Simulated
Acid Rain
on Crops
Special Report 739
May 1985
Agricultural Experiment Station
Oregon State University, Corvallis
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SIMULATED ACID RAIN ON CROPS
AUTHORS: M.D. Plocher1, S.C. Perrigan1, R.J. Hevel1, R.M. Cooper*, and
D.N. Moss , Department of Crop Science, Oregon State Univer-
sity.
PREFACE: The research described in this report was funded by-Oregon
State University and the United States Environmental Protec-
tion Agency under cooperative agreement No. CR-808864-01 and
was planned in cooperation with US-EPA researchers J.J. Lee
and G.E. Neely. The purposes of this report are to document
the work performed under this cooperative agreement and to
make the information obtained available to interested parties.
ACKNOWLEDGEMENTS: We wish to express our appreciation to J.M. Waters
and the crew at Schmidt Research Farm, Department of Crop
Science, Oregon State University, for their technical assis-
tance; to L.C. Grothaus for his statistical analysis of the
1981 studies; to B. Rossbacher for her typing of the manu-
script; and to R. Gearheard and C. Bustamante for their
illustrations to accompany the appendix.
^Research assistants, Department of Crop Science, Oregon State
University.
2
Professor and principal investigator, Department of Crop Science,
Oregon State University.
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TABLES
Number Page
1 Pre-study soil test results for 1981. 3
2 A summary of the treatments and application dates
for the 1981 studies of the effect of acid rain
on crops. 6
3 Summary of 1981 natural and simulated rainfall
and irrigation for 1981. 7
4 The effects of simulated 1:0 and 2:1 sulfuric-nitric
acid rain on top dry weight production and percent
leafiness of "Vernal" alfalfa grown in the field in
1981. 14
5 The effects of simulated 1:0 and 2:1 sulfuric-nitric
acid rain on top dry weight production (g m-2) of
"Alta" tall fescue grown in the field in 1981. 15
6 The effects of simulated sulfuric acid rain on con-
centration of crude protein (CP), acid detergent
fiber (ADF), and 11 mineral elements for two analyses
of "Vernal" alfalfa grown in the field in 1981. 16
7 The effects of 2:1 sulfuric-nitric acid rain on con-
centration of crude protein (CP) and acid detergent
fiber (ADF) of 'Vernal' alfalfa grown in the field
in 1981. 17
8 The effects of 1:0 and 2:1 simulated sulfuric-nitric
acid rain on uptake and concentration of crude protein
(CP), acid detergent fiber (ADF), and 11 mineral ele-
ments in 'Alta1 tall fescue grown in the field in 1981. 18
9 The effects of simulated sulfuric acid rain on dry
weight production (g m-2), number of tillers and heads
per m2, and percent fertile tillers of 'Fieldwin'
wheat and 'Steptoe' barley grown in the field in 1981. 20
10 The effects of simulated sulfuric acid rain on the
yield of Russet Burbank potatoes grown in the field
in 1981. 21
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Number Page
11 The effects of simulated sulfuric acid rain on the
yield of 'Kennebec' potatoes grown in the field
in 1981. 22
12 The effects of simulated sulfuric acid rain on fruit
fresh weight, top dry weight, and the number of
fruit of 'New Yorker' tomatoes grown in the field
in 1981. 22
13 The effects of simulated sulfuric acid rain on root
weights, top dry weights, total dry weights, and num-
ber of plants per plot of 'Cherry Belle' and 'Scarlet
Knight' radish grown in 1981. 24
14 The effects of 2:1 simulated sulfuric-nitric acid
rain on ear weight, grain dry weight, stover dry
weight, and kernel number of 'Pioneer 3992' corn grown
in the field in 1981. 25
15 The effects of 2:1 simulated sulfuric-nitric acid
rain on yield components of single-eared plants of
'Pioneer 3992' corn grown in the field in 1981. 26
16 Summary of amount and acidity of natural and simulated
rainfall and irrigation for the 1982 corn experiments. 30
17 Air temperature (°C) for the 1982 simulated acid rain
events. 31
18 Pre-study field soil characteristics for the 1982
corn experiments. 33
19 Soil analysis results at the conclusion of the 1982
corn experiment. 36
20 The effects of 2:1 sulfuric-nitric simulated acid rain
events with different pH levels on ear fresh weight,
ear dry weight, top dry weight, and grain dry weight
of 'Pioneer 3992' grown in the field in li?32. 38
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Number Page
21 The effects of 2:1 sulfuric-nitric simulated acid rain
events with different pH levels on ear fresh weight,
ear dry weight, top dry weight, and grain dry weight
of 'Northrup King PX39' corn grown in the field in
1982. 39
22 The effects of 2:1 sulfuric-nitric simulated acid rain
events of different pH levels on single-eared plant
stover and grain dry weight and kernel number per plant
for 'Pioneer 3992' corn grown in the field in 1982. 40
23 The effects of 2:1 sulfuric-nitric simulated acid rain
events of different pH levels on single-eared plant
stover and grain dry weight, and kernel number per
plant for 'Pioneer 'Northrup King PX391 corn grown
in the field in 1982. 41
24 The concentrations of 11 mineral elements in leaves of
two corn cultivars treated with 2:1 sulfuric-nitric
simulated rain of two different pH levels. The corn
was grown in the field in 1982. 42
25 The effects of pH 4.0 acid rain events having differing
nitric to sulfuric acid ratios on ear fresh weight and
dry weight, and stover and grain dry weight of "Pio-
neer 3992' corn grown in the field in 1982. 43
26 The effects of pH 4.0 acid rain events of differing
nitric to sulfuric acid ratios on single ear plant
stover and grain dry weight and kernel number per plant
of 'Pioneer 3992' corn grown in the field in 1982. 44
27 The effects of variation in acidity of individual 2:1
sulfuric-nitric simulated acid rain events, but aver-
aging pH 4.0, on stover and grain dry weights of 'Pioneer
3992' corn grown in the field in 1982. 45
28 The effects of variation in acidity of individual 2:1
sulfuric-nitric simulated acid rain events, but aver-
aging pH 4.0, on single-eared plant stover and grain
dry weight and kernel number per plant of 'Pioneer 3992'
corn grown in the field in 1982. 46
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CONTENTS
£*2£
INTRODUCTION 1
1981 MATERIALS AND METHODS 3
Forage Crops 5
Cereal Crops 8
Potato 9
Tomato 10
Radish 11
Corn 11
STATISTICAL ANALYSES 13
1981 RESULTS AND DISCUSSION 14
Forage Crops Yield Data 14
Forage Crops Tissue Analysis 15
Cereals 19
Potato 19
Tomato 19
Radish 23
Com 23
1981 SUMMARY AND CONCLUSIONS 27
1982 MATERIALS AND METHODS 29
1982 RESULTS AND DISCUSSION 38
GENERAL DISCUSSION 47
RECOMMENDATIONS 52
APPENDIX 53
The 1981 Simulator 54
The 1982 Simulator 58
REFERENCES 63
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Abstract
In 1981, simulated H2S04 acid rain was applied to alfalfa and tall
fescue, and a 2:1 ratio of HgSO^HNO-j acid rain was applied to alfalfa,
tall fescue, barley, wheat, potato, tomato, radish, and corn crops
growing in the open field at Corvallis, Oregon. Careful attention was
given to effects of the acid rain on the appearance of the foliage, and
the effects on yield were measured. The simulated acid rain treatments
had no effect on foliage of any crops. The yield of corn was reduced at
pH 4.0 but was not affected by rain of pH 3.5.
