CHAPTEE V. 

 THE ANALYSIS AND COMPOSITION OF SOILS. 



IN this chapter only a brief outline of the methods of sampling and 

 analysing soil will be given. For full details a treatise on soil analysis 

 should be consulted. The methods described here are such as the 

 author himself uses, and variations may be made in them to suit 

 special cases. 



Sampling. This is an important operation, and careful considera- 

 tion should be given to it. Much depends upon the particular object 

 for which the analysis is to be made. If it be desired to report upon 

 the soil of a farm or field as a whole, and much difference exists in the 

 soil from different parts of it, care must be taken that in the final 

 sample, each different soil should be represented, as far as possible, by 

 a quantity bearing a proportion to the total sample equal to the pro- 

 portion (of the whole area) covered by that particular soil. Better 

 knowledge of the nature of the soil, however, is obtained if samples 

 representing notable differences be kept apart and analysed separately. 



Then, too, the depth to which the samples are taken is a matter 

 for consideration. Generally speaking, the samples should be taken 

 down to the line of separation of the soil from the subsoil, which is often 

 very clearly visible by a difference in colour, the soil proper being 

 darker (because of organic matter) than the subsoil. The depth is 

 usually from 6 to 10 in. In many cases it is also required to examine 

 the subsoil, when, of course, separate samples must be collected. 



Of the various methods of taking the samples the following may be 

 mentioned : 



(1) Having selected the place, the vegetation growing upon it 'is 

 removed and a hole is dug with a sharp spade to a depth of about 12 

 in., one side of the hole being trimmed so as to be quite smooth 

 and perpendicular. A slice from this side is then cut with the spade 

 to a suitable depth and about 3 or 4 in. in thickness. This is placed 

 on a clean board to be mixed with the other samples obtained in a 

 similar way from other parts of the field. Finally, these sub-samples 

 are mixed together thoroughly with trowel or spade, the sticks, 

 large stones and roots being removed, and a sample of 2 or 3 kilo- 

 grams taken for analysis. 



(2) Another, more laborious, plan is to have wooden boxes 6 in. 

 square and 12 in. in depth to hold the samples. A large hole is then 

 dug at the selected spot and a square prism of soil is left in the middle ; 

 this is carefully trimmed with the spade until the box will just slip 



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