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VI. METHODS FOB THE ANALYSIS OF SOILS. 



Seventeenth Convention, 1900, Bui. 62. 



Page 71, fourth paragraph, use a 3-mm sieve when the determi- 

 nations are to be made on 100 grams or more of soil. 



Page 74, under " (i) Provisional method for the determination of 

 the more active forms of phosphoric acid in soils/' make determina- 

 tions of phosphoric acid by fifth normal nitric acid as well as by 

 fifth normal hydrochloric acid. 



Eighteenth Convention, 1901, Bui. 67. 



Page 71, following " 1. Preparation of sample," insert the following: 



All samples of soils taken for analysis should be composite and should be composed 

 of representative samples taken from at least five different places in the field sampled, 

 each individual sample to be a column of uniform soil extending through the stratum 

 sampled. 



One composite sample should be taken from each important and distinctly different 

 soil stratum to a depth of 40 inches, or 1 meter, including a composite sample from the 

 arable stratum, or plowed soil, usually about 6 inches or 15 cm deep. 



If the plow line and the subsoil line coincide, and the subsoil is a fairly uniform stratum 

 to a depth of 40 inches, then only two composite samples need be taken, one of the arable 

 soil and one of the subsoil. But if the subsoil line is lower than the plow line and not below 

 40 inches, then both strata below the arable soil should be sampled, which would make 

 three strata to be sampled and necessitate the taking of three composite samples from the 

 field one from the surface or arable soil; one from the subsurface soil, that is, from the 

 stratum between the plow line and the true subsoil line, and one from the true subsoil. 



Nineteenth Convention, 1902, Bui. 73. 



Page 71, so amend the provisional method for soil sampling (Hop- 

 kins) that it will be possible to determine the available potash and 

 phosphoric acid in each stratum sampled to a total depth of 3 or 

 4 feet. 



Page 77, insert the following quantitative method for the determi- 

 nation of the acidity of soils as provisional: 



PROVISIONAL QUANTITATIVE METHOD FOR DETERMINING THE ACIDITY OF SOILS (HOPKINS, 



KNOX, AND PETTIT). 



Place 100 grams of the soil in a stout, medium wide-mouthed bottle of about 400-cc 

 capacity; add a sufficient quantity of a 5 per cent sodium chlorid solution to make 250 cc 

 of liquid, including the moisture contained in the soil, but independent of the volume of 

 the soil itself (the moisture content of thoroughly air-dry soils will not cause an appreciable 

 error, if neglected); close tightly with a rubber stopper; place in a shaking machine, and 

 shake for three hours. (Shaking by hand every half hour for about twelve hours will 

 accomplish the same result.) Place the bottle in a suitable centrifuge and whirl till the 

 soil is thrown down sufficiently to allow at least 125 cc of clear liquid to be blown off by 

 means of two glass tubes held in a rubber stopper and arranged about the same as in the 

 ordinary "spritz" bottle, except that the exit tube should be about 2 mm at the end instead 

 of terminating in a fine jet. Instead of using the centrifuge the bottles may be allowed 

 to stand a few hours, or 125 cc of the liquid may be filtered off, care being taken to avoid 