Because the effect of pH 4.0 rain on corn yield was the only
significant effect noted in the 1981 studies, in 1982, more extensive
studies of the effect of simulated H^SO^/HNOg rain on corn were con-
ducted. No significant effects of acid rain were found on foliage
appearance, or on yield of grain or stover in the 1982 studies.
The results of these tests, combined with results of earlier
studies, suggest that acid rain per se is not a serious problem for crop
production. This report is the final report of a research project which
has studied the effects of acid rain on many different crops.
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INTRODUCTION
Before these experiments few crops had been exposed experimentally
to acid precipitation (Cohen et al., 1981). In 1979, 1980, 1981, and
1982, studies were conducted by the Oregon State University Crop Science
Department at the Department's Schmidt Research Farm near Corvallis to
determine foliar and yield responses by crops exposed to simulated acid
precipitation.
During the 1979 growing season, 28 different crop cultivars from 24
species were grown in pots in closed top chambers and exposed to
simulated sulfuric acid (H^SO^) rain treatments. Yield and quality
characteristics of these crops were measured. Yields of approximately
two-thirds of the surveyed crops were not affected by simulated F^SO^
rain treatments of varying pH and, of the remaining crops, equal numbers
exhibited stimulatory and inhibitory yield responses. Thus, in general,
acid rain treatment did not appear to either inhibit or stimulate crop
productivity (Cohen et al., 1981).
In 1980, 15 crop species were exposed to simulated sulfuric and
sulfuric-nitric (HgSO^-HNO^) acid rain, both in the open field and in
pots in chambers (Cohen, et al., 1982). Yields of seven of the 15 crop
cultivars were not affected by either ^$0^ or f^SO^-HNO^ rain. The
remaining crops showed both stimulatory and inhibitory responses. In
the field HgSO^ rain studies, no significant effects on yields of
radish, mustard greens or spinach occurred, but yields of alfalfa and
tall fescue were stimulated by acid rain treatments. Yields of field-
grown alfalfa, tall fescue, radish, and spinach were not significantly
affected by HgSO^-HNOg rain simulants but a yield decrease occurred in
mustard greens exposed to pH 3.0 H^SO^-HNOg rain. Corn grain dry weight
was reduced at pH 4.0 in HgSO^ rain. After adjustment for differences
in ear number by covariance analysis, however, no significant effect was
identified (means within ±3 percent of the control). Thus the effect at
pH 4.0 was on ear number. In contrast, rain of pH 3.0 or 3.5 had no
significant effect on yield or yield components of corn.
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2
In chamber experiments in 1980 (Cohen et al., 1982), all crops
except lettuce and onion showed foliar injury from acid rain. This
contrasts sharply with results obtained with field grown plants where,
in 11 studies of six crops, only alfalfa and spinach showed any acid
rain foliar injury, and in those two crops, foliar injury was minimal,
rarely exceeding 1-2 percent of total leaf area. In the chambers in
1980, root crops exhibited both yield stimulation and depression but all
leaf crops showed yield depression in response to acid precipitation.
These results supported the conclusions of the 1979 study.
This report describes work done in both 1981 and 1982. In 1981,
the crop survey was continued to determine sensitivity to simulated
^SO^-HNOg rain of several important crop species grown in a field
environment. In addition, studies were designed to determine if dif-
ferent cultivar responses existed within selected crops. The alfalfa
and tall fescue studies of 1980 were continued in 1981 to examine
cumulative effects of acid rain that might occur in these perennial
crops and to see if response to H2S0^ acid rain differed from the
response to HgSO^-HNOg rain.
The only significant effect of acid rain on crop yield in the 1981
studies was found in corn. Therefore, in 1982, all experiments were
conducted on field corn. Different cultivar responses to HgSO^-HNOg
rain were examined with more treatments over a narrower pH range than
used in 1981. The effect of rain composition was investigated further
using HgSO^, HNOg, and three treatments with different HgSO^HNOg ratios
but the same pH. In addition, an experiment was designed to determine
whether plant response to individual rain events of a constant pH 4.0
treatment differed from response to a series of individual rain events
over a range of pH's that averaged 4.0 for the season.
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3
1981 MATERIALS AND METHODS
All experiments were conducted at Oregon State University Crop
Science Department's Schmidt Farm near Corvallis. The soil at Schmidt
Farm is a Willamette silt loam with a well drained surface layer about
60 cm thicker over a silty clay subsoil. Pre-study soil test results
are listed in Table 1. Field preparation consisted of plowing, discing,
and harrowing. The seedbeds were then cultivated with a rotary tiller
and hand-raked to give a uniform seedbed.
The yield response of 10 crop cultivars to simulated acid rain was
studied in the field in 1981. Alfalfa (Medicago sativa cv. Vernal) and
tall fescue (Festuca arundinaceae cv. Alta) were tested with both
simulated h^SO^ and H^O^-HNO^ rains. Corn (Zea mays cv. Pioneer 3992),
barley (Hordeum vulgare cv. Steptoe), wheat (Triticum aestivum cv.
Fieldwin), potato (Solanum tuberosum cv. Russet Burbank and Kennebec),
tomato (Lycopersicon esculentum cv. New Yorker) and radish (Raphanus
sativus cv. Cherry Belle and Scarlet Knight) were exposed only to the
h^SO^-HNO^j rain. All crops were exposed to simulated acidic rains of
approximately pH 4.0, 3.5, 3.0, and pH 5.6 (control).
Table 1. Pre-study soil test results for 1981.
pH P K Rg B Ca Lime
requirement
ppm MEQ/lOOg ha"1
Wheat/Barley 6.3 42 207 1.8 .55 13.6 6.5
Potato 5.8 39 243 1.7 .51 9.3 6.0
Tomato 5.8 46 279 1.9 .51 11.2 6.2
Radish 5.7 59 174 1.2 .63 10.5 6.1
Corn 5.8 52 202 1.5 .53 9.8 6.1
Background ion concentrations for rain simulations were derived
from precipitation data averaged over seven years from Hubbard Brook,
New Hampshire (Likens and Borman, 1972). Rain simulants were prepared
2+
from a stock solution of deionized water with 0.220 mg/1 Ca , 0.216
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4
mg/1 NH^+, 0.115 mg/1 Na+, 0.078 mg/1 K+, 0.060 mg/1 Mg^+, 0.539 mg/1
S042-, 0.744 mg/1 NOg", and 0.425 mg/1 Cl~added. The control rain
consisted of stock solution in equilibrium with atmospheric CO2 result-
ing in a pH of approximately 5.6. Acid treatments were prepared by
adding 3.6 N I^SO^ and 1.8 N HNO^ to the control rain to achieve the
desired pH and acid equivalent ratios. The h^SO^-HNOg rain pH treat-
ments were achieved using the acids in a 2:1 H+ equivalent ratio.
