98 VEGETABLE FORCING 
and most growers feel that it is unwise to take chances 
of losses that can be averted by proper methods of 
disinfection. 
After-treatment.—Soils that have been sterilized by 
either steam or formalin require careful after-treatment. 
This is particularly true of silty and clay soils, the 
structure of which is affected by these treatments. 
They become more compact, and their water-holding 
power is increased so that there is danger of overwater- 
ing such soils until normal relations become established. 
As soon as dry enough the surface of the ground should 
be stirred and water applied with extreme caution after 
the plants have been set. 
Formalin Sterilization 
Strength of solution—Most growers who employ this 
method of steri- 
Ni a lization use 
G 1) either three or 
©) 
four pints of 
ae. commercial for- 
= malin of 40 per 
tee cent purity to 
50 gallons of 
L 24) a lis water. Two 
pints often 
prove effective. 
wr but a stronger 
nue alee Solution is gen- 
erally pre- 
MG ferred. Rhizoc- 
tonia or rosette 
Fig. 33.—Apparatus for formalin sterilization. (W. T. 
—Water tank. F. T.—Formalin tank. G.—Water-glass of lettuce pas 
gauge to show quantity of formalin. A.—Air cock. Vi be controlled 
Valve. F.—Funnel. E.—Air pipe to maintain same : 
pier ut neh tanks. Be —Orain-ef cock. H. and with less than 
.—Supports. .—Base, -—Outlet. S.—Glass tube = 
through which the formalin drops to tank below.) two pints to 50 
le 
B = 
