186 



THE SYSTEM OF FARM-YARD MANURING. 



It is evident that the action of farm-yard manure 

 upon a field can be properly estimated only if it is 

 known beforehand what amount of produce the field 

 will give without any manure : and first of all we shall 

 consider the crops produced on five fields in five differ- 

 ent parts of Saxony, in the four-year rotation above 

 mentioned. 



These results lead to the following considerations. 



The term unmanured, as applied to these fields, is 

 meant to designate the condition in which they were 

 left at the end of a rotation by a succession of crops. 



These fields had been manured at the beginning of 

 the rotation ; and had they been manured afresh, they 

 would have produced the same crops as before. In the 

 crops yielded by them in the manured state, the con- 

 stituents of the soil and those of the manure had a cer- 

 tain definite share ; if the fields had not been manured, 

 the crops would have been smaller. Now if we at- 

 tribute the increased produce during the course of the 

 rotation to the supply of farm-yard manure, and suppose 

 that the constituents of the farm-yard manure have 