Rain treatments were applied through stainless steel nozzles
calibrated for even distribution over the plot study area at a rate of
0.7 cm/hr (see appendix for a designation of the nozzles and chambers).
Rain events were 100 minutes/day, 2 days/week for a total rainfall of
2.2 cm/week. The pH of the rain solutions was checked during each rain
event using an Orion 901 Research Microprocessor Ionanalyzer calibrated
to standard pH buffer solutions of 4.01 and 7.00.
A randomized complete block design with four treatments (pH levels)
and four replications was used for all studies. Each plot was a 1.8 m
square area within a 3-m diameter circle defined by the placement site
of the rain application chambers. The circle was centered in a 5-m by
4.5-m crop area, which gave 1-m borders on the ends and between chamber
sites. A split plot design was used with barley, wheat, radishes, for-
ages, and potatoes, with crop or cultivar making up the subplot. These
designs are discussed under the heading of the individual crops. Six-
teen portable cylindrical chambers measuring 3 m in diameter and 2.4 m
in height were placed over the plots during a rain event. The chambers
had open tops. The walls were formed of polyvinyl chloride tubing cov-
ered with Monsanto 602 plastic. The entire structure was then covered
with a a horticultural shade cloth to simulate cloud cover while allow-
ing free air movement through the chamber top. The four chambers within
each replicate block were rotated within the block from one rain event
to the next to reduce variation associated with possible chamber differ-
ences. As the plants grew, the chambers were placed on extensions to
maintain uniform rain distribution pattern at the top of the crop
canopy.
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5
Forage Crops
The forage crop plots were planted in a split plot with rain pH
constituting the main plots and forage species the subplots. The main
plot area consisted of 10 rows each of 'vernal' alfalfa and 'alta' tall
fescue spaced 15-cm apart and 5-m long, the alfalfa to the north and the
tall fescue to the south in each plot. The circular rain exposure sites
were laid out in the center of the main plots so the 1.8-m square cali-
brated rain area contained 6 rows of each species. The two adjoining
center rows were left as border and 5 rows, 1.8 m long, were harvested.
Thus, the harvested plot area was 1.35 m2 for each subplot.
Alfalfa and tall fescue h^SO^ and h^SO^-HNO^ study plots from
the 1980 crop season (Cohen et al., 1982) were well established. How-
ever, the 1981 alfalfa F^SO^-HNOj plots were damaged extensively by
gophers over the winter and were tilled under. The damaged area was
replanted using the same methods and plot layout used in 1980 (Cohen et
al., 1982). The alfalfa seed was inocculated with Rhizobium meliloti
before planting.
After planting the alfalfa HgSO^-HNO^ study, both alfalfa studies
were fertilized with 44.8 kg/ha S broadcast and 6.7 kg/ha B applied with
a boom sprayer and followed by irrigation. Both tall fescue studies
received 56 kg/ha N and 44.8 kg/ha S by broadcast application. Manual
weed control was performed as needed. Malathion and Sevin were used for
insect control and Maneb fungicide was used to control downy mildew.
There was an initial harvest of the l^SO^ rain-treated alfalfa plots on
May 7, before the 1981 rain treatment began. The yield of the initial
harvest was not included in the crop response yield data.
The alfalfa and fescue H^SO^ and fescue HgSO^-HNOg plots received
the first simulated rain exposures May 14 (Table 2). The first treat-
ment exposure for the H2S04-HN0g alfalfa (new planting) was June 25.
Natural and simulated rainfall were supplemented with sprinkler irriga-
tion (Table 3) when soil moisture content indicated need (Lorenz and
Maynard, 1980).
The alfalfa rain studies were harvested on July 2, August 5,
and October 21, and the alfalfa HgSO^-HNO^ study was harvested on
October 10. All harvests were at about the 10% blossom stage. The tall
fescue HgSO^ rain studies were harvested July 16-17 and October 14-15,
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Table 2. A sunwary of the treatments and application dates for the 1931 studies of the effect of acid rain on crops
Total fertilizer
First
Last
Total
Crop
Cultivar
Rai n
application kg/ha
Seeding
rain
rain
rain
Harvest date
type
N-P205- K20-S-8
event
event
events
Alfalfa (Medicaqo sativa)
Vernal
1:0
0-0-0-44.8-6.7
5/19/80
5/14/81
10/20/81
44
5/07, 7/02.8/05, 10/21'
2:1
0-0-0-44.8-6.7
5/26/81
6/25/81
10/08/81
30
10/10
Tall Fescue (Festuca arundinaceae)
Alta
1:0
56-0-0-44.8-0
5/20/80
5/14/81
10/15/81
42
5/06, 7/16-17,10/14-152
2:1
56-0-0-44.8-0
5/20/80
5/21/81
10/13/81
33
5/04,5/17, 10/162
Barley (Hordeum vulgare)
Steptoe
2:1
78-67-67-24-0
4/27-28/81
5/21/81
08/10/81
24
8/12/81
Wheat (Triticum aestivum)
Fieldwi n
2:1
78-67-67-24-0
4/28/81
5/21/81
08/27/81
28
8/31/81-9/01/81
Potato (Solanum tuberosum)
Russet Burbank
2:1
224-134-168-47-0
5/13-14/81
6/02/81
09/01/81
27
9/02, 9/163
Kennebec
2:1
224-134-168-47-0
5/14-15/81
6/02/81
09/01/81
27
9/02, 9/16-17/813
Tomato (Lycopersicon esculentum)
New Yorker
2:1
84-U2-90-31-0
4/17/81
6/05/81
10/20/81
33
8/10, 10/05, 10/06/81 **
Radish (Raphanus sativus)
Cherry Belle
2:1
56-1112-112-40-1
9/25/81
10/2/81
11/10/81
12
11/12/81
Scarlet Knight
2:1
56-112-112-40-1
9/25/81
10/2/81
11/10/81
12
11/12/81
Corn (Zea mays)
Pioneer 3992
2:1
224-134- 134-45-1
6/01-02/81
6/12/81
10/02/81
33
10/26-27/81
'Harvest dates for pre-rain havest, harvest 1, harvest 2, harvest 3
2Harvest dates for pre-rain harvest, harvest 1, harvest 2
3Tops harvested 9/2/81, Tubers 9/16-17/81
''Seventeen fruit harvests beginning 8/10/81, ending 10/05/81, tops 10/06/81
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Table 3. Summary of 1981 natural and simulated rainfall and irrigation
Natural rainfall
Study
hLSO.:HN0o
ratio
from
emergence
to harvest
(cm)1
on same
days as
simulated
(cm)2
Total
simulated
rainfall
(cm)
3.0
Average pH of natural
simulated rainfall
treatment pH —
3.5 4.0
plus
3
5.6
Total
irriga-
tion
(cm)
Alfalfa
1:0
26.3
4.3
49.1
3.1
3.6
4.1
5.5
43.9
2:1
8.1
.8
35.7
3.1
3.5
4.0
5.5
38.1
Tall Fescue
1:1
26.3
4.3
49.1
3.1
3.6
4.1
5.5
43.9
2:1
27.7
3.1
38.0
3.2
3.7
4.2
5.5
43.9
Barley
2:1
13.0
.8
26.7
3.1
3.6
4.1
5.5
8.1
Corn
2:1
10.4
3.0
36.8
3.1
3.6
4.0
5.5
45.9
Potato
2:1
6.9
1.8
30.0
3.0
3.5
4.0
5.5
20.0
Radish
2:1
17.6
6.3
13.3
3.3
3.8
4.2
5.5
0
Tomato
2:1
12.0
1.2
36.7
3.1
3.5
4.0
5.5
27.6
Wheat
2:1
13.1
.8
31.1
3.1
3.6
4.1
5.5
8.1
1. Includes all natural rain from the date seedlings emerged from soil until harvest (date of trans-
plant for tomatoes and first acid rain exposure for 1:0 alfalfa and 1:0 and 2:1 tall fescue).
