18 MASS. EXPERIMENT STATION BULLETIN 195. 



merit" above 8,000 pounds CaO, the crops of which were normal as far 

 as grow-th was concerned, and many of them were very fine. In this 

 group we find the acidity as measured in terms of the CaO requirement 

 running as high as 13,500 pounds per acre. The highest value closely 

 approaches the acidity of our virgin soils, such as are used when new 

 tobacco plantations are established. Two of these virgin soils gave a 

 "lime requirement" of over 15,000 pounds per acre. 



From the preceding we can see that the situation with respect to liming 

 is still further complicated. We have, on the one hand, the hme question 

 and its effects on the growth of tobacco, pure, and simple, and on the 

 other, the effect of the soil reaction on the fungus which causes the 

 Thielavia root-rot. If we lime continually and excessively land on which 

 this root-rot is established, we are constantly getting it into a more nearly 

 neutral condition, and hence into a more favorable condition for the 

 development of the root-rot. In the end we will have a soil in which 

 every year, irrespective of other factors favorable or unfavorable to the 

 growth of the fungus, it will be able to develop vigorously and do great 

 damage. In such cases soil reaction (changed by liming) should be 

 looked upon as the primary cause of the trouble, and the presence of root- 

 rot as secondary to this. 



We find that this root-rot is not present to any great extent on soils 

 showing a very low '"lime requirement," which indicates that the soil 

 is too alkaline for the development of the fungus, and also too alkaline 

 for tobacco to make a satisfactory growth. At any rate, in this group 

 (soils showing 0-3,000 pounds CaO requirement) the fungus is rarely 

 found, though usually the crop of tobacco is very light and of poor quality. 

 In the second group we find a large number of soils showing from 3,000- 

 8,000 pounds CaO requirement, and it is to be observed that the Thielavia 

 root-rot is present in a large number of fields. On these soils the crop 

 varies from year to year, and in many cases is not of a satisfactory nature. 

 On soils of this character in some years, however, good crops are produced, 

 so we cannot here lay the damage to the lime alone, but must look to 

 other additional factors. 



In the third group we have soils which are acid and which show a high 

 "lime requirement," — 8,000 pounds CaO and up, — but which are 

 practically free from root-rot, and these soils are in practically all cases 

 producing a good crop of tobacco. Does this not seem to indicate that 

 the relationship between liming and Thielavia root-rot just discussed is a 

 potent factor in many cases in the development of our troubles? There 

 are, however, other factors to be taken into consideration, and in some 

 cases these are of great importance also. 



There is this fact patent, that on new land the tobacco always makes 

 a good growth, although the quality of the leaf may not be all we desire. 

 In these times, when the first consideration of the grower is apparently to 

 get weight and let the quality come later, this is important, at least to 

 the grower who has new land at his disposal. Most of the growers, 



