INCREASE OF TRODUCE BY GUANO. 



269 



many liekls poor in silicic acid, Avliilst on others abounding 

 in this substance it does not occur. On many soils this 

 tendency may be cured by dressing with lime before 

 applying the guano ; and in other cases it may be les- 

 sened by mixing dung made from straw with the guano. 



If we calculate the increase in the produce of cereals, 

 potatoes, and clover, obtained severally in the years 1851 

 to 185-1, from 100 lbs. of guano we find 



100 /6s. of guano gave increase of produce 



These results show that the same quantity of guano has 

 an equally dissimilar effect upon different fields as farm- 

 yard manure, and that it is quite impossible to draw from 

 the crops obtained any inference as to the quality or 

 quantity of the manuring agent employed to produce 

 them. The field at Mausegast had received the same 

 amount of guano as the Kotitz field, both, accordingly, 

 the same quantity of nitrogen and phosphoric acid ; yet 

 in cereals and potatoes the increase of produce was twice 

 as great, and in clover much greater in the former than 

 in the latter. 



How very little the crops will enable us to draw com- 

 parisons between the effects of the several constituents of 

 one and the same manuring agent, may be clearly seen 

 from the results of the experiments at Cunnersdorf and 

 Oberbobritzsch. 