2. Includes only natural rainfall on days when simulated rain was applied.
3. Volume weighted average (computed using crop growth season natural rainfall).
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8
and the ^SO^-HNOg studies were harvested July 15 and October 16. All
forage plots were cut to a stubble height of 7.5 cm.
Subsamples of the forages for chemical analysis were taken at the
final harvest. A subsample of 100 stems per plot from the final alfalfa
harvest was separated into leaf plus petiole, and to stem fractions,
from which percent leafiness was calculated. Percent crude protein
(CP), acid detergent fiber (ADF), total sulfur (S), potassium (K),
phosphorus (P), calcium (Ca), magnesium (Mg), manganese (Mn), iron (Fe),
copper (Cu), boron (B), zinc (Zn), and aluminum (A1) were determined on
samples from the third harvest of f^SO^ rain-treated alfalfa and from
the second harvest of both HgSO^ and ^SO^HNOg rain treatments in tall
fescue. The HgSO^-HNOg rain alfalfa was analyzed for CP and ADF only.
The fescue samples for chemical analysis consisted of 15 g (fresh
weight) of tissue from each of the five study rows per plot. Tissue,
oven dried at 60°C for 48 hours, was ground to pass through a 0.5-mm
screen. Percent crude protein was calculated by multiplying percent
nitrogen (N) by 6.25. Acid detergent fiber primarily contains cellulose
and lignin residues and is used as an indicator of forage digestibility
(Matches, 1973). The Forage Analytical Service, Oregon State Universi-
ty, determined percent N using a standard Kjeldahl procedure (AOAC,
1975) and ADF using the method of Goering and Van Soest (1970). The
Plant Analysis Laboratory, Oregon State University, determined total S
using a Leco Sulfur Analyzer as described by Jones and Isaac (1972) and
the 10 other elements using direct reading emission spectrometry as
described by Chaplin and Dixon (1974).
Cereal Craps
The response of spring wheat and barley to simulated I^SO^-HNOg
rain was measured in 16 contiguous plots, planted in a split plot
design, with pH comprising the main plots and 'Steptoe' barley and
'Fieldwin' wheat comprising the split plots. The calibrated rain areas,
1.8-m square, contained five harvest rows of each species separated by
one border row of each species. Row spacing was 15 cm. Thus, the
harvested subplot area was 1.35 m2.
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9
Seeds were planted 1 cm apart at 2-cm depth. The plots were fer-
tilized, following recommendations based on soil analysis (Table 1),
with 78-67-67-24 kg/ha N^O^-I^O-S incorporated before planting. Weeds
were removed by hand. Malathion and Bayleton were used to control
insects and fungal diseases, respectively. Loose smut (Ustilago nuda)
infected heads of barley were rogued as they appeared.
Plots received the first f-^SO^-HNC^ rain May 21 (Table 2). Addi-
tional irrigation was applied (Table 3) when moisture in soil cores from
plot areas outside the simulated rainfall area indicated less than 50
percent field capacity (Lorenz and Maynard, 1980).
Barley was harvested August 12-13. Wheat was harvested August
31-September 1. Tillers per plot were counted. The plants were har-
vested at ground level. Heads were removed and bagged separately from
the straw. Samples were dried at 60°C and dry weights were measured for
heads and straw. Heads were then threshed, the grain weighed, and
kernels counted.
Potato
'Kennebec' and 'Russet Burbank' potatoes were compared to see if
cultivars differed in their response to HgSO^-HNOg rain. Sixteen
contiguous plots were planted in a strip using a split plot design with
rain pH as the main plots and cultivars as split plots. The split plot
consisted of equidistant hills on 45-cm centers (approximately 48,200
plants/ha) with each cultivar making up one half of the harvest area.
The cultivars were bordered on the plot edges and ends by two hills on
all sides. The harvested subplot consisted of eight hills of a given
cultivar in an area of 1.6 m2.
Seed pieces weighing approximately 50 g were treated with Captan
five percent dust and planted on May 13-15, one seed piece per hill, at
ten cm depth. Fertilizer, based on soil analysis, was broadcast and
incorporated at the rate of 224-134-168-47 kg/ha N-PgOg-KgO-S. Dyfonate
granules at 4.5 kg/ha were incorporated with the fertilizer to control
wireworms. A pre-emergent herbicide, 1.1 kg/ha EPTC (Eptam), was
applied and additional weed control was done by hand. Malathion and
Sevin were used for insect control.
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10
Plots received the first rain treatment exposure June 2. Supple-
mental irrigation was applied when soil cores from plot areas outside
the simulated rainfall area indicated less than 50 percent field capac-
ity (Lorenz and Maynard, 1980). After senescence, the potato vines were
harvested on September 2. The tubers were left to age in the soil until
September 16-17. Boundaries of the 1.8-m square harvest area were cut
precisely with a shovel blade. All partial potatoes cut with the shovel
blade within the study area were bagged separately. Whole potatoes were
classed by weight (less than 110 g, 110-170 g, 170-230 g, 230-280 g, and
more than 280 g). Fresh weights for each class per variety per plot
were measured. Potato tubers and vines were oven-dried at 60°C and dry
weights were measured.
Tomato
The response of field grown 'New Yorker' tomatoes to simulated
H^SO^-HNOg rain was measured in 1981. Seeds were planted in 5-cm pots
on a mist bench April 17. On June 3, plants 36-43 cm in height were
selected and transplanted in the field in rows 75 cm apart, in an east-
west strip of 16 contiguous 3 x 5 m plots. Transplants were spaced 60
cm apart in each row. The calibrated rain area contained two study rows
of three plants each in a 2.7 m2-harvest area. The harvest plot was
surrounded by two border plants on all sides. Based on soil analysis,
6,720 kg/ha lime and 56, 112, 90, and 31 kg/ha of N, P205» and ^
fertilizer, respectively, were incorporated into the soil (Table 1). An
additional 28 kg/ha N was applied as a foliar spray on July 2. Manual
weed control was provided as needed.
