234 THE SYSTEM OF FAEM-YARD MA:ffURmG. 



Oberbobritzscli as for Kotitz. While tlie arable soil at 

 Milusegast, in consequence of the large clover crops pro- 

 duced by it, still continues to gain in potash, the corn- 

 crops are gradually reducing the rich store of potash in 

 the Kotitz field. 



These three fields show the effect of a pure system of 

 farm-yard manuring, from which is excluded all supply 

 of manure extraneous to the farm itself. 



An additional supply of fodder purchased from other 

 farms, or hay grown on natural meadows, answers the 

 same purpose as an additional supply of manure. 



It is self-evident that we cannot give more farm-yard 

 manure to a field than it produces, unless we take the 

 constituents of the manure from some other field, which 

 in that case must lose just as much as the former field 

 gains. 



If we direct our attention to manured fields, we find 

 that they give larger corn-crops, and in many cases also 

 larger clover or turnip- crops ; the arable soil losing more 

 by the removal of the corn-crop, and receiving more 

 back by the increased produce of farm-yard manure, still 

 the idtimate results remain the same. 



In the system of cultivating by rotation of crops, it is 

 found that, for a long time, the arable soil grows with 

 each period of rotation very much richer than it is by 

 nature, in potash as well as in lime, magnesia (the prin- 

 cipal constituents of clover and turnips), and in silicic acid. 



These substances are the principal conditions for the 

 formation of roots and leaves ; their accumidation in the 

 soil tends to make the ground rank and prone to grow 

 weeds*, as the farmer says, an e\al which arises as a 



* Tlie most noxious of these weeds are the wild radish (^Raphanus 

 raphanistrirm), the corn cockle {Agroste?7ima cithago), the corn-flower 

 or blue-bottle {Centaurea cyanus\ the German camomile (J^Iatricaria 



