26 
As we are engaged in discussing general principles, it is no part of the subject to consider the 
case of particular soils and manures; but it may be remarked with regard to these, that if the soil be 
peculiar, as calcareous, green sand, etc., or the accessible manures, as gypsum, marl, refuse fish, be not 
perfect composts, the rotation must be adapted to the case and does not require the elaborate system 
necessary for more complex soils and manures. We must either give such land the complex 
character of the most fertile soils, an expensive process, or adapt the crops to meet its defects. But 
an opinion is not to be hastily formed of the nature of any soil ; we may readily ascertain if clay or 
sand predominate, if it be rich in organic matter or lime, but before an accurate conclusion can be 
reached we must be certain that it does not contain alkaline silicates, phosphoric or sulphuric acid, 
and these are not readily detected even in the richest soils. 
When the land or manure contains every kind of plant-food in legitimate proportion, with no 
great excess of any, as is the case in good soils, the problem to be solved is the system of rotation 
which shall economize all these ingredients. As to the question of market, it is local; nor do 
we consider whether grazing be adopted or the crops directly sold, as this in no way interferes with 
the principles in hand. If we sell oxen, sheep or wool, we deprive the soil of certain of its saline 
and organic matters, and the rotation must be filled up so as not to waste such as are not sold in this 
form. If we employ complex manures, true economy does not alter the rotation, each crop is 
enlarged, but the substances removed from the land or lost will be similar. It may be well to con¬ 
sider one point more fully. If a short rotation be adopted to improve the soil, a time will arrive 
when the improvement being effected, a new class of more exhausting plants may be introduced, but 
these are in all cases introduced according to the same principles. There is nothing gained after the 
soil has reached a certain tilth in continuing the improving system, the object is now to reap our 
reward; but to do this in such a way that at the end of the rotation the soil shall not have fallen 
below a certain standard, it is then to be refreshed either by manure, meadow grasses, lucern or other 
suitable means not now under consideration, but belonging to the topic of improving the soil, and 
not that of rotations. 
The farm having reached its high point of tillage, by suitable means, is now to be cropped for 
profit, and reduced thereby to a certain practical standard—what are the general principles on which 
this cropping is to be conducted? Obviously by a system of rotation, during which every saline 
and azotized matter that becomes soluble is removed, and no part is wasted. This can be accom¬ 
plished only by introducing such crops as have severally an affinity for the various kinds of plant 
nutriment, and adapting them to the proportion of food present in the soil. Phosphoric acid is the 
rare ingredient of soils and manures, excepting guano and bones, the former of which contains 12 
and the latter 25 per cent, of this body. Next after this is the azotized matter which forms a small 
