THE SOIL. 



19 



NOTES ON SOIL ANALYSES. 



The most striking feature exhibited by the above tabU' is found in 

 the fact tliat the soils represented are abnost pure sand. In one 

 instance more than 9!) per cent of the soil is insoluble in stronjr, hot 

 hydrochloric acid, while the number of soils containinji: inoi-e than 

 !»5 per cent of insoluble matter is very large. The only soils in the 

 list which are not decidedly of a sandy nature are Nos. 1^2450, 22-454, 

 2265G, 22657, 22(;63, 22665, 22671, 22672, 22673, 22950, 22957, and 23579. 

 Of these a few are distinctly vegetable or liuraus soils, viz, 22656, 

 22657, and 22663. All three of these soils contain large quantities of 

 humus and other organic matter. 



The second characteristic of the soils, Avhicli is very prominently 

 shown in the lablc of analyses, is the absence of any large? (luanlity 

 of potasli soluble in hot hydrochloric acid. Only the following soils 

 contain notable quantities of soluble potash, viz, 22449, 22663, 22672, 

 and 22673. 



Phosphoric acid is also deficient in most of the soils, but not to the 

 same extent as potash. One of the soils find the subsoil going with 

 it, viz, Nos. 22453 and 22454, have a very high quantity of phosphoi-ic 

 acid, and these samples, as will be seen, were from Florida, in the 

 vicinity of the heavy phosphate deposits of that State. 



The other mineral constituents of soils are less important, viewed 

 as plant food. Two of these, however, are found constantly in j)lants, 

 viz, lime and magnesia. As is to be expected in soils of this charac- 

 ter, these two mineral constituents are deficient in cjuantity as com- 

 pared with the standard of soils of the usual textui-e. In a few of the 

 soils there is an abundant supi)ly of iron and alumina, and these could 

 be classed as clay soils in which the percentage of clay is not ver}^ 

 large. Among the most prominent of this type are Nos. 22656, 22657, 

 22663, 22672, 22673, 22943, and 23579. 



The percentage of nitrogen in all the soils, with the exception of 

 two or three of the vegetable soils, is quite low, and also, as would 

 be expected, the quantity of humus. In only tlii-ee instances does 

 the percentage of humus rise above 3. Evidently these are soils 

 which are not well suited to retain niti-ogen constituents foi- any 

 great length of time, in fact, one of the chief physical characteristics 

 of these soils is the ease with which water percolates through them 

 and the consequent rapidity with which soluble substances are leached 

 out during heavy rains. 



In the estimation of i^otash and phosjihoric acid, by dilute hydro- 

 chloric acid, the purpose in view is to secure some idea, not of the 

 total quantity of these plant foods present in any given sample, but 

 of their relative availability. Pot experiments made by this IJureau 

 have shown that a reasonably good approximation to the availabh^ 

 plant foodrin a soil maj^ be made by treating a sample of it with N/200 



