• TOBACCO INVESTIGATIONS. 31 



further experimental work at this time. The cost of this material and the 

 labor involved, together with the large amount of water which is necessary, 

 render it inadvisable to recommend this treatment on large areas. Small 

 areas in a field might be so treated. 



The sulfuric acid treatment did not give the results anticipated, but 

 possibly a variation in amount applied might give more beneficial results. 

 In this case, however, we should have to take into consideration the 

 possible residual effect of the SO4 radical (sulfate). Further data on this 

 point will be available later. It would seem that, in view of the fact that 

 Thielavia is so susceptible to acids, this might be a method of at least 

 partial control. 



The benefits to be derived from increasing the organic matter and 

 general condition of the soil, in relation to the Thielavia root-rot, have 

 already been briefly discussed, and further mention of them will be 

 omitted. 



Much laboratory work is in progress with the Thielavia fungus to 

 determine the specific action of the different acids and bases on the growth 

 and development of the fungus in culture, as well as to determine the 

 limits between which the fungus is actively parasitic. The results, 

 however, will not be discussed in this report, as additional work is neces- 

 sary on this phase of the problem. 



Fertilizer Experiments in Progress. 



Beginning in 1917 there were established three experimental field plots 

 on different soil types in the tobacco section. The yields on these fields 

 were very low, so low on one of them that the crop had not been harvested. 

 On one of the fields there was abundant evidence of a very serious Thielavia 

 root-rot infection; on the other two, however, although the root-rot was 

 present it did not appear to be of primary importance. 



The experiments were designed to be general in character, and dealt 

 with three principal cjuestions, namely: (1) Are our soils in need of organic 

 matter, and if so what is the response of the crop to the direct addition of 

 the same in the form of peat, or in the form of stable manure? (2) Are our 

 soils lacking in potash, owing to the inability of the growers to procure 

 the usual amounts of the same since 1914, and if there is a lack how is it 

 evidenced? (3) What benefits, if any, are to be derived froni the addition 

 of increased amounts of phosphoric acid in the form of acid phosphate to 

 the normal fertilization? This question was suggested by the fact that 

 very good results have been obtained in many cases by rotating tobacco 

 and onions, and the latter crop is usually treated with a fertilizer con- 

 taining a large amount of acid phosphate. 



The results of 1919 are not at present ready for publication, but some 

 rather definite results were obtained in 1917 and 1918. These will be 

 briefly discussed here. The details of the experiments will not be taken 

 up in this report, as the work is of sufficient volume to require a separate 

 report, which is to be issued as soon as possible after the 1919 crop has 



