84 Dilute Acids and Phosphorus Gompo^mds in the Soil 



1894. But all acids are affected. The only way to get precise deter- 

 minations of the easily soluble phosphate in the soils is to adopt a 

 diffusion method whereby the reverse reaction becomes eliminated. 



This is perfectly feasible. But so long as the conditions of the ex- 

 periment are constant and the soils are of the same character, possessing 

 similar adsorptive capacities, dilute acids may be expected to give 

 comparable results. Not otherwise, however. 



Comparable results may be of great value to soil analysts. Obviously 

 they can be obtained only by first selecting typical soils and determining 

 the data for them as fully as can be. This involves a soil survey, and 

 is one of the many justifications that can be urged in favour of surveys. 

 When typical soils have been studied it is not difficult to compare any 

 soil of the same Jcind with them, and to give information of value to the 

 farmer; but our results show the hopelessness of trying to compare 

 two dissimilar soils. 



Absolute results could be obtained by the diffusion method, but 

 until we have had more experience with it we are not prepared to say 

 what sort of value they would have for the analyst. 



Experimental. 

 The soils and methods used. 



Heavy soils. Rothamsted. Heavy soil, Clay-with-FIints formation. 



Agdell field. This is under a rotation,- — clover, wheat, swedes, and 

 barley, and has been for many years. The soil was taken from the 

 space between the plots unmanured since 1843, and has neither carried 

 crops nor received manure. 



Hoos field. Continuous barley plots. 1.0. — Unmanured since 1852. 

 2(7. — This has received 1(K)() lbs. of rape cake, and 3| cwts. super- 

 phosphate each year since 1852. 



Lighter soils. Saxmundham. A Boulder Clay from the Experi- 

 mental field of the East Suffolk County Council. 



Rotation I. Plot 6. — Unmanured since 1900. Plot 4. — This has 

 received 2 cwts. superphosphate each year since 1900. 



Woburn. Lower greensand formation. From the continuous wheat 

 plots in Stackyard field of the Royal Agricultural Society's farm. This 

 plot has been unmanured since 1872. 



Lightest soil. Bramford. A light gravel soil from the farm on which 

 the East Suffolk County Council experiments were carried out during 

 the years 1893 to 1910. 



