ROTATION OF CROPS. 273 



broached and ingeniously defended by the powerful name of 

 Decandolle, and which the closest scrutiny of scientific ob- 

 servers since, has pronounced unworthy of credit, does not 

 form another reason for rotation. It is because principles 

 essential to successful vegetation have been abstracted, not 

 that others hurtful to it have been added to the soil by pre- 

 ceding crops, which renders rotation necessary. 



From all that has hitherto been learned on the subject 

 of rotation, either from science or practice, two general prin- 

 ciples may be assumed as proper to guide every farmer in 

 his course of cropping. First, to cultivate as great a variety 

 of plants as his soil, circumstances and market will justify ; 

 and second, to have the same or any similar species follow 

 each other at intervals as remote as may be consistent with 

 his interests. From the foregoing observations on the sub- 

 ject, it is evident that the proper system of rotation for 

 any farmer to adopt, must depend on all the conditions by 

 which he is surrounded, and that it should vary according 

 to these varying circumstances. 



It is a practice with some to alternate wheat and clover, 

 giving only one year to the former and one or two years to 

 the latter. This will answer for a long time on soils adapted 

 to each crop, provided there be added to the clover, such 

 manures as contribute to its own growth, and such also, as 

 are exhausted by wheat. The saline manures, ashes, lime, 

 &c., maybe added directly to the wheat without injury; but 

 gypsum should be sown upon the clover, as its benefits are 

 scarcely perceptible on wheat, while upon clover, they are 

 of the greatest, utility. But there are objections to this 

 limited variety, as it does not allow an economical or advan- 

 tageous use of barn- yard manures, which, from their com- 

 bining all the elements of fertility, are the most certain in 

 their general effect. In different countries of Europe, fields 

 which have been used for an oft-recurring clover crop, have 

 become clover-sick, as it is familiarly termed. The plant will 

 not grow luxuriantly, sometimes refusing to vegetate, or if 

 it starts upon its vegetable existence, it does so apparently 

 with the greatest reluctance and suffering, and ekes out a 

 puny, thriftless career, unattended with a single advantage 

 to its owner. This is simply the result of the exhaustion 

 of one or more of the indispensable elements of the plant. If 

 it be desirable to pursue this two-course system for any 

 length of time, nothing short of the application of all such 

 inorganic matters as are taken up by the crops, ivill sus- 

 12* 



