RESPONSE OF SELECTED SMALL GRAINS,
RANGE GRASSES AND ALFALFA
TO SULFUR DIOXIDE
CERL - 050
February 1979

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RESPONSE OF SELECTED SMALL GRAINS,
RANGE GRASSES AND ALFALFA
TO SULFUR DIOXIDE
CERL - 050
February 1979
This paper also appears as Chapter 15 in The Bioenvironmental Impact of a Coal-
fired Power Plant, Fourth Interim Report, Colstrip, Montana. E.M. Preston and
T.L. Gullett, eds. USEPA Ecological Research Series, Corvallis Environmental
Research Laboratory, Corvallis, OR 97330. in press.

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RESPONSE OF SELECTED SMALL GRAINS, RANGE
GRASSES AND ALFALFA TO SULFUR DIOXIDE
by
Raymond G. Wilhour
Grady E. Neely
David E. Weber
Louis C. Grothaus
Terrestrial Systems Division
Corvallis, Oregon 97330
CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330

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RESPONSE OF SELECTED SMALL GRAINS, RANGE GRASSES
AND ALFALFA TO SULFUR DIOXIDE
Raymond G. Wilhour, Grady E. Neely, David E. Weber and Louis C. Grothaus
ABSTRACT
Experiments were conducted to determine the
effects of various sulfur dioxide (SO2) treatments on
yield of small grains (spring wheat, Triticum aestivum
'Olaf'; Durum wheat, Tritioum tirgidwn 'Ward'; barley,
Hordeum vulgare 'Hector') and alfalfa (Medicago sativa
'Ladak-65') growing in a field environment. The
experiments were: 1) chronic exposure experiment to
determine the effects of weekly exposure to SO2
treatments of 0, 3, 5, 10 or 15 pphm for 72 continuous
hr; 2) multiple exposure experiment to determine the
effects of varying the frequency of exposure to SO2
treatments of 0, 25, 40, 80 or 120 pphm for 3 hr; and
3) a growth stage experiment to determine if phenolog-
ical stages exist during which plants are most sensi-
tive to a single SO2 treatment of 0, 25, 40, 80 or 120
pphm for 3 hr. Another study was included to deter-
mine the effects of 3-hr treatments to 0, 25, 40, 80
or 120 pphm SO2 repeated at two-week intervals on the
yields of range grasses (crested wheatgrass, Agropyron
desertorum 'Nordan'; western wheatgrass, Agropyron
smithii', Russian wild ryegrass, Elymus junceus\ blue
grama grass, Bouteloua gracilis', needle and thread
grass, Stipa comata) and alfalfa grown in containers.
The yields of Durum wheat and barley treated
weekly with 15 pphm SO2 for 72 continuous hr were 42
and 44% of the controls, respectively. These results
were not significant at the 95% probability level, but
the data suggested that weekly, 72-hr exposures to SO2
concentrations as low as 10-15 pphm could suppress
yields. The yield of spring wheat was not affected by
a similar treatment. Varying the frequency of 3-hr
exposures to SO2 concentrations up to 120 pphm from as
often as once every week to as infrequently as once
every 5 weeks had no effect on yields of the small
grains and alfalfa. No growth stage was identified
1

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during which the small grains or alfalfa were most
sensitive to a single 3-hr exposure to SO2 concentra-
tions up to 120 pphm. The growth of tops and roots of
range grasses and alfalfa were not affected by 3-hr
exposures to concentrations of SO2 up to 120 pphm
repeated at 14-day intervals during September and
October.
INTRODUCTION
The increased reliance of the United States on energy produced by coal-
fired power plants will result in elevated concentrations of SO2 in areas
sharing airsheds with electrical generating stations. The Poplar River Valley
of Montana, due to the current and planned construction of coal-fired power
plants in neighboring states and Canada, will experience increased SO2 concen-
trations. This study was initiated due to the concern of EPA Region VIII in
Denver, Colorado regarding the potential detrimental effects of elevated SO2
concentrations on agricultural crops important to the economy of the Poplar
River Valley.
Several studies have described injury symptoms (Lamb, 1972; Hill et al.,
1974; Tingey et al. , 1978), changes in various plant processes (Bennett and
Hill, 1973; Rabe and Kreeb, 1976; Neely et al., 1977; Dodd et al. , 1979) and
yield effects (Davis et al., 1966; Booth et al., 1976; Brough and Parry, 1976;
Heitschmidt, 1977; Neely et al., 1977; Dodd et al., 1979) of SO2 on plants
similar to those economically important in the Poplar River Valley. Although
these studies demonstrated probable response characteristics of several plant
species to SO2 and provided some dose/response data, knowledge remained incom-
plete for a reasonable assessment of the effects of increased SO2 levels on
the agricultural economy of the Poplar River Valley.
A research program was planned to broaden the knowledge concerning the
response of important plant species grown in the Poplar River Valley to SO2.
Two studies were conducted utilizing different species and emphasizing differ-
ent objectives. Small grains and alfalfa were included in a study which had
three objectives: 1) to determine if more frequent exposure to given concen-
trations of SO2 resulted in greater yield reductions; 2) to assess the effects
of a range of SO2 concentrations on yield; and 3) to determine if periods of
time exist during which a species is more sensitive to SO2• Another study
utilized native range grasses and alfalfa and was designed to assess the
effects of a range of SO2 concentrations on yield.
MATERIALS AND METHODS
The experimental SO2 exposures were conducted at the Schmidt research
farm which is located approximately 5 miles east of Corvallis, Oregon. The
farm is owned and operated by Oregon State University.
2

