SOME PHYSICAL AND BIOCHEMICAL EFFECTS
OF FUMIGANTS IN SOILS

by
JEROME J. SIEGEL

A THESIS
Submitted to the School of Graduate Studies of
Michigan State College of Agriculture and
Applied Science in partial fulfillment
of the requirements for the degree of
DOCTOR OF PHILOSOPHY
Department of Soil Science
1951

ProQuest Number: 10008696

All rights reserved
INFORMATION TO ALL USERS
The quality of this reproduction is dependent upon the quality of the copy submitted.
In the unlikely event that the author did not send a complete manuscript
and there are missing pages, these will be noted. Also, if material had to be removed,
a note will indicate the deletion.

uest
ProQuest 10008696
Published by ProQuest LLC (2016). Copyright of the Dissertation is held by the Author.
All rights reserved.
This work is protected against unauthorized copying under Title 17, United States Code
Microform Edition © ProQuest LLC.
ProQuest LLC.
789 East Eisenhower Parkway
P.O. Box 1346
Ann Arbor, Ml 48106- 1346

ACKNOWLEDGEMENT

The author expresses his sincere appreciation
to Dr. L. M. Turk who gave generously of his time and
experience throughout the course of this study.

He

also wishes to thank Drs. R. L. Cook, A. E. Erickson,
and J. F. Davis for their contributions of advice,
suggestions, and physical labor which are reflected
in sections of this discourse, and who, along with
other members of the Soil Science Department, provided
the kind of environment which makes any work pleasant.
In addition, he desires to thank the Dow Chemical Com­
pany for providing a fellowship which made this study
possible, and especially Drs. C. M. Dieter and ¥. C.
Dutton of that organization for their interest and
assistance.

SOME PHYSICAL AND BIOCHEMICAL EFFECTS OF FUMIGANTS IN SOILS

By

Jerome J* Siegel

An ABSTRACT
Submitted to the School of Graduate Studies of Michigan
State College of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of
DOCTOR OF PHILOSOPHY
Department of Soil Science

1951

Approved

ABSTRACT

Jerome J. Siegel

Some Physical and Biochemical Effects
of Fumigants in Soils
The dispersion characteristics of 1-3 dichloropropene
and 1-2 dibromoethane were studied using adsorption isotherms and
radioactive tracer techniques.

It was determined that the compeunds

were sorbed by soils and that this sorption was primarily a func­
tion of the organic soil colloids.

Diffusion of the compounds

was greatest in a sandy soil, next greatest in a clay loam, and
least in a muck.

Optimum diffusion was obtained in a soil at the

moisture equivalent.

Diffusion in a water saturated soil was

limited by the low solubility of the compounds in water, while
they were strongly sorbed in an air-dry soil in a small volume
around the injection point.

The compounds diffused laterally and

downward with little penetration into the soil mass above the
injection point.

Field and greenhouse experiments Indicated that

Dowfumes N and W-40 were also fixed in soils and under certain
climatic conditions, it was possible to attribute certain plant
Injuries to residual effects of these fumigants in the soils.
The use of 1-3 dichloropropene and 1-2 dibromoethane
as soil fumigants accomplished a partial sterilization of the
soil and resulted In a reduced activity of the oxidizing organisms.
This caused a lowering of the bio-electric potential of the
soils.

Also, nitrification was inhibited permitting the accumu­

lation of large quantities of ammonium in the soils.

Dowfumes N,

W-40, and MC-2 retarded nitrification of ammonium which was
added to soils with Dowfume N being most effective in this respect.
Soybeans grown in culture solution with ammonium as
their source of nitrogen responded favorably to an increase in
calcium in the nutrient substrate.

The plants were characterized

2

Jerome J. Siegel

by an abnormally high protein content and matured earlier than
soybeans whose sole source of nitrogen was nitrate• The
ammonium decreased the uptake of other cations by the plants.
Soybeans growns on soils which had been fumigated with Dowfumes N,
W-40, and MC-2 also showed favorable growth responses when the
calcium content of the soils was increased.

There was a decrease

in the mineral content of the plants grown on the fumigated
soils which was attributed to the fact that large amounts of
ammonium were taken up by these plants.
The growth of soybeans and onions on muck soils which
were treated with Dowfume N showed that fumigation could be
of benefit at a time when available nitrogen is a limiting factor
in plant growth.

The plants matured earlier than those on the

untreated soils, had a higher protein content, and produced
higher yields.

TABLE OF CONTENTS
Page
INTRODUCTION ..................................

1

EXPERIMENTAL SOILS ANDMATERIALS ................

2

PART I - Adsorption and Diffusion of Fumigants in
S o i l s ..............................

3

LITERATURE SUMMARY .......................

4

EXPERIMENTAL............................

5

Adsorption of Dichloropropene and
Ethylene Dibromide on Soils .........

5

Dispersion of Dichloropropene through
S o i l s ........... . .................

13

Dispersion of Ethylene Dibromide through
S o i l s ................ . ............

25

Field and Greenhouse Observations . . . .

37

DISCUSSION.........................

41

PART II - Effect of Fumigation on Soil Biochemistry
LITERATURE SUMMARY .......................
EXPERIMENTAL.......................

45
45

47

Carbon Dioxide Production and Redox
Potential after Fumigation .........

47

Ammonification and Nitrification in Soils
Fumigated with Dichloropropene and
Ethylene Dibromide .................

63

The Effect of Fumigation on the
Nitrification of Ammonium Sulfate Added
to S o i l s .....................
73
Field Experiments and Observations
DISCUSSION..........................

...

7$
36

PART III - Calcium and Nitrogen Relations with
Respect to PlantGrowth ............

91

LITERATURE SUMMARY .......................

91

EXPERIMENTAL............................

94

Growth of Soybeans in Sterile Sand
Culture Supplied with Different
Sources of Nitrogen and Varying
Levels of Calcium...................

94

The Relationship of Calcium to Soybean
Growth on Fumigated S o i l s ............

105

DISCUSSION..............................

110

GENERAL S U M M A R Y ..............................

113

LITERATURE CITED ..............................

116

INTRODUCTION
Various volatile soil fumigants have been employed
in recent years in an attempt to control certain pathogens
which attack numerous host plants and thus decrease crop
production.

They have been used with varying degrees of

success against organisms such as the bulb nematode,
Ditylenchus dipsaci, which infests certain onion fields
and, H. schactti, a sugar beet nematode.

They have also

been used to control weeds in the preparation of seed beds
and green-house benches.
Investigations concerning the use of these fumigants
have been reported which indicate that they affect plant
growth in a manner which cannot be explained by pathogen
or weed control.

It is obvious that the successful use of

any toxic material for the control of organisms will depend
upon the ability of this material to disperse through the
soil and reach these organisms in their micro-habitats.
The subsequent growth of plants in this soil will then
depend upon the ability of the soil to give up the fumigant
to the atmosphere or the tolerance of the plant to the
fumigant if it remains in the soil.

It is also obvious

that if certain species of the micro-biologic population
are eliminated from the soil, the subsequent dynamic balance
which is established will have its effect on plant nutrition.
The purpose of this study was to investigate certain
of these factors using commercially available fumigants and

-2-

their active components.
EXPERIMENTAL SOILS AND MATERIALS
Unless otherwise stated, the following soils were
used in this study:
1.

Oshtemo loamy sand: pH 5*6, organic matter 0.4$$•

2.

Brookston clay loam: pH 6.3, organic matter 7«$6$.

3.

Carlisle muck:

a well decomposed organic soil

with a pH of 6.5 and 13.6$ mineral matter upon
ashing#
The soil class was determined by the Bouyoucos
hydrometer method (10), the pH by a Beckrnan pH meter, and
the organic matter content by oxidation with 30$ hydrogen
peroxide (37)*
The fumigants used were:
1.

Dowfume N: active components are isomers of

1-3 dichloropropene.
2#

Dowfume W-40: ethylene dibromide in an inert
solvent.

3*

Dowfume MC-2: methyl bromide with 2$ chloropicr’in.

4 * 1-3 dichloropropene.
5.

1-2 dibromoethane.

(This term is synonomous with

ethylene dibromide and the two are used inter­
changeably in this study.)

-3-

PART I
Adsorption and Diffusion of Fumigants in Soils
With the advent of a more widespread use of soil
fumigants, a reconsideration of certain aspects of the
general problem has become necessary.

Among these aspects

is the movement of the fumigant vapors through the soil
mass and their retention in the soil.
It is a well known fact that both the colloidal in­
organic and colloidal organic fractions of the soil are
capable of sorbing polar and semi-polar compounds (11,30).
Thus, the ability of a fumigant to disperse through the
soil will depend upon the chemical nature of the fumigant
and the composition of the soil.

An experiment was devised

to test the degree of adsorption of certain fumigant vapors
in selected soils and the ability of the soils to retain
the vapors.
The use of radioactive isotopes in tracer work has
been widely practiced in recent times.

This technique

applied to the tracing of fumigants in soils has the advan­
tage, through its unusual sensitivity, of being able to de­
tect very low concentrations of material whether it exists
as vapor in the soil air, dissolved in the soil water, or
sorbed by the colloids.

It was possible to prepare "labeled"

samples of 1-3 dichloropropene and 1-2 dibromoethane and thus
use a direct approach in tracing the movements of these
compounds in soil.

LITERATURE SUMMARY
Most of the literature concerning the dispersion
of fumigant vapors through the soil deals with the
practical aspects of injection spacing for maximum control
of organisms.

Taylor (50) set up certain hypotheses for

the most efficient distribution of fumigant vapors through
the proper spacing of injections.

This was based on exper­

imental determinations of dispersion ranges for satisfac­
tory control of specific organisms.

With a biological assay

method using the larvae of Popilia japanica, Fleming and
Baker (1&) found that vapors of carbon bisulfide did not
diffuse uniformly in all directions but moved laterally and
downward from the point of injection forming a cone-shaped
region with an apex close to the point of injection. Higgins
and Pollard (22) concluded that soil fumigated with carbon
bisulfide is characterized '
03^ a high concentration of the
fumigant in the injection zone and immediately below it.
There is a rapid decrease in concentration as the surface
is approached.

Schmidt (40) in another bio-assay method

using the rice weevil, Sitophilus oryza L ., reported that
the vapors of chloropicrin and D-D mixture (a mixture of

1-2 dichloropropane, and two isomers of 1-3 dichloropropene)
move most rapidly in a soil of moderate moisture content.
The movement is less rapid in dry soil and least rapid in
very wet soil.

Retention time of the vapors in the soil is

of the same order.

-5-

Polyakov (33) reported that chlorine penetrates
sand to a considerable depth.

However, absorption of the

chlorine increases with the increase of organic matter in
the soil.

Chisholm and Koblitsky (14) found that methyl

bromide was strongly sorbed by peat.

Clay was less effect­

ive and sand still less in sorbing the compound.
found that dry soil sorbed more than wet.

They also

Fuhr and

Bransford (20) however, found little to no sorption of
methyl bromide in a sandy clay containing 11$ water.

They

reported marked sorption of COCI2 , HgS, HCN, and SOg on the
same soil.
EXPERIMENTAL
Adsorption of Dichloropropene and Ethylene Dibromide on Soils.
Under constant conditions of temperature and pressure
the amount of vapor adsorbed by an adsorbent will vary with
the nature of the vapor and the nature of the adsorbent.
The illustration in figure 1 depicts the apparatus
used in this experiment.

The soils used were a Brookston

clay loam, a muck, and Wyoming Bentonite (montmorillonitic
clay).

The soils were air-dry containing 3 *2, 12.4, and

9.2 percent moisture respectively.

After screening through

a 0.5 mm. sieve, the soils were individually placed in the
adsorption bulb.

1-3 dichloropropene and 1-2 dibromoethane

vapors were then drawn through the bulb at the rate of 50 ml.
of vapor per minute.

(The rate of flow was determined by

i.

APPARATUS

FLOW
REGULATOR

fioure

a

THE

FUMIGANT

OF

ANHYDRONE

BUBBLE
BOTTLE

ADSORPTION

CHARACTERISTICS

DETERMINATION

DESORPTION

FOR

-6-

cr

<

3
3

2

O
<
>

-7-

inserting a gas burette into the system.) Periodically,
the adsorption bulb was removed from the system and
weighed on an analytical balance.

The quantity of vapor

adsorbed per gram of soil (x/m) was then calculated.
The data for the adsorption of the dichloropropene
and dibromoethane on the two soils and on the Bentonite
are presented in table 1.
temperature of 25° C.

The data are for a soil

-S-

0

£

0

X!

1
o

-P
0

O

£
rQ

£

*H
X*

-P

O

nO
CM

ON

VO

ON

rH

-4

to

on

to

nO

£ cd
,0 Xl
•H P

O
O

o
o

-4
C\i

CM

-4"
NO
cm

O

O

o

CM

1
—1

1
—I

o

-4
[> CM
O

to
•
rH

01
o

1— 1
•rl 0
O
0
cd
0 £
XI bO
P
£
XJ 0
bO ft
£
O xi
• £ 0

£

£
PQ

O

1—
I

0

Pi ft

£ •H
0 O

CO

UN

to

ON

CM

C"-

CNi

O
o

o
o

o

o

0

-GO

-4

on

ON

01
o

CNi

on

UN
ON

o

o

1
—1 1—I

CNi
CNi

o

o

o

ON
o

to

UN
o

NO

NO

o

UN
o

CNi

-4

-4

-4

o

o

o

o

o

I
—I
UN

•GO

NO

ON
ON
O

On
ON
O

O
o

o

CNi CNi

Q ft

0

£ £
0 O

ftp
o 0

£M
fto

I
O

a
o

o o
£ £
O CQ

X!

|P r £

x; xJ
'H CCS

o

xJ

£

1o

O

1—
I

<P

o

-oo

UN

un

ON

I
—I

CNi

o
o

CNi

o
o

UN
O
O

CM

1
—I
O

GO

O-

ON

rH

o

I
—I

-4

O
O

O
O

O£

UN

O

ftp
cd £

rH

-4

£

£ P £
O
O
•H XJ 0
P 0 xJ
0 0 0
£ 0
•jH cd 0
s ft ^
£
a
0 £ £
P O bO
0 ft
x) cd £
> •iH
0
0 CH £
£ 0 O
X!
ft
P >» cd
P >

o

-4
O

Q ft
I
O

0

0 PQ

a

11

o

O

0

£

0

0
-p

0

•H

X!

X> Xl
•H P
Q

£

rH
CNi

O
O

O

on

CM

ON

to

nO

CNi

GO

ON

ON

on

O

CM
O

-4

ON

CM

O

O

ON
O

ON
o

on
o

On
rH

on

nO

GO
NO

O

ON
O

ON
O

ro
o

O
O
O
1—1

O
O
ON
rH

O
O
ON
1
—1

0
0
-4
CM

0

O

-P

I
O

0

£

£
O

£

*H

CQ

0

O£

1—
I

ft

£
O
0

o
o

o
O

0
0 -P
O *H
*H £
P O
CO p
*H £

-P

0

XI ft
o

o

o

o
o

£

rH Pi

£

NO

I
o

ONrXJ

XI

ON

CNi

•H P
Q 0

0 £

£

to

£

I
—1

0

Xl ft

X!

o

o

I
—I

o

O

I
—I

o
CM
O

NO

GO

CM
o

CM
O

0
UN
CM

O
O
1
>-

O
UN
GO

•H £

on

-4

C£ ft

Xi
cd
0

xl
EH

0
rH

£>
cd
E-t

£
O

■» -H
-J?- P
£ cd

> 0
o
£
O
o

•
-1
1

£ 0
•H 0

I
o

O
o

1

0

Q 0

W

M

XJ

O£

a

a
0

O
O

O P Cm
£ O
0 0
b 0£ p
cd CT*XI
bO
£
0 0
> X! <D
<tj Eh

#

X

X

-if

-if

0

£

ai

Pi
0

o

S

0
ouo
•H

s
n
o

cm

1

rH -*

Xl

0

i
—l
,.Q
-p

<Q
■H
0
sn
0
C
O
0
!Q

P

Oh

0

SO
aj

•H P

I
O
S-4
o

CQ

rH

£ •H
0

•rO

O

CQ

Oh

0

0

!004

I
£
O0
O
O 03

SO

O PQ
i

—I

on x i
0 sn

•H cxj
X)

*
04

O
0

i
Q
o

*H

P
Oh

U

o

C
O
0
Xl

0

.a

o

0

Pi

UA

o

-4

O

CM

o

ON

ON

I
O
£0

to

PQ

Sh a3

PA

CM

O
-£•
o

rH

o

PA

O

CM

CM

O

CM

O

to

CM

O

On

to

CM

O

O

O

UA

UA

rH

CQ O,

0 P

o

0

so
0 CQ

o sn

P

o sn
aJ o

£

aj

on
o

0

on on

p

•H P

•H

p

Oh

o
0

CQ

ON

o

On

O

-4" O
r
—I O o
o
O o

to

p 0

sn
o

I
o
£

p

sn
o
•H

-Sfr
s

o

rH 0

on O h
o o

O

*H S
h

0
0

CQ O h

nO
vQ PA
v£> m- too
i
—I o
CM
PA
I
—I o o
O o
o
o o

to

Xl

0

Eh

£
o

If P

* 03
CNi

0

o
SO

I
—I

p

eh

on

o

sn
o

P

OH
hO
m

1
—I i—I
O o

in­
to

•H O

0 P

on
0

UA

O

CM

O
O
o

on Oh
o o

£
•H

o

CO o
m
- m- mo o o
o o o

PA

rH 0

0

•h
p
•h

O

UN
UN

to

•H P
CQ 0

O *H
aj
p
aj
xl

ON

to
CM
O

on on

PAC4
1O
H tg
<P ^
O

UA
PA
CM

o

Oh O
O O

u

0
0

SQ

on O h
O O

X

sn sn
0 o
OhP
O

■00 PA UN UA UA
pa
m- -4- O i
—I
rH
CM
CM
CM
o
O O O O O

CQ 0

04
O
O
!0

aj o
CM

so
on on

p
0

xl

Xl

The source of fumigant was then disconnected

I
o
£
o

P

on
aj

S
O
S
OP
H <Q
0

o
sn
o

o

o

UA
CM

O
o
1—1

o
o

UA

O
O
to

o
o
o
I—1

Average of three determinations.
The quantity of air passed through the soil in ml.
Weight of vapor in grams adsorbed per gram of soil.

from the system

and air was passed

-9-

-10-

The adsorption and desorption data are presented
graphically in figures 2 and 3*
Both the dichloropropene and the ethylene dibromide
were adsorbed by the three soils.

