96 The Control of the Soil [pt. ir 



deep, sufficiently suppKed with water during the growing 

 period of the plant, and exposed to suitable climatic 

 conditions. 



Perhaps the most wddespread soil defect is "sourness " 

 or "acidity." "Sourness" is a state that cannot easily 

 be defined although a good cultivator easily recognises 

 it. It arises through lack of lime and shows itself in a 

 bad physical state of the soil and in the poor growth and 

 obvdously unhappy appearance of the vegetation, especi- 

 ally of clover. It is partly due to deflocculation of the 

 cla}^ but apparently partly also to the presence of certain 

 harmful substances formed mider these special con- 

 ditions. Unfortunately few investigations have been 

 made in this country on "sourness," but it can be cured 

 by additions of lime an d proper cultivation . ' ' Acidity ' ' 

 can be recognised readily by litmus paper ; a blue piece 

 changing to red in contact with an "acid" soil. Until 

 sufficient lime has been added to correct "sourness" or 

 "acidity" no scheme of husbandry is likely to be 

 successful. 



As a general rule no soil is satisfactory unless it can 

 be got into the nice crumbly condition or "tilth" which 

 the gardener aims at in preparing a seed bed. This re- 

 quires that the clay should be flocculated, which, as we 

 have seen, can be done by (1) adding lime or chalk, 

 (2) adding organic manures, (3) leaving the soil turned 

 up and exposed to winter frosts, (4) cultivating the soil 

 only when it is in the right condition and carefully' re- 

 fraining from touching it when it is too wet. Heavy clay 

 soils can rarely be got into a good tiltli and hence are 

 unsuitable for cultivation : light soils easily acquire the 

 proper tilth: in between come a whole series of soils 

 which a skilful farmer can manage while an unskilful 



