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 
ammonia-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 Ibs. 
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 soil are stated in the subjoined scheme. 
Available { Ammonia 0.00220 per cent = = Nitrogen ‘i a pet cent 
nitrogen { Nitric acid 0.00034 ‘“ 10009 ho. 0019 per ct. 
Inert nitrogen—of organic eompoinile, pie SACHS eee eat Meeeme enacts 0.2501 8% 
Total nitrogen...... ........ 32 diy Westend deedes oc pate bed 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. 5 grama.* 1 gram. 
Potato, e 190 ** 2A2 we 3 grams. 
Tobacco, single plant, 470 ‘ 555 ee Lace 
Hop, three plants, 2900 ‘* 3488 oS 44 
* 1 gram = 15 grains avoirdupois near ly. 
17grams= 1 oz. 
983 oh = 1 lb, he “a 
Indirect Feeding of Crops by the Organic Nitrogen 
of the Soil.—In 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- 
