362 
Journal of Agricultural Research 
Vol. XXXI, No. 4 
the first and practically none in the second and third seasons, except 
that the sodium chromate plot showed fair growth the third season. 
None of the plots treated with sodium chloride or borax produced 
growth during the first year. In the second season the five borax 
plots exhibited from poor to fair growth and in the third season 
exhibited fair to normal growth. Results with sodium chloride were 
more variable, the four plots ranging from no growth to good growth, 
and with no apparent cause other than that differences in soil types 
or drainage may have been the determining factor. Plots treated 
with these chemicals showed subnormal growth the third year. 
Pyroligneous acid, though showing much injury the first season and 
little the second, was highly variable in its effect on growth. During 
the third year normal growth occurred. 
Mercuric chloride alone, and in combination with salt, except in 
the dry applications, killed the potatoes the first season and showed 
considerable toxicity the following year, both in the amount of growth 
which occurred and in the spindling character of plants (pi. 1, B, pi. 
2, B). Growth during the third season was poor in the two plots 
treated with a 1 per cent solution of mercuric chloride at the rate 
of 1 gallon per square foot and in one of the plots treated with one- 
half gallon of the same solution, but was practically normal in the 
remaining plots. 
Kerosene, crude oil, and a mixture of the two inhibited growth 
the first season, but permitted fair growth the second. The third 
season growth was poor in one of the plots treated with crude oil 
and normal in the other plots. 
Formaldehyde showed injury during the first season (pi. 1, B), pro¬ 
portional to the strength of the application, and uniformly good 
growth for all plots the following two seasons. 
All applications of the sulphuric acid and sodium chromate clean¬ 
ing solution, familiar in the laboratory, used at full strength, killed 
the first plantings, but were sufficiently neutralized in the soil to allow 
some growth the following two years in two of the plots. 
Javelle water practically prevented growth the first season, but fair 
to normal plants were produced the second and third. 
When heavy chemical treatments are applied to sterilize soil, their 
toxicity, their alteration of the mechanical condition, and the changes 
which they may produce in their reaction may be injurious or not in 
variable degree. While it is true that as regards the growth of the 
potato plant the treated soil in many cases tends to return to the 
normal condition the second year, the reverse is sometimes the case, 
greater injury being evident the second season. 
Therefore in applying a chemical for partial sterilization of the 
soil, the substance used, the rate of application, and the particular 
soil and climatic conditions which prevail where it is applied deserve 
very careful consideration from the standpoint of possible injury to 
plant growth as well as of its efficacy as a soil disinfectant. 
(A summary is given at the end of each of Parts I, II, and III, 
pp. 320-321, 328-9, and 357-8). 
