ERROR IN" USING TOO MUCH MANURE. 209 



ing agents as affecting the increase of produce, he can, 

 of course, have no correct notion of their rational, which 

 means their truly economical, use ; he puts on his land 

 too much, or too little, or chooses the wrong agent. 

 The error of employing too little manure needs no ex- 

 planation ; for every one knows that the right propor- 

 tion of manure will, with exactly the same labour and 

 at a trifling additional outlay, ensure the maximum 

 produce of which the land is capable. 



The error of using too much manure arises from the 

 mistaken notion that the action of manures is propor- 

 tionate to the quantities in which they are applied ; 

 this is true up to a certain limit, but beyond this all the 

 manure applied is simply thrown away, as far as any 

 fertilising action is concerned. 



A manuring experiment made by Mr. J. RUSSELL, 

 of Craigie House (' Journal of the Royal Agr. Soc. of 

 England,' vol. xxii. p. 86), may, perhaps, serve to illus- 

 trate our meaning. In this experiment a field was 

 divided into a number of plots of three rows each, all 

 planted with turnips, some of the plots being left un- 

 manured, the remainder dressed severally with different 

 manuring agents, among others with superphosphate 

 (bone-ash dissolved in sulphuric acid). The produce, 

 calculated per acre, was as follows : 



Produce per acre. 



"No. of plots. Cwt. 



I. Unmanned 340 turnips (Swedes). 



II. " 320 



V. Manured with 5 cwt. of superphosphate 535 



VI. " 5 



VII. " 3 



VIII. " 7 



IX. " 10 



497 

 480 

 499 

 490 



As shown by^he difference of 20 cwt. in the produce 

 of the unmanured plots, the condition of the soil and 

 the store of mineral constituents differed, to some ex- 

 tent, in different parts of the field. Other experiments, 

 which we cannot describe more particularly, showed 

 that the soil was- poorer in the centre of the field than 

 on the sides. 



