POTASH MANURES 157 



similarly managed, is thoroughly justified. 

 But it is to be remembered that the per- 

 manent grass plots at Rothamsted are not 

 treated on any system that is met with in 

 commercial farming. Two crops of hay are 

 cut annually, or at least in those years when 

 the season permits of a second crop being 

 taken, and the whole of the produce is 

 consumed off the ground, no farmyard 

 manure being returned to the plots under 

 consideration. Under these circumstances 

 it is not surprising that potash has been 

 found to influence the yield in a very marked 

 degree. But in ordinary practice permanent 

 meadow land is dressed once in three or four 

 years with farmyard manure, with or without 

 artificials in the intervening years. If farm- 

 yard manure is not available, artificials 

 alone are depended on, but in any case it is 

 rare in Britain for two crops of hay in a 

 season to be taken off unirrigated permanent 

 grass land ; any growth that comes after the 

 hay crop is removed being pastured by live 

 stock, which necessarily furnish manurial 

 residues to the land. Where farmyard manure 

 is applied to grass land at reasonably short 

 intervals, it is rare that the use of potash in 

 artificial mixtures during the intervening 

 years produces a profitable result. 