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Field Exposure Study
Three distinctive experiments were included in this study. A chronic
exposure experiment was conducted to determine the effects on yield of small
grains (spring wheat, Tviticum aestivwn 'Olaf'1; Durum wheat, Tviticim turgidwn
'Ward1; and barley, Hovdeum vulgare 'Hector') and alfalfa (Med.iea.go sativa
'Ladak-65') from repeated, lengthy exposures to low concentrations of SO2•
Treatments in this experiment were ambient air (never covered by an exposure
chamber), 0 (ambient air filtered by activated charcoal), 3, 5, 10, or 15 pphm
SO2 (ambient air filtered by activated charcoal amended with desired SO2
concentrations). The duration of the SO2 treatments was 72 hr (Friday noon
until Monday noon) and the treatments were repeated each week for 12 weeks
beginning May 6, 1977.
The objectives of the multiple exposure experiment were to correlate
yields of small grains and alfalfa with 1) SO2 concentrations in the range of
0-120 pphm and 2) frequency of exposure to these SO2 concentrations. The
effects of all combinations of five SO2 concentrations (0, 25, AO, 80 or 120
pphm) and seven exposure frequencies (ranging from once per week to once every
five weeks*) were examined as they affect plant yields. The SO2 treatments
lasted 3 hr beginning at 8 a.m. The experiment was continued for 12 weeks,
beginning May 11.
A growth stage experiment was conducted to determine if phenological
stages of development exist during which a single exposure to SO2 concentra-
tions of 0, 25, 40, 80 or 120 pphm most affects yield of small grains or
alfalfa. Treatments representing all combinations of five SO2 concentrations
(0, 25, 40, 80 or 120 pphm) and six growth stages (two-week intervals) were
used in this experiment. The SO2 treatments were 3 hr in duration (8-11 a.m.)
and an experimental plot was treated only once during the experiment. A
different group of five experimental plots (one for each SO2 concentration)
was treated at 2-week intervals, beginning May 17.
The soil at the Schmidt research farm is a Willamette silt loam. The
surface layer is a well drained, very dark brown silt loam, about 60 cm thick
over a silty clay loam subsoil. A chemical analysis of the soil prior to
seeding identified the following chemical concentrations: nitrate (6.6 ppm),
phosphorus (45 ppm), potassium (252 ppm), sulfur (6.2 ppm) and boron (.42
ppm). The soil had a pH of 5.8, cation exchange capacity of 18.35 milliequiv-
alents per 100 grams and an organic matter content of 3.29%. The following
amendments were applied and incorporated into the soil prior to seeding: 16-
20-0-14 (N-P-K-S) and 0-0-52-17 at rates of 337 and 129 kg/ha, respectively,
boron (14.3%) at 3 kg/ha and agriculture limestone at 8980 kg/ha. The amend-
ments and rates were selected to provide an average growing condition capable
of adequately sustaining nutrient demands for the test plants.
Eight experimental blocks (2.7 by 60 m) were established in an east-west
direction. Within each block 16 plant rows were oriented lengthwise. North-
south divisions were made to divide each block into 20 plots which became the
* The once-every-four-weeks treatment was repeated three times using slightly
different starting dates.
3

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experimental units. An entire plot was covered by an exposure chamber during
treatment. Treatment plots measuring 2.4 x 2.4 m were selected within blocks
on the basis of uniform plant size and distribution. Treatments were assigned
to plots to minimize the possibility that a response trend would appear due to
variability asociated with location. This was achieved within an experiment
by assigning treatments with a common SO2 concentration to the same block
whenever possible and/or by assigning treatments which differed most to
adjacent plots.
The blocks were drilled on April 11, 1977 with wheat and barley at a rate
of 100 kg seed/ha, alfalfa at 11 kg/ha, and crested wheatgrass at 9 kg/ha.
All rows were drilled 18 cm apart. Sparse and spotty emergence of alfalfa
required replanting of this test species on May 10, 1977. Poor development of
crested wheatgrass resulting in its deletion from the field studies. One day
after the second planting of alfalfa, experimental plots were sprayed with
2,4-DB amine (.6 kg/ha) to control broadleaf weeds. The herbicide was not
applied to the alfalfa. Poor weed control resulted and weeding by hand was
necessary. No additional cultural practices (e.g. irrigation) were performed.
Sulfur dioxide exposures were conducted in exposure chambers similar to
those previously described by Heagle et at. (1972). The SO2 was dispensed
into exposure chambers and concentrations controlled as previously described
(Heagle et at., 1974). The portable exposure chambers covered the experi-
mental plots only during actual SO2 treatments. Ambient temperature (therm-
istors), humidity (Hygrodynamic Model 15-7012 Sensor), and sunlight (Solar-a-
Meter Mark I-G100) measurements were made during the study period. Ambient
SO2 concentrations during the experimental period were always less than 1
pphm. Pollutant concentrations were continuously monitored during fumigations
by drawing air from exposure chambers through Teflon sample lines to Meloy
Labs sulfur analyzers (Model SA 285). The SO2 analyzers were checked monthly
for accuracy with a Monitor Labs Model 8500 Calibrator.
Visible injury to the foliage of the grain species was estimated three
days after each fumigation and terminated in July due to the appearance of
natural chlorosis and necrosis.
The grain crops were harvested on August 15. The 180 cm center sections
of the two test rows per species were divided into two equal, 90 cm sections,
providing 4 samples per treatment per species. The number of plants and seed
heads per sample were counted. Grain heads were removed from each sample
area, bagged, air dried and threshed with a Vogel wheat-head thresher. Ker-
nels were oven dried at 50°C and weighed. Yields were expressed as gm of
grain per plant.
Alfalfa was harvested on July 29, 1977 when at approximately 10% bloom.
Sample areas were assigned as described for the grain species. Plants were
clipped at soil level, oven dried at 70°C and weighed. Yield values were
expressed as weight (gms) per plant.
4

