2l8 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



origin, such as the mineral phosphates of various kinds, super- 

 phosphate, basic slag, nitrate of soda, sulphate of ammonia, and the 

 mineral potash salts. 



I want to discuss the relative merits of these two classes of 

 manures and account for the superiority of the one over the other 

 for certain definite purposes, in order that the user may judge for 

 himself as to which will give him the result at which he is aiming. 



The first thing that strikes one in considering this question is 

 the very much higher price, especially in ammoniacal manures, 

 that the user will pay — and has paid for years — for organic ma- 

 nures. For instance, in normal times the unit price of ammonia 

 in crushed hoof or dried blood has stood at about 165. or 17s., 

 whereas the unit of ammonia in nitrate of soda or sulphate of 

 ammonia has cost only 12s. to 13s. Why this preference ? Most 

 chemists, and until quite recently the Board of Agriculture, have 

 said that the value of these manurial units is the same whatever 

 their source, the sole determining factor being their solubility. But 

 organic manures are less soluble than inorganic, and should, according 

 to this argument, be cheaper instead of dearer. 



It is obvious, therefore, that there is more in the respective merits 

 of these two classes of manures than the holders of the mineral 

 theory, as it is called, would have us believe. As A. D. Hall, 

 one of the greatest of our present-day authorities on the subject of 

 manuring, says, " The farmer has a strong preference, to which 

 credit must be given as founded upon experience, for the organic 

 sources of nitrogen." 



Before going further into our argument it will perhaps be inter- 

 esting to look at the results of a few of the Rothamsted experiments 

 that bear somewhat on the point. 



Table I. shows an experiment carried out over a number of years 

 with a view to ascertaining the comparative values of rape cake 

 (organic), sulphate of ammonia, and nitrate of soda (inorganic) as 

 nitrogenous manures for mangolds. The complete minerals (super- 

 phosphate and sulphate of potash) were the same in each case. It 

 will be seen that 4C, the rape cake plot, shows a far higher average 

 crop than either of the mineral plots, and further that the number 

 of plants on this plot — a significant fact to which I shall refer later 

 — is far in excess of those on either of the other two plots. 



Table I. — Effect of Manures on Mangolds. 



(Rothamsted, 1 876-1 902.) 



Plot. 



Manures. 

 • 



Average crop 

 per acre. 



Average No. of 

 roots per acre. 



4 c 



4 A 



4 N 



i Complete minerals with rape cake 

 j Complete minerals with ammonium salts . 

 Complete minerals with nitrate of soda 



Tons. 

 21-3 

 14-9 

 180 



Number. 



17.474 

 14,802 



I4.I30 



