RECAPITULATION. 
29 
5. The importance of organic matter in the soil, is sustained by many well established 
facts: 
a. In the removal of crops of beans, wheat, indian corn, etc., the soil is exhausted of 
not only inorganic but organic matter ; and in order to restore fertility, experience 
proves the necessity of adding nitrogenous matters. The most striking results flow 
from those manures which contain the most organic matter already prepared for 
the uses of the plant, such as guano and night soil; and in the application of these 
substances, we become aware of the value of their presence in the soil. Ashes, 
which is usually regarded as a manure wholly inorganic, is really complex, and 
contains much organic matter. Organic matter in fact adheres so obstinately 
with phosphoric salts, as well as the alkalies, that no form of matter which is 
applied to land as a fertilizer is entirely free from it. If there are any exceptions, 
it is in the use of lime of the oldest rock, and in pure gypsum. 
b. It is well established that one of the conditions necessary to secure the favorable 
action of lime, is the presence of organic matter. It is not sufficient that there be 
carbonic acid in the atmosphere, or ammonia : it is necessary that it should exist 
there in the condition of a product undergoing decay, by which the oxygenized 
products may be acted upon, and by which the peculiar organic acids may be 
produced. 
c. In regard to the entrance of nutriment into a plant, I can not but regard the root 
as its channel. Experience upholds the idea at least; and though the leaf has 
the power of absorbing carbonic acid and ammonia, yet it is really analogous to 
the power of the skin also to absorb matters : still it is not the function of the skin 
to supply food to the system. Vicarious functions are quite different from natural 
ones. Hence the argument that organic matter in the soil could not furnish 
enough for the wood produced in a forest, does not prove that the forest received 
its increase through the channels of the leaves. The ammonia and carbonic acid 
falling with the rains to the earth, supply additions of nutriment to the soil. 
Again, it is not enough that the inorganic manures be employed. Experience 
proves that their good effect on crops fails in due time : indeed, perfect seed can 
not be produced in their absence. All essential and perceptible increase of pro¬ 
ducts comes from manuring, and in proportion to the manure ; and trees or shrubs 
whose branches are cut off from the supply below, die, not from the absence of 
water alone, but from starvation : they can maintain but a precarious existence 
under the most favorable circumstances. 
d. The quantity of carbonic acid is about one-thousandth of the weight of the 
atmosphere. This is sufficient, no doubt, to preserve, so far as this is concerned, 
the balance of nature. Being produced by the respiration of animals and by 
combustion, and diffused through the atmosphere, it is again brought to the soil. 
So it is produced in vast quantities in the soil by slow combustion, and manures 
must yield the same product in the very place where it is particularly wanted. 