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Range Grass and Alfalfa Study
The objective of this study was to determine the effects of repeated SO2
exposures during the vegetative stage of growth on the yield of alfalfa, M.
sativa 'Ladak-65'; crested wheatgrass, Agvopyron desertorum 'Nordan'; western
wheatgrass, Agvopyron smithii; Russian wild ryegrass, Elymus junceus; blue
grama grass, Bouteloua gracilis and needle and thread grass, Stipa comata.
Ladak-65 alfalfa, Nordan crested wheatgrass and Russian wild ryegrass were
seeded and the remaining species were transplanted from cuttings on July 5,
1977. The growing medium was a mixture of three parts soil (sandy clay loam)
to one part Jiffy-Mix-Plus. This mixture was amended with 2.3 kg of 11-33-11-
5 (N, P, K, S) and 1.2 kg of hydrated lime per cubic meter of soil. Grasses
were grown in 10 cm dia. by 30 cm high pots and alfalfa in 20 cm dia. by 18 cm
high pots. Plants were thinned to one grass or two alfalfa plants per pot.
Treatments were 0, 25, 40, 80, or 120 pphm SO2 repeated every 14 days
between the hours of 8 and 11 a.m. The treatment plots were randomly arranged
in an east-west direction and within plots, test species were grouped in rows
oriented in an east-west direction. There were 13 to 14 pots per treatment of
each grass species and 6 pots of alfalfa per treatment. All plots received
five SO2 exposures, separated by two weeks, beginning August 25. Test plants
were covered by exposure chambers only during treatment with SO2. Plants were
watered as necessary to prevent moisture stress. Ambient environmental condi-
tions and SO2 concentrations were monitored as described in the earlier study.
All plants were harvested November 3 while in the vegetative growth stage.
Plants tops were clipped at soil level and roots were washed. Tops and roots
were oven dried at 70°C and weighed.
Data Analysis
Preliminary examination of the data from the field exposure study indi-
cated that a large block-to-block variation occurred, independent of treatment
differences. Because of this variation, treatment comparisons were limited to
those appearing in the same block. The effect of this limitation is variable
and will be discussed with the analysis of the results for each experiment in
the field exposure study.
The statistical treatment of the data involved analyses of variance and
calculation of LSD's by Tukey's multiple comparison procedure (Snedecor and
Cochran, 1967). The one exception was that in the multiple exposure experi-
ment Bonferroni's multiple comparison method (Neter and Waserman, 1974) was
used to compute significant t-values. The assumption inherent in the t-test
and analysis of variance that the data be normally distributed with variances
which do not increase with treatment means (Snedecor and Cochran, 1967) was
tested and found to be true. Therefore, no corrective data transformations,
such as the logarithmic transformation, were needed and the only modification
of the data was to express yield on a weight per plant basis to adjust for
differences in the number of plants between samples.
5

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RESULTS
Average temperature, relative humidity, solar insolation and rainfall
which occurred during the experimental periods are summarized in Table 15.1.
Comparisons of desired and actual SO2 concentrations for all experiments are
presented in Table 15.2.
Field Exposure Study
Chronic Exposure Experiment
Comparatively severe limitations were imposed on this experiment by the
large block-to-block variability which prevented comparisons of treatments
located in different blocks. Two analyses were completed comparing 0 pphm, 3
pphm and 15 pphm treatments or the 5 and 10 pphm treatments. The block-by-
block comparisons of the mean yields between SO2 treatments are given in Table
15.3. The yields of Durum wheat and barley were suppressed 42 and 44%, re-
spectively, comparing the mean at 0 to that at 15 pphm, and about 15% when
comparing the mean yield at 5 pphm to the mean yield at 10 pphm. The differ-
ences, however, were not statistically significant at the 95% level of confi-
dence. In the above comparisons, the mean yield at the highest SO2 concentra-
tion was always the lowest, suggesting that the yield of Durum wheat and
barley can be reduced by weekly, 72-hr exposures to SO2 concentrations as low
as 10 to 15 pphm.
Spring wheat seemed more resistant to the chronic SO2 exposures. The
mean of the 15 pphm treatment was actually greater by 7% than the 0 pphm
treatment mean (control). Further, only a 5% yield difference occurred be-
tween the 5 pphm and 10 pphm treatments.
Foliar injury was observed on all species of small grains exposed to SO?,
in the field experiments. Symptoms of SO2 injury appeared as chlorosis and
necrosis on the leaf tips and margins. No similar injury was observed on
plants not treated with SO2• Foliar injury on small grains in the chronic
exposure experiment was no greater than 15% at SO2 concentrations of 3, 5, or
10 pphm (Table 15.4). At 15 pphm, the highest concentration used in this
experiment, average injury values ranged from 25 to 50%.
Multiple Exposure Experiment
The block-to-block variability discussed earlier restricted comparisons
of exposure frequencies to SO2 concentrations completely contained within a
block (25, 80 or 120 pphm).
Analyses of variance for Durum wheat, spring wheat, barley and alfalfa
showed that 1) the pattern of differences in mean yields between exposure
frequencies did not vary with SO2 concentration (no significant exposure
frequency by SO2 concentration interaction) and 2) there were no significant
differences in mean yields between different exposure frequencies at either
25, 80 or 120 pphm (Table 15.5 gives means and LSD's). Thus, varying the
frequency of 3-hour exposures to SO2 concentrations up to 120 pphm from as
6

