282 HOW CROPS FEED. 
generally which have not been recently manured, ammonia 
and nitric acid are the exclusive feeders of vegetation with 
nitrogen. Such a view is not indeed absolutely demon- 
strated, but the experiments alluded to render it in the 
highest degree probable, and justify us in designating the 
organic nitrogen for the most part as inert, so far as vege- 
table nutrition is concerned, until altered to nitrates or 
ammoni.-salts by chemical. change. 
To comprehend the favorable results of garden-culture 
in such a soil, it must be considered what a large quantity 
of earth is at the disposal of the crop, viz., as Boussingault 
ascertained, 57 lbs. for each hill of dwarf beans, 190 lbs. 
for each hill of potatoes, 470 lbs. for each tobacco plant, 
and 2,900 lbs. for every three hop-plants. 
The quantity and condition of the nitrogen of Boussin- 
gault’s garden so:l are stated in the subjoined scheme. 
Available § Ammonia_ 0.00220 per cent = Nitrogen 0.00181 per cent {0.0019 per ct. 
nitrogen | Nitric acid 0.000384 ‘* “ = 0.00009 ‘+ ** 
Inert nitrogen—of organic compounds...........-..20-ceeceee seen ee 0.2581 > Fr 
Total nitrogen...... fase hs cio 2% eee - o, eter ereee 0.2610 per ct. 
Calculation shows that in garden culture the plants 
above named would have at their disposal in this soil quan- 
tities of inert and available nitrogen as follows: 
Weight of soil. Inert nitrogen. Available 
nitrogen. 
Bean (dwarf) hill 57 Ibs. 75 grams.* 1 gram. 
Potato, és 190 ‘‘ 242 te 3 grams. 
Tobacco, single plant, 470 ** 555 fs eos 
Hop, three plants, 2900 ‘* 34388 % 4 «= 
* {gram — 15 grains avoirdupois nearly. 
17 grams 1 oz. re 4 
983 sh 1 lb es bh 
Indirect Feeding of Crops by the Organic Nitrogen 
of the Soil.—tIn what has been said of the oxidation of 
the organic matters of the soil, (whereby it is probable 
that their nitrogen is partially converted into nitric acid,) 
and of the effect of alkalies and lime upon them, (whereby 
ammonia is generated,) is given a clue to the understand- 
