ROTATION OF CROPS. 
209 
The facts regarding manures then, are, that permanent ones must consist of a combination of 
organic and inorganic matters; or, that the elements of organic matter must, in some way, be 
combined with the inorganic. If fields are manured with inorganic matters, as leached ashes, 
gypsum, etc. those fields in time cease to be fertile. Thus the farmers of Long-Island, who 
have been in the habit of using leached ashes for a few years, find that the effects at first are 
quite decided, yet soon they begin to decline, and after a while cease to exert a favorable 
influence upon vegetation. There seem to be, in facts of this kind, a distant analogy in the nu¬ 
triment of plants and animals : a change of diet may be required in both kingdoms; the ap¬ 
petite in animals indicates this in the animal, and the general effects of one nutriment, long 
continued, indicates it in the vegetable kingdom. Dogs when fed upon gelatine alone, soon 
lose their appetite, and, if persisted in as food, they will starve upon it. Yet gelatine and 
starch, under some conditions, is nutritious, and, for convalescents from fever, is one of the 
safest kinds of nutriment, and one upon which the system is known to thrive, and gain flesh 
and strength. Combination of elements, and a change also of the compounded matters, are 
required by both classes of organized bodies. We find the organic elements in all cases in 
the ash of the organs, both of animals and vegetables. It is true some of the lowest forms of 
vegetation, as the mucors or moulds, according to Mulder, leave no ash or residue on being 
burnt. These may, and must be, however, regarded as mere exceptions to a general law. 
Those who feed animals for market know well that a change of diet is necessary to bring them 
to the highest state of perfection. The natural rotation of crops is a fact which points to the 
same principle. Experience then, and observation, agree in sustaining this important principle 
of cultivation and of feeding. The dictation of an appetite, in the case of animals, should be 
heeded ; and the deterioration of vegetables, Avhen fed with a single nutritive element, should 
also warn us that a change of treatment and diet is called for. 
ROTATION OF CROPS. 
A rotation of crops, as a means for increasing the products, has been regarded as one of the 
means for sustaining and prolonging the fertility of the soil. What is the foundation of a 
practice so general and so much approved by practical men 1 Observation has brought to light 
the fact that no crop can be sustained, for a long period, on the same area. This fact is not 
disproved by another—that there are spots of great fertility, and abounding in nutriment, which 
is stored up in the soil: some of the western bottoms on the Ohio and Mississippi are ex¬ 
ceedingly productive for years, even in Indian corn. These spots contain a great abundance 
of all the elements of nutrition required by the plant : but this is the case with very limited 
areas only ; the greater part of the earth’s surface has, at any one time, but a small amount of 
the essential food of plants in a condition fit for the nourishment of vegetables. 
When we find, therefore, that a crop begins to be less vigorous and productive, after culti¬ 
vation on the same field, we may conclude that it has exhausted one or more of the essential 
elements of nutrition. Now, although this same plant, or crop, may not thrive, still experience 
[Agricultural Report — Vol. iii.] 27 
