ARTIFICIAL MANURES AND THEIR USES.

Otago Witness, Issue 2523, 23 July 1902, Page 6

ARTIFICIAL MANURES AND THEIR USES.

When the farmer finds that it is necessary or advisable to ptirchase some manure for the use of a particular crop, he must exercise great judgment in selecting from the various manures on the market. He must know the nature of the food required b\- the crop he wishes to help, and the form in winch that food is best relished by that crop ; he must be acquainted with the composition and potentialities of the different fertilisers that are on sale ; he must consider the natural peculiarities of the climate in which his farm is .situate ; he must have regard to the nature of his soil and the condition in which it is : and ■he must have regard to tlie prices at whioh he can purchase those manures which are more particularly suited to his purpose. To afford farmers much needed information regarding the principles and action under various conditions and influences" of inherently valuable fertilisers, the following copious extracts from a leaflet headed .as above, recently issued by the English Board of Agriculture, are submitted for thoughtful consideration and future reference.

"There are three substances, and only three, that are valued in artificial manures — namely, nitrogen, phosphates, and potash. According, therefore, to the greater or less quantity of one or the other of these substances, the value of the manure will rise or fall. Some manures contain only one of these substances — for instance, nitrate of soda and sulphate of ammonia contain only nitrogen ; superphosphate and basic slag contain only phosphate ; and kainit. sulphate of potash, and muriate of potash contain only potash — while other manures hold two substances of value, as ia the case of bones, which furnish both nitrogen and phosphates, or saltpetre (very used, .however, as a manuie), which supplies both nitrogen and potash. Only one class of so-called artificial manure— namely, Peruvian or other similar guano, contains an important amount of all three substances."

In price lists, nitrogen is often expressed as ammonia. The relationship between the two substances is, however, a, very simple one, and need occasion no difficulty or uncertainty. Seventeen pounds of ammonia always contain exactly 141b of nitrogen or, what is the same thing from the farmer's point of view. 141b of nitrogen are the equivalent of 171b of ammonia. If. therefore, a sample of, say, "corn manure" is offered as containing 4.5 per cent, of ammonia, this is the same as saying 3.7 per cent, of nitrogen. Sometime*, though not often, the figure is made to look moie attractive by being stated a.« sulphate of ammonia, but this also need cause no difficulty, if it be remembered that 661b of this 'substance are equiv^ent to no more than 141b of nitrogen or 171b of ammonia. If, therefore, we take the above example the figures mean one and the same thing, whether they are stated 3.7 per cent, of nitrogen or 4.5 per cent, of ammonia or 17.4 per cent, of sulphate of ammonia. But a manure merchant who failed to make many iales of a fertiliser of ever so high-sounding a name on ;i statement of 1 per cent, of nitrogen or 1 2 per cent of ammonia, might be more successful with a certain class of buyer if he entered the nitrogen as equal to 4.7 per cent, of sulphate of ammonia, and yet the three figures- all represent the same fact. Under "The British Fertilisers and Feeding Stuffs Act, 1893," the Invoice must contain the minimum guarantee of nitrogen, stated as such.

Phosphates, or phosphate of lime, may also be entered in an analysis or price list in different ways, but as a rule this ingredient is either stated as above, o^ as phosphoric acid. In an invoice, liowever, the statement must be made as soluble or insoluble phosphates, as the case may be. The relationship between phosphates or phosphate of lime, whether soluble or insoluble, and phosphoric acid is quite as simple as that between nitrogen and ammonia. One hundred and foity-two pounds of phosphoric acid always form 3101b -of phosphate of lime ; so' that to convert the former into the latter one may multiply by 2 2. which, though giving an answer .slightly above the truth, is quite accurate enough for all ordinary purposes. If, therefore, the analysis of a manure is returned as 12 per cent, of phosphoric acid, it is equivalent to saying that it conInins fully 26 per cent, of phosphates, fiimilaily, '30 per cci t. of phosphates is equal to" nearly 14 per cent, of phosphoric acid.

Potash usually exists in manure in the two forms of sulphate of potash and muriate or chloride of potash. It takes 94.21b of pure potash to four 174.21b of sulphate of potash, viheieas the frame amount of potash will" form only 149.21b of the inuiicite or chloride In the foimer case, therefore, to couveit potash into terms of sulphate of potash, we multiply by 1.85, whereas in the latter ca<-e we multiply by 1.58. If, therefore, an unalysh of, cay, kainit is stated a.s 12.5 per cent, of pota&h, this is equivalent t& saj-ing that it holds over 23 per cent, of sulphate of potash ; while muriate of potash guaranteed to contain 56.8 per cent, of potash is of about 90 per cent, purity. Just as a buyer may sometimes be led into purchasing a manure through its nitrogen being expressed as sulcbitte of amjaottiaj so uaay the ggatento

of potash be made to look more" attractiva by being stated as sulphate of potash. In a a invoice, however, the contents must te stated as such. The rules for approximately converting the various terms into their equivalents may be thus summarised: — To convert nitrogen into terms of ammonia, multiply by 1.2 To convert nitrogen into terms of sulphate of ammonia, multiply by.. .. 4.7 To convert phosphoric acid into terms of phosphates, multiply by 2.2 To convert potash, into terms 01 sulphate of potash, multiply by 1.85 To convert potash into terms of muriate of potash, multiply by 1.58 Nitrogen and phosphates and, to a large extent potash vary in effectiveness, and, therefore, in value, according to their source or origin. Nitrogen is never so effective as when in the form of nitrate of soda. It is not quite so active, and for some purposes not so valuable, when in the form of sulphate of ammonia, though under certain circumstances this somewhat slower action may be regarded as an advantage. Nitrogen in what is called the organic form is in its least active condition, though here again the rapidity and effectiveness of action vary greatly. Nitrogen is in the organic form in blood meal, fish: meal, bones, shoddy, etc., and yet as a, source of plant food blood meal is more active than these other substances. It is claimed as an advantage for slow acting manures that they last longer, which is true ; but one applies manures not to last, but to act. It is only where it is convenient to apply manures at somewhat long intervals, as in the treatment of orchards, that the more inert manures are ■n orthy of much consideration.

