332 



SOIL CONDITIONS AND PLANT GROWTH 



retaining water for pastures to last through a hot summer, 

 consequently the grass land, except near the brooks, is parched 

 and scorched. The Lydd soil is certainly somewhat finer 

 grained, but not so very different that one would expect to 

 find it much better for pasture purposes, yet it produces one 

 of the best pastures in Romney Marsh, not only carrying but 

 fattening sheep throughout the summer. It has, however, a 

 constant supply of water 3 or 4 feet below the surface, while 

 at Shalford the water level is much lower down. 



This underground flow is one of the factors concerned in 

 the proverbial fertility of valleys. Soils lying towards the 

 bottom of a long slope receive not only the rainfall but also 

 the water steadily drifting downwards to the stream or marsh 

 at the bottom, and this advantage is further enhanced by the 

 gradual transport of soil down the slope which increases the 

 depth through which the plant roots can range. 



Effect of the Subsoil. — In general the subsoil is rather 

 heavier in type than the surface soil, especially in the case of 

 clays; examples are given in Table LXXXVII. The excep- 

 tions to this rule may arise through periodical flooding with 

 water containing much clay in suspension, or through the oc- 

 currence of a bed of sand just below the surface. 



Two cases described on page 314 may be illustrated here. 

 The bad effect of a layer of impermeable material near the 

 surface is shown by the Loddington soil (Table LXXXVII.), 