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TABLE 15.1. AVERAGE WEEKLY AMBIENT TEMPERATURE, HUMIDITY AND SOLAR INSOLATION OCCURRING DURING THE WEEKS
OF EXPOSURE
Average Ambient Environmental Conditions


Temperature (°C)


Relative
Humidity 1
(%)
Rainfall
(cm)

*/
1ax.—
*/
Min.-
Day^
Nightt^
Solar Insolation-^
*/
Max.-
' + /
*/ Day-
Min.— Avg.
Nightl^


Week >
Avg.
Avg.
(cal./cm2/min)
Avg.


5/6-5/12
18.1
-.4
13.4
3.8
.74
95
39
58
85
March
12.9
5/13-5/19
17.1
2.2
13.1
4.5
.62
96
42
58
87


5/20-5/26
19.0
2.0
14.8
6.0
.68
97
37
56
87


5/27-6/2
17.8
3.2
14.4
5.6
.64
96
45
63
91
April
2.6
6/3-6/9
25.1
9.0
20.8
11.9
.73
95
41
59
87


6/10-6/16
24.8
5.2
19.6
9.1
.79
95
32
52
86


6/17-6/23
26.3
6.8
21.2
11.0
.70
97
36
56
84
May
8.7
6/24-6/30
29.7
7.6
24.0
12.0
.89
89
22
34
73

7/1-7/7
24.1
6.8
20.0
10.4
.73
88
24
36
68


7/8-7/14
25.8
5.8
21.6
10.2
.74
93
26
39
76
June
2.9
7/15-7/21
28.2
7.0
22.6
11.3
.78
92
20
37
74


7/22-7/28
30.3
9.6
24.6
13. 7
.73
85
20
37
67


7/29-8/4
35.6
11.0
30.0
16.0
.83
79
11
24
58
July
.3
8/5-8/11
37.2
11.9
30.5
17.7
.79
72
11
25
52


8/12-8/18
35.9
8.7
28.6
16.4
.70
83
8
31
60


8/19-8/25
24.5
10.9
20.0
13.3
.43
92
33
54
80
August
4.8
8/26-9/1
24.8
10.2
20.0
12.4
.58
93
22
43
83


9/2-9/8
25.0
10.3
20.4
13.3
.54
90
24
44
78


9/9-9/15
26.2
5.5
20.1
10.8
.56
91
14
35
69
September
9.1
9/16-9/22
18.1
6.9
13.6
9.3
.39
96
36
64
87


9/23-9/29
17.3
5.7
13.0
8.0
.36
92
42
67
85


9/30-10/6
17.9
3.8
12.5
7.4
.43
79
30
54
66
October
6.5
10/7-10/13
19.3
3.7
13.4
7.2
.43
88
31
54
76


10/14-10/20
19.2
2.7
12.3
6. 7
.38
93
34
62
77


10/21-10/27
16.8
3.2
11.7
6.3
.32
97
51
73
91


* /
^Average of seven daily maximum hourly values,
x/Weekly average of hourly values between 7 am and 8 pm.
4- Weekly average of hourly values between 8 pm and 7 am.

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TABLE 15.2. COMPARISONS OF ACTUAL AND DESIRED S02 CONCENTRATIONS FOR ALL
EXPERIMENTS
Actual Concentration, pphm
<
% of time — stated value*
Study
No.
Obs.
Desired
Cone.
Min.
Avg.
Max.
5

