FARM CHEMISTRY

Lyttelton Times, Volume CXX, Issue 14976, 23 April 1909, Page 10

FARM CHEMISTRY

v ßy Mr JOHN PORTER, B.Sc., in “ Tho Scottish Farmer.”) It is not easy for a person who has had no training in chemistry to interpret unaided the many ways it is possible to state the analysis of an artificially compounded manure, but it does not follow', by any means, that he should give up in despair on account of this difliculty. All that is necessary for him, to bo able to read an analysis intelligently, is that ho should have it explained in. a simple way. It is no more difficult than our coinage system. Everyone knows that 24 halfpennies, 12 pennies, 4 threepennypieces, 2 sixpences, and 1 shilling havo the same value. The size varies, and so does the weight of the copper as compared with the silver, but the value in each case is identical. Tho same thing applies to manures, and with a little study it will be as easy to know tho “ manure table ” as tho “ money table.” Chemistry is a wonderfully exact science, and when nitrogen is mentioned, it stands for something quite definite; the same tiling applies to phosphoric acid and potash. These three things, although all mammal constituents, are, however, quite different and quite distinct—just as distinct as a horse from a cow, and a cow t from a sheep, which are all farm animals; and the only means we have of comparing them is as we compare horses, cattle and sheep, and that is on tho valuo basis. One horse may bo worth three cows or thirty sheep. Similarly, tho value of a given amount of nitrogen is valued at about six times that of soluble phosphate, and almost four times that of potash. Nitrogen can never take the place of phosphates, or phosphates of potash. These being essential for tho perfect growth of crops, aro contained in almost all compound manures. After having got some idea as to the distinctness of those three constituents—nitrogen, phosphates and potash—wo will now see how the analysis in any of these constituents may be stated.

There aro several ways in which tho percentage of nitrogen may be expressed in a manure—e.g. : (a) Containing 3 per cent nitrogen; (b) containing 3.64 per cent ammonia; (c) containing nitrogen equal to 3.64 per cent ammonia; (d) containing nitrogen 3 per cent, equalling ammonia 3.64 per cent; (e) containing nitrogen, ammonia, 3.64 per cent; (f) containing 14.14 per cent sulphate of ammonia. Some of these numbers vary very considerably, but to anyone who knows a little chemistry the differences are only apparent; in fact, they all como to the same thing in the valuation of the manure. Tho first three ways are quite easy, but the. last three are unusual., and to some extent misleading. All that is necessary here is to give the “manure table ” showing the relation between nitrogen, ammonia. and sulphate of ammonia .-—One per cent of nitrogen equals 1.214 per cent of ammonia ; 1 per cent of nitrogen equals 4.714 per cent of sulphate of ammonia, Where tho nitrogen is given in terms of ammonia or sulphate of ammonia, the percentage is simply divided by 1.214 (If nearly) or 4.714 (linearly) respectively, and we got the result in terms of nitrogen. This will give us the number of units’of nitrogen.

Phosphates in a manure analysis always mean insoluble phosphate of lime. If it means anything else there will bo a statement, to that effect. One does sometimes find the analysis stated in terms of phosphoric acid (P2 05), but never in a manure circular; but where such a case does occur it only requires to be multiplied by 2.183, then we get it in terms of phosphate of iime. It is very common to have tho percentage of eolnhlo and insoluble phosphites given in a compound manure, and these may be stated in three different ways —(a) containing 16 per cent- soluble phosphate, 4 per cent insoluble phosphate; (b) containing 20 per cent total phosphate, 16 per cent soluble phosphate; (c) containing 20 per cent total phosphate, of which 16 per cent is soluble.. A glance at llieso three cnee will show that they are all identical. The first is the correct way to state it, although they aro all quite legitimate. Whore an analysis gives the soluble and insoluble phosphates as hono phosphates, a slightly higher value should be given. Thee© may bo taken ns fellows:—Soluble bone phosphate, equals 2a 7d nor unit, insoluble bone phosphate, equals Is 4d per unit. Potash may bo stated <is “ potash ” or “ sulphate of potash.” The latter is by far tho more common—e.g. : (a) Containing 3 per cent potash ; (b) containing 5.55 per cent sulphate of potash; (c) containing 14 per cent alkaline salts, equal to 5.55 per cent sulphate of potash. The percentage of potash in these three cases is exactly the same for valuation purposes. Tho last one is rather misleading, ns the 14 per cent looks fairly well. Alkaline salts is a vague term, but if one reads further, its equivalent in sulphate of potash is inserted. although rather obscurely, behind it. The very name “ alkaline salts ” makes one suspect, that the potash is derived from some impure salt of potash like kainit. Our manure table for potash will now be : One per cant of potash equals 1.85 per cent of sulphate or potash. Wo nave now got all the necessary material to calculate the value of any compound manure. Tho unit value. l ) vary from year to year, but these can be obtained each year from the excellent leaflet published by the Highland and Agricultural Society in February. The whole thing is being able to re- j state an analysis in terms of nitrogen, solubable and insoluble phosphates, and potash ; then the rest is quite easy. One example will be given to show exactly how tho above data would be applied. Take a manure with the following analysts :—Nitrogen, 3 per cent — equalling ammonia, 3.64 par cent ; total phosphate, IS to 20 per cent; soluble phosphate-, 12 to 14 per cent; sulphate of potash, 3.7 per cent. This is certainly a had ease, and _ the ammonia ought never to he given in this way, as it appears to the unintiated as if it contains nitrogen and ammonia, when all the time the ammonia content ie simply a repetition of the nitrogen content. When two percentages are given the smaller number only is guaranteed, and this must bo kept in mind with the phosphates. Now, let us whip it into shape by applying our “ manure table,” when necessary. This is the result: — Nitrogen, 3 per cent; soluble phosphates, 12 per cent; insoluble phosphates (18-12). 6 per cent: potash (3.7 divided by 1.85), 2 per cent. No other constituent should receive any a t.tentiou in the analysis of a compound manure. The writer has known a ease where tho analysis of a manure j contained, among other things. 40 per j cent of organic matter. No valuo whatever must ho placed on such a statement. Farmers would do well to insist on a straightforward analysis, where the nitrogen, phosphates and potash are given as in the result above.