96 



MASS. EXPERIMENT STATION BULLETIN 204. 



vegetation, as the seed either did not germinate or the plantlets soon died. 

 In the spring of 1920 these barren areas were twice reseeded, and finally 

 the redtop grew and developed normally. 



In July and in October, 1920, samples of soil were taken from the 

 different sections of plots 5 and 6, the soluble manganese extracted by 

 water, and its weight carefully determined by Mr. C. P. Jones. 



Table XL — Manganese Sulfate in the Surface Soil of Plots 5 and 6. 



[Weight of one acre of soil 6 inches deep assumed to be 1,500,000 pounds.] 



The application of 225 pounds of sulfate of ammonia is theoretically 

 capable of forming 257 pounds of manganese sulfate. There were found 

 small quantities of aluminium sulfate, but only a trace of iron in the soils 

 that were longest without lime. 



The weight of evidence indicates that the injurious results were due 

 to the quantity of manganese sulfate present. The actual concentration 

 of the manganese in the soil solution is mere guesswork, but it is inter- 

 esting to note that its striking injury occurs in seasons of droughts or 

 following a dry period, while plenty of rainfall appears to remove the 

 poison or to dilute it to a harmless concentration. 



The effect of lime in preventing the formation of the manganese sulfate 

 is shown by the marked reduction in the amount found where lime had 

 been used as long ago as 1913. The actual quantities found have much 

 less significance than the wide difference between the amounts where 

 lime is lacking and where it is present. 



When lime is applied to prevent the injurious effects of sulfate of am- 

 monia, it should be borne in mind that the lime is not a quickly soluble 

 substance but is very slow to dissolve in water. Hence it must be 

 thoroughly distributed throughout the surface soil so that the sulfate of 

 ammonia is reasonably certain to come in contact with it. Long-con- 

 tinued fertilizer experiments clearly show that soil water has no appre- 

 ciable movement sideways, and the boundaries between limed and unlimed 

 areas are sharply defined. 



An experiment where lime to the amount of four times the calculated 

 chemical equivalent of sulfate of ammonia was applied to a small plot 