The maximum adsorption

in both cases occurred on the muck, the next greatest on the
Bentonite, and the least on the Brookston.
complete on the Bentonite.

Desorption was

However, the muck and Brookston

retained quantities of the compounds which could not be re­
moved by the passage of air.

These data are summarized in

table 3•
Table 3* The percentages of 1-3 dichloropropene and 1-2
dibromoethane adsorbed and immobilized by Bentonite, Muck,
and Brookston soil.
1-3 dichloropropene

Soil

Maximum
Immobilized*
adsorption
0

1-2 dibromoethane
Maximum
Immobilized*
adsorption

Bentonite

3*7$

Muck

1+

•0°/o

62.2$

4.1$

60.5$

Brookston

2.4$

30.1$

2.8$

18.0$

*

4.0$

0

Percentage of fumigant adsorbed which could not be removed
by aeration.
Apparently the great surface area of the Bentonite

adsorbs a considerable quantity of the compounds, but
probably the bonding forces are weak electrostatic or Van
der Waal's forces since the energy required to remove the
materials was not great.

On the other hand, the muck and

1000

CONCENTRATION

(M l .)

200010

TlTTf-Tr

AIR

t:IIn i

VflPQR

1000

CONCENTRATION

(M l .)

2000

-11-

-12

£

-13-

Brookston data suggest that the compounds enter into a
stronger chemical bonding with the organic colloids, be­
cause it was impossible, with the system used, to remove
more than a fraction of the amount adsorbed.

The amounts

of fumigant retained by the soils was related to their
organic matter content.

The relationship between the soil

organic matter and these fumigants is not difficult to
comprehend when it is realized that compounds such as resins,
alkaloids, phenols, organic acids and their derivatives,
(41, 30) exist as dynamically functioning parts of the
organic matter.
Dispersion of Dichloropropene Through Soils
It is possible to obtain an isotope of chlorine hav­
ing a radioactive nucleus with a mass number of 36 and an
extremely long half-life (tj = 10^ years) (3).

The disin­

tegration of this isotope proceeds according to the follow­
ing reaction:

17^^“ ’
^ 1 S ^ ^ + B“ . The maximum energy

of the negative beta particle spectrum is O .64 M.E.V.

The

assay of this radioactive isotope of chlorine depends on
the detection of these beta particles.

This can be accom­

plished with a G-M tube with a minimum window density, i.e.
1.9 mg. per cm . Because the ermnission energy is low, con­
siderable self-absorption occurs in the sample material.
Therefore, the samples must be kept as thin as possible for
maximum count s.

-14-

Radioactive 1-3 dichloropropene was obtained by
placing 3*5 ml. of the compound in contact with $ micro­
curies of 17ci36

in the form of 1.03N HC1 in a closed

glass container.

The contact was maintained for 24 hours

with occasional shaking.
propene

A' small sample of the dichloro­

was then removed and tested for beta emission.

The test indicated that a transfer of some of the radioactive
isotopes for the chlorine on the compound had taken place.
The emission from the dichloropropene was not due to
occlusion of the radioactive HC1 as can be seen in table 4Table 4« Titration data on HC1 after contact with 4 ml. of
1-3 dichloropropene for 24 and 4$ hours.
24 hours
1.0090 N
HG1
ml.
1.00
2.00

4& hours

0.1007 N
NaOH
nil.
10.02
10.02
20.03$
20.04

1.0090 N
HC1
ml.
1.00
2.00

0.1007 N
NaOH
ml.
10.015
10.02
20.03
20.03

A drop of the radioactive dichloropropene was placed
on the center surface of three soils contained in Petri
dishes.

The soils, at the moisture equivalent, were 1,

Oshtemo loamy sand (9*6 percent moisture), 2, Brookston
clay loam (31-6 percent moisture), and 3, muck (131 per­
cent moisture).

A strip of x-ray film was placed over the

dishes and kept in place for 24 hours.

Duplicate dishes

-15-

were set up and x-ray film was kept over them for 4$
hours#

Plates 1 and 2 show positive contact prints made

from these negatives.
The plates exposed to the Oshtemo soil show no
localization of the radioactive dichloropropene.

Appar­

ently the diffusion was lateral and downward since there
is no evidence of particle impingement on the film except
at a few scattered points.

Because of the low emission

energy, the radiation was for the most part absorbed by
the soil.

The Brookston soil plates show a strong local­

ization of radiation around the point of application.
There is an indication of lateral diffusion at the soil
surface.

The radiation distribution is even more local­

ized in the muck soil, indicating strong sorption at the
point of application.

There is little evidence of diffu­

sion outside of that accomplished by “wetting” at the sur­
face.

There are indications of slight surface diffusion

with time as a comparison of the 24 hour and 4$ hour radio­
graphs demonstrates.
The information gained from these radiographs is
purely qualitative, but it supports the evidence gained
from the adsorption studies as to the role of organic matter
as it affects the dispersion of the fumigants.
The labeled 1-3 dichloropropene was next injected in
the Brookston clay loam contained in 3 gallon glazed crocks

-16-

PLATE 1.
RADIOGRAPHS OF RADIOACTIVE DICHLOROPROPENE INJECTED AT
THE SURFACE OF SOILS CONTAINED IN PETRI DISHES.
(2 4 HOUR EXPOSURE FROM THE TIME OF INJECTION.)

IN OSHTEMO SOIL

IN BROOKSTON SOIL

IN MUCK SOIL

-17-

PLATE 2.
RADIOGRAPHS OF RADIOACTIVE DICHLOROPROPENE INJECTED AT
THE SURFACE OF SOILS CONTAINED IN PETRI DISHES.
(4 8 HOUR EXPOSURE FROM THE TIME OF INJECTION.)

IN OSHTEMO SOIL

/

\
IN BROOKSTON SOIL

7
\

IN MUCK SOIL

-13-

with a diameter of 22cm#

The Brookston soil was chosen

for this study because it had significant quantities of
both colloidal organic and mineral matter.

The soil in

one crock was at the moisture equivalent; in another, the
soil was saturated (54-1 percent moisture).
ture of the soils was 24*7° C.

The tempera­

An injection of the

dichloropropene of 0.369 gm. equivalent to 0.75 ml. was
made in the center of each crock and 6 cm. from the sur­
face of the soil.
The soil was allowed to stand for 3 days and was
then sampled with a 2 cm. diameter steel ”core sampler”
where indicated in figures 4 and 5*

The steel edge of

the sampler served to run the outside surface of the cores
together and minimize loss of any fumigant which might
exist as vapor in the soil air.

The cores were then divid­

ed into 6 cm. lengths and each length was placed in a flask
containing 30 ml. of toluene.
Because of the low emission energy of the beta
particles involved, it was necessary to devise a system
for isolating the labeled dichloropropene or a reaction
product from it containing the radioactive chlorine before
emission counts could be made.

It was found that if a

solution of dichloropropene in toluene were refluxed in
the presence of fused sodium, (this is possible because the
boiling point of toluene is higher than the melting point
of sodium), a water extract of the reaction products would

-19-

yield sodium chloride with the chlorine coming from the
dichloropropene.
The flask containing the soil and toluene was
agitated long enough to break up the soil core and the
toluene extract was decanted into a boiling flask.

Enough

additions of toluene and decantations were made to bring
the total extract up to 60 ml.

Sodium was then added to

the boiling flask (0.15 grams was calculated to give a
probable excess to that necessary for a complete reaction
with the dichloropropene in each sample) and the mixture
was refluxed for 2 hours.

Sufficient ethyl alcohol was

then added to react with the unreacted sodium.

The solution

was then mixed with several additions of water in a separa­
tory funnel and the water soluble extract was drawn off into
a small metal container and evaporated on a hot plate.
Solid sodium chloride along with sodium hydroxide
from the reaction of the excess sodium with the ethyl
alcohol formed a thin layer at the bottom of the container
and emission counts were taken directly from this layer.
The thickness of the layer was approximately constant be­
cause the same amount of sodium was used in each reaction
vessel.

Thus, the absorption of radiation could be con­

sidered to be constant.

The number of emission counts re­

corded on a scaler from each sample was taken to be propor­
tional to the concentration of dichloropropene in the toluene
extracts from the soil cores.

The data are tabulated in

-20-

table 5«
In order to extract the humus from the soil
samples, 50 ml. of a 2 percent solution of sodium hydroxide
was added to the soil and the mixture was vigorously agita­
ted.

After standing for a few hours, a 10 ml. sample was

removed by a pipette from the supernatent suspension and
was evaporated to dryness in a metal container.

The thick­

ness of this humus layer was approximately equal to that
of the salt layer described above.

The number of counts

recorded from this humus layer was multiplied by a factor
of 5 to compensate for the fraction of humus not evaporated
and counted.

In this instance, the number of emission

counts recorded was considered to be proportional to the
amount of dichloropropene tied up in or associated with
the colloidal organic matter.
table 5.

These data are presented in

-P

4

Table 5*

-4-0-0 O O
O C^v
rH

to o o
ctnO p'v
CM

-O60Lf\0 O O

MDvOMO iaia
to
1
-1

t o O N EH

OO

MOM0to

o cvo o o

OOOOO

0
P

P

-P p
O *H

ctfS
J-r

-p
P

P Jh
X! 0

0 0 P.
I
—I
ffi0
> OP
P P
P S P
O
C
o
0
0
0
P Po PP
P
-p
PP.
0 SH-H
•H p g
O X
h
e 0J
0
p>
a)ft

LTS P"\ O

-60

O

O

CM

of'N-jvO H

o

*r\o4-o
i
—I

rH

-60 0 0

0 0

CM

p
0 0
pp

O-CO -3-to Eh
CM »-r\iH
rH

o O'-O Eh o
CM

O LT\rH
H LTN-4-

roH 3
3
Eh O
O

CM
I—
I 0

•H H

o p

CO Fi
P

co

«rjJ «=3j «tj <tj

O H (V 0°v - 4

pqpqpqCOPQ O O O O O

O H 6 2 o"\-4

O rH CM O -4

of 30

tO CMMOo O
r^CwO
-4rH

The average of 3 close counts per each sample.
Calculated on the basis of 1024 counts for each determination less background
counts per minute.
(1) Little, but significant, radiation as determined by long counts.
(2) Symetrical core samples to those of the same code no.

U

P
ctJ
W

-P

CM lt\0 o o
UMT\
CM

*

ctf

p
3
PO-H
P
Pg
Jh
P Jh
X 0
0 P.
K
O P0
PP
S 3
OO
Toluene extract
Counts per minute

p
o
•H
P

Emission

counts from radioactive 1-3 dichloropropene injected
clay loam at 2 moisture levels. *

in Brookston

-21-

-22 -

Dispersion patterns incorporating the data in
table 5 are presented in figures 4 and 5-

It can be seen

that the dichloropropene disperses through the soil in
two phases; 1, the air-water phase or that part of the
dichloropropene which can be extracted with toluene, and
2, the humus phase.

Most of the fumigant is associated

with the humus and is tied up in a relatively small volume
of soil.

The fraction traveling in the air-water phase

diffuses farther and can be considered to form the boundary
limits of the dispersion pattern.

The symmetrical core

samples taken yield radiation counts of approximately the
same magnitude and thus indicates that dispersion of the
dichloropropene is horizontally symmetrical.
The dispersion of the dichloropropene in the humus
phase of the soil at the moisture

equivalent is limited to

a small volume around the point of injection.

The move­

ment in this phase is downward with a minimum of lateral
dispersion.

The movement in the air-water phase is also

downward with a tendency toward greater lateral dispersion
than exists in the humus phase.

It seems probable that most

of the dichloropropene in the air-water phase surrounding
and immediately below the injection point exists in the air
pores in equilibrium with a small amount of the compound in
the water phase.

As the fumigant

concentration diminishes

with lateral dispersion, it is probable that a greater pro­
portion of it exists in the soil water.

-2>

•oo
tu
CO

<
X

0.
<0
3
s
3
X

to
tz

3

o
o
m
o
in

THE
AT
_
i t

in
ir-/' i ^
F OJ
I.PF
MOI9T.I

QICHLOROPF jPENE
PATTERN

!f-

2

OF

o
oo
o

IN

BR00KST0N

<

DISPERSION

S

s

3
X

4.

I
O
<

M

0 2
-j
CO o
o cd

<

O

c

>-

0. 2
CO <
—
Q

CM

L

SURFACE

<
ro

£
i
2

Z
o
(0
2
Ui

figure

<

M-

Z
O
<0
2
UJ
Q; >
W (E
Q <
Q
ft* Z
UI -)
I- C>
< od

-24-

O
co

o

\-

<
/> ^
cl >
Ui

CL

a. <

o

CO ^

S
2
Q 3

o

£T
CQ
o
Ll I
h<

CO o

SURFACE

3 *D
2
3
X

or

SOIL

ZJ

UJ
Z

LJ
O
Q_

cr

o

« 2 cm.->

cr

3
X
O
Q
U0|

/

Z\

X
L I
I—
l

•oo

s
o
c/>

UJ
I—
3

Z

=

cr

UJ
CL

to
o

(0
Iz
o

3

to

o

o
1
0

lO

UJ

o:
3
O

-25-

There is a greater lateral dispersion of the
dichloropropene in the humus phase of the moisture saturated
soil.

Diffusion downward in the air-water phase is strongly

diminished and the small and relatively constant concentra­
tion of the fumigant in this phase, lateral to the point of
injection suggests that its movement is limited by its low
solubility in water.
Dispersion of Sthylene Dibromide Through Soils
Radioactive bromine can be obtained as KBr with the
bromine having a mass number of &2.

This isotope of bromine

has a half life of 34 hours and disintegrates to yield nega­
tive beta particles with a maximum energy of 0.465 M.E.V.
Associated with each beta disintegration are three gamma
rays in cascade with energy levels of 0.547* 0.7&7, and
1.35 M.E.V. (36).

This high energy gamma emission allows

for a different tracer technique than was used with the
dichloropropene since it is possible for the gamma radiation
to penetrate a relatively large mass of soil.
A quantity of radioactive KBr equal to approximately

40 millicuries of energy was dissolved in 2 ml. of water
and this was placed in contact with 4 ml* of 1-2 dibromoethane in a small glass reaction vessel.

After standing

for 24 hours, a small amount of the dibromoethane was re­
moved and tested for particle emission.

The fact that

some emission was detected indicated that an exchange of

-26-

some of the active bromide ions from the KBr solution had
exchanged with some of the bromide on the dibromoethane.
Approximately 0.75 ml* of the labeled compound was injected
into the Brookston clay loam which was contained in 3/16 in.
lead boxes.

The soil in one of the boxes was air dry and

in the other, at the moisture equivalent.
26 cm. square and 16 cm. deep.

The boxes were

One side and the cover of

each box had 6mm. holes drilled through in strategic places.
The injection of the compounds was made in the center sur­
face of the soils and 3cm. deep.

Periodic emission counts

were made by placing a G-M tube hooked into a scaler
against the sides and covers of the boxes.

The tube was

shielded with a lj in. lead casing and was attached to a
columnating device consisting of a 6 in. steel tube contain­
ing a series of lead discs with 6 mm. perforations in the
center.

Thus, the columnator could be placed directly

against the openings in the lead boxes and comparable counts
made repeatedly from the same place.
In order to ascertain the rate of decay of the Br^,
the columnated G-M tube was focused on the reaction vessel
containing the remainder of the dibromoethane and radio­
active KBr.

Periodic emission counts were made from a

standardized position.
figure 6.

The decay curve is presented in

Because the potassium in the KBr is also radio­

active (ti - 12.4 hours), the counts recorded on the scaler

2

-27fig u re

e. COMPOSITE DECAY CURVE FOR T HE
RADIOACTIVE ISOTOPES IN

TWO

K42 Bf)82.

100

COUNTS

PER

MINUTE

(X IO O )

50

too

50

TIM E

IN HOURS

50

-2g-

included particle emission from the potassium as well as
the bromine.

However, since the half-life of the potassium

is shorter than that of the bromine, after a time the counts
recorded were due primarily to the bromine.

When plotting

the decay against time using a logarithmic scale, it can
be seen that the decay curve becomes a straight line.
This straight line portion of the curve is due to the
emission from the bromine and if it is extrapolated to time
s 0, the decay for bromine alone is ascertained.

Using this

extrapolated value, it was possible to compare the emission
counts recorded from the boxes containing the soils at any
given time by adjusting the magnitude of these counts by
a factor which made them comparable to those at the time
of the first reading.

