THE ACTION OF BASIC SLAG ON THE 



ACIDITY OF THE SOIL AS MEASURED 



BY THE 'LIME REQUIREMENT' AND 



HYDROGEN ION CONCENTRATES 



OF THE SOIL 



IT is a matter of common knowledge that clovers, particularly 

 wild white clover, are very sensitive to what is vaguely called soil 

 acidity. The extent to which the clover plant is able to persist on 

 a 'sour' soil probably depends, however, not only upon the degree 

 of acidity as measured by the soil lime requirements, but upon such 

 other factors as climatic conditions and the water holding capacity 

 of the soil. 



On the Harpenden Common, Hutchinson and MacLennan 1 found 

 that wild white clover persisted where the soil had a lime requirement 

 of -22 %, and they illustrate this by the following table. 



TABLE L. RELATION OF LIME REQUIREMENTS OF THE SOIL 

 TO THE VEGETATION ON HARPENDEN COMMON 



Average lime require- 

 ment of soil Dominant flora 



Approx. 0-22 % CaCO 3 Wild white clover 



0-26 Fescues 



0-31 Mixed; yarrow, woodrush and moss 



0-39 Gorse 



0-43 Yorkshire fog 



0-53 Sorrel 



The botanical analyses of the hay at the various Essex experi- 

 mental centres shows that on poor heavy clay soils basic slag is able to 

 induce a vigorous growth of clover even if the soil has as high a lime 

 requirement as -45 %. The ability of the clovers to persist on such 

 sour soils is, however, in Essex at any rate to a great extent dependent 

 upon the distribution of the rainfall. 



A comparison of Tables XXXII and XXXIII shows that during 

 a moist growing season clovers form a large proportion of the hay 

 crop on the basic slag plots, even when the soil has as high a lime 

 requirement as *45 %. On a dry season, however, clovers are absent 



1 Journal of Agric. Science, vn. p. 102. 



72 



