MANURING EXl'EKIMKNTS WITH PADDV RICE. 



3/9 



principally due to the repeated mechanical treatment to which the 

 soil was subjected for many years before the experiments were com- 

 menced, and to the indirect action of the ammonium sulphate and 

 potassium carbonate, which were liberally supplied to the plots 

 without phosphoric acid. According to our previous researches, rice 

 plants consume 24% of phosphoric acid from superphosphate ; hence 

 its supply from the natural sources during the six experimental 

 years would, on the same assumption, be represented by the 

 following figures : 



]icr plot. per Ian. 



in 1889 ..2.17 grms. 2.60 kilogrms. 



1890 2.29 ,, 2.75 



1891 3.71 4.45 



1892 2.83 ,, 3.40 



1893 1.38 ,, 1.66 



1894 4.87 ,, 5.84 



Thus the annual supply of phosphoric acid from the natural 

 sources amounted on the average of six years to 3.45 kilogrms. 

 per tan of phosphoric acid equivalent to that of superphosphate. 

 This quantity is sufficient for the production of 2.50 kilogrms. of 

 unhulled grain.*'' 



(i) For the production of loo kilogrms. of unhulled grain a supply of i 42 kilogrms. 

 su]icqihnsphate-phosphoric acid is necessarj'. 



