No. 4.] GERMAN EXPERIMENT STATIONS. 401 



certain plants take the place of potash to a considerable 

 extent, and exerts a correspondingly beneficial influence. 

 This has been proved in the case of barley and poppies ; 

 further investigations on this subject are in progress. 



(?) Wagner's experiments have shown that nitrogen in 

 difterent manures has the following relative worth : — 



Nitrogen in Chili saltpetre, . . . . . 



Nitrogen in sulphate ammonia, . , . . 

 Nitrogen in blood, and in green j^lants as manure, 

 Nitrogen in fine bone, ground fish and tankage, 



Nitrogen in stable manure, . . . . . 



Nitrosren in fine-o;round avooI, . . . . . 



Nitrogen in fine-ground leather, . . . , 



100 

 90 

 70 

 60 

 45 

 80 

 20 



Extensive investiscations are beino; carried on to determine 

 the relative needs of the different crops for phosphoric acid 

 and potash, but as yet a detailed report of the results has 

 not been published. Small bidletins have, however, been 

 given out, from which one obtains the following facts :* — 



PJiospJioric Acid. 



(a) Placing phosphoric acid as found in dissolved bone- 

 black at 100, the phosphoric acid from Thomas slag and fine- 

 ground bone has the following relative worth : — 



(b) Thomas slag has been found to have rather more than 

 half the fertilizing value of soluble phosphate the first year. 

 This material becomes gradually soluble in the soil, but, on 

 the contrary, does not " revert" or become insoluble, as is 



* A very excellent translation of Professor Wagner's lecture on " The most 

 profitable use of commercial manures " has been made by Prof. Charles Wellington, 

 and published as a special bulletin of the Hatch Experiment Station, May, 1890. 



