336 SOIL CONDITIONS AND PLANT GROWTH 



carbonate suffices. The Stedham soil (Table LXXXV.) is an 

 example ; it is near the bottom of a slope along which water 

 containing calcium bicarbonate in solution is drifting, and 

 therefore shows no tendency to become sour. The 0*03 per 

 cent, of calcium carbonate present, hopelessly inadequate as 

 it appears, suffices for its needs and no increase in crop is ob- 

 tained by applying lime. The Lydd soil (Table LXXXVI.) 

 contains only '02 per cent, but is also well supplied with cal- 

 careous water from below and shows no sign of sourness. 

 Similar soils that have not this advantage of position stand in 

 great need of lime even when o*i per cent, is present. As the 

 amount of clay increases, the need for lime becomes greater 

 because flocculation is now wanted ; soils with 20 per cent, or 

 more of clay may need two or three times as much lime as 

 sandy soils. It is impossible to fix limits that shall hold 

 universally. Some soils free from lime appear to need none : 

 Hendrick and Ogg's Craibstone soil has already been men- 

 tioned (p. 118). Gregoire^ also found soils practically free 

 from carbonate and yet not acid, and presumably not needing 

 lime. Before an analyst recommends lime or chalk on a sandy 

 soil he should satisfy himself that the need is indicated by the 

 vegetation, and before he states that lime is not necessary on 

 a clay he should be quite sure that further additions would 

 have no beneficial flocculating effect. The need of lime is 

 indicated : — 



I. If clover fails to start well, or to stand the winter, or 

 if it looks bad in spring. 



Cases have been examined by the writer where clover 



or lucerne were failing in patches in the field and weeds 



were consequently getting a firm hold. The amounts of 



lime in the soil were : — 



On the good parts : Suffolk lucerne, o-8, Norfolk lucerne, 0-6, 

 Herts clover, 0*2 per cent, calcium carbonate. 



On the bad patches : Suffolk lucerne, 0"07, Norfolk lucerne, o"2, 

 Herts clover, o-oi per cent, calcium carbonate. 



Ann. Stat. Agron., Gembloux, 1913, 2, 87. 



