6 FIELD TREATMENT OF TOBACCO EOOT-ROT. 



that the suggestions offered can be utihzed this season by tobacco 

 growers who have fields affected with this disease. The results of 

 the wTiter's investigations thus far indicate that the tobacco is 

 much more severely injured by the fungus on fields where the soil 

 has been made alkaline by the long-continued use of large amounts 

 of lime, ashes, and fertilizers containing carbonate of potash. The 

 remedy for diseased soils appears, then, to consist in avoiding the 

 use of lime and in applying the necessary potash in the form of the 

 sulphate of potash, which is a neutral salt; and, if the field is badly 

 diseased, in applying the phosphoric acid in the form of acid phos- 

 phate in order to help neutralize the alkalinity of the soil. The 

 above view as to the cause of the development of the disease in 

 some of the tobacco fields of Connecticut is in harmony with field 

 observations, as will appear in the following pages. 



OCCURRENCE OF ROOT-ROT. 



The fungus causing this disease is one commonly found in leaf 

 mold and decaying organic matter, and therefore may reasonably 

 be expected in any new land. The fact that the disease does not 

 occur on tobacco fields until they have been in tobacco for several 

 years indicates that the fungus may be present in the soil without 

 attacking the tobacco. If we grant this point, then some condition 

 which favors the development of the fungus on the tobacco roots 

 must develop in the soil after several crops of tobacco have been 

 grown. 



Root-rot in the Connecticut Valley is especially prevalent in fields 

 on which unusually large quantities of fertilizers have been used. The 

 development of the disease is not, however, due to too high a per- 

 centage of soluble salts in the soil. This point was tested both in the 

 greenhouse and in the field, and it was found that the growth of 

 tobacco upon diseased soils was better when a liberal quantity of 

 neutral fertilizers was used than when smaller amounts were employed. 

 If the root system of the tobacco is greatly reduced by the root-rot, 

 the plants that are fertilized liberally and thus have a large amount 

 of available plant food immediately at hand will make the best 

 growth. Heavy fertilizing will not overcome the effects of the root- 

 rot, however, and if alkaline fertilizers are used the growth will actu- 

 ally be decreased, as the following experiments show: 



FIELD EXPERIMENTS SHOWING THE BAD EFFECTS OF ALKALINE 

 COMMERCIAL FERTILIZERS ON ROOT-ROT SOILS. 



During the season of 1907 a series of fertilizer experiments were 

 tried on two diseased fields in the Connecticut Valley. These tests 

 were confined mainly to fertilizers wlfich have been extensively used 

 in tobacco growing in Connecticut. No acid salts or ready-mixed 



[Circ.T.J 