The first H^SO^-HNO^ rain event was June 5. Sprinkler irrigation
was applied when soil moisture in the plot outside of the simulated
rainfall area decreased to 50 percent field capacity (Lorenz and May-
nard, 1980).
Ripe tomatoes were harvested twice weekly beginning August 10.
Final harvest of all fruit was October 5. Tomatoes were counted,
weighed, and size classed as < 6.4 cm, 6.4-7.6 cm, and > 7.6 cm in
diameter. An assessment of fruit abnormalities was conducted at each
harvest. Vines were cut at ground level on October 6, dried at 60°C for
48 hours and then weighed.
-------
11
Radish
'Cherry Belle1 and 'Scarlet Knight' radishes were exposed to
simulated h^SO^HNOg rain. Radishes and mustard greens were hand seeded
September 25 in a split plot design with pH as main plots and species as
subplots. The 1.5 x 3 m radish subplot was further split with the
sub-subplot being cultivars. The mustard greens did not mature and were
not harvested. Radish plant spacings of 15 cm between rows and 7.6 cm
within each row were used. One border row of 'Scarlet Knight' separated
the radish and mustard greens. Two 1.8 m rows each of 'Scarlet Knight'
and 'Cherry Belle' were designated study rows within the calibrated
spray area. The harvested sub-subplots for each radish variety had an
area of 0.55 m2. A border of 'Cherry Belle' radish was planted outside
the calibrated area. Between cultivar border rows were not necessary
because of similarities in plant characteristics. Based on soil analy-
sis, (Table 1) 6,720 kg/ha lime and 56, 112, 112, 40, and 1 kg/ha N,
P205, K20, S, and B fertilizer were broadcast and incorporated before
planting. Dyfonate granules at 4.75 kg/ha were incorporated with the
fertilizer to control wireworms. The first HgSO^-HNO^ treatment expo-
sure was October 2 (Table 2). Plots were weeded by hand as needed.
Simulated and natural rainfall (Table 3) provided enough moisture for
crop growth and additional irrigation was not needed. Radishes were
harvested November 12 when roots had reached marketable size. At
harvest, root fresh weight and top and root dry weights were measured.
Corn
The response of hybrid field corn cultivar 'Pioneer 3992' to
H2S04-HN03 simulated rain was studied. Harvest plots consisted of four
rows spaced 0.5 m apart and 1.8 m long. Corn was hand seeded June 1 and
2 using a planting dibble to maintain uniform seed depth. Seeds were
planted in hills 30 cm apart in rows 50 centimeters apart. This grid
pattern insured equal plant numbers in the calibrated spray areas of all
plots. Three seeds were planted per hill and thinned to a single plant
per hill after emergence, providing a plant population of approximately
64,200 plants ha"1. Each plot consisted of four east-west rows of six
plants. Plots were bordered by three east-west rows outside the cali-
brated rain area and separated from each other by a minimum of four
-------
12
hills in the row. Before planting, 6,720 kg/ha lime and 224, 134, 134,
45, and 1 kg/ha N, P2O5, 1^0, S, and B fertilizer were broadcast and
incorporated. Plots were hand weeded as necessary. Supplemental
sprinkler irrigation was applied to meet the requirements of border
plants outside the calibrated acid rain spray areas (Table 3). Fre-
quency of irrigation was determined by evaluating moisture content of
soil cores using methods of Lorenz and Maynard (1980).
The corn was harvested on October 26-27. Ear fresh weights, dry
weights, grain dry weights, kernel counts, and total top dry weight per
plot were measured. Data for single-eared plants were recorded separ-
ately from those for multiple-eared plants, tiller-eared plants and
plants without ears.
-------
13
STATISTICAL ANALYSES
A one-way analysis of variance (ANOVA) was used to compare treat-
ments. When the resulting pH-treatment F value was significant at the
five percent level of probability (P £ 0.05), two-sided t-tests were
used to determine which acid treatment means differed significantly (P <
0.05) from the control. Data are expressed as plot means unless
otherwise noted.
-------
14
1981 RESULTS AND DISCUSSION
Forage Crops Yield Data
'Vernal' alfalfa exposed to H^SO^ rain for a second crop year
showed no significant differences between treatments for top dry weight
or leafiness. Likewise, the H^SO^-NOg rain treatments, which were
applied in 1981 only, showed no significant differences in yield or
percent leafiness (Table 4). The HgSO^-NOg study was a new planting and
was harvested only once.
Table 4. The effects of simulated 1:0 and 2:1 sulfuric-nitric acid
rain on top dry weight production and percent leafiness of
'Vernal' alfalfa grown in the field in 1981
1:0 rain 2:1 rain
pH
1
Top dry weight, g m-2
2 3
Total
Leafi-
ness, %
weight
g m-2
Leafi-
ness, %
5.6
486
402
168
1,056
40
270
47
4.0
449
385
175
1,009
40
270
47
3.5
523
430
193
1,146
40
259
52
3.0
468
377
133
978
43
246
50
SEb
22.2
18.9
11.9
48.7
1.6
11.0
2
Fc
NS
NS
NS
NS
NS
NS
NS
Standard error of the mean,
Significance level of the F-test.
'Alta' tall fescue showed no significant differences in yield
between treatments when exposed to H^SO^ rain for a second crop year
(Table 5). However, the tall fescue treated with h^SO^-HNO^ rain
exhibited a significant decrease of 9% in top dry weight at the first
harvest at pH 3.5 (Table 5). There was no significant difference among
treatments at the second harvest or in the combined top dry weights for
both harvests.
This one example of a statistically significant response in tall
fescue is probably an anomaly, since the significant decrease occurred
only at pH 3.5, at one harvest only. In that same experiment there was
-------
15
no effect on yield of rain of pH 3.0. If acid rain were affecting
growth, the effect should have been more severe at the lower pH. Also
one would expect to have seen an effect at other harvests.
Table 5. The effects of simulated 1:0 and 2:1 sulfuric-nitric acid
rain on top dry weight production (g m-2) of 'A1ta1 tall
fescue grown in the field in 1981
—q £71
pH
Harvest 1
Harvest 2
Total
Harvest 1
Harvest 2
Total
5.6
383
306
689
390
244
634
4.0
397
304
701
369
257
626
3.5
399
293
692
354*
231
585
3.0
399
307
706
405
285
690
SEb
11.12
10.0
18.0
9.3
15.6
21.2
FC
NS
NS
NS
*
NS
*
Standard error of the mean.
Significance level of the F-test from a one-way analysis of variance
with * denoting P ^ 0.05.
Symbol after table value denotes significant differences from the
control mean with P £ 0.05 for two-sided t-test.
Forage Crops Tissue Analysis
Tissue analysis of stems and leaves of 'Vernal' alfalfa treated
with H2S04 rain showed a significant increase in sulfur content at pH
3.0 (Table 6). Because of the increase in sulfur content, the corre-
sponding N:S ratio exhibited a significant decrease. The increase in
sulfur content, though significant, represents only two tissue samples.
No significant differences were found for pH 3.5 or pH 4.0 treatments
and there were no significant differences between treatments for any
element in 1980, the first year of this study (Cohen et al., 1982).
