820 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 satisfied 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 which may stand at the actual service 
of a crop is beyond our power to estimate with 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 above interpreted, convey an 
exaggerated notion of the extent of solution. 
Proper Concentration of Plant-Food,— Let us next 
inquire what strength of solution is necessary for the sup- 
port of plants. 
As has been shown by Nobbe (Vs. Sé., VIII, p. 337), 
Birner & Lucanus (Vs. Sé., VIII, p. 184), and Wolff ( Vs. 
S¢t., VII, p. 192), 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 (approximately) be- 
low: 
In 100,000 parts of Water. Nobbe. Birner & Lucanus. Wolff. 
Lime, 16 19 19 
Magnesia, 3 61¢ 216 
Potash, 31 16 16 
Phosphoric acid, 7 24 14 
Chlorine, 21 none 2 
Sulphuric acid, 6 18 a 
Oxide of iron, 7A VW 4 
Nitric acid, 31g 36 51 
116 115 109 
Nobbe found further that the vigor of vegetation in his 
