MANURE, ARTIFICIAL 215 



Salt, however, even in England, is usefully applied to mangolds, and enters 

 largely into the composition of most artificial manures expressly prepared for this crop. 



5. Lime and Magnesia. All plants require lime and magnesia in smaller or larger 

 quantities. Many soils contain lime in superabundance ; in others it is deficient. To 

 the latter soils it must be added. This can be done by lime-compost, by slaked lime, 

 by marl, shell-sand, or gypsum. All these calcareous manures are cheap almost 

 everywhere, for lime and magnesia are among the most widely distributed, and most 

 abundant mineral substances. 



The addition of chalk, marl, and even gypsum, to artificial manures, should there- 

 fore be avoided as much as possible. 



At the best, carbonate and sulphate of lime in artificial manures must be regarded 

 as diluents. 



6. Soluble Silica. The artificial supply of soluble silica to the land, as far as our 

 present experience goes, has done no good whatever to cereals, the straw of which 

 soluble silica is supposed to strengthen. 



In the absence of reliable practical experiments with soluble silica, we cannot 

 venture to recommend the use of silicate of soda or soluble silica to manure-manufac- 

 turers. 



7. Organic substances; Humus. The importance of organic matters free from 

 nitrogen, as fertilising agents, is very trifling. Formerly the value of a manure was 

 esti muted by the amount of organic matter it contained, and little or no difference 

 was made whether the organic matter contained nitrogen or not. Under good culti- 

 vation, the organic matter in the soil regularly increases from year to year ; there 

 exists therefore no necessity of supplying it in the shape of manure. 



In artificial manures we should certainly exclude all substances that merely add to 

 the bulk, without enhancing the real fertilising value of the manure. Peat, saw-dust, 

 and similar organic matters, &c., are useful to the manure-maker only as diluents 

 and absorbents of moisture. 



8. Sulphuric acid is another constituent of manure, which possesses little value. 

 In artificial manures sulphuric acid chiefly occurs as gypsum. 



9. Chlorine. Exists in manures principally as salt. 



10. Oxide of Iron, Alumina, Silica. These constituents exist sometimes in manures 

 in the shape of burnt-clay, earth, brick-dust, and sand. 



It is hardly necessary to remark that good artificial manures should contain as 

 little as possible of these matters. 



It will appear from the preceding observations, that nitrogen in the shape of am- 

 moniacal salts, nitric acid or decomposed animal matters, and phosphoric acid are the 

 most valuable fertilising constituents. 



The manufacturers of artificial manure should therefore endeavour : 



1. To produce manures containing as little water as possible. 



2. To incorporate as much of nitrogenised organic matters, or ammoniacal salts, or 

 nitrates and phosphates, in general manuring mixtures, as is possible at the price at 

 which artificial manures are usually sold. 



3. To avoid as much as possible gypsum, salt, peat-mould, chalk, and other sub- 

 stances that chiefly add to the bulk, withoxit increasing the efficacy, of the manures. 



He should also endeavour to produce uniform finely-pulverised articles, that run 

 readily through the manure drill. 



It likewise devolves on the manufacturer of manures to render more effective, 

 that is to say, more rapid and energetic in their action, refuse materials which may 

 remain inactive in the soil for years before they entei into decomposition, and to 

 reduce by chemical means into a more convenient state for assimilation, raw materials, 

 which like coprolites, apatite, &c., produce little or no beneficial effects upon vegeta- 

 tion, even when added to the land in a finely-powdered condition. 



At the present time, two classes of artificial manures maybe distinguished: 1, 

 general manures, i.e. manures which profess to suit equally well every kind of agri- 

 cultural prodiice ; and 2, special manures, i.e. manures specially prepared for a par- 

 ticular crop only. 



The requirements of different crops, or perhaps, more correctly speaking, the con- 

 ditions that regulate the assimilation of food, vary so much, that we doubt the- 

 policy of manure-makers to prepare general artificial manures. At the same time, we 

 doubt the necessity of preparing artificial manures for every description of crop. 

 Special manures are extremely useful to farmers, if they .ire prepared by intelligent 

 manufacturers, who possess suSicient chemical knowledge to take advantage of 

 every improvement that is made in manufacturing chemistry, and at the same time 

 know sufficient of agriculture to understand what is really wanted in a soil. In other 

 words, except a manufacturer is a good practical chemist and a tolerably good farmer, 

 ho will not be able properly to adapt the composition of special fertilisers to the 



