314 SOIL CONDITIONS AND PLANT GROWTH 



In reclaiming or fixing sand dunes the first step is to grow 

 grass, e.g. Marram grass (Psamma), which will stabilise the 

 form and then allow a more varied vegetation, e.g. sand 

 binders (Carex arenaria, Festuca rubra, var. arenaria) and 

 ephemerals, to stabilise the surface, thus leading to the de- 

 velopment of a festuca sward or, in other conditions, to heath 

 and scrub.^ 



A soil underlain at a short distance below the surface by a 

 bed of gravel, a layer of rock, or a " pan," is liable to be either 

 parched or waterlogged, and its water supply is usually so 

 unsatisfactory that cultivation is unprofitable. Under low 

 rainfall the land becomes a steppe, under rather higher rainfall 

 a heath, but the vegetation is always xerophytic, consisting 

 of heather, ragwort, broom, etc., the trees being birch and 

 conifers — the latter often planted in recent times. No method 

 of cultivating these soils has ever been devised, and most of 

 them still remain barren wastes, defying all attempts at 

 reclamation. Two special cases have, however, yielded to 

 treatment : — 



1, When the layer of rock or the pan is only thin and is, 

 in turn, underlain by a rather fine-grained sand, its removal 

 brings about continuity in the soil mass and thus effects a 

 great improvement in the water supply. The soil now 

 resembles the fertile sands, and should be treated in the same 

 way. A good example is afforded by Cox Heath, Maidstone 



(p. 333)- 



2. Where the gravel or rock is not too near the surface, 

 systematic green manuring with lupines and other crops 

 fertilised by potassium salts and calcium carbonate will often 

 effect sufficient improvement to make cultivation profitable. 

 Examples are afforded by the Schultz-Lupitz estate, Germany 

 (255), and Dr. Edwards' experiments at Capel St. Andrews, 

 Suffolk, and at Methwold. On such land an industrious 

 cultivator may make a living but not a fortune. 



Under favourable conditions recourse may be had to 



^ See F. W. Oliver and E. J. Salisbury, Topography and Vegetation of 

 Blakeney Point {Trans. Norfolk and Norwich Nat. Hoc, 1913, 9, 485-543) 