10

50
(Median)
90

95
Multiple
192
25
9
24.0
80

14

17

25
27

30

192
40
0
39.4
130

26

32

38
45

51

192
80
29
74.6
110

46

56

78
83

84

192
120
25
114.9
160

84

90

120
130

135
Growth
36
25
5
25.1
33

16

18

26
30

31

36
40
0
36.5
47

0

30

38
44

44

36
80
33
77.1
87

45

55

80
84

84

36
120
25
112.8
135

25

85

123
130

130
Range














Grass
30
25
18
25.2
35

19

22

25
27

28

30
40
27
36.4
45

28

30

37
40

41

30
80
38
86.1
120

45

46

90
105

120

30
120
120
111.1
125

100

100

110
120

125
Chronic
864
3
0
3.0
9.
0
1.
8
2.
0
2.7
4.
.0
5.6

864
5
1.4
5.1
12.
0
3.
3
3.
6
4.8
6.
,8
8.0

864
10
0
9.7
20.
0
6.
6
7.
5
9.5
12.
0
14.0

864
15
0
15.0
53.
0
9.
0
10.
0
14.5
21.
0
23.0
* For example, the first line indicates that 5% of the time the concentration
was no more than 14 pphm, 10% of the time it was no more than 17 pphm, half
the time it was no more than 25 pphm, 90% of the time it was no more than 27
pphm, 95% of the time it was no more than 30 pphm.
often as once every week to as infrequently as once every 5 weeks had no
effect on yields of the test species.
A secondary objective of the multiple exposure experiment was to evaluate
the effect of various SO2 concentrations on yield. The lack of a significant
effect on plant yield by varying the frequency of exposure was discussed
above. Therefore, all plots which received the same SO2 exposure concentra-
tion can be considered equivalent and pooled to assess the effect on yield of
varying S02 concentrations. The results of pooling plots treated with a
common SO2 concentration and located in the same block are given in Table
15.6. No differences significant at the 95% level of confidence were found
between SO2 concentrations indicating the yields of Durum wheat, spring wheat,
barley and alfalfa were independent of SO2 concentration for these 3-hr dura-
tion exposures.
8

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TABLE 15.3. YIELD.'RESPONSE OF SELECTED SMALL GRAINS TO WEEKLY, 72-HOUR EXPO-
SURES TO LOW S02 CONCENTRATIONS
BLOCK 1


MEANS (gm/plant)
*/



SPECIES
0 pphm
3 pphm
15 pphm
X0 -
• X] 5
LSD^
Durum wheat
1.68
1.52
0.97
0.71
(42%)-/
1.28
Spring wheat
1.34
1.81
1.44
-0.10
(7%)
1.67
Barley
1.49
1.64
0.83
0.66
(44%)
1.35


BLOCK
2





*/
MEANS (gm/plant)—





5 pphm
10 pphm
X5 -
• X10
LSD^/
Durum wheat

2.71
2.28
0.43
(16%)—/
1.04
Spring wheat

1.85
1.76
0.09
(5%)
1.36
Barley

3.10
2.66
0.44
(14%)
1.10
*/
— Means based on a sample size of four.
—^Represents change" relative to the smaller of the means.
¦I^Least significant difference (LSD) based on Tukey's studentized range pro-:
cedure using error mean squares of .452 (Durum wheat), .760 (spring wheat)
and .502 (barley) with 11 degrees of freedom.
TABLE 15.4'., ESTIMATED PERCENT FOLIAR INJURY FOR SMALL GRAINS IN THE CHRONIC
EXPOSURE EXPERIMENT



Sulfur Dioxide
concentration, pphm

Species
3
5
10
15
Durum wheat
Spring wheat
Barley
*/
57—
5
15
10%
15
10
15%
15
15
25%
50
35

£ j
— Percent folia? injury readings made on June 30, 1977.
The foliar injury data are given in Table 15.7. No trends exist which
would suggest that greater foliar injury occurred with more frequent SO2
exposures; however, it is apparent that a positive correlation existed between
foliar injury and SO2 concentration. Averaged across species and frequency of
exposure, foliar injury ranged from about 5% at 25 pphm SO2 to about 35% at
120 pphm.
9

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TABLE 15.5. EFFECTS OF VARYING FREQUENCY OF 3-HOUR S02 EXPOSURES ON YIELD OF
SMALL GRAINS AND ALFALFA
Wks between repeated exposures
o\j 2
(pphm)
1
2
3
* /
4 a—
* /
4b-7
1 */
4 c—
5
VXm
LSD1

(gm)
(gm)
(gm)
(gm)
(gm)
(gm)
(gm)



i.ei'


DURUM
WHEAT




25
1.1
1.3
1.2
1.4
1.1
1.3
0.5
1.7
80
3.8
3.8
2.5
3.5
3.8
2.6
3.6
0.3
1.7
120
2.2
2.2
2.2
1.9
2.2
2.7
1.6
1.1
1.7




SPRING
WHEAT




25
2.0
1.4
1.8
1.8
1.2
1.6
1.8
0.8
2.2
80
2.7
3.1
2.2
2.5
3.0
3.1
3.4
1.2
2.2
120
3.0
2.5
2.1
2.2
2.0
2.1
2.3
1.0
2.2




BARLEY




25
1.9
2.0
1.8
1.9
1.9
1.8
2.3
0.5
1.8
80
2.4
3.8
2.4
3.7
2.7
3.1
2.5
1.4
1.8
120
1.8
2.5
2.7
2.2
2.2
2.8
1.9
1.0
1.8




