320 HOW CROPS FEED. 



its aqueous solution. Wunder, on the contrary, calculat- 

 ed that the Chemnitz soil yields insufficient matters for 

 the ordinary amount of vegetation ; and we see that as 

 respects potash, the wants of grass and root crops could 

 not be satiified with the quantities in our computation, 

 while sulphuric acid and phosphoric acid are nearly or en- 

 tirely wanting. We do not, however, regard such calcu- 

 lations as decisive, either one way or the other. The 

 quantity of water whicli may stand at the actual service 

 of a crop is beyond our power to estimate witli anything 

 like certainty. Doubtless the amount assumed by Ander- 

 son is too large, and hence the calculations relative to the 

 Bonn and Chemnitz soils as ahove interpreted, convey an 

 exaggerated notion of the extent of solution. 



Proper Concentration of Plant-Food. — Let us next 

 inquire what streiKjth of solution is necessary for the sup- 

 port of plants. 



As has been shown by Nobbe ( Vs. St., VIII, p. 337), 

 Birner & Lucanus {Vs. St., VIII, p. 134), and Wolff ( Fs. 

 St., VIII, p. 102), various agricultural plants flourish to 

 extraordinary perfection when their roots are immersed in 

 a solution containing about one part of ash-ingredients 

 (together with nitrates) to 1,000 of water. 



The solutions they employed contained the following 

 substances in the proportions stated (apjiroximately) be- 

 low: 



Nobbe found further that the vigror of vesfetation in his 



