134 MASS. EXPERIMENT STATION BULLETIN 176. 



treated with carbonate of lime is striking, and has been noted before in 

 our field work, and reported in Bulletin No. 161. 



There is a singular discordance between the ill results obtained with 

 manganese sulfate and calcium carbonate used together in water cultures 

 and the good effects produced by their joint action in experiments with 

 soil cultures. It is possible that in solutions the greater solubility of 

 manganese sulfate permitted its rapid absorption by the roots in compari- 

 son with the intake of the less soluble calcium carbonate, and injurious 

 results w^ere produced in advance of any possible antidotal effect of the 

 calcium. 



Table X. — Percentage Corn-position of Dry Clover from Pot Cultures.- 



The roots were carefully washed free of soil, dried and analyzed, but 

 the quantities were very small and determinations could not be made in 

 dupUcate in most instances; therefore the figures have not been included 

 here. 



Conclusions. 



The positive presence of soluble salts of iron, aluminium and manganese 

 in soils which have been repeatedly dressed with ammonium sulfate with- 

 out adding lime; the formation of one or more of these salts in soils that 

 were extracted with solutions of ammonium sulfate; and the positively 

 injurious action of manganese sulfate, iron sulfate and aluminium sulfate 

 on seedling plants in w^ater cultures and pot cultures when taken together 

 form a chain of facts which clearly indicates that the injurious effects of 

 sulfate of ammonia when used freely without the accompaniment of lime 

 are due to the formation of these soluble salts in the soils of the fields so 

 dressed. 