ALFALFA




25
0.64
0.38
0.44
0.71
0.42
0.57
0.22
0.49
1.2
80
0.39
1.01
0.82
0.80
0.80
0.98
0.76
0.53
1.2
120
0.67
0.51
0.55
0.54
0.38
0.58
0.65
0.29
1.2
a J
—	Experiments started on different dates (May 13, May 19 or June 2).
—^Maximum mean minus minimum mean.
-^LSD based on Tukey's studentized range procedure using error mean squares of
.452 (Durum wheat), .760 (spring wheat), .520 (barley), and .225 (alfalfa)
with 11 degrees of freedom.
§/
—	Means based on a sample size of four; means given in gm per plant.
Growth Stage Experiment
The block-to-block variability already discussed limited the analysis to
comparisons of growth stages at SO2 concentrations completely contained within
one block (40, 80 and 120 pphm). Analyses of variance for Durum wheat, bar-
ley, spring wheat and alfalfa showed that 1) the pattern of differences in
mean yields between growth stages did not vary with SO2 concentration (no
significant growth stage by SO2 concentration) and 2) there were no signific-
ant differences in mean yield between growth stages at either 40, 80 or 120
pphm (see Table 15.8 for means and LSDs). Thus, when yields were averaged
across the three SO2 concentrations, the growth stage mean yields typically
were within a range of plus or minus one standard error, indicating that the
sensitivity of the test plants to SO2 was not different with regard to growth
stage.
10

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TABLE 15.6. YIELD RESPONSE OF SELECTED SMALL GRAINS AND ALFALFA EXPOSED TO S02 FUMIGATIONS IN THE
MULTIPLE EXPOSURE EXPERIMENT
SO2 (pphm)
0	120
BLOCK 3
*/
+ /
y 	y
120 0
„ , §/§§/
t-value	
Durum wheat
1.96^ 2.12

0.16 (8%)i-
0.76

Spring wheat
2.41 2.31

-0.10 (4%)
-0.37

Barley
2.17 2.29

0.12 (6%)
0.53

Alfalfa
0.44 0.55

0.11 (25%)
0.74


SO2 (pphm)
BLOCK 4

t-values


0 40 80

^Max ^Min
40-0 80-0
80-40
Durum wheat
3.37 2.99 3.37

0.38 (13%)
-1.38 0.0
1.64
Spring wheat
2.28 2.39 2.86

0.58 (25%)
0.31 1.57
1.93
Barley
3.29 3.92 2.95

0.33 (11%)
0.88 0.29
-1.34
Alfalfa
0.39 0.96 0.77

0.37 (63%)
1.91 1.10
-1.16

SO2 (pphm)
BLOCK 5




25 40

X40"X25
t-value

Durum wheat
1.30 1.92

0.62 (48%)
2.94

Spring wheat
1.64 2.02

0.38 (23%)
1.39

Barley
1.92 2.07

0.15 (8%)
0.67

Alfalfa
0.48 0.41

-0.07 (17%)
-0.10

No t-values significant at the 95% level of confidence.
— Average plant yield (grams dry weight of grain and foliage of small grains and alfalfa, respectively).
Means were grouped over frequencies of exposures based on the following sample sizes: Block 3 (0 pphm-
16; 120 pphm-28); Block 4 (0, 40 pphm-12; 80 pphm-28), Block 5 (25 pphm-28; 40 pphm-16).
-J^Repr
§/
esents change relative to smaller of the means.
— Significance levels controlled simultaneously for group of 5 comparisons made per species.
§§/
— Based n=on error mean squares of .452 (Durum wheat), .760 (spring wheat), .520 (barley) and .225
(alfalfa) with 11 degrees of freedom.

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TABLE 15.7. ESTIMATED PERCENT FOLIAR INJURY FOR SELECTED SMALL GRAINS TN THE
MULTIPLE EXPOSURE EXPERIMENT
Species
Desired
Concentratic
(pphm)

Days
Between Exp
osures

)n 7
14
21
*/
28-
35
Durum wheat
25
5%-
5%
5%
15%
5%

40
5
15
15
5
10

80
10
25
30
25
20

120
20
30
40
45
30
Spring wheat
25
5
0
1
15
1

40
5
15
1
15
10

80
15
15
25
20
15

120
25
30
35
30
40
Barley
25
1
1
5
10
1

40
10
20
1
25
5

80
25
15
30
40
20

120
35
35
80
50
35
*/
— Average of three 4th week regimes.
— Percent foliar injury readings made on or about July 1, 1977.
Range Grass and Alfalfa Study
The analyses of variance indicated that significant differences existed
only for western wheatgrass roots and alfalfa tops (Table 15.9). However, the
significance in each case was due to a single mean being greatly different
than the others. For western wheatgrass, the 80 pphm mean was low, for alf-
alfa the 25 pphm mean was high. No systematic variation appeared among the
SO2 treatment means for any of the test species. The 25, AO, 80 and 120 pphm
treatment means tended to vary haphazardly about the control (Figure 15.1).
Among these four means, the minimum was typically less than 10% below the
control and the maximum no more than 25% above.
Species by species comparison of the four treatment means to the control
(Table 15.9) showed that 13 times the SO2 means were less than the control
means and 35 times they were greater. None of these differences were signifi-
cant at the 95% level. Since standard errors were typically less than 10% of
the means, the lack of systematic response to SO2 could not have beenn due to
excessive sampling variability. The results clearly indicate that under the
conditions of biweekly, 3-hr exposures, SO2 concentrations of up to 120 pphm
had no effect on the growth of either the roots or tops of these six species.
12

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TABLE 15.8. YIELD RESPONSE OF SELECTED SMALL GRAINS AND ALFALFA AT SEVERAL
GROWTH STAGES TO S02 FUMIGATIONS
Growth stage (biweekly) increments
S02
i±r
2
3
4
5
6
^Max ^Slin
LSD=




