46 AMOUNT OF FERTILISING MATTER 



(5) 3.78 to 1. This would give a mean of 3.32 to 1. 

 This is not the ratio in which these ingredients are 

 generally present in farmyard manure. Farmyard 

 manure may be said to be much richer in the mineral 

 constituents of plants than in nitrogen. Professor 

 Heiden found that in the case of a farm at Waldau, 

 the crops in the course of ten years removed from a 

 morgen (.631 of an acre) the following quantities : 



lb. 



Nitrogen 329 



Potash . . . . . . . 263 



Phosphoric acid 121 



In order to supply these 'amounts the following 

 quantities of manure would require to be supplied : 



1. For the nitrogen, 26 or 27 tons (manure contain- 



ing .606 per cent nitrogen). 



2. For the potash, 20 to 25 tons (manure containing 



.672 per cent potash). 



3. For the phosphoric acid, 13 to 19 tons (manure 



containing .315 per cent phosphoric acid). 



From the above it will be seen that farmyard man- 

 ure contains too little nitrogen in proportion to its ash 

 ingredients. 



It is not merely the amount of fertilising ingredients 

 removed by the crop we have to take into account in 

 estimating the value of certain manurial ingredients 

 for the different crops. Two other considerations have 

 to be remembered viz., the amount of the constitu- 

 ents already present in the soil, and the ability of the 



