14 



/. The Object and Necessity of Rotation. 



That no doubt may arise of the object to be gained by systems of rotation I will advance a 

 definition which may guide us in the following discussion. The object of a rotation is the produc- 

 tion of the greatest profit in crops with the least exhaustion of the soil. The views entertained by 

 practical men on the subject are however by no means fixed ; in many parts of the country it is 

 imagined that the only condition of a rotation is that the same plant be not cultivated annually, and 

 that a succession of corn, wheat and oats is as much a system of rotation as any olher plan — it is 

 indeed a rotation, but not a system. 



How far there is any practical necessity for rotations is also a point in much doubt. We are 

 often assured by good farmers that given crops as corn, wheat, hemp, have been grown in certain 

 districts from time immemorial. These are exceptions to a general rule and of no force whatever ; 

 they prove that there are spots on the earth's surface of extraordinary fertility, or, what is more 

 frequently the case, that in such districts there is some cause of reparation, by freshets, irrigation, or 

 the washings of adjacent hillsides. Wherever the fertility of new lands, which results from the 

 growth of forests or accumulation of uncut grasses for centuries, is exhausted and the soil reduced to 

 a state similar to the subsoil, it is necessary to adopt some means to increase its yield, either by 

 manures or a system of rotation. That this condition is ultimately reached in uplands will be readily 

 granted ; the only point worthy of further consideration is how far a rotation will economize manure 

 already in the soil in new lands, or manure added artificially. This is the immediate subject of the 

 memoir. 



Experience and analogy have led men to adopt rotations wherever agriculture has been prac- 

 ticed for a length of time. Experience has fully demonstrated that no plant will continue to luxu- 

 riate under ordinary circumstances for an indefinite period. To this rule trees are only an apparent 

 exception, for they submit in time to new species when left in a natural state ; they live indeed for 

 centuries because by the great development of their roots they penetrate year after year into new 

 strata of soil ; but it is well known that in northern forests the birch and maple follow the pine, and 

 in more temperate regions the pine succeeds the oak and allied genera. 



Analogy is remotely a guide to rotations in the case of forests, but if we observe the phenomena 

 of vegetation on new lands it becomes extremely instructive. The planter of the south-west makes 

 haste to cultivate cotton on his new lands, because, for a few seasons he is not overwhelmed with 

 grasses, but is called upon to combat annual weeds easily overshadowed by his crop. If a portion 

 of new land be left waste we discover that a succession of plants invades its surface and not certain 

 species, we find that however convenient the seeds may be, the plants of the first year give place in 



