6 FARMERS' BULLETIN 996. 



this process has been most extensively employed perhaps in the Con- 

 necticut Valley, but because of its many advantages and its effective- 

 ness it is being widely adopted in other tobacco-growing districts. 



PREPARATION OP THE SEED BED FOR STEAMING. 



The seed bed is thoroughly prepared in the usual manner for 

 sowing the seed. The soil is well worked, the fertilizers spread and 

 mixed in the soil, and the bed brought to fine tilth, so that after the 

 steaming is completed it is only necessary to rake the bed lightly 

 before sowing the seed. It is important that nothing but the seed 

 and the diluting material, also sterilized if necessary, should be 

 added to the bed after sterilization. 



A comparatively dry bed is the first requisite for successful steam- 

 ing, as it is practically impossible for the steam to penetrate wet soil. 

 Glass-covered beds may be dried with comparative ease by covering 

 them with sash several weeks before steaming. The bed is protected 

 from the rains and snows of spring, and the sun's rays warm the 

 soil and drive off excessive moisture. Cloth-covered beds may be 

 protected for two weeks before steaming when rain or snow threatens 

 by stretching over them cloths which have been painted with a thin 

 mixture of linseed oil and drier. 



EFFECT OF FROST IN THE SOIL. 



The presence of frost in the surface soil retards the penetration of 

 the steam and makes it necessary to continue the process for an 

 unusually long period. The ground must first be thawed before the 

 desired heating can be brought about, and this causes a fuel con- 

 sumption more than double that required where the soil is in proper 

 condition. Where there is frost in the surface soil the steam does 

 not penetrate more than a few inches, because of the condensation of 

 the steam in the cold ground. 



In order to thaw out the seed beds before steaming, a good practice 

 is to cover them with glass for several weeks, as has been suggested 

 for wet beds. The glass allows the heat from the sun's rays to be 

 confined within the bed during the day, warming the soil and put- 

 ting it in a mellow condition. Without such preparation even par- 

 tial sterilization would be impossible in some sections till late in the 

 spring. 



FALL STEAMING OF THE SEED BED. 



Steaming has been done in the fall by many growers because of the 

 disadvantages experienced in the spring due to rains and snows or 

 the frozen condition of the ground. Usually the seed-bed soil can 

 be put in excellent condition in the fall when the land is dry and 

 before the air temperature is low enough to freeze the ground. An 