As regards pliosphatic manures, it may bo said that, while soluble phosphates are all alike active, there is considerable difference in the value of Insoluble phosphates. The insoluble phosphate of bone meal, for instance, is less effective, and for most purposes less valuable than the in-i soluble phosphate of basic slag, precipitated phosphate, or even dissolved bones. Some of the insoluble phosphate of the last manure has ouce been soluble, and has '"reverted." and such phosphate is not muchless effective than soluble phosphate. But raw bones, as a manure, have been longer known to British farmers than other forms of phosphate, and for this reason thenprice lias kept relatively high. The most important purely nitrogenous manures are nitrate of soda and sulphate of ammonia ; others in less general use being rape dust, blood meal, shoddy, etc. Other tlrings being equal, nitrate of soda is specially suitable- — (a) For n=e In spring and early summer. (b» For use on heavy land. (c) For use as a top-dressing. (d) For use m a dry district. (c) For use where immediate effect 13 de« sued. Speaking generally, sulphate of ammonia suits better— (a) For tise on crops that make their growth late in the season ; for example, turnips. (b) For use on l'ght land. (c) For use on soil holding abundance or mild lime. (d) For use where it can be mixed with the soil (in. contrast to top-dressing).

(c) For use in a wet district,

It is, however, often difficult to say for which of the two manures the conditions are ny st suitable, and then the question should be decided either by the relative cost of the substances or by using a certain amount of both. Nitrogenous manures cannot be profitably employed on leguminous crops (peas, beans, clover, etc.) ; and on al mixed crop of, say, clover and grass, if the clover is to be preserved against suppression, tlrey must be used sparingly, if at all. They mus* also be used with caution on barley, and especially so where a fine sample rather tlian a large yield is looked for. Other crops, however, ■ generally respond freely to the use of this class of manure.

Nitrate of soda an.i sulphate of ammonia are apt to be lumpy ; therefore the buyer should look carefully to the mechanical condition. Nothing should be applied that will not pass a half-inch riddle. Lumps larger than this will often kill plants with which they may come in contact. Nitrate of soda is genenliy offered on the basis of 95 per cent, of purity (equal to 15.6 per. cent, nitrogen or 19 per cent, ammonia), while commercial sulphate of ammonia, usually contains 97 per cent, of the pur© article (equal to 20.6 per cent, nitrogen or 25 per cent, ammonia). Sulphate of ammonia is thus the more highly concentrated manure.

Of the purely pliosphatic manures, superphosphate and basic slag are the most important. The foimer is, speaking generally, more suitable for use under the following circumstances : — (a) Where rapid effect 19 wanted. (b) la spring. (c) For arable land. (d) Foi admixture with sulphate of am* moma. Basic slag is specially suitable (a) For use in autumn. (b) For use on grass land. (c) For use on land containing peat or vege* table matter. (d) For use on lands addicted to finger-and-toe. (c) For use in orchards.

(f) For admixture with nitrate of soda.

Basic slag generally .le-ives little to be desired as regards mechanical condition, provided the grinding be fine enough (80 per cent, through a No. 100 sieve — that is, 100 wires per linear inch, or 10,000 aper« lures per squara mch — should be the mini* mum requirement). Supeiphospliate some-* times is almost as dry and ziealy as slag,; but in other cases it is lumpy and sticky.

Samples of the latter character are of reduced value, and should be avoided. Super- "" jbosphate is of varying degrees of quality, the usual contents being 28 to 30 per cent. of soluble phosphate. Basic slag also varies in quality, the usual contents being 35 to 40 per cent, of insoluble phosphate. Phosphatic manures are of special value in the manuring of turnips, leguminous crops, hay, and pasture. They are of less importance for potatoes and mangels, and least of all for cereals. In the case of the last class of crops it usually happens that the plains are able to satisfy their requuements as regards phosphates from the natural supplies of the soil, or from residues of former applications. Whether, on any particular farm, it will pay to apply a direct phosphatic dressing to a corn crop can only be determined with certainty by means of a simple field experiment.

The most important of the nitrogenous phosphatic manures is diswlved bones, though bone meal, fish meal, etc., have their value for certain purposes. Dissolved bones lose their value through being damp and lumpy; they can, however, be bought as dry and almost as fine as superphosphate. They usually contain 32 to 34 per cent, of total phosphates (of which more than half should be soluble) and fully 3 per cent, of nitrogen. Bone meal should be "very fine and free from grease. Any particles one-tenth of an inch or upwards in size become available very slowly. It should hold about 50 per cent, of phosphates and 4 of nitrogen.

Genuine tainit contain.? about 12g per cent, of potash, besides which it holds over 30 per cent, of connaon salt. Where a farmer wants to use the latter substance he may find it to his advantage to use this manure. Sulphite of potash is offered in various degrees of strength, containing from 25 to over 40 per cent, of potash. Muriate or chloride of potash often holds over 50 per ceat. of potash. All potash manures are apt to be lumpy, and if they are stored long they may become so hard as to be almost unmanageable. Poor mechanical condition is here quite as undesirable as in the case of other manures. Potash manures are most important for root ai;d leguminous crops, less so for glass and cere.ils. There are many well-authenticated instances of potash manures doing positive harm to meadows, though in other cases they have been used effectively. Whether they are •wanted on any particular farm or not can only be determined by experiment.