The data recorded in tables 6 and 7

give the adjusted counts recorded from the soils through
time •

-P
£

0
i— 1

•M•

CM

to

0
U
3

-P

nO nO

i—1 c o ■—1nQ
CM 150
LO CM i—1

CM O n O - CM
O H O tO
CO c o CM

-4

0 - 0 - - 4 - ON
- 4 L O tO I> CO 1—|

c o to O -to
U A \Q cm O LO CM rH

rH t > - t 0 -4
rH CM rH tO

CM CM l o -4
H ' O I> - t O

CM o^vrH i r \
- 4 c o O to
U A c O rH

CM - 4 - 4 l o
nO rH O t o
CO CO CM

CO CO CM

-P

CO

•
0
•H .— .
O 0
Jh
a
3
p
O
cd
'— -

U

*H
<+-(
O

CD

a

-4

CM

0

•H

-p
o

■p

o
P

0

P

0

0

CM

S

C"-

•H
EH

a

i— 1
*H

u

0

O

-co
-4

0

Ph

>»

T3

0

-4

-p

fj
3

C O rH

0

U

cm

U
2

t O IA- OO O

0

CO CM rH

O

•rt
O

0

0

0

£

£

£
o
rH
0
JO

O
i— 1

0
JO
•

•

a

a

o

o

-4

CO

o o - o n -co t o
O - rH

0 \ CM O - CO
v O tO 0 - 0 co

i— 1 i—1 CO LO
O 00 o t o
O—i— 1 i— 1

H O - 4 - ia

L O C O O cm
o to o to

ONC\J[>
CM \ 0 -60 tO t>-

O - On "CO to

CO tO O n O n

i— 1

O

CO

o

CM CM - 4 CO
rH On i— I On
nO CM rH

i— 1
•H

•
a
o

-p
P

LOtO tO ON

U
3

— o
1— 1
0
rO

*H

*H

-4 0 N C M

i— 1
*H

*f“5

0

3
0

0

U
u
o
o

ch
nO

co

0
O
cd

cm

0

TO

0
o
cd

COrH

o

cti

i— i
•H d
O o
CO •H
P
O

O n c o C '- t O

rH rH

rH O L O O

CM LO £>-tO
CM rH

CM CM LO - 4

rH -4 t o t o
CM rH

o to o
O c o O nt o
CM rH

o

oO

O- rH - 4 0
On On

to H

CO 1—1

O L A 4 0

to— (
—1

O n - 4 On On

-4 t o On CM
CM rH t o On
rH I
—I

O CM NO O
i— 1

O CM VO O
i— 1

a

o jCJ
o o

6.

ONUOCM Lr\
4 'A 'C i O to
CO I—1

0
0

CH 3 a

Table

!>-

i>
•H
3
cr

hO
a
•H

0

•
—

40

•
£ P o •H 3

0 O O
nj
-P 0 * n Q h*-— «•
0 •H CJ
X -H

Q

aj

O

CM nO O
H

Average of three close counts for each determination.
All counts recorded below 95 per minute are considered to be part of a variable
background and are not considered to be indicative of the presence of the compound.

Emission counts from radioactive 1-2 dibromoethane injected in Brookston
soils at two moisture levels: lateral dispersion from vertical axis
through point of injections. *

-29-

-30-

0
O
P
CO Ch
o
p
o
o 0
0 •H
CO X
0
a
-H 0
P
P P
0
P hO
o S3
0 o
• O H
S3 0
•H
0
0 O
•H
S3
0 0
Pi 0
P 0
0 O.
O 0
a •H
o p
Sh
P rH
■H 0
P O
•H
CM P
1 0
i— 1 0
>
0
>
•H
P ••
O 0
0 i— 1
o 0
•H >
•0 0
0 rH
0
0

*
■ifbO

0 P
o 0
•H
0 0
tQH
•H •H
a O
ro 0

0
I

—I
p
0
B-t

OH

>
-H

0
•H
P

0

0
0
0

0
to

0

4

0

0
p
0

0
0
•H

-H

ch

o

a

Ch

4
4

CM
O
Ob

I— 1
CM

O

rH

to

rH

to

Ub
CM
i—1

•
--* n}"
0 cm
0

Ob

4
Ob
i— 1

Mb

to

Mb

4

Ob

O
CM

CH
4
Ub

On
vO
4

CM
vQ
Ob

[> i— 1

CM
i—1
\Q

Ub

to

CM

i—1

Ob
Ob

ON

to

ON

On

Mb

cCM
i— 1

0

O

P

0
0

a

rH

•H
P

-H
O
CO

O
P

O
P
—
ob

0

ub

Mb

o
•H

P
O
0
•<“3
0

P

0

■■»
O
0

0

0

0
P

0
O
O

<H

0
P
0
0
•H
a

0

0
CM

a O•H
Eh

4
4

i— 1
CM
CM

to

rO-

E>-

i—1
O

to
Ub
4

CM
i—1
CM

Mb
CM
rH

to

Ub

to
•to
-4

O
O
CM

CM

O
I>-

O

NO

o

CM
rH

rH

-h
o
0
>,
0

0

0
o.
0

p

p

0

0

O

<$

o

to
4
4

CM

-*
•
0
O
*H
P
O
0
*r-3
0
*H

i— 1
vO
Mb

cj

P

F
*
'0

O 0
0 P
<H 0
■H
to O
P a
0
0 o
O £
O P

P
0
0
rH
0

Ob

C"-

ON

c

to
Ub

4

CM
rH

CM

i— 1

ON

to

Mb

to
4

ON

nO nO

bO

0 0

0

I—I I—I

P

O p

rCt

00

rH bD

0

0 sz;

p p

0

H *H P '— **

0 0
0 0

O O •
P c3 •
fl P O -H s
0 0 oo
p 0 *r-3 a -CO -H 0
•H X *H

Q ccj

4
i
—I

CO CO

-31-

That the volume occupied by the compounds in either
soil consisted approximately of a symmetrical solid of
revolution with a vertical axis running through the point
of injection and perpendicular to the soil surface can be
seen from the data in table $.
Table S. Emission counts from radioactive 1-2 dibromo­
ethane injected in Brookston soils at two moisture levels:
counts taken from the soil surfaces.*
Distance from
vertical axis
running through
injection point.

Counts per minute recorded 24 hours from
the time of injection and corrected to
the three hour readings.**
Air dry soil

Soil at moisture equivalent

0
2
2
2
2

cm. 90°
cm. ISO
cm. 270°
cm. 360°

1492
327
34$
33$
31$

1114
374
361
34$
359

■6
6
6
6

cm. 90°
cm. ISO0
cm. 270°
cm. 360°

$6
$6
90
$2

179
191
1$7
1$7

*
**

See table 6.
See table 6.
The rates of diffusion of the ethylene dibromide at

the two moisture levels are presented in figures 7 and $.
It can be seen that the movement of the compound is more
rapid in the vertical than in the horizontal direction.
Also, the concentration of the compound shows a greater
localization along the vertical axis through the injection
point.

The greatest amount of dispersion takes place within

-32-

cebui

-

33 -

m
\T&U

-34-

the first three hours after injection and the dispersion
limit was for all practical purposes, reached after 24
hours.

It is interesting to note that at the 4& hour deter­

mination, there appeared to be a movement of the fumigant
against a concentration gradient in the immediate vicinity
of the injection point.

This can be seen in the soil hav­

ing the greater amount of water.

Since it is improbable

that movement against a concentration gradient took place,
it seems more logical that the reaction with or adsorption
of the compound by the organic matter gave it new character­
istics, and a solution effect with the water could cause
this movement in localized areas.

It is also possible that

hydrolysis of the ethylene dibromide in areas of high concen­
tration could result in the formation of bromides which would
diffuse through the water phase.
The stabilized dispersion patterns of the ethylene
dibromide in the Brookston soil at the two moisture levels
are given in figures 9 and 10.

It can be seen that the

compound disperses through a greater volume of soil when
the soil is at the moisture equivalent than it does when
the soil is air-dry.

It is also evident that the area of

greatest concentration around the point of injection is
more diffuse in the wetter soil.

In neither case was there

any significant penetration of the compound into the soil
mass above the point of injection other than that caused
by a surface effect due to wetting.

3
0

CM

1

O

40

<

UJ
>
I—

oc

UJ

UJ
h<
o
Q

CD

UJ
CD

2
3
Z

OC

BROOKSTON

PATTERN

UJ

DRY

O

AIR

o

DISPERSION

CC

STABILIZED

SOIL

OF

Z
O
H*
<

9.

ETHYLENE

(/)

f i gu r e

DIBROMIDE

IN

-

35 -

pL

HO

STABILIZED
DISPERSION
PATTERN
OF
BROOKSTON SOIL AT THE MOISTURE

ETHYLENE DIBROMIDE
EQUIVALENT
POINT

Ll_

OC

UJ

10.

u:

figure

IN

-36-

-37-

Field and Greenhouse Observations
Certain qualitative data on the spread and retention
of certain fumigants in soils was gained from the following
observations.
It is not uncommon to notice the odor of Dowfume N
or Dowfume ¥-40 in muck soils for periods of one year or
longer after fumigation has taken place.

This is usually

true if the interceding time is characterized by a great
deal of rainfall.

Thus, the fumigant is believed to be

carried to the surface by a rise of the water table.

How­

ever, consideration must also be given to the fact that
if the period following fumigation is wet and cool, and if
a certain quantity of the fumigant is fixed in the soil
and localized around the point of injection, then biological
TldetoxicationIT of the fumigant will be retarded and quanti­
ties will remain in the soil per se for long periods of time.
A field of muck soil in ChandlerTs Marsh near St.
Johns, Michigan was fumigated in the fall of 1949 with
Dowfume N at the rate of 40 gallons per acre.

The field

was planted to carrots in 1950, and abnormal branching of
the roots was noticed.
pulled from this field.

Plate 3 shows some typical carrots
That this branching was not due to

root knot nematode damage can be seen by the fact that the
roots do not have the knotted appearance typical of this
kind of damage.

It seems more probable that the carrot

roots grew down into the soil until they reached a

-

33-

Plate 3« Typical branched carrots pulled from
a field of muck soil fumigated with Dowfume N.
concentration of a toxic substance which damaged the
meristems which in turn stimulated lateral branching
and growth from the crowns.

In this case, the fumigant

was injected approximately three inches below the surface
which was also equal to the extent of vertical growth of
the carrot roots. Spot$ checks made of the stand showed
that approximately 30 percent of the carrots were branched
in this manner.

Those carrots which were not branched

were also not greater than three inches in length for the
most part.

They were, however, grouped so closely togeth­

er that lateral branching was probably impeded.
One-gallon crocks were filled with Oshtemo loamy
sand and Brookston clay loam and soy beans were planted

-

in them.

39-

After the seeds germinated the plants were

thinned to three per pot which approximately formed an
equilateral triangle of about five inches on each side.
When the plants were about, nine inches tall, 1 ml of
dichloropropene or ethylene dibromide was injected into
the soil half way between two plants and one inch below
the surface of the soil.
equivalent at the time.

The soils were at the moisture
The dosages used were far greater

than the amount normally recommended for field use.
Plates A and 5 show the results of the use of these com­
pounds in the two soils.

Plate 4. Crock 1 contained Brookston clay loam.
Ethylene dibromide was injected between the two
plants on the right.
Crock 2 contained
Oshtemo loamy sand. Ethylene dibromide was in­
jected between the two plants on the left.

-

40

-

Plate 5* Left - Oshtemo loamy sand. Dichloro­
propene was injected between the plants on the
lower right.
Right - Brookston clay loam.
, Dichloropropene was injected between the plants
on the left.

All the plants wilted after injection of either compound
in the Oshtemo soil.

The wilting took place within 12

hours after the injections were made.

The plants never

recovered from the wilting and died from what appeared
to be an inability to take up water through the root
systems.

Examination of the roots showed that the surfaces

were highly corroded.

This corrosion was probably due to

direct contact with the fumigants.

In the Brookston soil,

there was only a slight wilting, of the two plants between
which the fumigant was injected.

This was true upon the

use of either of the compounds.

The third plant in each

crock was unaffected and continued normal growth.

After

a few days, the visible symptoms of wilt on the affected
plants disappeared and all plants continued to grow.
Examination of the roots of these plants showed only

-41-

small areas of corrosion and this only on those roots
which were adjacent to the point of injection of the
compounds.

Though the roots of each of the three plants

in each pot were dispersed more or less through the entire
soil mass, the effective area for absorption of water
could be considered to be unaffected in those plants not
adjacent to the point of injection.
It is believed that the above observations support
the hypothesis that large quantities of the fumigant are
fixed in certain soils and that this fixation is primarily
a function of the amount of colloidal organic matter
present.

As was previously shown, a colloidal inorganic

soil fraction of large surface area would probably adsorb
certain quantities of the fumigants, but the bonding energy
is not strong enough to give the concentration gradients
exhibited in these cases.
DISCUSSION
The results of these experiments indicate that the
extent of dispersion of dichloropropene and of ethylene
dibromide are approximately equal in identical soils at
the same moisture level.

There is little, if any, pene­

tration of the fumigants into the soil mass above the
point of injection if the soils are allowed to remain un­
disturbed after treatment.

The dispersion is lateral and

downward from the point of injection with the greatest

-42-

concentration of the fumigant localized around a vertical
axis through the point of injection.

Probably because of

its greater weight per unit volume, the ethylene dibromide
shows a greater concentration at the lower depths of pene­
tration than does the dichloropropene.
There is evidence as indicated by the data that
large proportions of the compounds are concentrated in a
relatively small volume of soil around the point of in­
jection, and that this concentration is primarily due to
an association of the compounds with the colloidal organic
matter present in the soil.

This association may be due

to strong chemical adsorption or to mutual solution.
Thus, it was shown by the use of radioautographs that
dispersion of the dichloropropene was greatest in the
sandy soil containing very small amounts of organic
matter; next greatest in the clay loam containing relative­
ly large amounts of organic matter; and least in the muck
which contained extremely large amounts of organic matter.
There is evidence to believe that the same relationships
hold for the ethylene dibromide.

It was shown that a

colloidal mineral soil constituent does not play a great
role in fixation of the compounds in the soil.
In consideration of the moisture content of the
soils at the time of fumigation, the soils at the optimum
moisture level (moisture equivalent) allowed for the
greatest vertical penetration of the vapors.

There was

-43-

also an indication of lateral dispersion but a very great
concentration gradient existed around the point of inject­
ion.

With the soil containing enough water to saturate

it, vertical movement of the dichloropropene was decreased,
but lateral dispersion was more extensive and the concen­
tration gradients were not so severe.

It seems probable

that dispersion of the organic fraction is more extensive
under these soil conditions.

Also, the unassociated

fraction of the applied compound has more water in which
to dissolve and movement of the compound in the water
phase is limited by its low solubility in water.

There is

evidence to believe that the ethylene dibromide behaves in
the same manner.

Dispersion was least extensive in all

directions in the air-dry soils.
Further evidence which showed the effects of certain
soils as they pertain to fumigant dispersion was gained
from observations made on soybeans which were grown in the
Oshtemo and Brookston soils and later fumigated with Dowfumes N and W-40.

The plants growing in the sandy soil all

died in a very short time after treatment with either
fumigant.

The roots were strongly corroded and it appeared

as though the plants died from an inability to take up
water.

Treatment in the clay loam soils did not materially

affect the plants.

It was apparent that large quantities

of the fumigants were fixed within the immediate vicinity
of the point of injection and thus did not reach the plant
roots and damage them.

Further observations made on carrot

-44-

roots growing in a muck soil nine months after the soil
was treated with Dowfume N showed damage to the roots
which was attributed to a residual effect of the fumigant
in the soil.
There were indications that dispersion of the
different compounds and fumigants used was almost complete
after three hours and that a stabilized equilibrium was
reached within 24 hours.

It also became apparent that

the compounds traveled through two phases; the humus phase
and the air-water phase in which an equilibrium exists
between the compound vapor and solution forms.

The effect­

iveness of these fumigants will thus depend upon the rela­
tive concentration in these two phases and the severity
of their action in the different phases.

-45-

PART II
Effect of Fumigation on Soil Biochemistry
Though soil fumigants are used to control specific
plant pathogens, attention must also be paid to the
effects that these treatments have on the microbial popu­
lation as a whole.

One finds many instances in the liter­

ature of reported effects on crop growth different from
that which could be expected from control of the pathogens.
The purpose of this portion of the study was to study cer­
tain changes which occurred in the biochemistry of the soil
as a result of fumigation.

LITERATURE SUMMARY
Early research with chemical disinfectants has
established the fact that their use as fumigants accomplish­
es only a partial sterilization of the soil (15).
Wakeman and Starkey (57) confirmed this and showed that
partial sterilization results in an increase in the
bacterial population and in ammonium accumulation.

Work

by Matthews (26) indicated that fumigation with certain
compounds increased the bacterial population while other
compounds did not affect it.

In general, the majority of

the early workers agreed that the beneficial results ob­
tained from soil fumigation was due to increased bacterial
activity which made increased amounts of nutrients available

-46-

for plant growth (16, 3$> 39)•
More recently, Stark and Smith (47) reported that
low dosages of chloropicrin had little effect on nitrate
formation, but as the dosage was increased, nitrification
was inhibited.

In no case was ammonification inhibited,

r

but the total amount of nitrogen made available for plant
growth was materially increased only where high dosages
of the chloropicrin were used.

