STEAM STERILIZATIOX OF SEED BEDS. 13 



The permanent seed beds are usually equipped with a water-supply 

 system; where this is not the case the transportation of water for 

 the boiler is an additional item of expense. 



In considering costs, one should bear in mind the fact that a 

 thoroughly steamed seed bed is practically free from weed seeds, 

 thereby eliminating the cost of weeding. The amount saved in weed- 

 ing will probably more than cover the cost of sterilization, as two 

 good weedings usually cost more than $G per 1,000 square feet. Figure 

 1 illustrates the effectiveness of the steaming-pan method in killing 

 weed seeds. On the right of the partition it will be seen that the 

 sterilized area is practically free from weeds, whereas the unster- 

 ilized portion on the left was worthless because the weeds had forced 

 out nearly all of the tobacco plants. Additional advantages are that 

 the plants are more vigorous and are ready for transplanting 10 to 14 

 days earlier than plants in unsterilized beds. As has been stated, 

 where root-rot or other fungous diseases are present, some form of 



Pi645T 



FIG. 4. A tobacco seed bed, showing a partition between the steamed and the unsteamed 

 portions. Both sections were sown at the same time with similar seed, but the weeds 

 in the unsteamed section (at the left) practically killed the tobacco seedlings. No 

 weeds grew on the steamed part. 



sterilization is essential for the production of healthy seedlings, and 

 steaming is decidedly the most effective process yet developed for 

 insuring the elimination of these diseases. 



IMPORTANT CONSIDERATIONS. 



Sterilization so improves the soil conditions that less fertilizer is 

 necessary than on unsterilized ground. One should exercise caution 

 against reinfecting the soil by walking on the steamed bed, using in- 

 fected rakes, water from stagnant ponds, a solution of manures, or 

 seed sown with unsterilized vegetable matter, such as decayed wood, 

 punk, or decomposed leaf tissue. Finely sifted raw bone meal, 

 thoroughly sterilized punk, and land plaster are excellent materials 

 for spreading the seed. They should be very slightly moist to spread 

 well between the fingers and to retain the seed in the mixture. 

 Root-rot is found in some seed beds that have been thoroughly steam 

 sterilized. Such infection may have been carried by fertilizers ap- 

 plied after the steaming, by decayed vegetable matter used to spread 



