224 THE SYSTEM OF FAEM-YAED MANTJEING. 



crops as large as the latter gives, but merely that the 

 unmanured plots have, at some antecedent period, given 

 better crops than in the year 1851. Without an addi- 

 tional supply of niineral elements derived from mea- 

 dows or other fields not included in the rotation, the 

 produce must go on continually decreasing, as the sup- 

 ply of mineral constituents brought up by the clover 

 from the subsoil, in these two places, is far from suf- 

 ficient to make up for what is taken away in the corn- 

 crops. 



In the following calculation it has been assumed 

 that of the crops obtained, rye and oats were actually 

 removed, and of potatoes and clover one-tenth was car- 

 ried away in the form of cattle.* 



Cunnersdorf. 



Phosphoric acid. Potash. 

 Ibs. Ibs. Ibs. 



The arable soil lost by removal of 1176 rye-grain. . 10'2 5 -5 



2019 oats 15-3 7'7 



" " -j 1 },- potato crop 2'3 l*lf 



" " fo clover crop 4'0 2'0f 



Total loss 31-8 16'3 



The arable soil had returned to it, in -& of 9144 Ibs. 



of clover-hay 36*18 95'5 



Balance in excess . 4-38 79-2 



The arable soil of the Cunnersdorf field received, 

 accordingly, in the farm-yard manure, more phosphoric 

 acid and more potash than had been carried off by the 

 corn-crops. 



In this calculation, it is a question of no importance 

 how much of the rye or oats was carried off. More 



* The amount of phosphoric acid and potash is estimated in the cal- 

 culation as follows : 



Eye Oats Potatoes. Clover-hay. 



Corn. Straw. Corn. Stra\v. 



Phosphoric acid 0'864 0'12 0-75 0'12 0'14 0'44 



Potash 0'47 0'52 0-38 0'94 0'58 1-16 



j- The quantity of potash is calculated here upon the proportion of 

 phosphoric acid in corn, one part by weight of potash to two parts by 

 weight of phosphoric acid. 