Bogopolskii and Bershova

(9) reported an increase in the yields of tomatoes, oats,
and potatoes after fumigation with chlorine and phenol.
The activity of the ammonifying and nitrogen fixing
bacteria was increased, while that of the nitrifying
bacteria was decreased.
Smith and Wenzel (46)

Similar results were reported by
using benzene hexachloride as a

fumigant.
As a result of the increased microorganism
activity and the elimination of certain species, other re­
lated effects have been noted in soils after fumigation.
Beames and Butterfield (7) reported that the oxygen content
in non-sealed pots was decreased by
with methyl bromide.

after fumigation

Sherman and Fujimoto (43) showed that

the exchangeable iron in the soil was increased after treat­
ment with chloropicrin and D-D mixture and Timonin (52),
while working on the manganese deficiency disease of oats,
reported that plants grown on "manganese deficient" soil
were free from manganese deficiency symptoms after the soil

-47-

was treated with chloropicrin or formaldehyde.

The

treatments greatly reduced or completely eradicated the
bacteria capable of oxidizing manganese.
EXPERIMENTAL
Carbon Dioxide Production and Redox Potential after Fumi­
gation
One method for measuring changes in the metabolic
activities of soil microorganisms is to measure carbon
dioxide production in the soil (56).

Also, in view of

the fact that the bio-electric or redox potential is the
sum total of the oxidizing and reducing tendencies in the
soil, it was believed that investigation as to the nature
of this potential would offer a valuable insight on the
state of the soil system after fumigation.

Redox potential

in and of itself is probably not too important since it
varies so greatly from soil to soil, but changes in the
potential may be related to the state of the soil after
treatment and help to explain certain of the phenomena
observed after treatment.

Volk (55) has developed a

laboratory method for the determination of redox potential
where measurements are made on a soil sample immersed in
nitrogen saturated water.

Bueher, (12), however has noted

that the bubling of nitrogen through soil suspensions
results in a decrease in the redox potential whether or
not the soils were puddled or sterilized.

Quispel (35)

has suggested that accurate measurements of the redox

—if$—

potential of the soil system can only be made in place
and has developed a method to accomplish this*
An experiment was devised to simultaneously
measure the carbon dioxide production and redox potential
in soils after fumigation*
in figure 11*

The apparatus used is diagrammed

Oshtemo loamy sand, Brookston clay loam, and

Carlisle muck were placed in the spherical glass containers
and saturated with distilled water.

The quantities of

soil necessary to bring the soil surface to one-half inch
of the opening at the top of the containers was 500, 450,
and 175 grams respectively.

The soils were then brought

to approximately the moisture equivalent by draining off
the excess moisture with a 40 cm* column of water attached
to the small opening at the bottom of the glass container.
The cork containing the platinized platinum electrode,
the KC1 in agar bridge, and the intake and outlet tubes
were placed in the opening of the container and saturated
with paraffin to insure an air-tight seal.

Carbon dioxide

free, moisture saturated air was then passed over the soil
and bubbled through a standard barium hydroxide solution.
The rate of air flow was maintained at approximately 40 ml.
per minute.

Periodic titrations of the barium hydroxide

with standard sulfuric acid indicated the quantities of
carbon dioxide evolved from the surface of the soil
through given periods of time.

_____

APPARATUS

FOR

'

DIOXIDE

DETERMINATION
CARBON

THE

e l e c tr o d e "

PLATINUM

PRODUCTION

OF REDOX

POTENTIAL

1--------

POTENTIOMETER

AND

-50-

Simultaneous with the measurement of carbon dioxide
evolution, the redox potential was measured by attaching
the platinum electrode to a potentiometer and completing
the circuit through a calomel cell connected through a
saturated KC1 solution to the KC1 in agar bridge.

In this

system the redox potential of the soil could be measured
in place and variations in the potential through time
plotted as a continuous function.

The soil was considered

to function as a half cell being compared to a standard
calomel cell in order to obtain a measurement of the over­
all state of its oxidation-reduction tendency.
After the electrodes in the soils had come to a
state of equilibrium as determined by constant voltage
readings, the soils were fumigated with 0.50 ml of 1-3
dichloropropene and 1-2 dibromoethane. The compounds
were introduced into the center of the soil mass by push­
ing a hypodermic needle attached to a syringe through
the cork stopper and slowly ejecting them.

The hole in

the stopper was then resealed with paraffin.

The carbon

dioxide which evolved from the soil and reacted with the
barium hydroxide was subsequently evaluated for two hour
periods at various intervals after fumigation and a
comparison was made, with these quantities of carbon
dioxide and that evolved from untreated soils.
presents these data.

Table 9

-51-

Table 9*

Dibromo­
ethane

A comparison of carbon dioxide-production in Oshtemo, muck, and Brookston
soils after treatment with 1-3 dichloropropene and 1-2 dibromoethane.

xJ

0 to
Pi rH
cd *H

ao
a w
O

o xi

0
XJ P
0 cd

tO ( A O r l ^ f ^ n I A \ D
^ ) C M O H C M > O M N
CM CM CM rH
rH rH

O CM CM ICN CM cr\ -4- c*\0
4 - 4 0 i— | LT\ lf\ i
— |vQ
i— 1CM O^v -4 ro CM rH

-4 0NrH o"\ CM O CM <r\0
CM rH t30 O rH C^-tO I>- rH
rH CM
i— I

r H O O C v- - 4 C M O r H U N ,
4 H 0 C M I A H 0 4 H
i—1i—1i—1i—1i—1i—1i—1

-CO '-T\tO H c ^ O M ) H t O
« • • • • • • • •
4 4
c^ cm 4 ixn 4 o~\

to O nO -4 o"\ O n - 4 0 CM

CM O O

O O

c

W VI/

3 Pi
Xi P

1

o
Pi
o

o PJ

0
PS
1—1 0
P ! sa
o o
■H Pi

P« 3
p*
P
CMP
O *H

O

Q

Ph

XJ
0
P

cd

•
P

0
Pi

p

P

O r H O O t O t O r H 4 4
i—1i—1i—1i—1
i—1

PS
P

CM
f
M

0

PL,

0
p

XJ xf
0 O
> *H
I—1 Pt
O 0
J> 0.

pi

0
s
p

l

o

S 0
o £
p, 0

p

p

ir \to ON<TNCM 14

c^rH 4 0

O O

co\40

•H P

cd

•

*

CM 4 CM UN 4 O n 4
#

• • • • • •

4 4 4 CM O n O 4 O n CM
i—1CM CM
C°s i
—I i—|

-4

0

0

U

0
CM
O

o

1

O
P. 0

o

•
hp

1
—1
p
o
*H

Pi

0
P-i
O

i—1ON i—1i—1 On i—| O O CM
• • • • • • • • •
rH O
cr\ 4{Y*\ c^\ <^\ 4

Pi

4tO O

CM tO CM 4 I N 0

4 H O 0 C M H r l O 0
i—11—1i—11—1i—1i—1

a,
Pi
0
P
Cn
cd

P
Pi
0 0
g Pi
PS
0 cd O

p

C \ ir\tO O -60 O

O O O
rH CM -4*0 -4* O -4 O
rH CM 4 4 0

•H
O
co

rH CM 4 0 4 O 4 O
rH CM 4 I N O
rH

—

i 1

fi <1>P

•H Pi
Eh P

i
—1

CN cr\to O to O O O O

o
s
0
p
p
W
o

p
o
Pi
£

xi
0
O
P
xi

o

CO
1
*H
o
03

i—

Xi
CD
-P
CIS
CD
S-i
P
£

opCM>-f\opupl>~-4n4cM
- 4 up to o p o u \ - 4 u p v £ )
rH CM o p o p o p CM o p CM

1

o

P

Sh
P

ethane

TJ
CD
Sh
cd
P
S
O
O

Dibromo-

-52-

P CD
O £
i— 1 CD

si
CMP
O *H
O
£

xi a,
O o

-00 CM I>-\0 t o up - 4 t 0 M 0
o p C^- u p O o p r-H u p u p O
i— 1 CM i— 1 i— 1 i— 1 i— 1 i— I

•H S-,
CP Pi

XJ
CD
P
cd
CD
u

•
P

XJ

CM > A ! N O -60 C M P CM i A
O

O O CT\vQ o - U P !>- up
i
— 1 i— 1

p

CM

p
o

c.
M
o>

1

P

xJ X5
CD O

> *r-t
i
—1 u

CD

O
> P
<D

CO

o

(D

a
O
P

p
p
S

P
cd
CD
p

CD

£

cd

x> xi
•H P
Q a)

O O u P O t O C M n t - 4 - 4
«
• • • • • • •
- 4 M O O O M O t o o p u p _4
i
— 1o p o p CM CM i— ICM i— |

+

Eh
C\i
O
O

i

o
P

CD

rH

a)

o p

•

xi p
O o

.--H

•H Sh
CP

u p \ Q t o u p -4-1— 1 u p - 4 to
• • • • • • « • «
t>-\0 t o O o t o rH
i i 1

p-\

P

UP
i
—I

—!—

U
Xf
CD

P
P
-p
sd
o
o

CD -P
P P —»
C
m CD co
cd s P
P P
CD c
dO
^ CD-Xi
•H U —•
E
hp

o

—!

P

On
0)
i
—
I
£>
cd

Eh

O

i
—1
•H

O

CO

oo

op up to
to O O
rH CM - 4 v O 4 0 4
i CM - 4

P
CO

o
o
p

PQ

0
O

.-f

-53-

As could be expected there were variations in
the amounts of carbon dioxide released from both the
treated and untreated soils from time to time.

It was

felt however, that a comparison between the magnitudes
of carbon dioxide produced by the treated soils and that
produced by the untreated soils for a given period of
time (the quantity produced by the untreated soil was
taken to be 100 percent for the time interval under con­
sideration) gave a valid index of the state of microbial
activity in the soil.

Of course, these variations do not

take into account the micro-variations which exist through
smaller increments of time.
The data on the redox potential measurements made
simultaneously with the carbon dioxide production measure­
ments are presented in table 10.

It was possible to ob­

tain potentials of remarkably close magnitudes for the
soils within each type so that the variations within each
type are comparable.

It can be seen that there is a

tendency which is especially noticeable in the untreated
soils for the potential to rise with time.

This was

probably due to increased aeration caused by a slight
drying of the soils.

The rise in potential is most pro­

nounced in the sandy Oshtemo'soil and least in the muck.

•
OA
d
o
p
CO

•
O

•
w
p
1— I

CM

o

to

nO

NO
NO
-4

O

UA

4

4

oa

H
OA

UA
O
OA

O
i— 1
OA

UA
1— 1
OA

OA
i— 1
rA

NO
OA

O
OA
OA

•to

CM

4

NO
-4

nQ
nO

NO
1— I

4

O
vO
-4

d
cq
•

o

>
*H
_n_t
rH
•H
s

H

CD
>
•H
P
•H

•
oa

CO

nO

o

•

d
•rH

o
d
S

l— 1
ctf
*H
P
d
0
p

i— 1

UA

to

to

to

-4

4

4

UA

OA
O

O
On
i— 1

CM

«
i— 1

CM

O-4

O
Pn

-4

CM

On

to

•to

ON

4
ON

-4

CM

CM

UA

OA
UA

UA
r4

to

i— 1

!>4

to

CM
to

to

4

4

4

UA

OA
O
OA

4
O
OA

4
O
OA

O
OA

OA
oA

i— 1
4
OA

OA
4
OA

4
4
OA

O

o

OA

to

O

CM

to

OA
OA

t>~
4

CM
to

O

to

to

O

to

4

4

C'4

to

4

to
to

OA
ON
1— 1

UA

1— 1

OA
ON
1
—1

to

rH

O
ON
rH

t>-

to

rH

i— 1

UA
On

o

UA
ON

ON

0ON

I>ON

CM

CM

NO
ON
CM

CM

OA
NO
UA

nO

I— 1

o

UA

CM

1— 1
OA

CM

4

o

Pi

X
o

T1
0
Ph

•
oa

o
S
0
p
P!

•
cm

CO

o

•
1— (

oa
ua

t>UA
UA

UA

UA

UA

O

UA
UA

nQ

ON
UA

UA

UA

UA

UA

O

o

UA

OA
O4

OA

O
UA

u\

UA
UA

O
UA

CM
CM

NO

ua

UA

UA

O
UA

to

-4

UA
OA
4

nO

UA

O

CM

CM

OA
4

O
4

4

O
4

On
OA

UA

to
CM

O
4

to
to

to

o

UA

o

ua

-4

UA
OA
4

o

rH

OA

-4

o

to

4

•}f

Redox

potentials of Oshterno, Muck, and Brookston soils after treat­
ment with 1-3 dichloropropene and 1-2 dibromoethane.

-54-

4

J>UA

!>4

O
ON
OA

u

Table 10.

0 P

-p

a
CD
P

CO
d
d

<D oi o
g psS

*H S-t'— '
Eh P

i— 1

NO
1— 1

4

CM

O
O
4

-55-

•
c'N

u-\
to
-4

O
O n
-4

IT\
ON
~4

ON
-4

♦
CM

CM
O
CH

i— 1
■— 1
c^

1— 1
o~\

60
rH
<r\

•
i— 1

CM
-4
tH

CM
-4

NO
-4
cn

O
tf\
OA

CM
to
-J

ir\
-Co
-4

rH
ON
-4

O
O n
-4

£
O
P
(0
o
o
«.
H
PQ

0
p
r~t

o
>

•rH
•H

a
CD

>

•
o^v

£

•H
i
—ctf
I
•H

o

.
CM

£

•

P
£

rH

.•
1— 1

tf\
OrH

i— 1
to

-4
O

O
i I

rH

r^v
■60
rH

cH
60
i 1

•H
O
0

CM
i 1
CN

CM
i 1
OA

0
0

—

O

0

— —
C^

—

£
•H

P

O
Oh
«
o
"d
<d
cd

Ti
0
0
£

•
cr\

o

rH
to
IT\

NO
•60
ir\

CM
ON
ua

O
a

0
p

(continued)

,£
0
O

•
CM

1
T
\
£>-4

•
rH

*

O

, O'
o^\

ON
NO
-4

CM
On

O

NO

-4

-4

[>•

i
p
\ o
o
ON
-4

0
P
£
0
S
P
0
0

U

£
O
i—!

i—1
O

p £'-'•
<P a> to

tDSB
p

£

0

ctf o

g

0 ,£

•H Sh—"
Eh P

X

o
•H

X

60
OA
UA

p

•H

X

l

CM
1

rH

rH

H
O

O

oa

i—1
a

H
a

UA
.
O

ua

•

—1
«H i

O -4 O
-4 60 o
60 o
1—1

0
£
0
r£
P
0
o
a
o

P
fctO
£

u
0 p

Table 10.

0
£
0
£

0
£
0
Oh
o
£
ft
O
£
O
i—1

0
X

Eh
-it-

.

O

check, 0.5 nil of distilled water

*H
P
•H
0
O
Oh

•
CM

< r\

-

56 -

Both the redox potential and carbon dioxide
production data are graphed for each soil and treatment
in figures 12 through 17.

In all cases where the soil

was fumigated, there is an initial depression of the
carbon dioxide produced followed by a rise above that
of the untreated soils after approximately 40 hours.
The rise is somewhat earlier in the dibromoethane
treated soils than in those treated with dichloropropene.
This might possibly be explained by a more rapid hydrolysis
of the former forming ethylene glycol which is available
as a source of energy for the microorganisms.

The even­

tual rise in the carbon dioxide production is also greater
in those soils treated with the ethylene dibromide than in
those treated with the dichloropropene.

The magnitude of

the rise is greatest in the muck soil followed by the
Brookston and then the Oshtenio.

It can be seen that the

high carbon dioxide production was sustained in the
fumigated muck and Brookston soils throughout the length
of tnis experiment (1000 hours).

The Qshtemo soil

returned to its "normal” dynamic equilibrium after
approximately 400 hours.
The redox potential of the soils dropped within
an hour after fumigation.

That this drop was not due to

the addition of a liquid to the soil can be seem from the
fact that the untreated soils did not show a drop in
ootential
with the addition of a quantity of water equiv_L
1
alent to that of the fumigant.

There appeared to be no

-

57-

£

fH

ft

1

1

3

llTL

rf

HIE it!

1

IJM E M O JJR S i

ffi

I

i
i

:

i t:

It

4l

uih

I Ofi,„

TIMF

(HOURS)

-

H
1

J\

62 -

Bf

-63-

significant difference in the potential drop between
fumigants, but the drop was greater in the muck than
in the soils containing less organic matter.

The drop

in potential leveled off followed by a second drop when
the carbon dioxide production rose to a maximum.

This

second drop was accentuated in the Oshtemo soil,
Ammonification and Nitrification in Soils Fumigated With
Dichloropropene and Ethylene Dibromide
Because the data on carbon dioxide production and
redox potential indicated that there was an increase in
microbial activity and that the oxidation-reduction state
of the soil was altered after treatment with these two
compounds, an attempt was made to determine the effect
of these fumigants on the quantities of available nitrogen
in the soil and the forms in which this nitrogen existed.
Investigations on the nitrogen nutrition of plants
(25) have shown that there are three important factors
which must be considered with respect to the nitrogen
supplying power of soils.

They are, 1, the total amount

of nitrogen which can become available to a plant through
a period of time, 2, the form of tnis available nitrogen,
and 3, the rate of mineralization of the organic nitrogen
or the regeneration of the nitrogen after the supply has
been reduced to a minimum because of plant feeding or
leaching.

In order to study the effect of fumigation

on the regeneration factor as well as the others in the

-64-

Oshtemo, Brookston, and muck soils, the soils were
first leached with distilled water to remove the nitrate
nitrogen.

All the ammonium nitrogen was also removed

except for a small amount which was adsorbed by the
colloids.

The leaching was accomplished in 500 ml.

spherical glass containers with an opening at the bottom.
The soils were then immediately brought to the moisture
equivalent and fumigated with 0.5 ml. of 1-3 dichloro­
propene and 1-2 dibromoethane by injection of the compounds
into the soil mass 1 cm. below the soil surface.

