APPENDIX. 



THE METHODS OF SOIL ANALYSIS. 



How to Take the Sample of Soil. Owing to the variation in composition of 

 the soil at different depths it is particularly necessary that the sample should 

 always be taken .to the same depth and with a tool making a clean vertical 

 cut. Samples taken with a spade are of very doubtful value and do not 

 justify any lengthy examination. A simple tool is shown in Fig. 9 and 

 consists of a steel tube 2 in. in diameter and 1 2 in. 



{ t\ 



long, with a | in. slit cut along its length and all its 

 edges sharpened. The tube is fixed on to a vertical 

 steel rod, bent at the end to a ring 2 in. in diameter, 

 through which a stout wooden handle passes. A mark 

 is made 9 in. from the bottom so that the boring pro- 

 cess can be stopped as soon as this depth is reached. 

 On withdrawing the tool the core of soil is removed 

 by a pointed 'iron rod. Five or six samples should be 

 taken along lines crossing the field so as to get as 

 representative a sample as possible ; the whole bulk 

 must then be sent to the laboratory. Samples should 

 not be taken from freshly ploughed or recently man- 

 ured land. 



FIG. 9. Tool for taking 

 Soil Samples. 



In very stony soils it is easier to use a 2 in. auger, but this does not in our 

 experience yield as satisfactory a sample as the tool shown here. 



The Analysis. On arrival at the laboratory the soil is spread out to dry, 

 and is then pounded up with a wooden pestle and passed through a 3 mm. 

 sieve. The stones that do not pass through, and the fine earth that does, are 

 separately weighed, and the proportion of stones to 100 of fine earth is calcu- 

 lated. Subsequent analytical operations are made on the fine earth. 



Moisture. Four or five grams of the soil are dried at 100 C. till there is no 

 further change in weight. 



Organic Matter. No accurate method of estimation has yet been devised. 

 It is usual to ignite at low redness the sample dried as above. The loss in- 

 cludes organic matter, water not given off at 100 C., and carbon dioxide from 

 the carbonates ; allowance may be made for the latter, but not for the com- 

 bined water. The carbon is sometimes determined either by the ordinary 

 combustion or by some wet combustion method. Methods have also been 

 described for determining " humus," but they have not come into general use. 

 For ordinary purposes it is sufficient to determine the loss on ignition, and to 



call this organic matter. 



170 



