Mr Purvis, Bracken as a source of potash 261 



Bracken as a source of potash. By J. E. Purvis, M.A. 

 [Read 17 February 1919.] 



The Master of Christ's College, Cambridge, in the autumn of 

 1917, had some correspondence with Mr J. A. A. Williams of 

 Aberglaslyn Hall, Beddgelert, in regard to the use of bracken as a 

 fertiliser. Mr Williams had burnt the bracken growing on a peaty 

 soil on his estate at Beddgelert, ploughed in the ashes and obtained 

 highly satisfactory crops of potatoes. It seemed to be of some 

 importance to find out what amount of potash could be obtained 

 from the ash; and in October 1917 a sample of bracken from the 

 Botanic Gardens, Cambridge, was analysed. This grows on a poor 

 sandy soil. 



It is known that bracken contains larger quantities of potash 

 in the summer months than in the autumn and more complete 

 investigations were deferred till the summer of 1918. Meanwhile 

 in the April (1918) number of the Journal of Agriculture (vol. 25, 

 no. 1, p. 1) Messrs Berry, Robinson and Russell published an 

 article on " Bracken as a source of potash " which contained the 

 results of the analyses of material collected from various districts 

 in England, Scotland and Wales from May to October 1916, and 

 from June to October 1917. The numbers show that the amount 

 of potash is much higher in the summer months than in the autumn. 

 For example, bracken gathered June 1st, 1917, from Harpenden 

 Common, Rotharnsted, which is mainly gravel and clay, produced 

 4"1 ° I ^ of potash (KoO) on the dried material and only 1'8 7o when 

 gathered September 1st, 1917. The authors also considered that 

 their evidence indicates a more rapid falling off of the potash from 

 bracken growing on sandy and peaty soils than on heavier soils 

 rich in potash : and that, therefore, its chances of success as a 

 fertiliser would be greater in these heavier soils. 



In view of these results the investigations were continued with 

 the bracken growing in the Botanic Gardens, Cambridge, and also 

 with that on Mr Williams's Welsh estate. The following tables 

 summarise the results. 



Generally, the numbers are of the same order as those obtained 

 by Messrs Berry, Robinson and Russell, and confirm the opinion 

 that in the summer months there is more potash than in the later 

 months. Also there is a clear indication that, on an average, the 

 Welsh peaty soil yields more potash than the Cambridge poor 

 sandy soil. 