The soils

were kept at the moisture equivalent throughout the study
by periodically adding enough distilled water to bring the
soil and container up to weight.
The soil was then periodically sampled and tested
for ammonium and nitrate nitrogen.

The testing methods

used were those described by Peech and English (32),
that is, the use of brucine for the determination of
nitrate nitrogen and a modification of NesslerTs reagent
for ammonium.

The determinations were compared with

standards in a photoelectric colorimeter.

A modification

of the sampling and extracting procedure suggested by the
above authors was used.

Instead of extracting the soil

in an air dry condition with sodium acetate extracting
solution, it was extracted in the moist state immediately
after sampling.

It was felt that this would give a truer

picture of the state of the ammonium and nitrate in the

-

65 -

soil at the time of sampling because the aeration and
time necessary for drying was bound to alter the nitrogen
status.

Approximately 5 gm. of soil was removed from the

container and placed in an Srlenmeyer flask containing
50 ml. of the extracting solution (10% sodium acetate
buffered at pH 4.$ with acetic acid).

After shaking the

flask for two minutes, the contents was filtered through
Whatman ^40 filter paper.

The determinations were made

on the extract and the soil remaining on the filter paper
was dried in an oven and its dry weight determined.

The

amounts of ammonium and nitrate were then calculated on
the basis of the oven dry weight of the soil.
Table 11 gives the data on the amounts of ammonium
and nitrate nitrogen present in the soils after 2 days,
7 days, and then weekly intervals from the time of fumi­
gation.

Periodic tests for nitrite nitrogen using the

sulfanilic acid-naphthylamine method (19) showed no
significant accumulation of this form in any of the soils.
The greatest amount recorded was 2 p.p.m. and this only
at one week after fumigation in the muck soil.

Despite

the fact that the brucine test for nitrates included
nitrites, its use seemed to be warranted because of its
rapidity and accuracy and the fact that nitrite concentra­
tions were very low.

It is apparent from the data that

treatment with dichloropropene and ethylene dibromide
retarded nitrification in all three soils.

This resulted

-

CO
i— 1
•rH
O
CO

PA

66 -

O

o
523

•

o

O

•

o

O•
o

o•
o

to

O•

O•

O•

rH

rH

rH

i—1

OA
•
-00
1— 1

ua

•
-4"
CM

-4
•
ON
i— !

OA
•
to
1— 1

NO
•
1— 1
CM

PA

UA

CM

OA

NO

•

•

ON
rH

CM

•to
•

•

o•
1—1

to

i— 1
•
c1— 1

1— 1
•

UA
•

1— 1

1— I

i— 1

i— 1

OA

•

rH

0
r-^ "Jfr
O
3
*
S Q)
P
xJ P
^ XI
cd P
CD
- O
P S

p
p

-4

XI
p
0
o

a
o

i— i

p
X

•

o•

i— i

on

O

•
«H

cd

p
o
Eh

•H
Q

o o
-P P
03 X>
^ -H

o

S3
£3

!>•
ON

•
•to
(— I

•
-4
CM

•
rH
CM

O

O

O

to

•
-to

CM

•
"00
rH

rH

CM

O

O

-to
9

to
•

rH

rH

OA
•
-to
iH

•

O

O XJ
O

P cm

H
*H
PA
O O
ra S

OQ 1

rH

*>

O xi
B 3
CD Cd

p
Xi CD
CO P
O

0

O

o

o

o

rH

rH

OA
•
•to
CM

NO

OA

NO

•

•

9
I-1

•

rH

•
t— 1

•
i— 1

OA
•
i— I
CM

r— 1
■
rH

OA
•
i— 1
CM

OA
•
CM
CM

i— 1
•
-to
i— 1

rH
9
OA
CM

i— 1
•
O
CM

-4
■

NO

P

0

Eh

d,

S5

O

a
/-■■■i

Sh
Pr

0

Eh

O

Ph

<
&q

P

XJ O
CD P
Xi P
O O
cd P
CD O
i— 1 i— 1

O
•

04
Eh

>>

p
xi

-4
XI

• S3
bO
.id

O
rH

P i— 1
0 cd
p. p
o
S Eh

si
o
•H

Q

9

g
&q

O

.

rH

Eh

I>-

rH

1-1
•
ON
CM

•

l>CM

OA
•
nO
rH

XI
CO

O

O
•

rH

i— I

•
e^
i
—i

•

-to
CM

•
to
CM

rH
•
O
OA

•
to

-4

-4

oa

NO

NO

rH
O

rH

rH

•

xi

p o

■

O -H

SxD

X*
cd
-P o a
cd i
X* rH
P Xl
O -P

<r\
o
S3

p

•

O

-to
•
-4

i— 1
•
i— 1
i
—1

•

rH

•
-4
rH

O

O

•

-4
•

-4•

nO

•
1— 1

to

NO

i— 1

CM

•H

1— 1

o

OA

O

O

Xi
0

-4

P
p £
cd
P P
CD O
P *H
CD p
b0 Cd
0 txO
P *H

o

cd

XI

0
P
p
P
P3

rH
P
P
O
Eh

o

•

rH

o

•

rH

o

•

o

•

CM

CM

to

i— 1

-4
•

N0

OA

to

rH

rH

•

•

•
1— 1

•

CM

-4

•
[>rH

•
rH

•
r— 1

•

CM

OA

-4

ON

UA
i
—1

rr— i

OA

ON

CM

iH

•

o

•

•
1-1

•
t— 1

-4-

~4

•

•
Oi— 1

§

0 C
h

b0
O P
P 0
1"1 -M
1^
-M
•H Ch
S

cd

P P
•

0 O

H
rH

P *H
<H P
P P
bO
0 *H

0
i— 1

rO

cd

EH

a a

•H 3
Eh <H

CO
!>■»
P
X5
O

CM

0

C

£
H

D
CM

C

t
OA

c
-4

e

r
UA

n
nO

s

:
"CO

-67-

o

o•

s

rH

4
IP
P

o»

OH

0
a
0
p
■p

0

CM

r\
u
s

U

1— 1
cd

o•

P

P

OH

o

•H
Q

o
Eh

TREATMENT

rH
•H

o

0

p

0
a

>»

O

S-t
a.

o

P
•
hO

-4"
P

U
0

i— 1
0

ft

P

■H

Q

\D
•
rH
CM

•

-4*
•
OH

to
•
rH

4

CM
•
OH

UH

UH

to

4

CM

•

•

UH

to
•
to

rH
•
rH
i— 1

•
o
1— 1

to

-4

-4

NO

o
4

i— 1
•

UN
•

UH

NO

•

•

•
rH

ON

4

UH

-4

4

•

O•

OH

CM

UH

rH

0H

-4

i— 1

UH

UH

to

•

•

UH

•
to

•
0H

•

•

E>-

-4

UH

UH

UH

O

OH

CM
•
4

UH

i— 1
•

i— I
•

CM
•

UH

UH

•

UH

UH

UH

-4

O
i— 1

•
o
1— 1

•
IH-

•oo
•
o

o•

O

to

to•

CM

o

vO

nQ

1—1

OH

CM

UH
•
NO
NO

UH

UH

rH
•
CM

OH
•
O

O-

UH
NO

OH
•
CM

•
0H

NO

NO

UH

E>-

i—1

OH

CM

•
on

•
OH

O

O

on

Eh

OH

CM
•
4

4

w

oh

o• ■

UH

rH
■

o•

•
rH

UH

CM

pcj
PQ

to

OH
CM

o•

o

P

•
rH

P
o
E-h
CQ
o

o

o

•
1-1

o

Jh

1— 1
p

O

oh

O

0

to

o

•

UH
NO

*

O

•
CM

•

OH

UH

•

!> -

NO

NO

i— 1
•

rH
•
CM

o•

to
C-

•

S'
f=H
on
O
P
P
0
p

4

0

P
p

0

u

o•

to

1— 1

i—1

OH
•

•

o•

CM

4

OH
•

-oo
•

oh

un

nO

CM

CM

i—!

O-

ON

UH

CM

CM

OH

-4

CM
•

UH
•

O

i— 1

ON

to

CM

■

•

•

•
ON

•

•

-4

•
i—!
-4

4

4

CM

CM

O

nO

•

•

■
UH

•
c *-

•
r -

to

•
c --

OH
•

OH
•
ON
4

•
to

EH-

E>-

r— 1

UH

\Q

•

p

rH

£

1—1
cd
P
O

P
0
3
a
•H
£
O
o

Eh

in a
0 o
p *H
Ch

0

>>

.p

cd cd

0
(
—I
cd

Eh

tn

0 -H

0
•H 3
EH Ch

O

4

•
vO
i
—i

i— 1
•

CM

nO

to

OH

-4

CM

OH

•

o

UH

4

•

•

UH

ON
4

I>~

to

Jb*1
0
0

cd
P

£

CM

1— 1

-63-

o

OA
O
s

•
OA

-4
03
S

o

•

o

150
•
4

0A
•
MO

rH
•
1-1
i— 1

•
C'MO

CM
*
ON
ON

rH
•
-4
<— 1
rH

oa

O

•

o•

-4•

r>-

o
1— 1

t\2
i— 1

-4
•
O n
i— 1
i— I

•

oa

oa

MO
•
H
i— 1

MO
•

O

MO
•
-4
i— 1

MO
•
MO
-4

oa

-4
■
NO
1— 1

150
•
40
i— I

i— 1
*
MO
On

-4
•
O
i— 1
i— 1

UA

-4
•

150
m
NO
CM
rH

CO
•
to

-4• '
•
MO
to
i— 1

i— 1
•
r— 1
rH

o•

0A
•
1-1
CM
rH

-4
•
i— 1
CO
i— I

CM
•
ON
I— 1
I— 1

t>•
r-

-4
•
ON
OA
i— t

o

0
d

0
&
-P
0
o
a
Cn
O
5H
rO
•H
Q

i— 1
0
P
O
£—i

1— 1
•H
oa
o
CO a

o•

TREATMENT

o

0
d
0
PH
O
u
Ph
o
u
o
1— I
X!
o
•H
Q

-4
03
• S
hO
M
U i— t
0 0
Oh P
o
E-t
S

W

o

o

0A
«
OA

CM
•
tH-

1— 1
•
H
i— 1

i— 1
•
j— 1
i— 1

to
•

CM
•
O

-4
•
1-1

•

1— 1

ua

MO
•
150
CM
i— I

i— 1

O
C\i
i— 1

40
•

UA

UA

oa

is
"d

oa

-4

o o

150
•
P^\
I-1

oa

•
0A

UA

UA
ca

1— 1

oa

•
CM
-4
rH

•
c\i
r^v
i— 1

CM
•

•
to

o

m
to
rH

1— 1

UA
I— I
rH

o

oa

rH

0A
•

CO
i
—1

•
ON
150

o

rH

to

ca

•
CM
i— I
i— I
•

UA
O
I— 1
-4
•
i— 1
i— I

UA
•
O
i— 1

O

OA
*
CM
OA
i— 1

o

•
On
4
i— I

40
•
CM
4
1— 1

CM
•
CM
ON

rH
•
NO
40

J— I
•
CA

O

•
I-1
-j"
I-1

ca

O

o•
oa

Til
0
P

-4

0
0
P
P
H
d>

1
—1
0
p
o

TJ
0
d
d
•H

■to
•
-4

UA

o

ua

\0
•
-4

oa

-4"

ua

-4•
O
MO

-4*

0A

•

4

•

o

to

1— 1
ON

I—

1

150

n

150
-4

oa

CM

i— 1

O

CM
j— I

MO
CM

ua

ua

-4"

UA

toM0

MO

UA

O

oa

M0
•

10-

UA

O
O

rH

UA

CM
i— 1

CM

i— 1

1— 1

CM

OA

-4-

UA

•

•

m

OA

O

UA

rH

UA

l— I

<r\

JO-

•

*

•

EH

•

•

•

•
UA

•

o•

O

•

•

U\

150
m
ON

CA
•

0A

OA

i— I

i— I

4
i— I

MO

[>-

«
ON

UA

•
i— 1
-4

rH

•
tCM

P

d
o
o
u
0

•
rH
i— 1

0
i— 1
£5
0

4)

d

o

P -H

<H P
0 0
h.0
0 *H
S £
*h d
4 4)

O

0
t>»
0
40

0
0

CM

rH

£
to

Average of two determinations

hi)

-69-

in large accumulations of ammonium nitrogen for at least
eight weeks after treatment.

There was little evidence

to indicate that this condition would not prevail for
extended lengths of time beyond the eight weeks.
The nitrogen regeneration graphs developed from
these data and presented in figures IS, 19, and 20, more
clearly demonstrate some of the other relationships.

It

can be seen that there was a steady rise in the available
nitrogen present in the soil after leaching until a
maximum was reached.

From then on, there was a fluctu­

ation around this maximum with time.

This was to be

expected and is a function of the dynamic nature of the
soil organisms.

The height of the curves or the maximum

nitrogen made available in any given soil is a partial
function of the quantity and nature of the organic matter
present.

Thus the muck soil regenerated more available

nitrogen than the Brookston soil and the latter more'than
the Oshtemo.

However, within the Brookston and Oshtemo

soils, fumigation raised the total amounts of available
nitrogen somewhat above that present in the untreated
soils.

The dichloropropene was more effective in

accomplishing this than was the ethylene dibromide.

This

difference in the total available nitrogen was not as
apparent in the muck soil.

Perhaps of greater significance

than the total amount of available nitrogen in the soil
as affected by fumigation was the rate of regeneration of

-

71 -

QWDE

±:

+

T-

gfiiitii
Hi

m

r

'* - 7 2 -

-73-

this nitrogen.

It can be seen from the regeneration

curves that slope of the line is much steeper in the
curves representing the fumigated soils than in those
representing the untreated soils.

This rate is especially

emphasized in the soils treated with dichloropropene.
This accelerated rate of regeneration would probably be
of benefit to plant growth if the seeding took place when
environmental conditions were not favorable for nitrate
production.

It is also conceivable that the accelerated

rate of regeneration could maintain the supply of readily
available nitrogen to the plant as the plant roots take
it up from the soil.
The Effect of Fumigation on the Nitrification of Ammonium
Sulfate added to Soils
Much of the nitrogen added to the soil as fertilizer
is in the form of ammonium sulfate, and it is Apparent that
fumigation will have its effect on the nitrification of
this ammonium and thus affect the form of nitrogen available
to plants.

An experiment was devised to study the effect

of Dowfumes Nf ¥-40, and MC-2 on nitrification of ammonium
sulfate added to soils.
Quantities of air dry Oshtemo, Brookston, and muck
soils were thoroughly mixed in a rotating drum with enough
ammonium sulfate to bring the soils up to approximately

300 mg. of nitrogen determined as ammonium per kg. of dry
soil.

A quantity of calcium carbonate was added to the

-74-

soils to neutralize the effect of the added ammonium
sulfate.

The soils were then brought to the moisture

equivalent and placed in one-gallon glazed pots.

The

ammonium nitrogen was determined on the moist soil as
previously described.

The soils were then fumigated with

two levels of Dowfume N (equivalent to 40 and 30 gallons
per acre), Dowfume W-40 (23 and $0 gallons per acre), and
Dowfume MG-2 (1 and 2 pounds per 100 square feet). Duplicate
pots were set up.

The actual dosages used were 0.$ and 1.6

ml. of N and MG-2, and 0.3 and 1.0 ml. of ¥-40.

The N and

¥-40 were injected 2 inches under the surface of the soil
from a burette while the MC-2 was applied with a t!jiffy
applicator” under a tar paper cover which was kept sealed
for 48 hours.

The temperature of the soils at the time

of fumigation was 27° G.
After one week, the soils were removed from the pots
and sifted through a one-cm. mesh screen.

Every effort was

made to prevent reinoculation of the soils during this
process.

The soils were returned to their individual pots.

Samples were then taken at 30, 90, and 130 days and analyzed
for content of ammonium nitrogen.

The soils were maintained

at the moisture equivalent with periodic additions of dis­
tilled water.

The results of the ammonium nitrogen deter­

minations are recorded in table 12.
It can be seen that all the treatments retarded
nitrification.

More of the added ammonium was recovered

<H
o

•
rH
o a
-4
1o
& •
1
—
1
0 ___

•
hO

u

C
D
PH
-4

a

to

P

0

a
-p

£

ctS

•rl

*
«H rH
£ e
O
C3 UT\
•

o

O CMi—|
-4 to MO rH
o-\ <r\ <r\ C
M

O -4MD C
M
H O to O
o^p-\CM C
M

C
MO tO U"\
it\-4CM ON
r^ o ^ r^ H

O C
Mt>-rH
-4-O^fY^r-1
p'n o~\c°\ C
M

i—
1
•H
O
0

rH
■H
O CM-4*0
O
rHtO O rH 0
C^CM CMrH

CMrlO-C^
tfN W 0 4 H

a
o

o
S

p
0

•
1—I
s

EH

-P
0

•

O
O

0

o

O O -4 to
rH 4 r \ H H
MrH
*rH P"\ 0^ C
O
0
mj
a
J3

p

0

T$
&

CM'O cm o
1
f\cr\0 CM
c*\<r\<r\cm

0

0

£3

U

O O O <r\
i—
1i—
1On*-T\
P>P"\CM CM

i—
1

jzi •
Pi »
—
1
£ S
o
Q tO
•
vj

u

o o t o 'O
-4-r--u-\cM

u

PQ

C
M4 t O t>u-\CM O to

O -4*\0 to

(AfAO JH

CM CM to CM
IAH0 4
<^vrr\ C\2 rH

O o^cM <r\
-4 P's-4to
n(ACMrl

O -4c"vrH
i— 1i— 1CN'C
-fN
o^\ i—!

