CHAPTER IX 



SOIL ANALYSIS BY THE UNITED STATES BUREAU OF SOILS 



THE United States Bureau of Soils Bulletin 54 (December, 

 1908), on "The Mineral Composition of Soil Particles," contains 

 data from which can be computed 1 accurately the total amounts 

 of phosphorus, potassium, magnesium, and calcium, in the ignited 

 surface soil of twenty-seven important soil types of the United 

 States. The loss on ignition of ordinary soils usually approaches 

 10 per cent, and includes chiefly the combined water, organic 

 matter, and more or less carbon dioxid, if carbonates are present; 

 consequently, the results given on the basis of ignited soil are, as a 

 rule, about one tenth higher than if given on the usual basis of 

 dry soil. 



The following general statements regarding these soil samples 

 are made by the Bureau of Soils (Bulletin 54, page 15) : 



"Our extensive collection of soils from important and well-marked soil 

 types enables us to select samples fully representative of the soils of the country. 

 Accordingly, agricultural soils of known character were selected so as to include 

 those from various geographical sections and from a number of soil provinces. 

 Thus we have taken soils from the Coastal Plains, the Piedmont region, 

 glacial soils, nonglacial soils of the interior, and those of the arid region, the list 

 comprising 27 soil types." 



"We have but two soils of the arid region to compare with the twenty-five 

 of the humid region. The latter were collected to represent soils of all classes 

 those of low, of medium, and of high productivity ; sandy soils, clay soils, 

 calcareous soils, and those intermediate between these extremes. They may 

 be taken as fairly well representing the humid soils. The two arid soils cannot 

 be considered to represent so well those of the region because of their limited 

 number and similarity of texture, both being fine sandy loams." 



"The Coastal Plains soils have resulted, to a large extent, from material 

 washed from the Piedmont Plateau and deposited in water at lower levels. 



1 The Bureau of Soils Report shows, for example (Bulletin 54, page 19), that 

 Leonardtown loam contains 29.5 per cent of sand, 55 per cent of silt, and 15 per 

 cent of clay, and that the total PaOs which these particles contain is .01 per cent 

 in the sand, .02 per cent in the silt, and .03 per cent in the clay. 



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