PRINCIPLES OF MANURING 101 



favourable and assuming also that there 

 are large stocks of potential nutriment 

 the system can no doubt be practised in- 

 definitely. The permanent meadow land at 

 Rothamsted furnishes an example of what 

 can be obtained, throughout a long series 

 of years, from unmanured ground. Ever 

 since 1856 two plots of land there have 

 received no manurial treatment, and annually 

 the hay crop is reaped and carried off. The 

 yields obtained during the past fifty-six 

 years show a gradual diminution, but even 

 now, in an average season, a crop yielding 

 about three-quarters of a ton of hay per 

 acre is being obtained. One of the wheat 

 fields at Rothamsted similarly contains a 

 plot which has received no manure for more 

 than sixty years, and at the present time 

 the yield is practically steady in the neigh- 

 bourhood of 13 bushels of grain and half a ton 

 of straw per acre. This, of course, is a yield 

 which is less than half the average produce 

 of the wheat lands of Great Britain, but it 

 is as great as the average of the returns of 

 wheat in the United States of America. 

 After sixty years without manure, the 

 barley crop at Rothamsted is also producing 

 a considerable annual return, amounting as 

 it does to about 10 bushels of grain and a 



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