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MASS. EXPERIMENT STATION BULLETIN 351 



These results, while not complete and consistent enough to warrant definite 

 recommendations, were sufficiently encouraging to suggest the value of further 

 experimentation with salicylic acid as a soil fungicide, at least with such species 

 of plants as are relatively tolerant of it. 



Tannic Acid 



Tannic acid, as used, gave no evidence of being fungicidal, but the growth of 

 foxglove was much improved by 3 to 6 gm. per square foot, even 19 weeks after 

 seeding. Growth of columbine was also improved, although less than was fox- 

 glove. These treatments had no effect, however, upon the growth of Rhododendron 

 carolinianuni, R. catawhiense, R. Schlippenbachii, rocket and sweet pea. 



Tannic acid apparently affected these soils physically, improving tilth and mak- 

 ing them looser and less sticky, with this effect first noticeable immediately after 

 treatment. This may be related to the response of foxglove, a species which grows 

 well in loose-textured soils, rich in leaf mold. 



There is an occasional statement in horticultural literature, for example that 

 by Durand (33), to the effect that the acidity of a moderately acid soil may be 

 increased by tannic acid; but it did not appear in this work that such effect as 

 tannic acid may have on plants has much if any relation to soil reaction. When 

 it was applied to soil which had an initial pH value of 6.2, amounts up to 12 gm. 

 did not have any effect on pH value 9 weeks after soil treatment; and 20 gm., 

 as far as it affected soil reaction at all, made soil a little less rather than more 

 acid 3 weeks after soil treatment. According to Laurie and Chadwick (57), 

 earlier investigators have secured similar results, 500 pounds of tannic acid per 

 acre having little or no effect on soil reaction. 



Ammonium Hydroxide 



As applied to soil by Johnson (54), ammonia did not control damping-off, 

 and Hartley (43) concluded that its effect is too fleeting to protect conifer seed- 

 lings. 



Ammonium hydroxide, if applied to soil heavily, is, however, an effective soil 

 fungicide and it has been used successfully by Neal, Wester and Gunn (68) to 



