RESPECTIVE VALUES OF ORGANIC AND INORGANIC MANURES. 219 



Table II. shows the same experiment with farmyard manure 

 added. Rape cake, it will be seen, is not only far superior to the 

 inorganic ammonias, but gives a better result than farmyard manure 

 in spite of the fact that the amount of nitrogen applied in the latter 

 case is more than double that contained in the rape cake dressing. 

 The moral of this is, I think, the value of the soluble form of organic 

 over the insoluble, the ammonia in the rape cake being more available 

 for the plant than that in the dung. 



Table II. — Mangolds, different Manures, Rothamsted; 



Plots. 



Manure. 



Containing N j Average pro- 

 per acre. ^duce per acre. 



4 N 

 4 A 



f 



Nitrate of soda 



Ammonium salts . . . . . k 



Rape cake ..... .j 



Farmyard manure ..... 



86 i 7 -95 

 86 1512 

 98 20-95 

 200 1744 



Table III. shows the effect of the same three sources of nitro- 

 gen with different combinations of other manures. It will be 

 noticed that the nitrate of soda plot beats that receiving rape cake 

 when no potash is added ; that is owing to the fact that, as is well 

 known, soda liberates potash in the soil, and potash is very necessary 

 for mangolds. The beneficial effect of soda in this respect, and its 

 consequent superiority over sulphate of ammonia, are noticeable also 

 in Tables I. and II., and to a slight extent in the last two columns 

 of this table ; it is interesting, but has no direct bearing on the subject 

 under discussion. 



Table III. — Average Yield of Mangolds, 

 (Rothamsted, 32 years, 1 876-1 907.) 





Superphosphate. 





Dung. 



No potash. 



Potash, Sec. 1 



Alone. 





With 

 phosphate 

 and potash. 



Rape cake = 98 lb. N . 



IF I 



22'0 



24*5 





25' 7 



Nitrate of soda = 86 lb. N . 



153 



l8o 



25" 9 





26' 4 



Ammonium salts = 86 lb. N . 



75 



152 



I] 



22- 5 





240 



When potash is added together with the superphosphate the 

 rape cake again shows its superiority. The most interesting fact 

 about this experiment, however, is that when dung is added the rape 

 cake plot shows no marked increase, proving that the amount of 

 organic matter present in the rape cake is almost sufficient for the 

 crop, or in other words the humus required by the crop can be 

 supplied by artificials alone, and that the addition of dung is not, 

 as so many think, absolutely essential. This fact should reassure 

 those who regard the increasing scarcity of dung with so much 

 misgiving. 



