H. B. Hutchinson and K. MacLennan 



07 



2(3 parts. Somewliat similar data were obtained with the soils from 

 the permanent wheat plots, although in this case the crop was more 

 resistant to acid conditions, and persisted until the soil showed an 

 absorption of over 0-22 per cent. 



The Reldlion between Lime Requiremenls and Galeium Carbonate 



Content. 



The relation between tlie lime reijuirements of a soil and the amount 

 of calcium carbonate contained therein is of importance in certain 

 cii'cumstances. In the first place, the mass of data now being collected 

 under numerous soil survey schemes is open to misinterpretation on 

 account of the view commonly held that normal soils must contain a 

 certain (often purely arbitrary) content of carbonate. Secondly, and 

 related to the first consideration, field experiments which are initiated 

 on the basis of a low carbonate content of the soil are sometimes liable 

 to give only negative results. This has already occurred from time 

 to time. 



Hall and Russell (39) and later Gregoire and his colleagues record a 

 considerable number of soils neutral in character and yet possessing 

 little or no carbonate. We have also met with many of this type, 

 chiefly in our case, light sandy soils. Conversely, many acid soils are 

 encountered where a certain amount of carbonate is present, but this 

 appears to be largely due to localisation of the carbonate (posssibly 

 past applications of lime) in the field. Some examples of each type 

 may be found in the following table, and the authors wish to emphasize 

 the fact that acidity — and not merely carbonate — determinations 

 should be made in estimating the needs of any particular soil. 



C'aCOj present % 

 CaCO, req. % 



a 



(8 



o 



P3 



nil 



J3 



0-890 

 nil 



o 

 o 



O 



0-003 00;(j 0005 

 0-015 0-032 10-100 



0-097 

 0-117 



a 



-a 

 < 



W 



0-005 

 0-135 



^ 



0-003 

 0-260 



'« 

 O 



nil 

 0-430 



nil 

 0-470 



•Journ. of Agric, Sci. vii 