C
MM
O -4- C
M
i-C\ UAtO r P'Ni— I

O 4 Hto

o o o o
cr\ O nto
i
—
1

o o o o
O''-to
1—I

o o o o

O CMlA O
rH m o m
P"\CM C
MC
M

a-\a-\cr\(M

-4^0 ~4>-T\

cV7\o'\p\CM

0 rH

•

P •
> rH
o a
Q

■to
•
o

00^00
rH O

0

P

cd
0

P

4 tO rH O
P\ CMrH rH

rt

S3

Table 12♦

U £

0o
P H"—

C
h P

IU

|

treatments

•
1
—
1
•H
O
0

CM-4-vO C
M
vrwO -4“ i—
1
cr\P'\p'vcn

0

fuOcd
0 •H td
—^
S 3'
•H 3
Eh Ch

P'\OMO

1
-1

.

of samples from each of the duplicate

•
0

O -4 0 -4
rH O O O

of two determinations

i—
1
c\z a
i
0 \0

75 -

Average

The nitrification of ammonium sulfate added to Oshtemo, Brookston, and muck
soils, and fumigated with Dowfume N, Dowfume ¥-40, and Dowfume MC-2. *

-

-76-

from the treated soils than from the untreated soils.
This relationship held for the entire incubation period
of six months.

The efficiency with which the different

fumigants retarded nitrification was greater at the high­
er dosages.

Also, Dowfume N and Dowfume MC-2 were more

effective in retarding nitrification than was Dowfume ¥-40.
This might be correlated with the ability of the different
fumigants to disperse through the soil, though an attempt
was made to overcome this difference by screening and
stirring the soils after fumigation.

The general relation­

ship between the kind of fumigant and rate of application
and their effect on nitrification is shown in figure 21.
These relationships are plotted for the Oshtemo soil, but
it can be seen from the data in table 12 that except for
the differences in intensity, they hold for the Brookston
and muck soils.
The ammonium recovery was almost 100 percent of
the amount of ammonium added six months after fumigation
with the higher levels of Dowfumes N and MC-2.

It was

noted that there was an increase in ammonium in the soils
containing great quantities of organic matter after treat­
ment with the above fumigants.

This was probably due to

the increased ammonification coupled with decreased
nitrification after fumigation.

In every soil used and

with every treatment, it was possible to recover more of
the added ammonium six months after fumigation than was

-

77 -

§f

*

it-

-78-

present in the untreated soils.
Field Experiments and Observations
Two 800f x 12T strips of muck soil on the Michigan
State College Muck Experimental Farm were fumigated on
April 14, 1949*

One strip was fumigated with Dowfume N

at the rate of 40 gallons per acre and the other with
Dowfume W-40 at the rate of 25 gallons per acre.

A 121

untreated strip was kept between the two treated strips.
Alternate six foot sections the length of the plots were
planted to lettuce and Henry spring wheat. The crops were
harvested and no significant differences in yield were
recorded between those grown on the treated and untreated
plots.
On Nov. 4, 1949, 400r sections of the same plots
were refumigated with the same fumigants at the same rate
of application.

No nitrogen was included in the fertili­

zation program and Henry spring wheat and Flambeau soybeans
were planted in June, 1950 in alternate six foot strips
running the length of the plots.

During the growing season,

periodic samples were taken from the treated and untreated
plots and ammonium and nitrate determinations were made
on them.

The plots treated with Dowfume N had a slightly

higher ammonium content than did the Dowfume N and un­
treated plots.

Observation of the soybeans during their

growth period showed that the plants on the Dowfume N

-79-

treated soil were making better growth and were greener
than the plants on the Dowfume W-40 treated and untreated
soils.

The differences between the plants on the Dowfume

N treated and untreated plots can be seen in plates 6 and
7.
The soybeans were allowed to dry on the vine and
the bean yields obtained are reported in table 13*
Table 13*

Yield of soybeans on muck soil fumigated with
Dowfume N and Dowfume W-40.
Date of treatment

Treatment

November, 1949

April, 1949

untreated

16.2 bu. / acre

16.4 bu. / acre

Dowfume N

21.1 bu. / acre

27.4 bu. / acre

Dowfume W-40

13*9 bu. / acre

l$.l bu. / acre

The soil treated with Dowfume N on November, 1949
yielded 68 percent higher than the untreated soil.

A

possible explanation of this remarkable increase in yield
may be deduced from the fact that all crops grown on the
muck farm that year showed a tremendous response to
additions of nitrogen to the soil.

The weather conditions

that year were wet and cool far into the growing season
which would retard mineralization of the soil organic
nitrogen.

-

30 -

Plate 6. Soybeans on right on muck soil treated
with Dowfume N.
Plants on left on untreated
soil.

Plate 7. Soybean plants on left removed from
Dowfume N treated plots.
Plants on right
removed from untreated plots.

-31-

Similar responses were obtained for onions planted
on muck soil which was fumigated in November, 1950.
Fumigation was at the same rate as mentioned above, and
the plots were 12T X 200T with an untreated plot separat­
ing the fumigated areas.

Periodic sampling of the soil

gave indications of a higher ammonium content in the
Dowfume N treated soil than in the Dowfume W-40 and un­
treated soils.

The ultimate yield of onions is presented

in table 14.
Table 14*

Yield of onions on muck soil fumigated with
Dowfume N and Dowfume W-40.

Treatment

Yield of onions

Untreated

232 bu. / acre

Dowfume N

327 bu. / acre

Dowfume W-40

290 bu. / acre

The Dowfume N treated area yielded 16 percent more onions
than did the others.

No nitrogen was added to the soil

in the fertilization program, but a response attributed
to a greater quantity of nitrogen available to the plants
can be seen in the greener color of the onions on the
Dowfume N treated plot

(plate 3).

These soils were not fumigated to control any
pathogens.

There was no history of crop reverses on

these soils due to an infestation of organisms and

-

32

-

Plate S. Sight rows of onions on the right
(two sections) on muck soil fumigated with
Dowfume N.
Center two sections untreated
and onions on the left fumigated with Dowfume ¥-40.
examination of the plant roots did not give any indica­
tions that growth restriction on any of the plots was
due to nematodes or other organisms.

Though the level

♦

of available nitrogen in the Dowfume N treated soils
was not materially higher than in the other soils,
analysis of the plant sap showed significantly higher
concentrations of ammonium in those plants grown in the
Dowfume N treated areas.

It is well known that the

relative level of available nitrogen in the soil is not
too indicative of crop response since the plants are
constantly taking this nitrogen up from the soil.

-

33 -

Other factors affecting the growth of plants after
fumigation can also be attributed to the ammonium and
nitrate relationships in the soil after treatment.

In

order to control an infestation of nematodes in his muck
soil, an onion grower in Gun Swamp near Plainwell, Michi­
gan fumigated his soil with Dowfume N at the rate of 40
gallons per acre.

The soils were fumigated in the fall

of the year and were planted to onions the following spring.
Narrow strips of soil were left untreated as a control.
Observations made on the onions from the time of planting
on through the growing season showed that the onions on
the fumigated soils were making better growth and that
they had a deep green color.

Plate 9 shows this onion

as it appeared the first part of August.

Note that the

Dowfume N
Plate 9. Onion field fumigated
Light streak through the center of the picture
is an untreated area.

-

34 -

onions on the untreated soil are a lighter green color
than those on the fumigated soil.

The ammonium nitrogen

concentration in the fumigated soil averaged 34 p.p.m.
while that in the untreated soil averaged 6 p.p.m. at
the time this picture was taken.

The nitrate nitrogen

content of both the treated and untreated soils averaged
53 p.p.m.

Examination of the roots of the plants in the

untreated areas did not show an extensive nematode in­
festation so the differences in growth were attributed
to the difference in ammonium nitrogen content of the
soils •
Towards the middle of August, the onions in the
untreated areas began to surpass those in the fumigated
areas in vegetative growth.

Color differences, though

still noticeable, were less distinct.

Plate 10 shows

typical onions taken from the treated and untreated
soils at that time.

Protein analysis on composite

samples taken from these plants showed that those grown
on the fumigated soil had 27*3 percent protein on a dry
weight basis compared with 19.2 percent for those grown
on the untreated soil.

The final yield of onions on the

treated plots was materially lower than on the untreated
plots though.there was no difference between the two in
the thickness of stand.

The onions on the treated soil

matured earlier than the others and did not put on normal
bulb growth.

This was attributed to the large amount of

-55-

Plate 10, The onions on the right are from
muck soil fumigated with Dowfume N. Those
on the left were taken from untreated soil.
ammonium available to the plants throughout the growing
season.

-56-

DISCUSSION
It has long been considered that the quantities
of carbon dioxide produced in a soil during a given
period of time is an index of the activity of micro­
organisms in the soil.

In the soils treated with

dichloropropene and ethylene dibromide the carbon dioxide
produced by the soil organisms was increased after a
short initial period of depression.

This would indicate

that the compounds are toxic to selected species of
organisms, and those which are not affected increase
their activity because of the decreased competition and
antagonism of the other species.

It seems highly probable

that it is the oxidizing organisms which are most affected
by these fumigants.

One indication of this is the fact

that the bio-electric potential in the soils was lowered
after the soils were treated.

It could thus be considered

that the soils were in a "more reduced” state after fumi­
gation with these compounds.

The length of time which

the abnormally high carbon dioxide production persisted
in the soil was a function of the quantity of organic
matter present in the soil but the reduced bio-electric
potential persisted after the carbon dioxide production
began to approximate that of the untreated soil.

A lag

in the return of the potential to normal is always to be
expected, but in this case, there is evidence to indicate

-

67 -

that though the microbial activity does not indefinitely
maintain its induced maximum, the new biologic equilib­
rium persists for an indefinite length of time.

Evidence

to substantiate this fact exists in the great quantities
of the reduced form of nitrogen (ammonium) which accumu­
lated and persisted in the soils.

The reports of various

investigators showing that iron and manganese have become
more available to plants after soil fumigation with
various compounds could also be explained as a result of
the lowering of the redox potential in the soil since it
is known that both these elements are more available to
plants in their reduced forms (23, 24).
In all cases where the soil was fumigated with
either dichloropropene or ethylene dibromide, subsequent
mineralization of the soil organic matter produced
quantities of ammonium nitrogen which were not oxidized
to the nitrate form.

This has important implications

as to the subsequent growth of plants in these treated
soils.

The total amount of available nitrogen was also

increased though perhaps not significantly so.

However,

in all cases where the soils were treated the rate of
regeneration of the available nitrogen was materially
increased.

It is felt that this fact is of great impor-,

tance with respect to plant growth.

In the temperate

climate regions, many of the annual crops are planted in
the soil at a time when the available nitrogen in

-dd-

relatively high (the total amount depends upon the
environmental conditions and the amount of organic
matter present in the soil).

This, for the most part,

is due to the relatively active mineralization of the
organic matter during the warm days of early spring
when there is little or no vegetation to take up the
nitrogen.

However, when the seedlings start growing,

they rapidly remove this available nitrogen and continued
growth depends upon the ability of the soil to release
more available nitrogen.

If the rate of mineralization

is too slow, more nitrogen must be added to the soil in
the form of chemical fertilizer to carry the plant
through.

With this in mind, it can be seen that if the

rate of mineralization of the organic matter could be
increased, there would be an ultimate benefit to crop
growth.

Dichloropropene was most successful in increas­

ing the rate of nitrogen release in the soils used.
Ethylene dibromide was less successful but better than
the untreated soils except in the case of the muck soil
where the great quantities of organic materials present
seemed to negate the advantage.

An increased rate of

nitrogen release would also be beneficial at times when
a cold, wet spring retarded microorganism activity and
the available nitrogen was leached out of the soils
during winter fallow.

These phenomena were demonstrated

with the increased growth of soybeans and onions on the

-39-

fumigated muck soils of the Michigan State College
experimental Farm during 1950.
The use of Dowfume N, W-40, and MC-2 in soils
effectively decreased the rate of nitrification of
ammonium sulfate added to soils.

The high levels of

Dowfume N and Dowfume MC-2 (1.6 ml. per gallon crock)
practically eliminated nitrification for at least six
months.

Lower doses of these two fumigants and high and

low levels of Dowfume W-40 inhibited nitrification for
lesser periods of time.

This inhibition becomes impor­

tant when it is realized that a large portion of the
mineral nitrogen now added to soils in the form of
chemical fertilizers is added in the ammonium form.

In

normal untreated soils, it is to be expected that most
of the added ammonium will be converted to nitrates
within a relatively short period of time.

In a soil

fumigated with these compounds, the added ammonium will
remain in its original form for much longer periods of
time.

Since the compounds were all effective to a

certain degree in inhibiting nitrification, it could be
concluded that probably the differential effectiveness
between compounds and also between dosages was due to the
varying abilities of the different compounds to disperse
through the soil and saturate it with the vapors.

It is

to be expected that the oxidizing organisms which are
not reached by the fumigant will eventually begin to

-

90

-

multiphy and increase their effectiveness.

However,

the differential effectiveness could also possibly be
attributed to a difference in the severity of action
or toxic properties of the different fumigants.

-91-

PART III
Calcium and Nitrogen Relations with Respect
to Plant Growth
It was shown that fumigation with the compounds
used in this study retarded nitrification and favored
the accumulation of ammonium in the soil. The question
now arises as to how plant growth would be affected with
its primary source of nitrogen in this reduced form.
LITERATURE SUMMARY
Tam, Tam and Clark (4$, 49) grew pineapple plants
on soils fumigated with D-D mixture, chloropicrin and
other disinfectants.

With ammonium as the chief source

of nitrogen, the plants were characterized as having
high N, were dark green, fast growing, and succulent.
In connection with this, it is interesting to note that
ammonium requires no reduction before it can be utilized
in protein synthesis while the nitrate ion must first
undergo reduction.

However, an adequate supply of carbo­

hydrate in the plant is essential for protein synthesis
when ammonium is the source of nitrogen.

Carbohydrate

does not appear to be as limiting a factor when the
nitrogen is supplied in the form of nitrate (44, 53, 54).
Though it had long been considered that only high pH
values allowed for adequate ammonium assimilation, Arnon
and Johnson (6) among others have shown that the hydrogen

-92-

ion concentration has no effect on ammonium or nitrate
assimilation provided that there is no deficiency of
other essential elements.
Concerning ionic relationships in plants, Bear (3)
considers that total cation and total anion uptake are
each equal to a constant, and he suggests that substitu­
tion of ammonium for nitrate may lower the intake of
mineral cations and increase that of mineral anions.
Arnon (5) in a study on the mineral composition of
barley when supplied with ammonium or nitrate as
nitrogen sources found that the ammonium-supplied plants
had a lower base content but were higher in phosphate
than the plants whose nitrogen source was nitrate.

Soy­

beans were grown by Hamner (21) in a culture containing
large amounts of phosphorus and little nitrate.

The

plants showed typical phosphorus toxicity symptoms, but
this condition could be alleviated with small additions
of nitrate to the culture.

These and many other studies

including one by Sideris and Young (45) using pineapple
plants indicate that cation and anion balance are most
important in plant nutrition.

They suggest a need for

high levels of potassium and other cations when the
source of nitrogen to the plant is in the form of ammonium.
Prianischnikov (34) showed that high levels of calcium
supplied to cotton plants whose source of nitrogen was
ammonium allowed the plants to grow extremely well while

-93-

lower levels of calcium retarded growth.

An interesting

effect of ammonium nutrition was cited by Schropp and
Arenz (42) who noticed that in certain instances,
ammonium was actually excreted from the plant roots un­
less the level of potassium was sufficiently high.
An excellent summary of the various aspects of the
nitrogen nutrition of green plants is presented by
Nightingale (29) where additional nitrogen relationships
such as are affected by oxygen supplied to the plant roots
and photoperiodic effects are elaborated.

An important

related factor was brought out by Burstrom (13) who
concluded that in wheat leaves, nitrate reduction depends
upon the photosynthetic process while ammonium can be
elaborated in darkness.
The effects of carbohydrate content of plants on
ammonium and nitrate assimilation and elaboration has
already been mentioned.

From this and other data, Night­

ingale (29) concluded that ammonium nutrition results in
a rapid depletion of the carbohydrate reserves of a plant
if environmental conditions are not favorable for carbo­
hydrate accumulation.

An additional consideration, how­

ever, is the fact that ammonium assimilation is more
rapid than that of nitrate if an adequate supply of
oxygen is present and sufficient quantities of other
cations are available to the plants.

The considerations

might explain why Afanaseva (1) found that sterilization

-94-

of soils with formalin decreased the time of wheat
ripening by four to five days.

EXPERIMENTAL
Growth of Soybeans in Sterile Sand Culture Supplied
with Different Sources of Nitrogen and Varying Levels
of Calcium
In order to determine the effect of different
forms of nitrogen on the growth of soybeans under con­
ditions where there would be no microbial oxidation or
reduction of the forms supplied, the following experiment
was devised.
Sterile nutrient solutions were added to liter
Erlenmeyer flasks containing quartz sand which had been
autoclaved at 15 pounds pressure for two ij hour periods
with a 24 hour interval between treatments.

The nutrient

solutions contained salts recommended by Ellis and Swaney
(17) for the soilless growth of plants.

Soybeans were

germinated by the vertical paper towel method under
sterile conditions and when tjie plumules began to emerge
from between the cotyledons, the seedlings were trans­
ferred to the Erlenmeyer flasks and kept in place with a
cotton plug.

