TOBACCO INVESTIGATIONS. 17 



some of the fertilizers used are alkaline, and that most of the brands 

 contain in the neighborhood of 200 pounds of some form of lime added 

 for various purposes. 



The question as to whether the addition of large quantities of lime is 

 necessary on our soils for the best development of tobacco — and its 

 effect on the burn, ash, etc. — is still open to investigation. It depends 

 to a certain extent on the type of soil. Recent investigations by the 

 Dutch East Indies station have shown that the addition of lime had 

 little effect on these factors. On the contrary, in some cases where the 

 burn was injured there was a beneficial effect on the quality and color. 

 Other experiments showed opposite results, and in general no particularly 

 good effects were observed. 



There is no question but what some lime is necessary for the best 

 development of the tobacco plant, but a small application every few 

 years seems to be preferable to a heav}^ application two or three years 

 in succession. The mechanical composition of the particular soil to 

 which the lime is to be applied should also be carefully considered. 



There is another factor, connected with the liming of our fields, aside 

 from that of the direct injurious effect of lime on the growth of tobacco 

 as a result of the changing of soil reaction toward neutrality. Certain 

 of our experiments have show7i that the fungus Thielavia basicola, which 

 causes root-rot, is very susceptible to acids, and we have found that it 

 is very difficult for the fungus to thrive on very acid media. On the 

 other hand, on media approaching neutrality the fungus develops rather 

 better and makes a far more rapid growth. We are at present testing 

 out in the laboratory different concentrations of acids and different acids, 

 together with soil extracts, to determine if there is any difference in their 

 reaction on the fungus. 



These data regarding Thielavia root-rot substantiate the findings of 

 Briggs,^ who in 1908 reported results on the intensity of root-rot infec- 

 tion on tobacco in alkaline and acid soils, and who also recommended the 

 stopping of lime applications on infected fields. 



Referring again to the preceding table it might be stated that the 

 roots of plants on the various soils which were analyzed were examined 

 for Thielavia root-rot infection, and some interesting data were secured. 

 It was found that in the soils of Group I, as it has been called for the 

 sake of convenience, — that is, those soils which showed a "lime require- 

 ment" of from to 3,000 pounds CaO requirement, — the crop was very 

 poor; but there was little or no Thielavia root-rot evident. On the 

 soils which I have designated as Group II, the crop was poor and patchy, 

 or good, and on many plants the Thielavia root-rot was present in suffi- 

 cient amount to cause a marked loss of root-feeding area. These soils 

 all fell within a range of CaO requirement of from 3,000 pounds to 8,000 

 pounds. In Group III were placed all the soils showing a "lime require- 



1 Briggs, W. The Field Treatment of Tobacco Root-rot. U. S. D. A., B. P. I., Circ. No. 7, 

 190S. 



