59 



in the soil to which amnioniuin sulphate was applied. 

 The evidence presented indicates that the addition of 

 certain nitrogenous fertilizers to acid soils from the 

 Pennsylvania plots may increase the infertility of these 

 plots hy hringing into solution relatively large quanti- 

 ties of manganese. 



In order to study the toxicity of the extracts of the 

 Pennsylvania soils, the following methods w ere used : 

 Eight hundred gram portions of the soil were weighed 

 out and treated with one gram of dried blood, and 0.8 

 gram of ammonium sulphate, respectively, and thor- 

 oughly mixed. Each portion of soil was then placed in 

 a percolator, the required amount of distilled water 

 added, and incubated at 28 C. from October 12 to De- 

 cember 29, 1917. Each pcroclator was then leached 

 with distilled w^ater until 1600 cc. had passed through 

 the 800 gms. of soil contained. Samples of the air dry 

 soil were also leached to make possible a comparison 

 of the extracts of the original soil with those of the 

 same soil that had been treated. Pea cultures w^ere 

 set up in the usual way and permitted to grow^ from 

 Jan. 5 to Jan. 26, 1918. A photograph of all cultures 

 grown in the extract of the soil from plot 32 is show^n 

 in Plate VI, fig. 1, and the complete data is presented 

 in Table XII. 



