MINERAL MATTEES LOST IN CROPS. 225 



than the field produced could not be carried away, and 

 if less were removed the only effect would be that phos- 

 phoric acid and potash would accumulate all the more 

 in the field. 



Mausegast. 



Phosphoric acid. Potash. 



Ibs. IbB. 

 The arable soil lost by the rye-grain, barley-grain, 



-fa potatoes, fo clover 35'4 18'1 



The arable soil received in -,% of the clover crop . . 22 62'0 



Loss 13-4 Gain 43-9 



Kotitz. 



Phosphoric acid. Potash. 



Ibs. Ibs. 

 The arable soil lost in the rye, oats, and in the -j^- of 



the potatoes and clover 26*4 12*7 



It received in the clover 8'5 11-0 



Loss . 17-9 1-7 



The calculation is about the same for the field at 

 Oberbobritzsch as for Kotitz. While the arable soil at 

 Mausegast, 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 sup- 

 ply 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 



10* 



