ix.] CHALKING 313 



has been found that the particular field had escaped the 

 chalking process, and that the land could be brought 

 into order by a good chalking or liming. On the lighter 

 soils ground chalk or limestone is more suitable than 

 lime. With the carbonate, though larger quantities 

 have to be applied to produce the same effect and the 

 action is slower, there is not the same risk of giving an 

 excess, as is the case with caustic lime. An excess of 

 caustic lime begins by causing a partial sterilisation of 

 the soil and a disturbance of the micro fauna and flora, 

 which results in a depression of the first crop, followed 

 by a comparatively rapid decay of the plant reserves 

 and increased yields later, though accompanied by 

 waste of these reserves. The action of the carbonate 

 of lime in ground chalk or limestone, even in large 

 excess, does not cause either the preliminary depression 

 or the too rapid decay and waste of the organic matter 

 of the soil. 



A large proportion of the soils of Great Britain are 

 in need of lime, by the lack of which their fertility is 

 impaired, cultivation is rendered both more difficult and 

 uncertain, and disease is more prevalent among the 

 crops. On many of the sands and clays that cover 

 much of England, as, for example, on the New Red 

 Sandstone, the Lias, Oxford and London Clays, and 

 the Tertiary Sands, the output of the soil might be 

 enhanced and its value increased by from 10 to 20 per 

 cent, by the proper use of lime. 



A comparatively simple chemical determination, 

 which can be obtained from the laboratory of any 

 agricultural college, will provide the necessary informa- 

 tion as to whether the soil needs lime. There are also 

 several trustworthy natural indicators. The presence 

 among the weeds of the arable land of any quantity of 

 spurrey (Spergula arvensis and Spergularia rubra) on 



