162 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



merical results obtained by analysis show the like quantities of silic<i, 

 lime, magnesia, soda, potash, phosphoric acid, &c., and yet a certain 

 crop — clover, for instance — will flourish on the one and not on the other. 

 The physical nature of such soils, their depth, character of subsoil, as- 

 pect, texture, climatic conditions, &c., have likewise to be taken into ac- 

 count. Thus the many problems that enter into the study of soils are 

 so various that chemical analysis alone does not afford, in most cases, 

 a sufficient guide to an estimate to their agricultural capabilities, nor 

 to point out the particular manure that is adapted for the special crops 

 intended to be grown. 



The most detailed chemical analysis usually gives only the proitor- 

 tion of the different constituents, and without any reference to the 

 state of combination in which they exist in the soil or to their absorp- 

 tive and retentive powers. 



GREAT CARE NECESSARY IN OBTAINING THE SAMPLE FOR ANALYSIS. 



On the care with which the soil is sampled of course depends the an- 

 alytical results, and too much stress cannot be laid on the necessity that 

 exists to obtain a fair average sample, representing as far as possible 

 both the good and bad qualities of the soil that is to be submitted to 

 analysis. As the chemical analysis of a soil is a very long, tedious, and 

 delicate operation, and the difference of a one-thousandth of 1 per cent, 

 in any one constituent is equivalent to 20 or 30 pounds to the acre lost 

 or gained in that element, the importance of the sample truly repre- 

 senting the soil is apparent. 



THE CHEHnCAL COMPOSITION OF SOILS. 



Soil consists of an organic and of an inorganic or mineral part, the 

 former derived from the decay of plant-life for many ages, together with 

 the dung and remains of animals, and the latter arising from the weath- 

 ering of the rocks. 



The organic matter varies in different soils, being most deficient in 

 sandy soils and poor clays, and even in very fertile lands occurring 

 only in small quantities. In the famous black soil of Eussia, which is 

 found in the provinces of the Ural Mountains and in those that border 

 them, it varies from 5 to 12 per cent. In some of our own prairie soils 

 the amount is nearly as high. In leaf mold it occurs considerably 

 higher and in peat more than 50 per cent., very often. From its dark 

 color it is a good absorbent of heat, its own specific heat being much 

 above that of the soil generally. It is hygroscopic and greatly increases 

 the water-holding power of sandy soils ; besides, it has the power of ab- 

 sorbing and retaining animoniacal salts. By its decomposition it forms 

 a source of carbonic acid, which is readily absorbed by plant-life. The 

 mechanical condition of a soil is much improved by its presence when 

 ill moderate quantities, but when present in excessive amount it acts 

 injuriously by deoxidizing ferric salts and in other ways. (Vcrsuchs 

 Stationen Orgau, vol. xiv, pp. 218-300.) 



The inorganic or mineral portions of the soil is, with the addition of 

 alumina, composed of the same substances as make up the inorganic 

 portion of plants, and which form their ashes when burnt. The min- 

 eral soil-constituents include the following substances : 



Silica, SiOi. Potash, K2O. 



Alumina, AI2O3. Soda, NajO. 



Lime carbonate, CaCOs. Magnesia, MgO. 



Ferric oxide, FezOs- Cblorino, CI. 



Phosphoric acid, PjOs. Sulphuric acid, SO3. 



(Phosphoric anhydride.) (Sulphuric anhydride.) 



