V. 



THE ANALYSIS AND COMPOSITION OF SOILS 



91 



A good example of such failure is seen in the following analyses of 

 two soils from pasture land at the Experimental Farm at Garforth, 

 made by the author in June, 1900 : 



From these figures it would appear that soil A is better provided 

 with lime, potassium and phosphoric acid than soil B, and inasmuch 

 as there is also more nitrogen present one would conclude that soil B 

 would receive much more help from phosphatic and lime manures than 

 soil A. 



Actual practice shows exactly the opposite, for it is found that 

 basic slag produces a large increase and great improvement in the crop 

 on the field from which soil A was taken, while the field from which 

 soil B was derived does not respond to applications of basic slag. 



From such disagreements between the results of chemical analysis 

 and actual farming experience, which are often met with, it is evident 

 that to know what a soil contains is not sufficient to enable one to form 

 a judgment as to its fertility ; one must know, in addition, something 

 about the state of existence of the important items of plant food 

 must know, in fact, the amounts of these lohich are directly available 

 to the plant. 



Many methods of extracting soil so as to obtain some measure of 

 the phosphoric acid and potash particularly, which are in an, assimil- 

 able form, have been suggested. One of the most successful is that of 

 Dyer. 1 This method is based upon the extraction of the soil with a 1 

 per cent solution of citric acid, which Dyer found to be about the aver- 

 age acidity of the juices of the roots and root hairs of a large number 

 of plants examined by him. 



The method is thus carried out : 200 grammes of the air-dried 

 soil which has passed the 3 millimetre sieve are, without further 

 treatment, placed in a flask or bottle, and treated with 2000 cc. of 

 water containing 20 grammes of pure crystallised citric acid. The 

 two are left in contact, with frequent stirring or shaking, for 



1 Jour. Chem. Soc., 1894, Trans., 141. 



