Liebig's Theory put to the Test. 185 



by Liebig, according to which all the constituents, neither 

 more nor less, removed in crops, should be returned to the 

 soil. Liebig wrote, in his " Principles of Agricultural 

 Chemistry : " " Our first object will naturally be, to restore 

 to the soil the mineral constituents in the same quantity and 

 in the same proportions as those in which they have been 

 removed in the crops ; and none must be omitted" Another 

 object of this experiment was to acquire data as to the 

 proportion in which the several constituents artificially 

 supplied would be removed in the increase of crop. 



The manures actually applied, and the constituents they 

 contained, were as follows : 



/38-Olb. potash 

 761b. commercial chloride of potassium < 7*01b. soda 



C36'71b. chlorine 



351b. sulphate of magnesia J * 61b " m agnesia 



(. 11 'lib. sulphuric acid 



(261b. bone ash .. ( H'Olb. lime 



(. 8'21b. phosphoric acid 

 (.261b. sulphuric acid (sp. gr. I' 7) 1 6' 91b. sulphuric acid 



501b. silicate of soda ( ?lb - 8od a 



(. 23'Olb. soluble silica 



501b. silicate of lime ( Plb. lime 



I 8-Olb. soluble silica 

 YSO'llb. nitrogen 



1641b. " ammonia-salts " J 44'41b. sulphuric acid 



(46'2lb. chlorine 



If the quantity of constituents as shown in the right-hand 

 column be compared with the contents of IJtons of hay as 

 given previously in Table XXIX., page 142, it will be seen 

 that fully sufficient of each constituent has been supplied for 

 an increase of 1 ton of hay, whilst of soda, sulphuric acid, and 

 chlorine there is more than sufficient. 



The experiment was carried on for eleven years, and in 

 Table XL VI., page 186, comparison is made with the results 

 on the unmanured plot during the same eleven years. 



It may be seen that the average yield of hay over the 

 first half of the period was about 35cwt., and over the second 



