348 ELEMENTS OF CROPS. 



beet there grown it would certainly be requisite to diminish the 

 number of cattle, or else to annex more meadow land. It is only 

 indirectly, therefo: e, that the manufacture of home-sugar can pro- 

 mote the breeding of cattle, and so prove serviceable to agriculture. 



From the definition given by me of the mosi advantageous course 

 of crops, theoretically considered, it may be inferred how closely the 

 study of rotations is connected with that of the exhaustion of the 

 soil. Hence, to discuss the value of divers rotations, we must, in 

 consonance with theory, compare the quantity of organic matter in 

 a sequence of crops, with that in the manure expended upon them. 



From a well-managed farm, where for a series of years an invari- 

 able system of culture has been steadily pursued, we must look for 

 data. This I have done, as regards Bechelbronn, determining by 

 analysis the composition of the manures and crops, and also of the 

 more ordinary kinds of fodder or food. For a long time, a five 

 years' rotation has been there adopted in tbe following order : 



1st year. — Potatoes or beetroot mnnured. 



2d year.— Wheat sown the autumn of the first year ; clover interposed in the spring. 



3d year. — Trefoil (clover) two crops ; the third crop ploughed in or smothered. 



4th year. — Wheat on the clover-break, turnips after the \\ heat. 



5th year. — Oats. 



The crop of oats which ends the rotation is generally scanty. 

 The soil is then brought back to the point of fertility which it had 

 before being dunged ; and it is known by e.xperience that it will not 

 now yield a crop of any value. 



I now proceed to detail the analyses of the different substances 

 which enter into the rotation, indicating at the same time the average 

 produce per acre. 



POTATOES. 



In the rather strong soil of Bechelbronn one acre pro<luces upon 

 an average about 105cwts. of potatoes. This is below the ordinary 

 rate of Alsace, where the crop amounts to from 155 to 165 cwts. 

 per acre. The leaves and stems are left upon the ground. 



A potato was cut in two, in order to subject it to analysis with a 

 proportional part of the pod. The half weighed 335.*2 grs. Stove- 

 dried and reduced to flour, it weighed 2*^9.3 jjrs. By absolute desic- 

 cation in vacuo, at a temperature of •J30'' F. it was found that one 

 of moist tuber became 0.2 U ; 15.1 grs. left of ash 0.030. 



The average quantity of azote is 1.2. In 183G, I four>d 1.8 of 

 azote. This notable ditTerence, perhaps, depends on the analysis 

 not having been made immc<liately after the harvest; or it may be 

 partly due to meteorological induences. To convin(;e myself that it 

 did not depend upon any error jf analysis, I examined anew the 

 potato of 1836, preserved in the farinaceous slate : it yielded 1.8 

 uf azote. I shall, therefore, reckon the azote at 1.5 : 



1. II. 



Carbon H.TJ 43. -10 



Hydrogen f..(M» 3.6() 



Oxygen 44-88 45. 6Q 



A«ote 1-50 150 



Ash 30O 3.90 