No differences were found in the 1981 alfalfa acid detergent fiber
(ADF) content. This result contrasts with the 1980 result in which the
sulfuric acid rain-treated plots showed an increase in ADF at all pH
levels, compared to control.
-------
Table 6. The effects of simulated sulfuric acid rain on concentration of crude protein (CP), acid
detergent fiber (ADF), and 11 mineral elements for two analyses of 'Vernal' alfalfa grown
in the field in 1981
Leaves and stems separated
Treatment
CP
ADF
S
K
P
Ca
Mg
Mn
Fe
Cu
B
Zn
A1
rtl4
P"
A)
- ppm
5.6 leaves
23.2
16.9
0.29
0.97
0.25
2.90
0.27
60.5
548
5.00
76.5
12.0
501
3.0 leaves
23.8
15.9
0.38
1,02
0.25
2.95
0.27
55.5
462
5.00
85.5
10.5
385
5.6 stems
10.4
45.1
0.13
1.01
0.20
1.21
0.26
21.5
312
3.00
21.0
5.0
288
3.0.stems
11.0
43.0
0.17
1.17
0.25
1.34
0.23
18.5
202
3.00
26.0
12.5
204
SEbr
2.4
5.2
0.04
0.06
.01
0.31
.01
7.3
58
.42
11.1
1.6
49
CVd
40
49
47
17
13
42
15
53
43
30
60
45
41
F
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
Leaves and
stems
combined
Treatment
CP
ADF
S
K
P
Ca
Mg
Mn
Fe
Cu
B
Zn
A1
nL|
1
pn
h>
ppm
5.6
15.7
32.2
.23
1.1
.25
2.55
.23
41.0
236.5
3.5
56.0
12.0
208.0
4.0
16.3
34.9
.22
1.0
.24
2.55
.24
39.2
308.0
4.2
50.2
11.0
248.2
3.5
16.0
34.5
.21
1.0
.23
2.39
.25
35.7
354.0
4.2
47.0
9.0
315.7
3.0.
15.7
32.2
.32*
1.0
.25
2.62
.29
42.5
312.5
5.0
52.0
11.5
221.5
SEr
0.2
1.0
0.02
0.0
.01
.04
.01
1.6
28.5
0.2
2.5
0.7
29.6
CVd
5
10
23
8
7
6
16
15
32
15
17
23
39
F
NS
NS
*
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
Concentrations are expressed on a dry weight basis for both separated and combined leaves and stems.
^Standard error of the mean.
Coefficient of variation for the mean (percent).
F^Significance level of the F-test with * denoting P 5 0.05.
~Symbol after table values denotes significant differences from control means with P £ 0.05 for
two-sided t-test.
-------
17
Analysis of alfalfa tissue from HgSO^-HNOg rain treatments in 1981
showed no significant differences between treatments (Table 7). This,
too, differs from 1980 when the first harvest of the HgSO^-HNO^ rain
treatment showed an increased N content at pH 4.0 and increased S at pH
3.0, and the second harvest had a significant increase in ADF at pH 3.5.
Table 7. The effects of 2:1 sulfuric-nitric acid rain on concentration
of crude protein (CP) and acid detergent fiber (ADF) of
'Vernal' alfalfa grown in the field in 1981
Separated 1
eaves and
stems
Combined 1
eaves and
stems
Treatment
CP (%)
ADfU)
Treatment
CP {%)
ADF (%)
5.6 (leaves)
21.8
17.5
5.6
15.9
31.8
3.0 (leaves)
20.3
16.9
4.0
15.7
30.6
5.6 (stems)
9.6
46.7
3.5
16.2
30.4
3.0 (stems)
8.5
46.4
3.0
15.4
33.1
SEb
0.1
0.6
CVc
3
7
Fd
NS
NS
Concentrations are expressed on a dry weight basis for separated and
combined leaves and steins.
bStandard error of the mean.
cCoefficent of variation for the mean.
^Significance level of the F-test.
'A1ta' tall fescue tissue showed no significant treatment effects
for CP, ADF, S, P, K, Mg, Cu, B, Zn, or A1 for either H2S04 or H2S04-
HNOg simulated rains (Table 8). However, compared to the control, Ca
content was significantly lower (P s .01) at pH 3.0 and pH 3.5 in the
HgSO^ rain treatments. The 1980 second harvest HgSO^-HNOg samples had a
significant decrease in Ca at pH 4.0 but not at pH 3.0 or pH 3.5. Thus,
the data suggest that acid rain does decrease Ca content in tall fescue
under some conditions. In the HgSO^-HNO^ treatments, there was a signi-
ficant increase in Fe at both pH 3.0 and pH 3.5. These differences,
although significant, again represent only two tissue samples.
-------
Table 8. The effects of 1:0 and 2:1 simulated sulfuric-nitric acid rain on uptake and concentration
of crude protein (CP), acid detergent fiber (ADF), and 11 mineral elements in 'Alta' tall
fescue grown in the field in 1981
1981
1:0
CP
ADF
S
K
%
P
Ca
Mg
Mn
Fe
Cu
B
Zn
A1
fd
~~ PPm
5.6
9.68
36.0
.28
1.52
.32
.36
.21
96.5
448.2
.88
3.25
7.00
651
4.0
9.35
7.0
.28
1.51
.31
.34
.22
95.7
345.5
.75
2.75
6.75
510
3.5
9.43
36.9
.29
1.50
.31
.32**
.20
102.0
531.7
.75
3.50
7.50
804
3.0
9.54
37.6
.31
1.50
.29
.28**
.20
105.2
606.5
.88
2.50
6.75
914
S.E.b
.14
.3
.01
.04
.01
.01
.01
2.1
60.3
.06
.29
.48
102
CVc
6
3
16
10
9
10
12
9
50
31
38
28
57
Fd
NS
NS
NS
NS
NS
**
NS
NS
NS
NS
NS
NS
NS
1981
2:1
5.6
10.31
33.90
.30
1.70
.33
.35
.20
83.50
161.2
.75
4.00
8.75
315
4.0
9.61
34.33
.29
1.58
.33
.35
.20
88.25
287.7
.75
3.75
8.25
378
3.5
9.77
35.56
.30
1.58
.35
.33
.22
88.50
333.7*
.87
3.50
7.50
471
3.0
9.78
35.52
.31
1.59
.32
.29**
.21
93.25
396.2**
.87
3.25
7.25
567
S.E.b
.13
.57
.01
.04
.01
.01
.01
2.35
36.2
.06
.30
.44
58
CVC
5
7
13
10
8
9
12
11
49
31
33
22
53
Fd
NS
NS
NS
NS
NS
**
NS
NS
*
NS
NS
NS
NS
.Concentrations are expressed on a dry weight basis.
Standard error of the mean.
.Coefficient of variation for the mean (percent)
Significance level of the F-test with * and ** denoting P s 0.05 and 0.01, respectively.
*,**Symbols after table values denote significant differences from control means with P i 0.05 and
0.01, respectively, for the two-sided t-test.
