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4. Foliage and root crops differ in their affinities for saline matters, and the amount which 
they remove from the soil; and should be so introduced in a rotation as to economize those which are 
rendered soluble. These are also ameliorating or exhausting as respects azotized matters, and are to 
be selected in such a manner as to fulfill the indications of the second and third principle. 
It may be proper to test the accuracy and practical value of these principles, by examining a 
rotation of undoubted value. For this purpose I have selected the Norfolk system, because it is well 
known to be the most successful ever devised ; it has raised entire counties in England from sterility 
to the highest prosperity, and has extended wherever the soil and market were available. It consists 
of the following succession : first year, manure, followed by turnips ; second year, barley sown with 
clover ; third year, clover, the first crop cut, then depastured and ploughed for wheat; fourth year, 
wheat, succeeded by manure and turnips, as before. In this system the manure is followed by the 
plant requiring the most azotized matter, this is also a soda and sulphuric acid crop. Barley, the 
second crop, requires very much less azotized matter and exhausts the soil of only a limited amount 
of phosphoric acid and potash. This is succeeded by a lime plant, clover, which recruits the azotized 
matter and loosens the soil by its long roots. Wheat, which completes the rotation, is a potash and 
phosphoric acid crop, requiring a medium supply of organic matter. This rotation, when we con¬ 
sider the soil and the manures used, the former siliceous and the latter farm-yard compost and bone 
earth, is a perfect embodiment of the foregoing principles. Reached entirely by experimental means, 
it is strictly conformable with science; and is a striking illustration of the correctness of the doctrine, 
that rotations form a chemical study, which, originating with Chaptal, has been maintained to 
our day. 
In conclusion, I beg to present a few instances of the application of these principles in the con¬ 
struction of rotations. The plants proposed for the several soils are indicated by the probable excess 
of mineral matters and phosphoric acid therein. The crops which may be substituted are placed 
vertically under the principal plant. There is in the rotation for clay soils, a mechanical impediment, 
arising from the difficulty of keeping them in tilth, which influences the plan ; and in sandy soils, 
also, it is necessary that too many hoed crops be not introduced, and that grazing be practised to ren¬ 
der the soil compact. The rotations given are applicable north of Carolina. 
