September r, 1S82.] THE TROPICAL AGRICULTURIST. 



267 



the winter. When the surface is covered by a crop, as 

 iu the case of permanent pasture or clover, then the 

 maximum quantity of nitrogen is absorbed, and the least 

 waste occurs, A very important fact brought out by the 

 experiments at Kothamsted is, that the capacity of a crop to 

 absorb nitrogen depends upon the presence of suitable 

 mineral food, especially potash and phosphoric acid. 



"We do not entirely receive the Rothamsted experiments 

 as chara(^teristic or illustrative of ordinary cultivated land. 

 The proportion of ammonia is very much grtater iu the soils 

 at Rothamsted than those under ordinary cultiu-e. The 

 drains, as a rule, are only two feet below the surface; 

 nevertheless, they are of great value, as indicating the 

 nature of the changes going on in the soil, and guiding 

 us as to our practice. It is evident that the practice of 

 applying farmyard manure on the stubbles in autumn, 

 once so common on deep good soils, and still practised, 

 is not economical, whereas the dressing of artifical grasses 

 may take place with safety at any time, and the application 

 of manure iu spring and summer time for root crops is 

 a safe and sound practice. It is further evident that some 

 loss of nitrogen may occur when our land is clean and 

 uncropped in winter; but we cannot at present go with 

 those who estimate the loss so highly that they would 

 prefer allowing perennial weeds to flourish, and run the 

 risk of not being able to clean the land at all, rather 

 than secure a clean soil with a certain loss of nitrogen. 

 —Field. 



EXPERIMENTS IN MANURING SANDY SOIL. 



Sir, — Will you permit me to call the attention of your 

 readers to the very interesting report just furnished by 

 the Sussex Association for the Improvement of Agriculture? 

 I could wish that a copy of that report were in the hands 

 of every agriculturist; but, as this is impossible, perhaps 

 you will allow me to allude to one or two of the lessons 

 which the experiments of the society appear to teach. 



On one of the stations (Hassock's Gate) the society had 

 a soil to work on which was almost pure sand, containing 

 only '260 per cent of organic matter, and '458 of soluble 

 ingredients — in fact, almost entirely destitute of plant food; 

 and perhaps I had better leave Mr. Jamieson, the chemist 

 of the association, to describe in his own words the effects 

 of manures upon it: "He would merely say that, when 

 they gave no manure to that sandy soil, the plants never 

 got beyond the first few germinal leaves. When they gave 

 all the ingredients essential to plant life, omitting only 

 the phosphates, they had a little better plant, giving about 

 half a ton per acre; but when they supplied the phosphate 

 in the form in which it had long been said to be of no 

 use, the produce rose to about eighteen or twenty tons 

 per acre. This he thought Iiad given the finishing point 

 to the battle of the phosphates. The form of phosphate 

 he had found to answer best in Sussex was a mixture in 

 two equal parts of finely ground coprolite and steamed 

 bone flour, and this mixture was far more economical than 

 superphosphate or dissolved bones." 



Mr. Jamieson goes on to estimate the saving which can 

 be effected by using the more economical manure which 

 was found to answer best in Sussex and in Scotland. 

 He calculates that iu the county of Sussex alone the 

 saving would be £35,000 annually. Blr. Jamieson was not 

 content i,\-ith weighing the produce of each plot of land; 

 but he proceeded to estimate the solid matter contained 

 in the turnips grown by the application of each form of 

 phosphate, and the conclusion was forced upon him that 

 the finely grounil un<lissolved coprolite and steamed bone 

 flour produced a turnip containing less water, and con- 

 sequently not so liable to rot as that grown by dissolved 

 bones or superphosphate. 



