3i6 



SOIL CONDITIONS AND PLANT GROWTH 



and air relationships, and arising from differences in the com- 

 pound particles. Unfortunately no method of investigating 

 the compound particles has yet been devised, and a study of 

 the ultimate particles by a mechanical analysis is alone 

 possible. But even though the differences are thus attenuated 

 they can still be traced, as shown by the analysis in Table 

 LXXXII. of soils in Kent, Surrey, and Sussex, known to be 

 well suited to the particular crops. 



Low amounts of clay and fine silt, and high amounts of 

 coarse sand, whenever the clay begins to approach 12 per 

 cent., characterise the potato soil ; these are the most porous 

 of the series, allowing free drainage and aeration. Barley 

 tolerates heavier and shallower soils. Fruit and hops both 



Table LXXXII. — Mechanical Analyses of Soils Well Suited to Cer- 

 tain Crops in the South-Eastern Counties ; Limits of Variation. 

 Hall and Russell (122a). 



require deep soils, and seem to find their most favourable circum- 

 stances only in a restricted class of soils : the fruit soils gener- 

 ally contain rather more sand and less silt than the hop soils. 

 But the fruits differ among themselves ; the best nursery stock 

 is raised on soils of the potato class, where the conditions are 

 for some unknown reason very favourable to fibrous root 

 development ; strawberries prefer the lighter and apples the 

 heavier kinds of fruit soil. Even different varieties of the 

 same plant show distinct preferences for one class of soil over 

 another: the finest varieties of hops are found only on the 

 typical hop soils, and have to be replaced by coarser varieties 

 directly it is desired to grow hops on heavier soils. Prefer- 

 ences for certain soil conditions are also shown by varieties of 