DURUM WHEAT




40 pphm
1.7 gm
1.3 gm
1.6
gm 1. 4 gm
1. 9 gm
2.5 gm
1.2
1.7
80
1.2
1.6
2.0
1.4
1.5
1.7
0.4
1.7
120
2.2
2.5
2.0
2.9
2.5
2.3
0.9
1.7




SPRING WHEAT




40
1.8
1.5
1.7
1.4
1.3
1.2
0.7
2.2
80
1.4
2.0
2.1
1.5
1.6
1.8
0.7
2.2
120
2.1
2.4
1.4
1.9
1.4
2.3
1.0
2.2




BARLEY




40
2.8
2.6
2.3
2.4
3.1
2.0
1.1
1.8
80
1.2
1.7
1.8
1.6
1.3
1.1
0.7
1.8
120
3.4
4.9
3.5
2.2
3.2
3.7
2.7*
1.8




ALFALFA




40
0.36
0.77
0.57
0.50
0.45
0.86
0.50
1.2
80
0.49
0.40
0.52
0.51
1.14
0.36
0.78
1.2
120
0.57
1.34
0.61
0.98
0.52
0.64
0.82
1.2
*Significant at 95% level of confidence.
"t* /
— Average plant yield in (grams dry weight of grain and foliage of small
grains and alfalfa, respectively) based on a sample size of four.
¦t^LSD based on Tukey's studentized range procedure using error mean squares of
.452 (Durum wheat), .760 (spring wheat), .520 (barley) and .225 (alfalfa)
with 11 degrees of freedom.
DISCUSSION
Weekly exposure of Durum wheat and barley for 72 hr at an SO2 concentra-
tion of 15 pphm suppressed average grain yields 42 and 44%, respectively,
compared with the 0 pphm treatment. This suppressive effect was also observed
as the S02 concentration increased from 5 to 10 pphm, but the effect was
considerably less. Though these yields differences were not significant at
the 95% level of confidence, it is probably that the lack of statistical
significance between the treatment' means for Durum wheat and barley was due to
1) the small sample size which was related to experiment limitations (prevent-
ing treatment replication) or 2) the inability to make block-to-block compari-
sons .
A similar yield suppression was not observed with spring wheat indicating
that this species was more resistant. Compared to Durum wheat and barley, the
13

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TABLE 15.9. YIELD RESPONSE OF RANGE GRASS SPECIES AND ALFALFA TO S02 FUMIGATIONS.
SPECIES
Crested wheatgrass
Tops
Roots
9.1 gm
7.7
+ /
TREATMENT MEANS—'
0 pphm 25 pphm AO pphm 80 pphm 120 pphm
9.1 gm
7.4
9.6 gm
7.9
9.7 gm
8.6
9.7 gm
8.7

0.6
1.3
LSD
2.1
1.8
SE-/
0.53
0.46
0.38
1.62
Western wheatgrass
Tops
Roots
3.7
7.5
4.6
7.3
4.2
7.7
4.2
6.5
4.0
8.0
0.9
1.5*
1.1
1.2
0.28
0. 31
1.40
3.30-
Russian wildrye
Tops
Roots
5.9
4.3
7.7
5.7
6.3
4.4
5.8
4.0
6.4
4.8
1.9
1.7
2.0
1.8
0.49
0.43
2.42
2.24
Blue grama grass
Tops
Roots
0.58
0.34
0.63
0.30
0.58
0.31
0.39
0.23
0.69
0.40
0.30
0.17
0.48
0.31
0.12
0.08
0.86
0.68
Needle & Thread Grass
Tops	2.4	3.0	2.2
Roots	1.2	1.6	1.3
3.1
1.7
3.0
1.4
0.9
0.5
1.3
0.7
0.33
0.17
1.50
0.46
Alfalfa
Tops
Roots
5.4
7.7
7.5
6.5
8.9
5.0
7.9
5.5
8.2
2.5"
1.2
2.1
3.5
0.50
0.85
3.88 -
0.40
"Significant at 95% confidence level.
.j. j
—Means based on sample sizes of 14 (crested wheatgrass, western wheatgrass), 13 (Russian wildrye, blue
grama grass, needle and thread grass) and 6 (alfalfa); grams per plant.
¦^Maximum mean minus minimum mean.
— Standard error.

