74 AGRICULTURE 



has been practised in the past over extensive 

 areas in the United Kingdom, is drainage, 

 that is to say, the artificial withdrawal from 

 soil of surplus supplies of water. While a 

 certain amount of moisture is an essential 

 condition of the growth of plants, and is 

 necessary for the maintenance of many 

 processes in the soil, too large supplies can 

 interfere to a serious extent with the growth 

 of crops, and of the higher plants generally. 

 While, therefore, it is in theory desirable to 

 get rid of surplus water, the expenses attend- 

 ing the operation are usually so great that 

 in practice artificial drainage is now resorted 

 to only to a comparatively limited extent. 

 To drain land thoroughly, an outlay of 

 6 to 10 an acre is usually necessary ; and 

 when interest on this outlay, and the creation 

 of a sinking fund for the redemption of the 

 capital, are taken into account, it is found 

 that the annual charges on the land are 

 increased by something like 10s. per acre, 

 and this is more than most land can bear 

 with agricultural profits at their present 

 level. It may be said generally, that tillage 

 land which is over-wet cannot in such a 

 condition be profitably retained under the 

 plough, so that, if it be necessary to keep the 

 land under tillage, drainage becomes im- 



