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In such cases, the slight absorptive capacity should be mentioned first 

 of all as a hinderance to cultivation. The diseases caused by scarcity of 

 water and food substances are pre-eminently peculiar to sandy soil. The 

 more clayey and humus admixtures present, the more the danger disappears, 

 in so far as it is not brought about again in another way by the washing 

 away of considerable amounts of easily soluble mineral substances. 



Such an erosion takes place much the more quickly when the decom- 

 position of organic substances, which occurs easily under the influence of 

 warming and aeration, is increased by other conditions. On this account 

 one must be especially careful in removing forests and litter. In deep, sandy 

 soils, the removal of the litter holding its moisture is disadvantageous since 

 the organic substances present are but very little decomposed by atmospheric 

 influences and bacteria, and accumulate as raw-humus, which can finally 

 give rise to the formation of meadow ore. According to Ramann, in lower 

 positions the deposition of raw-humus gradually leads to complete marshi- 

 ness, as in the large moors of North Germany, which almost without excep- 

 tion have originated from land which at one time was covered by forests. 

 The humus is beneficial only when mixed with sand, since the friability of 

 the soil and its water content is increased and its capacity for heating re- 

 duced. 



This capacity for heating and giving ofif heat of sandy soils is an 

 essentially harmful quality. Pure sand possesses the greatest capacity for 

 giving off heat and consequently the greatest capacity for becoming wet 

 with dew. The process of taking up and giving off heat decreases as the 

 sand is finer grained and whiter. Sand of the latter kind, for example, is 

 that rich in calcium, while, of colored sands, the ones rich in iron hydroxid 

 are very warm and cool off slowly, behaving therefore like sand mixed with 

 some clay. 



Associated with the great fluctuations in temperature peculiar to sand 

 is the poor capacity for conducting warmth. As a result of difficult equali- 

 zation its subsoil has a more even temperature, since it is warmer in winter 

 and cooler in summer than under more binding soil coverings. The danger 

 from frost is increasedly greater and more injurious. The rapid warming 

 in spring days forces vegetation prematurely and the great drop in tem- 

 perature at night is injurious, while the plant would be uninjured if it 

 started later in a soil containing water and rich in clay. 



The sandy soils of fine constitution and slight coherence present the 

 greatest possibiUties for injury to crops. The injurious effects of drifting 

 sand are shown in the sand dunes. Even if the dunes reduce the severity of 

 the sharp sea winds for plants near the coasts, they are nevertheless injurious 

 since they advance further and further inland, covering all plants. The 

 inability of the land breeze to blow back during the night the sand which 

 the sea breeze has swept over the land by day is due to the fact that the land 

 breeze is heavily laden with dew and tends to compact the sand again. If 

 the danger of being covered with sand threatens and artificial protection is 



