520 THE HOME, FARM AXD BUSINESS CYCLOPAEDIA. 



without evil effects. A limit has been reached, even in many of the most 

 fertile soils of the States and Canada, where wheat cannot longer be grown. 



The first result of the exhaustion of land in a more or less nomad con- 

 dition of society would be the migration of the cultivator to fresh fields, 

 and the relinquishing of the worn-out lands to natural pasture. This in 

 itself would be rest, and it is not necessary here to go over the reasons for 

 the gradual recovery of such relinquished lands. Suffice it to say that 

 fertility would in time return to them, and they would once more be cap- 

 ible of remunerative cultivation. This in itself would be a sort of rotation 

 or alternation between a series of years in grain and a series of years in pas- 

 ture. Convenience would suggest the advantage of sowing one portion of the 

 land with spring grain and another with winter grain ; and systematic 

 working of fallows would shorten the period necessary for renovating an 

 exhausted field ; and the three-field course would thus gradually shape 

 itself, and all the more readily as the increase of population rendered 

 better cultivation imperative. 



Bearing in mind the disintegrating forces that are always at work in a 

 soil, the benefits of a fallow no longer remain a mystery. What might 

 require years to produce, if the soil were left entirely to nature, is accom- 

 plished in a single season by pulverizing and aerifying effects of tillage 

 implements, assisted, as they invariably are, by the action of the atmos- 

 phere, moisture, and changes of temperature. 



The benefits of a fallow were known to the Israelites, who were required 

 to fallow all their land once in seven years. The Romans introduced the 

 practice into England ; but a systematic tillage of bare fallows is said to 

 have been unknown in Scotland till about a hundred years since. The 

 old three-field course is still practised in certain stiff land districts. It 

 consists in taking a crop of wheat, followed by beans, oats, or sometimes 

 clover, and the third year it is fallowed. Such a system is not likely to 

 be remunerativ 3 at present grain prices, and if a better system of cropping 

 cannot be profitably introduced, such lands ought to be laid away to 

 permanent pasture. In the better classes of clay lands, bare fallows are 

 made occasionally, if a field is exceptionally foul, or when the season is 

 unpropitious for root cultivation. As the quality of the clay land rises, the 

 intervals between the fallows are lengthened. 



PRINCIPLES ON WHICH ROTATIONS ARE CONSTRUCTED. 



A clear view of the principles which should guide an agriculturist in 

 constructing rotations will be best obtained by dividing all soils, in the 



