THE SOIL IN RELATION TO PLANT GROWTH 309 



reclamation schemes of the seventeenth century, when Vermuy- 

 den, the engineer, and the Duke of Bedford and other enter- 

 prising capitalists took the matter in hand and erected the 

 great dykes, drains, and pumps that alone keep the land dry 

 and usable. The water is thus artificially kept down and it 

 can be maintained at any desirable level within the capacity 

 of the pumps : the land is thus subirrigated, a feature which 

 contributes no little to its extraordinary fertility. 



Farmers distinguish two types of fen : the clay fen on the 

 western side and the sandy fen on the eastern side of the 

 region ; the difference lies probably in the subjacent material, 

 there being little evidence of any difference in the actual fen. 

 The Kimeridge clay on the west lies about 5 feet below, but 

 occasionally it comes above the surface and forms the rising 

 ground on which alone dwellings could be built before the 

 reclamation — the " eys " or islands of the old days. On the 

 east the fen is underlain by sand. 



The most suitable crops are oats, wheat, and above all 

 potatoes, the introduction of which some thirty years ago 

 Completely revolutionised fen husbandry. In smaller quanti- 

 ties mangolds, celery, mustard seed, cole seed, rye grass seed, 

 buckwheat, and other seeds are grown. Corn crops, however, 

 do not finish well : they start well but do not " corn out ". 

 But where clay lies underneath a complete remedy lies in bring- 

 ing up the clay and spreading it : this is done about once in 

 twenty years. The soils shrink very much on drying, forming 

 large cracks dangerous to animals and sometimes destructive 

 to cart wheels. Oxidation is continually proceeding at a rapid 

 rate and within living memory the fen has shrunk several feet : 

 in many cases it only has another 5 or 6 feet to fall before 

 disappearing altogether. 



Fen soils do not require lime or nitrogenous manures, or, 

 as a rule, potash. But they do respond in a marked degree to 

 superphosphate, as shown by the following experiments made 

 by the Cambridge Department of Agriculture : — ^ 



^ Cambridge Farmers' Bull. No. 6. Two of the soils overlay clay, the third 

 was over gravel. 