-------
19
No foliar acid rain injury was observed in alfalfa or in the
H2S04-HN03 tall fescue experiments. Slight foliar acid rain injury was
observed on H2S0^ treated tall fescue but only at pH 3.0. In that
treatment, whitish spots, sometimes associated with a brown halo,
appeared on some leaves, especially along the leaf margins. Injury
amounted to less than one percent of leaf area and was not noted before
June 22 or after September 22.
Cereals
No significant differences of any kind were found in the cereal
studies (Table 9). There was no foliar injury. The grain dry weight,
non-grain head dry weight, stubble dry weight, total top dry weight,
head number, tiller number, percent fertile tillers, and dry weight per
kernel of 'Fieldwin' wheat and 'Steptoe' barley were not affected by
simulated H^SO^ acid rain treatments (Table 9).
Potato
Acid rain did not affect any measured trait of either 'Russet
Burbank' (Table 10) or 'Kennebec' (Table 11) potatoes. Likewise, there
was no foliar injury from acid rain treatment on either variety.
Tomato
'New Yorker' tomato plants showed no significant differences in
treatment response for mature fruit fresh weight, number of mature
fruit, average fresh fruit weight of mature fruit, total fresh weight of
immature fruit, total number of immature fruit, total fruit fresh
weight, total fruit number, and total top dry weight (Table 12). The
number of mature fruit in each of the three diameter size classes was
not significantly different for any pH treatment when analyzed for early
season (August 10-24), mid-season (August 31-September 17), and late
season (September 21-0ctober 5) harvests. However, the number of mature
fruit greater than 7.6 cm in diameter for all harvests combined was
significantly greater at pH 3.0 (F-test P = 0.02, t-test P s 0.01).
Foliar injury from acid rain occurred only at pH 3.0. On those
plants, a small amount of white circular flecking covering less than one
percent of the leaf area was observed on July 24, 31, and August 6.
-------
Table 9. The effects of simulated sulfuric acid rain on dry weight production (g m-2), number of tillers
and heads per m2, and percent fertile tillers of 'Fieldwin' wheat and 'Steptoe' barley grown
in the field in 1981
WKeat
PH
Grain
dry wt
Straw
dry wt
Non-grain
head dry wt
Total
dry wt
Harvest
index, %
Tiller
number
Number
of heads
% Fertile
tillers
5.6
269
599
126
994
.18
516
448
87.7
4.0
263
634
118
915
.16
472
442
94.9
3.5
260
606
122
988
.37
489
411
83.1
3.0
256
574
120
950
.15
479
437
91.0
SEb
14.8
25.0
3.7
32.6
.10
15.6
22.5
4.3
Fc
NS
NS
NS
NS
NS
NS
NS
NS
PH
Barley
5.6
370
366
94
930
.40
444
395
89.8
4.0
396
491
96
983
.40
453
410
91.6
3.5
411
495
99
1005
.41
461
411
89.0
3.0
379
469
92
940
.40
. 452
381
84.2
SEb
11.2
22.5
5.9
37.0
.08
11.5
15.7
2.2
Fc
NS
NS
NS
NS
NS
NS
NS
NS
^Standard error of the mean
Significance level of the F-test.
-------
21
Similar appearing insect injury masked acid rain treatment differ-
ences after that date. No acid rain injury to the fruit occurred at any
of the treatment levels.
Table 10. The effects of simulated sulfuric acid rain on the yield of
Russet Burbank potatoes grown in the field in 1981
T uber Tuber Av. Av. VTne Total
Treat-
ment
FW
(kq m-2)
DW
(kq m-2)
tuber
FW (g)
tuber
DW (g)
DW
(kq m-2)
DW
(kg m-2)
5.6
6.52
1.61
80
19.6
0.24
1.85
4.0
6.20
1.60
81
20.9
0.22
1.82
3.5
6.30
1.62
80
20.5
0.22
1.84
3.0
6.53
1.66
79
20.0
0.24
1.90
SEa
0.24
0.06
3.6
.9
0.02
0.08
Fb
NS
NS
NS
NS
NS
NS
aStandard error of the mean.
^Significance level of the F-
test.
Table 11,
The effects of simulated sulfuric acid rain on the yield of
Kpnnphpr potatoes grown in the field in 1981
Treat-
ment
Tuber
FW
(kq m-2)
Tuber
DW
(kg m-2)
Av.
tuber
FW (q)
AV.
tuber
DW (g)
vine
DW
(kg m-2)
Total
DW
(kg m-2)
5.6
6.26
1.42
124
28
0.28
1.70
4.0
6.40
1.60
134
33
0.27
1.87
3.5
5.93
1.39
149
35
0.29
1.68
3.0
6.75
1.64
144
35
0.30
1.94
SEa
0.34
0.10
6.5
2
0.01
0.11
Fb
NS
NS
NS
NSN
NS
NS
aStandard error of the mean.
^Significance level of the F-test.
-------
Table 12. The effects of simulated sulfuric acid rain on fruit fresh weight, top dry weight, and the
number of fruita of 'New Yorker' tomatoes grown in the field in 1981
Mature
Mature
Mature
fruit
fruit
fruit
Immature
per m2
per m2
per m2
Total
Treat-
Fruit fresh weight (kc
1 m-2)
Top DW
fruit
6.4 cm
6.4-7.6 cm
7.6 cm
fruit
ment
mature
immature
total
(kg m-2}
per m-2
diam
diam
diam
per m-2
5.4
7.89
1.75
9.64
0.20
32
53
18
6
109
4.0
7.88
2.26
10.14
0.21
37
53
16
7
113
3.5
8.35
1.97
10.32
0.22
28
53
20
6
107
3.0
8.70
1.86
10.56
0.20
31
50
18
g**
108
SEb
0.43
0.32
0.58
0.01
2.9
2.5
1.6
0.6
4.7
Fc
NS
NS
NS
NS
NS
NS
NS
*
NS
aMature fruit were divided into three categories, 6.4, 6.4-7.6, and 7.6 cm.
^Standard error of the mean.
Significance level for the F-test with * denoting P £ 0.05.
*,**Symbols after table values denote significant differences from the control mean with P = 0.05 and
0.01, respectively, for two-sided t-test.
-------
23
Radish
Simulated I^SO^-HNOg acid rain treatments had no significant effect
on the yield of 'Cherry Belle' or 'Scarlet Knight1 radishes grown in the
field in 1981 (Table 13). Similar results for 'Cherry Belle' were found
in the 1980 field studies.
Some injury to the cotyledons of both varieties was observed at pH
3.0, but not in other treatments. In the pH 3.0 treatment, irregular
shaped gray spots in areas of rain drop accumulation covered less than
two percent of the surface area. No acid rain injury was observed on
any true leaves.
