APPENDIX. 



THE METHODS OF SOIL ANALYSIS. 



C 



How to Take the Sample o/Soil.—Omng 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. The simplest tool is shown in Fig. 7 and 

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

 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. 



TAe 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 suflScient to determine the loss on ignition, and to 

 call this organic matter. 



149 



FlQ. 



7. — Tool for taking 

 Soil Samples. 