The cultures were aerated periodically by

forcing air through the solution through a glass tube
which was kept in place in the flask and extended to the
bottom.

Distilled water was also added through these

-95-

■Msoybeans were grown.

Oh

O

CM
.
1— 1

CP
•
1— 1

UP
CP
•
rH

Up
CM
•
i— 1

CP
•
1— 1

UP
CP
•
1— 1

O
up
•
1— 1

up
up
•
1— 1

O
vQ
•
I— 1

•

P
P
P

vO
•

vQ
•

vO
•

-4"

-4

-4-

up
•
-4"

up
•

up
■

■co

■Co

■co

-4-

-4

CP

CP

cp

•

•

•

O
S
o
o
P

p

O
o
H

o o
o o
1
—1 rH

o o o o o o
o o o o o o
1
—1 1—1 1—1 1—1 1—1 I—1

o
p
o
•H
0

Xl
P

P

in which

0
o
a
p
p

Sterile nutrient

E
P

solutions

•H
P

o o o
o o o
1—1 1—1 rH

rH

o
o

rH

o
o
H

O
O

rH

O o
o O
1—i i—1

•

p
Xl
bO
•H

P
r-P
hO

0

0
UP o
o
o

o
UP

o

UP

o
o

rH

o

ITS
rH

o
up

£

£

P

P

o
o

o
up

s

f—I

i— I

H

• •H

0 o
O 0
P
o
P
O X3 •H

0

0

s
a
p
p

«H
o

o

!M

t—I

o

N

i—I

o
N

(—I

O O
CM
CM
—I
i
—I I

o
cm

o

o

o

W
W W
i*| |-J rH
-'t-

0
ni

p

p
p

Table 15.

o
o

0

P

0
p
p

•
£H
5 •H

0

P
0

P

P

*H

0 0 0
P P
•H *H •H
O O O
0 0 0
O O o
•PH *PH •pH
4

■H
P
O
ci

•H P P
P 0 P
P o 0
O s P
PP 0
o 0 0
p
p p ^
•H O

0

up

Xi 0
P P t5
P P
0 0 0

00
00
P
0 P*HP
P

O

•H O
c: •H i
— 1-

P P bO

0O
0 0S ' o
Q O up
P

P

O
•H
P
P

rH

O
CO

CM

rp

-4*

up

vO

O-

-CO

-x-X- 7T

X

-

96

-

tubes in order to keep the solution levels constant.
The nutrient solutions as indicated in table 15
were so made up that the variables were the form of
nitrogen and the levels of calcium.

Among the other

cations, the levels of potassium and magnesium were kept
constant.

Phosphorus was also present in the solutions

and the remainder of the anions were primarily sulfates
and chlorides.

Equal amounts of micro elements were

added to each solution in the form of ferric sulfate,
manganous chloride, boric acid, and copper sulfate.
The flasks containing the soybeans were then
placed in a green house.

There were three replications

of each nutrient solution.

Plates 11 through 14 show

pictures of the soybeans after 1, 2, 3> and 4 weeks of
growth.

It can be seen that after one week^ growth,

there was no visible difference between the plants re­
ceiving the ammonium and those receiving the nitrate.
The plants growing in the amino acid solutions were
definitely retarded in growth and had a deeper green
color than the others.

There was no indication of

differences due to the different levels of available
calcium.

After two weekTs growth, the plants on the

nitrate substrate began to grow more rapidly than those
on ammonium and chlorosis was beginning to show up in the
leaves of the ammonium-supplied plants at the lowest level
of calcium.

After three weeks, the nitrate supplied plants

-

97-

Plate 11, Soybeans in sand culture one week
after transplanting. 1. nitrate and 50 ppm Ga,
2. nitrate and' 100 ppm Ca, 3* nitrate and 150
ppm Ga, 4* ammonium and 50 ppm Ca, 5. ammonium
and 100 ppm Ca, 6. ammonium and 150 ppm Ca,
7. amino acids and 50 ppm Ca, S. amino acids and
100 ppm Ca, 9. amino acids and 150 ppm Ca.

Plate 12. Soybeans in sand culture two weeks
after transplanting. Same legend as plate 11.

-

93-

Plate 13• Soybeans in sand culture three weeks
after transplanting. Same legend as plate 11.

Plate 14* Soybeans in sand culture four weeks
after transplanting. Same legend as plate 11.

-

99

-

continued a vigorous growth pattern while those on the
ammonium substrate had put on no new vegetative growth
since the previous week.

They also showed severe

chlorosis at the lower levels of calcium and incipient
chlorosis at the highest level.

The amino acid supplied

plants, however, began to put on some vegetative growth
and were of a deeper green color than the other plants.
At this time, solution samples were withdrawn from
the cultures and tested for the presence of nitrate and
ammonium.

There was no change in the nitrogen status of

those solutions which were made up of ammonium or nitrate
but the amino acid solutions indicated the presence of
approximately 20 p.p.m. nitrogen in the form of ammonium.
Since there was no evidence of microbial activity in
these solutions, the presence of ammonium was attributed
to acid hydrolysis of the amino acids which yielded the
ammonium.

Thus, the plants in the amino acid cultures

could be considered to be on nlow level" ammonium
nutrition.
After the fourth week of growth, the nitrate supplied
plants were lush and vigorous while there was complete
necrosis in the ammonium supplied plants.

The only green

tissue visible on the latter was on those supplied with
the highest level of calcium.

The amino acid-supplied

plants (low level ammonium) were growing well, had a deep
green color, and had begun to blossom and set pods.
After four weeks, the plants were cut and the tissue

-100-

was analyzed for protein content.

Portions of the tissue

were ashed and the ash analyzed for calcium, potassium,
and magnesium.

The protein analyses were run using a

modification of the Kjeldahl process and calcium and
magnesium were determined by the methods accepted by the
A. 0. A. C. (4).

The potassium determinations were made

with the use of a flame photometer.

The results of these

analyses are presented in table 16.
It is interesting to note that in the nitrate
supplied plants the calcium content increased with an
increase in calcium in the substrate.

The increase in

calcium was accompanied by a decrease of the potassium and
magnesium.

The higher levels of calcium in the nutrient

solution also produced more vegetative growth.

There was

little difference in the protein content of the plants at
the different calcium levels.
The ammonium supplied plants had a very high protein
content which was almost double that of those supplied with
nitrate.

However, plant growth was at a minimum.

This

could be attributed to the fact that great quantities of
carbohydrate were necessary for the synthesis of protein
under the given conditions of ammonium nutrition.

The per­

centages of protein decreased slightly as the calcium in
the substrate was increased.

In these instances just as

when the plants were supplied with nitrate, an increase in
the calcium content resulted in a decrease in the potassium
and magnesium content.

However, at the lowest levels of

Table 16.

Composition

of Soybeans Grown in Sterile Sand Culture with Different
of Nitrogen and Three Levels of Calcium*

Forms

-101-

m
S
cd
ft
f*0
'—

£P

e^t

i—
1
co
•

C
M
C
M
•

O
\D
co
O
O
•

i—
i
O
CO
O
O
•

-C
O
ON
1
—
1

ON

1—1

CO

H

d

•

ON
CO
•

•

UN
id
O
o

C
M
i—
1

h

m

CO
•

UN
iH
i—
|

o•

O
-d
O
O
O
•

C
M
NO
O
O

o•

O
a

LTV
1
—
1
«

LTV
d
•

d
-d
•

-4“
C
M
•

H

On
d
O
O
O
*

NO
-d
O
O

o

o•

o
oa

o
oa

o

c,
to
cd

ih

H

-p

CO
•

CO
C
M
^d
O
O
•

IH
UN
C
M
O
«

UN
C
M
C
M
O
O
«

C
M
-d
•

-d
-d*
•

d
IH
o

ON
C
M
•

IH
CO
•

CO
d
a

to

CO
On
-d
O

UN
•co
UN

ON
ON
o
H
O
•

o
CO
o
o
o•

to

o
o
o•

H
IH
O
O
O
•

CO
UN
CO
o
O
•

to

-d
IH
•
H

o
ih

H

H

1
—
1
•
-d
CO

ON
•
IH
C
M

ON
•
-d
C
M

O
O
i—
1
•

CO
O
H
•

IH
NO
i—
1
a

cd
o

cd
o

•
a
*
ft
•

a
•• a
a *
3 ft
•H *

•

ft

CO
a

cd

H

ft

ft

H

M

0}
ft
O

o

UN
C
M
r—
1

-d
O

o
oa

•p
Cll
o
cd
o

cd
O

o•

ft
■H
C
D

£H
•
vO
i—
I

O

ft

o
o•

H

•

CO

-d
a

NO
-d
•
On

H

CL.

• co-—
p ft C
O
£ o S
p cd

•
i—
i

CO
-d
cO
*
i—
I

C
d

cd
O

ih

NO
h

ft

ft C
(—
i hi)
Q O—

o
ft

O
•H
p

ft
I
—1

cd

o

cd
o

•
••
C
D •
P ft
cd •

0 ft
P *
cd f t

P
•H O

P O
•H O

•H UN

SH

.3 H

ao
<tj UN

•
C
M

•
CO

•
d

ft ft

o

C
O

d
•
H

•
a
•• #
0 ft
p
•
cd f t

a

*

H

•

d

to

•m &a
ft

ft

p

o

••

•

|

H

•H f t
ft •

O ft
a

*•
a
3
•H

ft ft
O
a o
o

e

H

•
ir\

ft ft
O
a°

IH
C
M
IH
•

• • cd
C
DO
•H •
ft a
cd •

ft
o •
ft ft

a un
<3 H

•H
a
<q UN

•
NO

•
IH

o

-102-

i— I

O

to

o

o

I—I

to
to

rH

O
i— I

o
o

0
O

o

P

o

■H
-P

cd
o

1
—I
P"\

o

o

o
o

o

•H

rH
P.
0

«

0
0

o

E>-

P
Pi
Eh
0

Pi
-P

i-f\

'TJ

(
—I
\D

0
P

Ch
O
0
•H

0
>>

5
=
1

rH

*H

cd

p

p

o

o

•o

o

<Pc*
0

p
•rH
0

vD
0

rH

cd P .

cd P.

OP.

op.
p

•

•H

■H O

•

•H O
B

P>

0
fH

rH

to

LO

'=^» i— I

o

p.
B

o

o

-103-

calcium in the nutrient solution, there was no more calcium
in the plant ash than was present in the seed.

It can be

concluded that at the low level of calcium which was
supplied to the plants and with ammonium as the source of
nitrogen, little or no calcium was taken up by the roots.
Observations made during the growth of the plants and the
fact that there was some calcium taken up by the plants at
the highest level of supply (130 p.p.m.) would tend to
indicate that the plants would show better growth if their
source of nutrients was higher in calcium content.
The plants which were supplied with amino acids (low
level ammonium) contained approximately 1& percent more
protein than did those supplied with nitrate and matured
earlier.

However, they did not put on as much vegetative

growth as the latter.

The relationship between the amount

of calcium supplied and that determined in the plant ash
was not as precise as in the previous cases but, this could
be attributed to the fact that the amount of ammonium avail­
able to the plants was an unknown quantity and undoubtedly
varied from flask to flask.

The cation relationships in

the plant ash however, was the same as in the nitrate and
ammonium-supplied plants.
Recalculation of the mineral content of the plants on
the basis of the milliequivalents of each cation determined
in the analyses brings out some interesting relationships,
(table 17)

-104-

Table 17* Cation contents of soybeans grown in sterile
sand cultures with different forms of nitrogen and three
levels of calcium with the data presented in terms of
milliequivalents per 100 grams of dry matter.
Milliequivalents
Solution

JLt Nitrate and 50 ppm Ca

2.
3.

Mg

214

95

250

539

” ioO

n

I!

235

43

135

513

»

it

150

«

It

370

33

103

516

13d

110

339

537

5.

w

« 100

6,

T!

tt

150

n

ti

135

107

320

612

tt

TT

220

60

312

592

243

43

132

423

230

41

112

433

293

36

109

433

7. Amino acids and 50 ppm Ca

9.

K

ti

4- Ammonium and 50 ppm Ca

3.

Total

Ca

tf

»

" 100

ii

n

tt

it 150

tt

tt

The uptake of calcium, potassium, and magnesium by
the nitrate supplied plants was approximately equal to a
constant with the potassium and magnesium showing propor­
tional decreases as the calcium increased.

The cation con­

stant of the ammonium supplied plants was higher than that
of the nitrate supplied plants.

This could probably be

attributed to the fact that the plants did not put on much
vegetative growth and the carbohydrate content was materially
decreased.

Where the nitrogen source was amino acids (low

level ammonium), the cation constant was lower than in the
nitrate supplied plants.

This would tend to indicate that

-105-

ammonium enters into the relationship to the extent of
decreasing the uptake of the other cations and would
signify that greater quantities of available mineral
cations are necessary for the MnarraalM growth of soybeans
when their source of nitrogen is ammonium.
The Relationship of Calcium to Soybean Growth on Fumigated
Soils
It was apparent that ammonium affected the mineral
uptake of plants and that higher levels of calcium aided
plant growth, thus, an experiment was set up to determine
the effect of a high level of calcium on the growth of
soybeans in fumigated soils.
A soil was composited consisting of 50 percent clay
loam and 50 percent by volume of an acid peat (pH 5*6).
The soil was placed in one gallon crocks and a quantity of
ammonium sulfate equal to 100 p.p.m. N on a dry weight soil
basis was added to each pot.

In addition to this, 300

p.p.m. of calcium in the form of calcium chloride was added
to every second crock and the soil was thoroughly mixed.
The soils were then brought up to the optimum moisture and
four replicates at the high and four at the low calcium
levels were treated with Dowfumes N, W-40, and HC-2 at the
rate of 1.6, 1.0, and 1.6 ml. per gallon crock respectively.
Analyses for exchangeable mineral contents of the soils
indicated that they all contained approximately 37 p.p.m.
potassium and 49 p.p.m. magnesium.

The soils to which no

-106-

calciurn had been added contained approximately 74 p.p.m.
calcium and those which received the supplementary calcium
contained approximately 375 p.p.m.

The soils were allowed

to stand for one month after the treatment and were then
screened and returned to the crocks.

Analyses for avail­

able nitrogen showed that in the treated soils, the
nitrogen was predominately in the form of ammonium, while
in the untreated soils it was predominately in the form of
nitrate.

The pH of all the soils was 5.3.

Soybeans were planted in the soils and after germi­
nation, they were thinned to 3 plants per crock.

It was

obvious from observations made on the plants during the
growth period that those on the fumigated soils with the
high level of calcium were making better growth than those
plants on the fumigated soils with low calcium or on the
untreated soils with either high or low calcium.

The growth

of the plants on the soils high in calcium and treated with
Dowfume N was especially pronounced (plate 15)*

However,

the growth of the plants on the treated, low calcium soils
seemed to be less in comparison with those on the untreated
soils.

dome of the plants on the low calcium, treated

soils began to blossom at the end of six weeks growth.
There was no evidence of blossoming on the other plants. At
this point, the plants were harvested and analyzed for pro­
tein and mineral content.
given in table 13•

The results of these analyses are

H

*
0

p
O
E-i

O
On
rH

CO
•co
CM

o
uo
CM

to
CM

CM
CM

CO
CM

-d
co
.

O
CO

i—1
CO
•

I> CM
•

UO

LO
CM

o
On

CO
O
rH

to

ON
CO

co

co

o
o
co

o
uo
CM

nO
CO
CM

NO
co
•

O
co
•

to

cm
cm

cm

1— 1

LT\
o

1— 1

rH

i

b0

ON

U0

-d
-d
•

CM

-d"
•

U0
b£)

•

CM
•

•

•

•

CO

.

•

o

to
UO

UO

F—H

•
£

W

.
ctJ

.
£

O

o

ON

i— 1
•
rH

CM
■
i—1

o.

co
•
NO
1—i

UO

b0

O

UO

O
O

0

•

_j
jy

NO

-d
CO

O
uo

NO
CO

t— 1
-d
•

uo

uo
CM
-d

UA

O

o
uo

i— 1

•

*

o
uo
uo

■&

rH

—i

ON
CO

'-JO

(— 1
ON
•

-d

•

•

ON

•

o

to
-d

-d

CM
■to

nQ
On
•

-to

rH

rH

NO
•
Cs-

i— 1

CM

i
—1

CM

CO
ON

-d
NO
*
CM

-d

On

•to
•
co

UO

to

rH

to

O

ON
•
E>-

co
•

•
rH

*

.

£

•H
0
p
O

U

ft
■&
*
• 0
-P s
£ co

t>»uo

•

.

nO
i— 1

o
CM

1>-

rH

-d

CM

NO

•

CO

u

•

E>~
•

co

CM

•

-d

■
rH

•

to
rH

rH
-d
•
-d

«
CM

Q
d
O

cif
O

O

£
A

-d

A

IS

-d £
1 Or

0 O
£ O

0
£

£

ft

a,
o
o
co

-P

O
e
-p
cd

o

Sh
Eh

S
CD

s
p

1
T*
0

tJ
0

P

P

CTJ
0
Su
p
£

ccf
0
5h

P

t£z>

CO
o

o

o
Q

♦
rH
£
nO
•
rH

3 co
*t!

