124 BRITISH HUSBANDRY. [Ch.VIII. 



may be termed its 7ialural fecundity ; wliicli, although existing in various 

 jjFoportions according to its original fertility, yet, when capable of pro- 

 ducin'T five bushels of rye per acre, besides the seed, may be supposed 

 equal to 40 degrees : its full value being estimated at 100. Now, from 

 various experiments which have been made upon a large scale, it is sup- 

 posed tliat the application of about eight tons per acre, of well fermented 

 farm-yard manure, of average quality, are equal in their effects to 50 de- 

 grees of nutritive matter ; and that a bare summer fallow — not only by the 

 influence of its working on the land, but also by producing the decom- 

 position of the weeds which it destroys — is equivalent to 10 degrees; thus 

 bringing the soil round to its former state, and rendering it again fit for the 

 production of further crops. 



Independently of the fertilising properties which the fallow may be sup- 

 posed to draw from the atmosphere, the richer the land may be, the greater 

 will be tlie quantity of weeds which it will produce. Their decomposition 

 will consequently add proportionably to the amelioration of the soil ; so 

 tliat if its original fecundity be 40 degrees, and tliat the fallow adds 10, it 

 will be increased to 11 when the former reaches 50, and to 12 when carried 

 to 60. 



The calculations of Von Thaiir are made upon the weights and measures 

 of Berlin ; by which, if the Journal of land be divided into J 000 parts, 

 15S6 constitute an English acre; and he assumes five loads, each of 20 

 centners Prussian, or 18^ cwt. British weight, as the quantity of manure 

 applied to tlie Journal. If the scheffel be also divided into 1000 parts, 645 

 are equal to the Winchester bushel* : and the absorption of nutritive matter 

 by the crops of grain is presumed to be — 



by Wheat . . 6^ degrees-> ^ or, about 4 degrees -j 

 ,, Rye ... 5 , , I -g • • 3? 

 ,, Barley . . 3^ ,, T^ • • 2| 

 ,, Oats . • ^3 > ) J eu • • lyo" 



These estimates, however, although founded upon extensive experience, 

 being yet to be considered as partly hypothetical, and only intended to 

 give a general idea of the subject, we do not deem it necessary to reduce 

 them to our standard, and therefore state them as they there stand. In 

 order to demonstrate the proportion of exhaustion occasioned by the 

 growth of particular crops, he has furnished detailed accounts of several 

 rotations, from which we extract those of the triennial and alternate 

 systems ; by which the state of the soil will be'seen at the close of each 

 course, supposing the land to be of the original fecundity already men- 

 tioned, and to produce, on an average, the following crops per Journal. 



TRIENNIAL SYSTEM. 



Fecundity. 

 Crops ami Manure. 



Fallow . • 



6^ loads of manure 

 Rye, 6 scheff. 

 Barley, 6 do. 

 Fallow . • 



Rye, 3^ scheff. 

 Oats, 4 do. 

 Fallow, light folded 

 Rye, 4 scheff. . 



Barle}', 3 do. 



115 deg. 109 deg. 



* The centner is == 103? lbs. English. Thw Dantzig scheffel is =: 1552 Winchester 

 bushels, and the last of 60 schtffels = 11 qrs. 3 bush. ; but wheat is shipped by the last 

 of 56i scheffels. 



