SULFATE OF AMMONIA. 95 



Peculiar Effects of Sulfate of Ammonia. 



A comparison of the crop yields from the plots receiving sulfate of 

 ammonia Avith those from the plots without nitrogen reveals some striking 

 extremes in the effects of the ammonia compound on plant growth. The 

 largest percentage of gain produced by the sulfate of ammonia was on 

 oats in the years 1897 and 1898, when rainfall was unusually high and 

 the actual yields were among the lowest of the entire period. There are 

 frequent instances, on the other hand, when the crops on the plots without 

 nitrogen w^ere better than those Avith sulfate of ammonia, which in some 

 cases appeared to have been positively injurious. These ill effects were 

 irregular, and seldom occurred on all three ammonia plots in one season. 

 A study of the rainfall has shown that these apparently injurious effects 

 occurred in seasons when there was a drought in May or June. Applica- 

 tions of lime have remedied the injurious action, but at the same time 

 have tended to bring up the yields on the plots without nitrogen, so that 

 the percentages of increase due to the ammonia are seldom large. 



Examination of the soils from the different plots of Field A has shown 

 that, in the absence of lime, the sulfate of ammonia forms soluble sulfates 

 of manganese, aluminium and iron, sometimes one, sometimes another, 

 and again all three. ^ Any one of these substances, if present in com- 

 paratively small amount, has been shown to be poisonous to plants, espe- 

 cially to clover. 



The rearrangement of the limed areas in 1919 resulted in four distinct 

 gradations of limed soil, as follows: — 



T „(. ,■ 1 • inn- [Plots 4, 5, 7, 9, Southwest quarter. 



Last limed in 190o, . . . . •/-,,,„ „. , ,n 



I Plot 6, West half. 



T 4. 1- J • inio I Plots 4, 5, 7, 9, Southeast quarter. 



Last limed 111 1913, . . . . ■ { „, ' , ,, 



1 Plot 6. East half. 



Limed in 1905 and 1919 j Plots 4, 5, 7, 9, Northwest quarter. 



\ Plot 8, West half. 

 Limed in 1913 and 1919 J ^'"^s 4, 5, 7, 9, Northeast quarter. 



\ Plot 8, East half. 



In 1919 there was a ver}^ striking injury to corn on the long unlimed 

 parts of plots 5 and 6. Injury was not apparent on plot 8, as the entire 

 plot had been limed that spring. The plants were stunted in size; the 

 lower leaves were light colored, reddish and yellowish in streaks, and 

 ultimately turned brown and became dry and brittle. Samples of these 

 leaves w^ere dried and incinerated, and the ash gave a bright greenish 

 blue reaction when fused with sodium carbonate, showing that manganese 

 was present in noticeable amount. This was undoubtedly the cause of 

 the injury. 



The field was seeded with a mixture of timothj', redtop and clover in 

 the late summer. The areas long unlimed on plots 5 and 6 were bare of 



1 Ruprecht and Morse. .Mass. Agr. Expt. Sta. Bulls. Xos. 161, 165, 176. 



