II. SOILS. 



1 DIRECTIONS FOR TAKING SAMPLES.— OFFICIAL. 



Sampling should be done preferably when the soil is reasonably dry. Remove 

 from the surface all vegetable material not incorporated with the soil. With a soil 

 auger or tube, whichever may be better adapted to the soil conditions, take a 

 sufficient number of sub-samples at properly distributed points to secure composite 

 samples representative of the entire tract. 



(a) Surface soil. — Take a composite sample representative of the entire tract 

 to a depth of either (1) 6 inches, (2) the average depth of the plowed soil if this ex- 

 ceeds G inches, or (3) a maximum depth of 12 inches when there is no clear line of 

 demarcation between the soil and sub-soil above this depth. 



(b) Siih-soil.— Take a composite sample of each important and distinctly different 

 soil stratum below the surface section already sampled to a total depth of 40 inches. 

 If a soil auger is used, before taking sub-soil samples the hole should be enlarged 

 and carefully cleaned out with the auger to prevent contamination of the several 

 substrata when the sample is being withdrawn. 



Mix each composite sample thoroughly and, after cutting down by quartering to 

 about 2-4 pounds, air-dry in a cool, well-ventilated place. 



It is recommended that the weight of a given volume of the soil as it lies in the 

 field be taken for calculating the percentage results obtained by analysis to pounds 

 per given area of the soil. 



2 PREPARATION OF SAMPLE. -OFFICIAL. 



After air-drying and weighing the sample, pulverize in a porcelain mortar, using 

 a rubber-tipped pestle to avoid the reduction of rock fragments, and pass through 

 a sieve with circular openings 1/25 inch (1 mm.) in diameter. Discard the detritus 

 and weigh. Thoroughly mix the sifted material and preserve in a suitable stoppered 

 container. 



For the quantitative determination of any of the constituents, prepare a very 

 finely pulverized sub-sample of the sifted material, using an agate mortar. 



3 MOISTURE.— OFFICIAL. 



Dry 2 or more grams of the sample, as prepared under 2, in a tared platinum dish 

 for 5 hours at the temperature of boiling water; cover the dish, cool in a desiccator, 

 and weigh rapidly to prevent the absorption of moisture. Heat, cool, and weigh 

 at intervals of 2 hours to constant weight. The loss of weight is reported as moisture. 



4 VOLATILE MATTER.-OFFICIAL. 



Heat the dish and dry soil from 3 to full redness, stirring occasionally, until all or- 

 ganic matter is destro3'ed. If the soil contains appreciable quantities of carbonates, 

 cool and moisten with a few drops of saturated ammonium carbonate solution, dry 

 and heat to dull redness to, expel ammonium salts; cool in a desiccator and weigh. 



17 