£
o
n

I

1

p

ch

£

o
Q

•
i—i
£

rH

NO
•

o

t—1

1=5

•

H

CM
1

O
'sd
cH

CM
I £

ft

O

j5ti P-r

0 O
£ O

0

P co
<H
£ 1
O
o

Ch
£

CH
£

Q

n

«

•
£

ft

CTJ
o

rH
£
o

•

rH

[3

o
•

1-- 1

0 O
£ O
p co

o
«

i—i

£

£

NO

NO

1—1

rH

•

*

|

***

»'•''1H

to

Average of 4 replications
Average wt. of 3 plants per crock
Me. calculated on the basis of 100 grams of dry plant tissue

•
0

**

Analyses of Soy-beans Grown on fumigated

to

t> ON

•

■ir

Table 1$.

i— 1

O

•
£

S

uo
.
-d

NO

•
o

.

co
•
CO
-co

CM
•
NO
ON

cm

*

Soils at Different

Calcium Levels,

-107-

-

103

-

Plate 15. Soybeans grown on soil fumigated with
Dowfume N.
1. Treated, low calcium soil.
2. Untreated, high calcium soil.
3 . Treated,
high calcium soil.
It is obvious that the plants on the treated soils
contained more protein than did those on the untreated
soils.

However, the dry weights of these plants were

significantly lower when the calcium level in the soil
was low.

(See analysis of variance in table 19 for

difference in weight necessary for significance.)

let,

when the calcium level in the soil was high, the plants
m

on the treated soils put on more growth in addition to
containing a greater percentage of protein than those on
the untreated soils.

This was especially true where the

soil was fumigated with Dowfume N.

Those plants grown

on the soils fumigated with Dowfume W-40 did not have a

-109-

Table 19* Analysis of variance of dry weight of soy­
bean plants grown on fumigated soils with low and high
calcium levels.

Source

D.F.

S.3

31

22.81

Replications

3

.06

.02

Treatments

7

20.80

2.97

21

1.93

Total

Error

M.S.

F

.22
33.00 *

* Significant beyond the l/o level. Application of
the nt test” indicated that the differences between
the averages of the dry weight of the plants
necessary for significance at the 1% level was 0.31
grams.
significantly greater amount of dry matter than did
those on the untreated soils when a comparison is made
between them on the high calcium level.

The responses

of the plants grown on the soils treated with Dowfume
MC-2 are similar to those of plants grown on the Dowfume
N treated soils, though not of the same magnitude.
The calcium uptake by the plants was partially
governed by the amount of calcium available in the soil.
However, the uptake was less when the primary source of
nitrogen available to the plants was in the form of
ammonium than when it was in the form of nitrate• An
increase in the uptake of calcium was associated with a
decrease in the potassium and magnesium content of the

-1 1 0 -

plants.

It can be seen that the mineral cation constants

in the plants were lower when the primary source of
nitrogen was ammonium.

It is also obvious however, that

an increase in calcium available to the plants growing
in the fumigated soils materially aided in the growth
responses.

This increase in growth due to an increase

in the calcium level of the soil was not as pronounced
when the primary source of nitrogen available to the plant
was in the form of nitrate.
DISCUSSION
It was shown that when the sole source of nitrogen
available to plants is in a reduced form, the plants will
respond favorably to an increase in calcium in the
substrate.

Though the protein content of the plants

supplied with these forms of nitrogen was higher, total
growth was low due to an inability of the plants to
synthesize enough carbohydrate which seems to be necessary
for elaboration of the ammonium.

These plants character­

istically matured earlier than plants whose sole source
of nitrogen was in the form of nitrate.

The mineral cation

uptake constant when expressed in milliequivalents per unit
of dry weight of tissue was less when the source of
nitrogen was ammonium than when it was nitrate.
indicates that ammonium enters into the

This

cation balance

relationships and reduces the uptake of other cations by

-111-

the plants.
When soybeans were grown on soils which were fumi­
gated with Dowfumes N, W-40, and MC-2, the growth re­
sponses brought about by high levels of calcium in the
soil were excellent.

There were indications that the

fumigated soils were much higher in ammonium content than
were the untreated soils and conversely lower in nitrate
though both forms were present in all soils.

It proved

futile to try to test the soils for ammonium and nitrate
content during the growth period of the plants because of
the difficulty of accurate sampling and the fact that
ammonium is very rapidly absorbed by the plant roots.
However, the responses of the soybean plants growing on
the treated soils indicated that their primary source of
nitrogen was in a reduced form.

The protein content of

these plants was higher than that of those growing on the
untreated soils and there was a tendency toward earlier
maturation.

The mineral cation uptake constant was also

lower than in the case of the untreated soils.

A high

calcium content in the soil seemed to reduce the amount
of carbohydrate necessary for elaboration of the ammonium
because the plants had a much greater dry weight under
these soil conditions.

At any rate, where there was a

large supply of carbohydrate present in the plant due to
favorable environmental conditions and a large supply of
available calcium in the soil, the growth responses of the

-112-

soybean plant to soil fumigation were better than those
of the plants grown on the untreated soil regardless of
the calcium level.

The plants grown on the low calcium,

fumigated soils did not put on as much vegetative growth
as those grown on the untreated soils.
It appears that a high level of calcium in the
soil is of benefit to the growth of soybeans after soil
fumigation and probably, increases in the other mineral
cations would also be of value.

-113-

GENERAL SUMMARY
It was determined that the dispersion of dichloropropene and ethylene dibromide through soils was approxi­
mately the same with the dispersion limits being reached
within 24 hours from the time of injection of the com­
pounds.

The dispersion is lateral and downward from the

point of injection with little, if any, penetration of the
compounds into the soil mass above thepoint of injection.
The extent of dispersion was greatest in the sandy soil,
next greatest in the clay loam, and least in the muck.
The amount of moisture exerted considerable influence on
the degree of dispersion of the compounds with T!optimum1T
dispersion taking place when the soil was at the moisture
equivalent.

Outward diffusion from the point of injection

was minimized when the soil was air-dry and a water
saturated soil cut down on the depth of penetration of the
compounds.

Quantities of both the dichloropropene and the

ethylene dibromide were fixed by the soils and it was
shown that this fixation was a function of the amount of
colloidal organic matter present.

There were indications

that the compounds dispersed through the soil in two
phases: 1, the air-water phase and 2, the humus phase.
It was shown that Dowfumes N and W-40 are also fixed in
soils and that it is possible to attribute certain plant
injuries to a residual effect of the fumigants in the
soils o

-114-

The use of dichloropropene and ethylene dibromide
as soil fumigants accomplished a partial sterilization
of the soil and resulted in a reduced activity of the
oxidizing organisms.

An indication of this was the fact

that the bio-electric potentials of the soils were lowered
after treatment with these compounds.

Also, the effect

of fumigation was to inhibit nitrification and permit the
accumulation of large quantities of ammonium in the soils.
The rate of ammonification was increased after fumigation,
though the total amount of available nitrogen was not
materially greater than in the untreated soils. Dowfumes
N, W-40, and MC-2 retarded nitrification of ammonium
which was added to soils with Dowfume N being most effec­
tive in this respect.

Thus, plants growing on fumigated

soils receive a great part of their nitrogen in the form
of ammonium, and their subsequent growth is to a large
degree dependent upon their ability to utilize this form
of nitrogen.
With ammonium as the source of nitrogen available
to soybeans, the plants responded favorably to an increase
in calcium in the nutrient substrate.

The plants were

characterized by an abnormally high protein content and
matured earlier than soybean plants whose sole source of
nitrogen was nitrate.

The calciun, potassium, and

magnesium content of the ammonium fed plants was less than
those on the nitrate substrate.

Soybeans grown on soils

-115-

which had been fumigated with Dowfumes N, ¥-40, and IiC-2
also showed favorable growth responses when the calcium
content of the soil was increased, and the mineral cation
content was lower than that of the plants grown on the
untreated soils.

The decrease in the mineral content of

the plants was attributed to the fact that large amounts
of ammonium taken up by the plants on the fumigated soils
decreased the uptake of other cations.

There were

indications that an increase in the cation contents of
fumigated soils (especially calcium) would be of benefit
to plant growth.
The growth of soybeans and onions on muck soils
which were treated with Dowfume N showed that fumigation
could be of benefit at a time when available nitrogen is
a limiting factor in plant growth.

The plants matured

earlier than those on the untreated soils, had a higher
protein content, and produced higher yields.

-116-

LITERATURE CITED
1*

Afanaseva, A. L. The mobilization of nutritive
substances in the soil by partial sterilization.
Khim. Referat. Zhur. No. 8: 64. 1940.

2. Allen, M. W. The use of soil fumigants for wirewormcontrol. Calif. Agr. Expt. Sta. Circ. 365:
62-65. 1946.
3*

4.

Anonymous. Availability of radioactive isotopes.
(Announcement from headquarters, Manhattan Proj.)
Science, 103: 697-705. 1946.
. Official and tentative methods of
analysis. Ed. 5. Assoc. Official Agr. Chem.,
Wash. D. C. 1940.

5. Arnon, D. I. Effect of ammonium and nitrate nitro­
gen on the mineral composition and sap character­
istics of barley. Soil Sci., 48: 295-307. 1939.
6.

, and Johnson, C. M. Influence of hydro­
gen ion concentration on the growth of higher
plants under controlled conditions. Plant Physiol.,
17: 525-539. 1942.

7.

Beames, 0. H. and Butterfield, N. W. Some physiolog­
ical effects of methyl bromide on horticultural
plants. Proc. Amer. Soc. Hort. Sci., 45: 31^-322.
1944.

8.

Bear, F. E. Cation and anion relationships in plants
and their bearing on crop quality, Agron. Jour.
42: 176-178. 1950.

9.

Bogopolskii, M. and Bershova, 0. Partial sterilization
of soils. Khim. Referat. Zhur. No. 5: 55* 1939.

10.

Bouyoucos, G. J. Directions for making mechanical
analyses of soils by the hydrometer method. Soil
Sci., 42: 225-229. 1936.

11.

Bradfield, R. The nature of the chemical reactions
of colloidal clay. Coll. Sym. Monog., 1: 369-383.
1923.

12.

Bueher, T. F. et al. Redox potentials of desert soils
under varying conditions of sterilization, aeration
and puddling. Soil Sci. Soc. Amer. Proc., 5: 241244. 1940.

-117-

13*

Burstrom, H. Photosynthesis and assimilation of
nitrate by wheat leaves. Ann. Agr. Coll. Sweden,

11: 1-50. 1943.

14*

Chisholm, R. D. and Kablitsky, L. Sorption of
methyl bromide by soil in a fumigation chamber.
Jour, of Econ. Entom., 36: 549-551. 1943.

15*

Coleman, D. A. et al. Can soil be sterilized with­
out radical alteration? Soil Sci., 1: 259-274.

1916.

16.

Coleman, L. C. Untersuchungen Uber Nitrification.
Centbl. Bakt. II., 20: 401-420. 1903.

17.

Ellis, C. and Swaney, M. ¥. Soilless growth of
plants. Ed. 2. Reinhold Pub. Co. N. I., N. I.
1947.

13.

Fleming, W. E. and Baker, F. E. The use of carbon
disulfide against the Japanese beetle. U. S. Dept.
Agr. Tech. Bull. No. 473. 1935.

19.

Fraps, G. S. and Sterges, A. J. Estimation of nitric
and nitrous nitrogen in soils. Tex. Agr. Exp. Sta.
Bull. 439. 1931.

20.

Fuhr, I. et al. Sorption of fumigant vapors by soil.
Science, 107: 274-275. 194$.

21.

Hamner, C. L. Growth responses of Biloxi soybeans
to variations in relative concentrations of
phosphate and nitrate in the nutrient solution.
Bot. Gaz., 101: 637-649. 1940.

22.

Higgins, J. C. and Pollard, A. G. Studies in soil
fumigation II. Distribution of carbon disulfide
in soils fumigated under various conditions. Ann.
Appl. Biol., 24: 395-910. 1937.

23.

Ignatieff, W. Determination and behavior of ferrous
iron in soils. Soil Sci., 51: 249-263. 1941.

24.

Leeper, G. W. The forms and reactions of manganese
in the soil. Soil Sci., 63: 79-94* 1947*

25.

Lindenbergh, D. J. and Harmsen, G. W. Investigations
on the nitrogen nutrition of plants. I. Plant and
Soil, 2: 1-29* 1949*

26.

Matthews, A. Partial sterilization of soil by
antiseptics. Jour. Agr. Sci. 14: 1-57* 1924.

-

113

-

27*

MeFarlane, J. S. and Matsuura M. The effectiveness
of D-D as a soil fumigant in Hawaii. Phytopathol­
ogy, 37: 39-43. 1947.

2d.

Michelbacher, A. A. et al. Two new soil fumigants,
D-D and E. D. B., for wireworm control. Calif.
Agr. Expt. Sta. Circ. 365: 56-61. 1946.

29.

Nightingale, G. T. The nitrogen nutrition of green
plants. II. Bot. Rev., 14: 135-221. 1943.

30.

Norman, A. G. Problems in the chemistry of soil
organic matter. Soil Sci. Soc. Amer. Proc., 7:
7-15. 1942.

31.

Parris, G. K. The nematocidal and fungicidal value
of D-D mixture and other soil fumigants.
Phytopathology., 33: 771-730. 1945.

32.

Peech, M., and English, L. Rapid microchemical
soil tests. Soil Sci.,' 57: 167-195* 1944*

33*

Polyakov, A. A. The reaction of chlorine with the
soil during disinfection, Khim. Referat. Zhur.,
No. 5: 62. 1941.

34*

Prianischnikov, D. Uber den Einfluss des Entwickelungsstadiums auf die Ausnutzung des Ammoniak und Nitratstickstoffs durch die Pflanzen. Trans. Third Int.
Cong. Soil Sci., 1: 207-209. 1935.

35.

Quispel, A. Measurement of the oxidation-reduction
potentials of normal and inundated soils. Soil
Sci., 63: 265-276. 1947.

36. Roberts, A. et al.

A study of the radiation from the
disintegration of bromine 32. Phys. Rev., 60: 544550. 1941.

37.

Robinson, W. 0. The determination of organic matter
in soils by means of hydrogen peroxide. Jour. Agr.
Res., 34: 339-356. 1927.

33.

Russell, E. J. and Hutchinson, H. B. The effect of
partial sterilization of soil on the production
of plant food. Jour. Agr. Sci., 3: 111-114* 1909.

39.

,
_______________ . The limitation
of bacterial numbers in normal soils and its
consequences. Jour. Agr. Sci., 5: 152-221. 1913.

-119-

40.

Schmidt, C. T. Dispersion of fumigants through soil.
Jour. Econ. Sntom., 40: 329-337. 1947.

41*

Schreiner, 0. and Shorey, E. G. Chemical nature of
soil organic matter. U. S. D. A. Bur. Soils Bull.
74. 1913.

42.

Schropp, ¥. and Arenz, B. Uber die Witkung des
Kaliums bei der Ernahrung der Pflanzen mit Nitrat
und Ammoniakstickstoff. Ernahr. Pflanze, 33: 97106. 1939.

43.

Sherman, 0. D. and Fujimoto, G. K. The effect of
the use of lime, soil fumigants, and mulch on the
solubility of manganese in Hawaiian soils. Soil
Sci. Soc., Am. Proc., 11: 206-210. 1947.

44*

Sideris, G. P. et al. Assimilation of ammonium and
nitrate nitrogen by pineapple plants grown in
nutrient solutions and its effects on nitrogenous
and carbohydrate constituents. Plant Physiol.,
13: 439-527. 1933.

45.

and Young, H. Y. Effects of
nitrogen on growth and ash constituents of Ananas
comosus (L.) Merr. Plant Physiol., 21: 247-270.
1946.

46. Smith, N. R. and Wenzel, M. E.

Soil microorganisms
are affected by some of the new insecticides.
Soil Sci. Soc. Amer. Proc., 12: 227-233. 1943.

47.

Stark, F. L. et al. Effect of chloropicrin fumi­
gation on nitrification and ammonification in
soil. Soil Sci., 43: 433-442. 1939*

43.

Tam, R. K. The comparative effects of a 30-50 mix­
ture of 1-3 dichloropropene and 1-2 dichloropropane
(D-D mixture) and of chloropicrin on nitrification
in soil and on growth of the pineapple plant.
Soil Sci., 59: 191-205. 1945.

49.

and Clark, H. E. Effect of chloropicrin
and other disinfectants on nitrogen nutrition of
the pineapple plant. Soil Sci., 56: 245-261. 1943*

50.

Taylor, A. L. Efficient spacing of soil fumigants
for field applications. Proc. Helminth. Soc. hash.
■6: 62-66. 1939.

51 . Thorne, G. and Jensen, V.

Use of D-D mixture against
sugar beet nematodes. Proc. Amer. Soc. Sugar Beet
Technol., 4: 322-326. 1946.

-120-

52.

Timonin, M. I. Microflora of the rhizosphere in
relation to the manganese deficiency disease of
oats. Soil Sci. Soc. Amer. Proc., 11: 2S4-292.
1947.

53*

Vickery, H. B. et al. Chemical investigations of
the tobacco plant VIII. The effect upon the
composition of the tobacco plant of the form in
which nitrogen is supplied. Conn. (New Haven)
Agr. Exp, Sta. Bull. 442. 1940.

54*

Vladimirov, A. V. Influence of nitrogen sources in
the formation of oxidized and reduced organic com'
pounds in plants. Soil Sci., 60: 265-275. 1945.

55.

Volk, N. J.
of soils.
1939.

56.

Waksman, S. A. Principles of Soil Microbiology.
Ed. 2., The Williams and Wilkins Co., Baltimore,
Md. 1932.

57*

The determination of redox potentials
Jour. Amer. Soc. Agr., 31: 344-351.

and Starkey, E. L. Partial sterili­
zation of soil, microbiological activities, and
soil fertility.
Soil Sci., 16: 137-156, 247-26S,
343-357. 1923.