I shall not trespass longer on your valuable space, but 

 would say in conclusion that Mr. Jamieson deserves the 

 thanks of every honest chemist by the way in which he 

 has exposed the present system of giving high analyses, 

 whereby a manure is made to appear to contain by analysis 

 far more pho.sphoric acid than is really present. It is 

 high time tliis practise was done away with, and it is to 

 bn hoped that Btr. Jamieson will succeed in giving the 

 finishing blow to this monstrous evil. — A.M'Donald Graham, 

 F. O. S., F. 1. 0., 3, Union-chambers, XTnion-street, Liverpool. 

 —Field, 



GYPSUM. 



Hill, — Oontiuuing this subject, which has been discussed 

 in your paper from time to time, I send you a translation 

 of an interesting German paper, which puts the question 

 of "fixing carbonate of ammonia by gypsum" on a more 

 scientific basis than heretofore. It needs no comment, ex- 

 cept as to its concluding paragraph. With regard to that, 

 in this country at least, gypsum is much cheaper thAn 

 magnesium chloride; so there is no necessity to risk the 

 poisonous influence credited to an excess of chlorides, even 

 though this alleged pernicious infiueuoe is combated by 

 the author. F. C. S. 



The following is a translation of a paper (from Jiiedenx/inn's 

 Central Blatt, Januai-y, 1882, pages 8, 0, and 10) originally 

 published in the report of the German Stations for Agri- 

 cultural Experiments, 1881. 



On the Powtee oi-' some Salts to "fix" Ajimonia. 

 By Dii A. Markek, 



For the purpose of fixing the volatile ammonium car- 

 bonate in manures, formerly gypsum^ and of late years 

 Stassfurt potassium salts, have been used; but as yet no 

 numerical data have been pubHshed on the subject. The 

 author, therefore, has undertaken to fill up this gap. Tho 

 experiments were tried with gypsum, kainite, kieserite, 

 magnesium sulphate, potassium sulphate, and magnesium 

 chloride. 



The questions to be solved were: (1) How much carbon- 

 ate of ammonia can be fixed, i. e., rendered not volatile, 

 by a given quantity of the substance? for example, by 

 one gram of gypsum, kainite, &c.; or, inversely, how much 

 of the substance would be required to fix one gram of 

 ammonium carbonate? (2) Does the one gram of substance 

 always fix a like quantity of ammonium carbonate, or doei 

 the quantity fixed depend upon the amount of ammonium 

 carbonate originally mixed with the gypsum or other sub- 

 stance used? 



The m«thod employed was this: Each of the substances 

 was mixed respectively with 10, 20, 30, 50, and 80 per cent 

 ammonium carbonate ; they were ground up together iu a 

 mortar, moistened with water, and left for twenty-four 

 hours. The unfixed ammonium carbonate was then th'iven 

 off by heatiug on a water-bath; the insoluble carbonates 

 were filtered off, the filtrate made up to a definite volume, 

 and the nitrogen estimated by the azotometer. The 

 ammonium carbonate was calculated from the quantity of 

 nitrogen found. The results are tabulated below. The 

 numbers represent the ammonium carbonate fixed for one 

 gram of the substance. 



— potassium sulj^hate excepteil — is not iusig:nificaQt, and, iu 

 fact, the fixing power of the substance increases, almost 

 throughout, with the amount of ammonium carbonate in 

 the mixture. It is hence probable that the quantity of 

 fi.xed ammonium carbonate does not depend upon an excess 

 of the fixing substance, but on the larger or smaller number 

 of iioint.s of contact between the two substances. There- 

 fore it is advisable in practice, in order to obtain the 

 best effect, to use the fixing substances as finely divided 

 as possible. 



It will be seen from the table that, with gypsum, the 

 mixture containing the smallest percentage fixes the least, 

 whilst the mixture with the largest percentage fixes the 

 greatest, quantity of ammonium carbonate. With magnesium 

 sulphate, however, this is not the case; and with k.ainite, 

 kieserite, and magnesium chloride, the fixing jjower is 

 near'y the same for all mixtures. 



The increase iu the fixing power of gypsum evidently 

 shows that, on accoimt of the insolubility of the salt, the 

 very large number of points of contact afford an unlimited 

 requisite for the fixing of a larger quantity of ammonia 



