| 14·11 tons of organic matter at 10s. | £7 0 0 |
| 14·86 " soluble phosphates at £30 | 446 0 0 |
| 15·13 " insoluble phosphates at £7 | 105 0 0 |
| 39·43 " sulphate of lime at £1 | 39 0 0 |
| 3·82 " alkaline salts at £1 | 4 0 0 |
| 2·10 " ammonia at £60 | 126 0 0 |
| ————— | |
| Value of 100 tons | £727 0 0 |
| or £7 : 5s. per ton. |
According to the second column, the numbers give the sum by which the per centages of each ingredient must be multiplied, to give its value in a ton of manure, and it is used for the same manure in the following manner:—
| 14·11 organic matter, multiplied by | 1-1/4d. | £0 | 1 | 5 |
| 14·88 soluble phosphates " | 6s. | 4 | 9 | 2 |
| 15·13 insoluble phosphates " | 1s. 5d. | 1 | 1 | 4 |
| 39·43 sulphate of lime " | 2-4/10d. | 0 | 8 | 10 |
| 3·82 alkaline salts " | 2-4/10d. | 0 | 0 | 9 |
| 2·10 ammonia " | 12s. | 1 | 5 | 3 |
| ———— | ||||
| Value per ton | £7 | 6 | 9 | |
The difference is due to the less minute calculation of fractional quantities in the latter case.
The calculation of the value of any other manure is effected in exactly the same manner, taking care, however, to use the higher value for phosphates in the case of a phosphatic guano. It will be obvious to every one who tries the two methods that the first greatly exceeds the second in convenience and simplicity in the calculations, and it is that most commonly in use, although some persons prefer the second.
Although the data just given must always form the basis of the valuation of any manure, there are a variety of other circumstances which must be taken into account, and which give great scope for the judgment and experience of the valuator. Of these the most important is the proper admixture of the ingredients, and the condition of the manure as regards dryness, complete reduction to the pulverulent state, and the like. A certain allowance ought always to be made for careful manufacture; and, on the other hand, where the manure is damp or ill reduced, a small deduction (the amount of which must be decided by the experience of the valuator) ought to be made on account of the risk which the farmer runs of loss from unequal distribution, and the extra cost of carriage of an unnecessary quantity of water.
It is also necessary to take into account the particular element required by the soil. Thus, a farmer who finds his soil wants phosphates, will look to the manure containing the largest quantity of that substance, and possibly not requiring ammonia, will not care to estimate at its full value any quantity of that substance which he may be compelled to take along with the former, but will look only to the source from which he can obtain it most cheaply. It may be well, therefore, to point out that ammonia is most cheaply purchased in Peruvian guano; insoluble phosphates in coprolites; and soluble phosphates in superphosphates, made from bone-ash alone. In general, however, it will be found most advantageous to select manures in which the constituents are properly adjusted to one another, so that neither ammonia, soluble nor insoluble phosphates, preponderate; but, of course, it must frequently happen that it will prove more economical to buy the substances separately and to make the mixture, than to take the manure in which they are ready mixed.
In judging of the value of any manure, it is also important to make sure that the analysis which forms the basis of the calculation is that of a fair sample, which correctly represents the bulk actually delivered to the purchaser, and not one which has been made to do duty for an unlimited quantity of manure, which is supposed to be all of equal quality, as often happens in the hands of careless manufacturers, and too great attention cannot be devoted to the selection of the sample, which is very often done in an exceedingly slovenly manner.