ROTATION OF CROPS. 197 



It was thus that The Four-course Rotation, or, in other Four. 



course 

 tion. 



words, the alternation of root-crops and of leguminous crops cc 

 with cereals, became established. Such alternation is, in fact, 

 the basis of all the various rotations which are adopted in 

 different parts of our own country, and also to a great extent 

 which are followed in many other countries. 



It is worthy of remark that, although we owe the introduc- Yield of 

 tion of the essential elements of our rotations to the example c ^fJ% 

 of our Continental neighbours, we, with one or two im- and foreign 

 material exceptions, obtain more per acre of all the staple countnes - 

 saleable products of rotation, grain and meat, under our 

 landlord, tenant, and labourer system, than any other country 

 in Europe, or than in America, under whatever advantages of 

 climate, or under whatever system of holding, or of size of 

 holdings. Thus, there is not a single country in Europe that 

 reaches our average produce per acre of wheat ; only Belgium 

 and Holland approach, but they do not equal, us in the pro- 

 duce of barley ; only Belgium, Holland, and Norway exceed 

 us in acreage yield of oats ; and no country approaches us in 

 acreage produce of potatoes. Again, whilst several countries 

 exceed us in number of cows to a given area, and some in 

 the number of pigs, not one equals us in weight per acre of 

 other cattle than cows ; and not one nearly approaches us in 

 the weight of sheep to a given area. Nor, notwithstanding 

 the great depression of our agriculture in recent years, the 

 result of the low prices of produce, is there any probability that 

 we shall soon lose our pre-eminence in production per acre. 



There can be no doubt that the effect of the extension of Beneficial 

 the growth of green crops was — to a great extent to get rid of l jf"el:n 

 unprofitable fallows, greatly to increase the supply of stock crops. 

 food, especially for winter feeding ; so to lead to a largely 

 increased production of meat and milk, to a greatly increased 

 supply of manure, and thus to enrich the land for the growth 

 of grain, which, accordingly, yielded much larger crops. 



We have now to endeavour to ascertain how the admittedly Benefits of 

 very beneficial effects of alternate, as distinguished from con- rota l^ /ed 

 tinuous, cropping are to be explained. It will be well first 

 very briefly to refer to some of the chief theoretical explana- 

 tions that have been put forward, and afterwards to discuss 

 the results of various direct experimental investigations con- 

 ducted at Kothamsted on the subject of rotation. 



The first definite theory as to the benefits of the alternation Theoretical 

 of crops assumed that the excreted matters of one description e ^^ na ' 

 of crop were injurious to plants of the same description, but 

 that they were not so, and might even be beneficial, to other 

 kinds of plants. 



