330 How LONG DOES LiME LAST IN THE SOIL ? [SEPT., 



(4) It seems to be established that the soil organism {Azoto- 

 bacter), which fixes nitrogen without the aid of leguminous 

 plants and is a great factor in the gain of fertility when land 

 is laid down to grass, cannot develop properly unless there is 

 a good supply of carbonate of lime. 



(5) Turnips are always liable to " finger-and-toe " when lime 

 is deficient in the soil. 



It cannot be doubted that the fertility of many of our fields 

 to-day is due to the liming and chalking that was done by the 

 farmers of the eighteenth and earlier centuries ; they, indeed, 

 made the soil, for it is through their labours that it remains in 

 profitable cultivation at the present time. Owing to the very 

 large amounts of chalk and lime which were then applied, it has 

 been possible for later generations to live upon the capital thus 

 accumulated and dispense v/ith any expenditure of their own 

 in this direction. But this spending process cannot continue 

 indefinitely, for natural causes alone — the percolating rain- 

 water — are steadily removing the lime in the surface soil ; for 

 example, the Rothamsted soil, which at the beginning of the 

 nineteenth century must have contained something like a 

 hundred tons of chalk per acre, has now less than fifty, and 

 many other soils which started with a smaller initial stock are 

 beginning to run dangerously short. All over the country 

 there is evidence that much of the land, especially on the 

 heavier soils, is in need of liming, and though it would not be 

 wise to return to the old wasteful dressings of six to ten tons 

 to the acre, a much smaller quantity, half a ton or so per acre, 

 could be profitably applied at least once in the course of each 

 rotation. 



A. D. Hall. 



Rothamsted Experimental Station, 

 Harpenden, Herts. 



