SOIL TREATMENTS AND SEED GERMINATION 5 



Table 1. — Damping-off and Final Stands in Difff.rent Media 



Although washing with hot water frees sand from fungi, it does not prevent 

 their growth if they are reintroduced. In one experiment in which where was no 

 damping-off in washed sand, damping-off was severe when this same sand was 

 inoculated with Pythium. In this connection it is of interest to note that, in the 

 experiments of Abdel-Salam (3), Pythium caused severe damping-off in inoculated 

 sand; but Rhizoctonia caused only 2 percent damping-off in inoculated sand, 

 although it caused 74 percent damping-off in loam. It would seem that washed 

 sands which later become contaminated with Pythium may be more dangerous 

 to seedlings than washed sands contaminated with Rhizoctonia. This defect of 

 washed sand is, of course, not unique with it, for disinfected soil may also become 

 recontaminated with tungi. 



As has been shown by Dunlap, the same sand may be used repeatedly if it is 

 well washed with hot water before each seeding. When this practice was followed 

 with sand-sphagnum or sand-peat moss in these experiments, however, there 

 was a little more damping-off than in sand so treated, indicating that washing 

 these media may not free them so completely of fungi as does the washing of sand. 



As may be seen by reference to Table 2, none of the species grew so well in sand 

 as in soil. This was true of beet and cress in five different sands, and also of Zinnia, 

 English daisy, and ten-weeks stock in the only sand in which they were seeded. 

 Growth was better in sand than in soil in a few instances, but only when Rhizoc- 

 tonia, without actually killing the seedlings, seriously interfered with their 

 growth in soil. 



Table 2. — Average Green Weight per Plant in Different Media 



(Weights expressed as relative numbers.) 



Media Calen- Canterbury Mari- Salpi- Viola Beet Cress Lettuce Spinach 



dula bells gold glossis cornuta 



Soil 100 100 100 100 100 100 100 100 100 



Sand B 



Sand H 



Sand P 



Sand N 



Sand S 64 34 68 50 82 48 80 78 



Sand S and 



sphagnum... 121 100 • 125 91 129 123 69 



Sand S and 



peatmoss... 88 100 106 105 112 112 53 