-------
TOPS
ROOTS
10
e e
2
<
uj
$

. Crested
Wheotgross
Russion
Wildrye
— Allolfo
U_ Wesiern
Jl Wheotgiois
Needle 9
Thread Grots
Tr
m T- Blue Gfomo
-¦ r~Cro«
0 25 50 75 100 125
S02 (pphm)
~
Eoch bar equals 2 standard errors.
I0r
e e
5 6
H
r
o
u
5
„ WncalQfOsi
AI to 10
Western
wheatuioss
Russian
Wildrye
IE
25
, Needle 8
" Thread Grass
. Blue Gromo
Grass
50 75
S02 (pphm )
100
125
Each bar equals 2 standard errors.
Figure 15.1. Yield response of tops and growth response of roots of range
grass species and alfalfa to various SO2 concentrations.
foliage of spring wheat was severely injured, but the yield of this species
appeared to be less affected by the SO2 treatments. This, along with results
of associated studies discussed below, suggests that within the environmental
conditions of this research, small grain species can sustain significant
foliar injury without accompanying yield suppression. Based on these observa-
tions, foliar injury is not a reliable predictor for estimating grain' yield
losses.
There was no stage of growth during which the yield of Durum wheat,
spring wheat, barley or alfalfa was affected most by a single, 3-hr exposure
to SO2 concentrations up to 120 pphm. These treatments repeated as frequently
as once a week also failed to affect yields. The average foliar injury to the
small grain species exposed to 120 pphm was approximately 35%. Apparently,
sufficient intervals of time were present between repeated exposures to allow
physiological recovery and a decrease in yields did not occur. This recovery
phenomenon was described by Zahn (1963), when he observed that plant yields
were less affected by SO2 as the period of time between successive exposures
was increased.
The small grain species and alfalfa were tolerant of the relatively
short, 3-hr SO2 exposures when treated under the environmental conditions
which occurred during this investigation. This tolerance to SO2 could be
related to the low rainfall levels which occurred in June and July (Table
15.1). Although soil moisture was not measured within the experimental plots,
the presence of low moisture values can be inferred from the low levels of -
precipitation during these months. It was also during this period of time
that grain heads were developing. Wells (1915), van Haut (1961) and van Haut
and Stratmahn (1970), found that the heading-out stage is one of the critical
phases of growth during which exposure of grain crops to SO2 would be most
likely to suppress yields. Therefore, the absence of adequate soil moisture .
15

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may have increased the tolerance of the crops to SO2 during this critical
growth stage. This aspect of the experimental studies can be related to
expected effects on non-irrigated land within the Poplar River Valley of
Montana, since average moisture conditions are typically low in this region
during the time when grain heads are developing. This ambient condition could
increase the tolerance of plants to SO2> similar to that suspected in this
research. The yields of small grains in this study were similar to average
yields for grain grown in non-irrigated areas of northeastern Montana (Bowman
and Shaw, 1976, 1977) which typically experience low rainfall during the later
growth stages.
Biweekly exposures (every 14 days) of five range grasses and alfalfa for
periods of 3 hr at concentrations of up to 120 pphm SO?, did not affect the
growth of roots or yield of tops. The range grasses failed to develop in
field plot studies, and cuttings transplanted from greenhouse cultures devel-
oped slowly. As a result, exposures to SO2 were not started until late summer
and were, therefore, associated with cool temperatures (Table 15.1). The
exact cause of the lack of response of the range grasses and alfalfa to the
SO2 treatments is difficult to assess, but two possibilities are apparent:
(1) low temperatures during treatment and (2) inherent resistance to SO2.
Cool temperatures which prevailed during this study tend to reduce plant
response to SO2 (Heck et at., 1965; Guderian, 1977). Other investigators
found that the injury (Tingey et al., 1978) and growth (Dodd et at., 1979)
responses of several plant species used in this study were not significantly
affected by a single SO2 exposure to 100 pphm for 4 hours or by seasonal
median SO2 concentrations up to 6.8 pphm (concentrations were lognormally
distributed with a standard geometric deviation of approximately 2.5), re-
spectively. A reasonable analysis of the response of the range grasses and
alfalfa used in this study is that they appear to be relatively tolerant
(based on foliar injury and growth response) to SO2 exposures. A similar
analysis, however, apparently does not exist with regard to another response
parameter—nutritive quality. An analysis of the nutritive quality of western
wheatgrass and prairie June grass demonstrated that seasonal median SO2
concentrations up to 6.8 pphm during two growing seasons reduced crude protein
content and digestibility of western wheatgrass (Schwartz et at., 1978).
CONCLUSIONS
The yields of Durum wheat and barley treated weekly with 15 pphm SO2 for
72 continuous hr were 42 and 44% of the control, respectively. These results
were not significant at the 95% probability level, but the data suggested that
weekly, 72-hr exposures to SO2 concentrations as low as 10-15 pphm could
suppress yields. The yield of spring wheat was not affected by a similar
treatment. Varying the frequency of 3-hr exposure to SO2 concentrations up to
120 pphm from as often as once every week to as infrequently as once every 5
weeks had no effect on yields of the small grains or alfalfa. No growth stage
was identified during which the small grains or alfalfa were most sensitive to
a single 3-hr exposure to SO2 concentrations up to 120 pphm. The growth of
tops and roots of range grasses and alfalfa were not affected by 3-hr expo-
sures to concentrations of SO2 up to 120 pphm repeated at 14-day intervals
during September and October.
16

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REFERENCES
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Colorado. 100 pp.
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Hill, A. C., S. Hill, C. Lamb and T. W. Barret. 1974. Sensitivity of Native
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Pflanzekesch. 70:81-95.
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ACKNOWLEDGEMENTS
The authors acknowledge the capable assistance of the following Oregon
State University Crop Science Department technical personnel in the conduct of
research described in this report: Alex March, Sharon Newton, Milton Plocher
and Rick Voelkel. The excellent supervision of employees and coordination of
research activities by Mr. Shelton Perrigan was greatly appreciated. The
skill of Nancy Lanpheare, the typist, greatly facilitated the preparation of
this manuscript.
This research was funded jointly by EPA Region VIII and the Corvallis
Environmental Research Laboratory. George Bolter, the Region VIII coordinator
for this project, assisted in the design of the experiment.
19

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