38 MASS. EXPERIMENT STATION BULLETIN 195. 



of disease-producing organisms; but these are "specific^' and not "general" 

 troubles as yet. 



7. The tobacco soils of Massachusetts fall into three groups, as regards 

 acidity or "lime requirement." Soils with a "lime requirement" up to 3,000 

 pounds CaO per acre are not producing good crops, as a rule, and are compara- 

 tively free from root-rots. Those with a "lime requirement" of from 3,000 to 

 8,000 pounds CaO per acre are in good tobacco condition; but in this group 

 pathogenic fungi are abundant in the soil, and the plants, during certain 

 seasons, are very liable to suffer from root-rots caused by some of these fungi. 

 Soils with a "lime requirement" of 8,000 pounds CaO up are usually com- 

 paratively free from such fungi, and even in unfavorable seasons little disease 

 is found, but the tobacco is perhaps of slightly inferior quality. 



8. Most of the tobacco soils in Massachusetts are deficient in humus or 

 organic matter. 



9. To supply this lack of organic matter cover crops, preferably timothy, 

 should be planted and plowed under. 



10. No satisfactory field soil treatment for the Thielavia root-rot has been 

 worked out. 



11. Many of the so-called "sick" soils are responding favorably to addi- 

 tional applications of organic matter and phosphoric acid in the form of acid 

 phosphate. Care should be exercised in the application of these materials to 

 guard against excess. 



12. Our fields, generally, are not yet suffering from a lack of potash, as 

 determined by plant groivth and development. 



