and whether it is an artificially compounded article or not, and what is at least the percentage of the nitrogen, soluble and insoluble phosphates, and potash, if any, contained in the article, and this invoice shall have the same effect as a warranty by the seller of the statements contained therein."
Different Methods of Valuing Manures.
The monetary value of a manure depends upon a number of more or less complicated commercial considerations, such as the questions of supply and demand, &c., which need not here be discussed, and which similarly regulate the monetary value of any other article of commerce.
"Unit" Value of Manurial Ingredients.
For the purpose of affording data for ascertaining the approximate value of a manure, tables have been drawn up giving what is called the "unit" value of the different manurial ingredients in various manures. This is obtained by dividing the market value of a manure per ton by the percentage of nitrogen, phosphoric acid, and potash it contains. Thus, for example, sulphate of ammonia of 97 per cent purity contains 25 per cent of ammonia, and at present (Dec. 1893) is valued at £13, 15s. per ton. In order to obtain the unit value of ammonia in sulphate of ammonia, we have only to divide £13, 15s. by 25, which gives us 11s. The value of such tables depends on the competence of those drawing them up, and they require to be subjected to constant revision. In the Appendix will be found two of these tables, taken from the 'Transactions of the Highland and Agricultural Society of Scotland.'[251]
Intrinsic Value of Manures.
But there is another way of valuing manures, and that is by attempting to ascertain what their intrinsic worth is in producing an increase in the returns of the crops. Of course it may be said that the intrinsic worth of manure affects directly its market value. This is doubtless true, but it is not the only factor in determining the market value of a manure.
Again, the intrinsic worth of a manure may be said to vary according to the soil to which it is applied and the climatic conditions. This being so, it is important for every farmer to try and ascertain for himself what the intrinsic value of different manures is on the soil of his farm; and this can only be done by carrying out manuring experiments for himself. This leads us to say a word or two on the important subject of
Field Experiments.
It is impossible that every farm should be able to support an experiment station for the purpose of carrying out elaborate experiments on the effect of different manures on different crops. Nevertheless it is possible and highly desirable for every farmer who is engaged in arable farming on any scale to carry out simple experiments for the purpose of ascertaining the characteristic manurial requirements of his soil. This can be done at the expenditure of a little time and trouble, and should be carried out in the following way. The field on which it is desired to carry out the experiments should be divided into the requisite number of experiment plots. These, which may be the tenth, twentieth, or fortieth of an acre in extent, should be, if possible, on a level piece of ground—all of them equally free from the shelter of hedge or tree, and otherwise subjected to the same conditions. The nature of the soil of the different plots, as well as its past treatment, should be similar. It is desirable, in order to minimise experimental error as much as possible, to carry out the experiments in duplicate, or even triplicate. In the first place, there should be what is called a nothing plot—i.e., a plot receiving no manure. The produce obtained from this plot, compared with the produce obtained from the other manured plots, will thus furnish data for estimating the respective amounts of increase obtained by different manures. One very simple kind of experiment is what is called the "seven-plot" test. It consists in testing the results obtained by using nitrogenous, phosphatic, and potash manures alone and in different combinations. Thus the plots would be manured respectively as follows:—