Aug. 15, 1925 
Soil Disinfection for Potato Wart 
355 
Attention is called to the remarkable increase in the penetration 
of kerosene as the percentage of moisture increased. Kerosene, 
when not present in excess, has a tendency to spread over the surface 
of water in a rather uniform film. In very dry soil the film of moisture 
on the soil particles will be so thin that the exposed surface of the film 
will extend almost to the points of contact with adjoining particles. 
A slight increase in the thickness of the water film would cause a very 
marked decrease of exposed surface in that part of the film in the acute 
angles near the points of contact. It is conceivable that the increase 
of 1,000 per cent (1.83 to 19.0 per cent) in the amount of moisture 
in the soil reduced the amount of exposed water surface so greatly 
that the 1 pint of kerosene covered this exposed surface with a film 
of approximately the same thickness as that obtained with 1 gallon 
in the dry soil. At. any rate, it seems likely that changes in the 
amount oi water surface and of surface tension are involved in the 
changes in kerosene penetration. 
FIELD NOTES ON PENETRATION 
A considerable number of field plots were treated with various 
chemicals, some of them liquids or in solution. No systematic effort 
was made to obtain data on the penetration of these chemicals and 
solutions. Where penetration was extremely slow or practically 
failed the fact was usually recorded. These scattered notes are here 
summarized (Table XX). 
Table XX. — Readiness of penetration of chemicals in field plots 
Chemical 
Penetration 
Chemical 
Penetration 
Alcohol... 
Good. 
Good. 
Very poor. 
Poor. 
Poor. 
Poor. 
Poor. 
Very poor. 
Good. 
Good. 
Javelle water _ 
Poor. 
Excellent. 
Fair. 
Excellent. 
Poor. 
Fair. 
Good. 
Good. 
Very poor. 
Bichloride of mercury solution_ 
Kerosene_ 
Bordeaux____ 
Lime-sulphur___ 
Woburn Bordeaux__ _ 
Crude oil_ _ 
Carbolic acid (crude)__ 
Carbolic acid solution of crystals_ 
Chloride of lime_ _ _ 
Potassium permanganate.. 
Pyroligneous acid_ _ 
Qua-sul___ 
Cleaning solution__ 
Sodium chromate_ 
Creosote_ . . 
Weed killer ___ _ 
Formaldehyde__ 
APPLICATION OF PENETRATION DATA TO FIELD WORK 
The study of the penetration of chemicals in the soil was under¬ 
taken to enable us to intelligently plan experiments looking to the 
extermination of the potato wart organism in those regions of 
Pennsylvania, Maryland, and West Virginia in which it is known 
to occur. There is a considerable variation in the soils of these 
regions and in the amount of moisture present in them at different 
times and seasons. It seemed likely that these and other variable 
factors would largely influence the possible effectiveness of treat¬ 
ments. The results herein recorded give a valuable insight into 
the influence of some of these variables and indicate that with data 
from more extended experiments it would be possible to plan soil 
treatments with as much assurance as spraying or other remedial or 
preventive measures are now planned. 
The influence of soil type, as shown in Tables VI, VII, VIII, IX, 
and X, is apparently not very marked in soils of similar nature, 
although the influence of the percentage of moisture present varied 
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