THE SOIL IN RELATION TO PLANT GROWTH 307 



break down. And, lastly, the pre-eminent suitability of the 

 chalk to plant and animal life has its disadvantages ; no soils 

 are more prone to carry weeds, turnip " fly," or wireworm. 

 Skilful management is the keynote of success and it generally 

 obtains, the bad farmers not usually surviving many seasons. 



Black Soils or Humus Soils. — In these the organic matter 

 dominates all other factors, but the case is more complex than 

 the preceding, because several varieties of organic matter occur, 

 giving rise to several types of soil. 



There is a sharp distinction between : — 



1. True peat, such as is found in moorlands, acid in 

 nature, and commonly occurring in wet districts and regions 

 of high rainfall or low temperature. This again is subdivided 

 into high moor and low moor. The organic matter shows 

 definite structure. 



2. Fen, neutral in nature, occurring more locally : in 

 England mainly in the Eastern counties. The organic matter 

 usually shows no structure. 



Fen land when drained has a high agricultural value, being 

 worth some £2 per acre annual rent and producing consider- 

 able crops of potatoes, celery, and wheat. 



True peat, on the other hand, has little agricultural value 

 in its natural state and where high-lying is largely waste land, 

 being unsuited to the growth of many plants and micro- 

 organisms ^ (p. 269). In this country it may have a certain 

 sporting value, but elsewhere it lacks even this. 



Peat Soils. — A number of schemes have been projected for 

 utilising the great peat areas, and they may roughly be grouped 

 into two classes : — 



I. Ameliorating substances (such as lime, artificial 

 manures, etc.) are added, and the peat is cultivated as if it 

 were normal soil. This is possible only when the deposits do 

 not lie too high. 



^ For studies of nitrification and other bacterial actions in moorland soils see 

 E. Gully, Dai Nitritzerstoruttgs und Nitritbildungverniogen der Moorboden 

 [Landw. Jahrb. Bayem, 1916, 6, 1-81) ; Th. Arnd (6), Zur Kenntnis der Nitri- 

 fication in Moorboden (Centr. Bakt. Par., II., 1919, 49, 1-51). 



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