272 AMERICAN AGRICULTURE. 



work in renovating the land for further use. The whole 

 course of her operations is not yet known ; but it is satis- 

 factorily ascertained, that she is incessantly engaged in pro- 

 ducing those changes in the soil, which enable it to contri- 

 bute to vegetable sustenance. Enough of lime, or potash, 

 or silica may have been disengaged to yield all that may be 

 required for one crop, which" by that crop is principally 

 taken up, and if another of the same kind follows in quick 

 succession, there will be a deficiency ; yet if a different crop 

 succeed, there may be found enough of all the materials it 

 needs, fully to mature it. A third now takes its place, de- 

 manding materials for nutrition, in forms and proportions 

 unlike either which has preceded it, and by the time a re- 

 currence to the first is necessary, the soil may be in a con- 

 dition again to yield a remunerating return. These remarks 

 apply equally to such soils as have, and such as have not 

 received manures ; unless, as is seldom the case, an accurate 

 science should add them in quantity and character (specific 

 manures), fully to supply the exhaustion. The addition or 

 withholding of manures, only accelerates or retards this 

 effect. 



Another prominent advantage of rotation, is in its en- 

 abling such crops to have the benefit of manure, as cannot 

 receive it without hazard or injury if applied directly upon 

 them. Thus wheat and the other white grains, are liable 

 to overgrowth of straw, rust, and mildew, if manured with 

 recent dung ; yet this is applied without risk to corn, roots 

 and most of the hoed crops ; and when tempered by one 

 season's exhaustion, and the various changes and combina- 

 tions which are effected hi the soil, it safely ministers in 

 profusion to all the wants of the smaller cereal grains. An 

 additional benefit of rotation is, by bringing the land into 

 hoed crops at proper intervals, it is cleared of any troublesome 

 weeds which may infest it. And a still further advantage 

 may be found, in cutting off the appropriate food of insects 

 and worms, which, in the course of time, by having a full 

 supply of their necessary aliment, and especially if undis- 

 turbed in their haunts, will ofttimes become so numerous 

 as seriously to interfere with the labors of the farmer. A 

 variation of the crop, exposure of the insects to the frosts, and 

 the change of cultivation which a rotation insures, will 

 make serious inroads upon their numbers, if it does not ef- 

 fectually destroy them. 



The noxious excretions of plants, a fanciful theory first 