Corn
In 1981, for the second year, the effect of H^SO^-HNO^ acid rain on
'Pioneer 3992' field corn yield and yield components was evaluated. In
1980, corn exposed to pH 4.0 had a lower grain yield than did the
control plots (P < .05). However, rain of pH 3.5 and 3.0 had no sig-
nificant effect on yield and there was no injury to foliage by acid
rain. It appeared that the pH 4.0 treatment had fewer two-eared plants
but since no significant effects were found at other pH levels, the
grain yield reduction at pH 4.0 was unexplained. The same treatments
were repeated in 1981 to check the 1980 results. Table 14 lists the
yield and yield components of 'Pioneer 3992' field corn exposed to
H2S0^-HN03 simulated acid rain in 1981. Surprisingly, there was again a
trend toward a depression in yield of corn at pH 4.0, although the
difference was not significant (P = .08). However, there was a highly
significant (P < .01) decrease in stover weight at pH 4.0 and a less
obvious decrease at pH 3.5 and 3.0. These results differed from 1980 in
that the effect was much more pronounced on stover production than it
was on grain yield.
Because of these decreases in corn stover production, the total
plant dry weights were significantly less than the controls in treat-
ments pH 3.0, 3.5, and 4.0. No other effects of acid rain on corn were
seen. The grain yields were not significantly different between treat-
ments although the average yield at pH 4.0 again appeared to be de-
pressed. There was no foliar injury on corn from acid rain.
-------
24
Table 13. The effects of simulated sulfuric acid rain on root weights,
top dry weights, total dry weights., and number of plants per
plot of 'Cherry Belle' and 'Scarlet Knight' radish grown
in 1981
(9 m-2)
Radish
(plot basis)
treatment
Root
fresh
wt
Root
dry
wt
Top
dry
wt
Total
dry
wt
Plants
per m2
5.6
487
28
22
50
87
4.0
431
25
22
47
87
3.5
496
29
24
53
87
3.0
496
29
24
53
88
SEa
25
1.4
1.0
2.3
1.3
Fb
NS
NS
NS
NS
NS
'Scarlet Knight1
(g
m-z)
Radish
(plot basis)
treatment
Root
fresh
wt
Root
dry
wt
Top
dry
wt
Total
dry
wt
Plants
per m2
5.6
618
37
29
66
87
4.0
615
36
67
67
86
3.5
686
40
33
73
89
3.0
582
35
31
66
89
SEa
24
1.3
0.9
2.2
1.0
Fb
NS
*
NS
NS
NS
aStandard error of the mean.
^Significance level of the F-test with * denoting P s 0.05.
-------
25
Table 14. The effects of 2:1 simulated sulfuric-nitric acid rain on ear
weight, grain dry weight, stover dry weight, and kernel
number of
'Pioneer 3992'
corn grown
in the field in
1981
Treat-
ment
Total
ear FW
q m-2
Grain
DW
q m-2
Stover
DW
q m-2
Biomass
yield
g m-2
Kernels
m-2
5.6
2070
854
980
1834
898
4.0
1780
738
799**
1537**
810
3.5
1922
785
880**
1665*
827
3.0
1967
822
908*
1729
860
SEa
65
28
23
48
17
Fb
NS
NS
**
**
NS
aStandard error of the mean.
^Significance level of the F-test with * and ** denoting P £ 0.05 and
0.01, respectively.
*,**Symbols after table values denote significant differences from the
control mean with P s. 0.05 and 0.01, respectively, for two-sided
t-test.
Since, in 1980, the pronounced effect of acid rain at pH 4.0 was to
reduce the number of two-eared plants, we analyzed the 1981 yield com-
ponent data for single-eared plants alone. The results are shown in
Table 15. About 80% of the plants in 1981 had only one ear and there
was no difference among treatments on the degree of prolificacy. How-
ever, when only single-eared plants were considered in the analysis,
there was a significant decrease in grain yield per plant at pH 4.0
(P < .05). Thus, qualitatively the 1981 results differed from the 1980
results in how the rain treatment affected yield components, but the
results were similar for the two years in that slightly acid precipi-
tation did affect the crop, whereas more acidic precipitation did not.
Because these results occurred in two years, it was decided to
study the response of corn in more extensive field studies in 1982. All
the acid treatments appeared to have a reduced biomass production in
1981. Thus, it seems possible that, among field crops, corn may be
especially sensitive to acid precipitation.
-------
26
Table 15. The effects of 2:1 simulated sulfuric-nitric acid rain on
yield components of single-eared plants of 'Pioneer 3992'
corn grown in the field in 1981
Treat-
ment
One-eared
plants
%
Grain
dry wt
g/plant
Stover
dry wt
g/plant
Grain plus
stover dry wt
g/plant
Kernels
per
ear
5.6
82
129
153
282
130
4.0
81
112**
124**
236**
121
3.5
79
125
141
266
126
3.0
78
127
145
272
128
SEa
5
3.9
4.8
8.5
3.6
Fb
NS
*
**
~
NS
aStandard error of the mean.
^Significance level of the F-test with * and ** denoting P i 0.05
and 0.01, respectively.
*,**Symbols after table values denote significant differences from the
control mean with P £ 0.05 and 0.01, respectively.
-------
27
1981 SUMMARY AND CONCLUSIONS
Yields of 8 of 10 crops were not affected by exposure to H^SO^ or
H2S0^-HN03 rain treatments in 1981. Only the forage yield of 'Alta'
tall fescue and stover yield of 'Pioneer 3992' field corn exposed to
h^SO^-HNOg rain showed significant yield differences between treatments.
In tall fescue, the forage yield was depressed at pH 3.5 at one harvest
only. Yields were not affected at other harvests or for other pH
treatments. Also, tall fescue showed no significant differences between
h^SO^ rain treatments for two harvests in 1981. (This is in contrast to
1980 when the first harvest and the total of two harvests were signifi-
cantly greater in simulated rain of pH 3.5 and pH 4.0.)
The lack of significant yield differences after the first harvest
of 1980 suggests that there was no cumulative effect of ^SO^ rain on
tall fescue yield. Although the first harvest of the h^SO^-HNOg rain
treatments in 1981 showed a significant decrease in yield at pH 3.5,
this decrease was not seen in the second harvest and the total yields of
the two harvests were not significantly different among treatments. The
HgSO^-HNOg treated tall fescue had no significant yield differences
between treatments for individual or combined harvests in 1980. Thus,
there was no clear effect of acid rain on yield of tall fescue.
'Vernal' alfalfa exposed to I^SO^ rains during two growing seasons
exhibited no significant differences between treatments for top dry
weight at any of five individual harvests. These results suggest that
^SO^ has no cumulative effect on yield of 'Vernal' alfalfa.
Though some individual harvest tissue samples for fescue and
alfalfa showed significant differences between treatments for mineral or
fiber contents, results were not consistent among successive harvests
over the two years of the experiment. Thus, our data did not show any
clear effect of acid rain, either positive or negative, on the compo-
sition of the forage.
Field grown 'Steptoe' barley, 'Fieldwin' wheat, 'Russet Burbank'
and 'Kennebec' potatoes, 'New Yorker' tomatoes, 'Cherry Belle' and
'Scarlet Knight' radishes showed no significant differences in yield
between HgSO^-HNOg simulated rain treatments in 1981.
-------
28
The effect of acid rain on corn is less clear than for the other
crops. In 1980, there was a significant reduction in grain yield in the
pH 4.0 HgSO^-HNO.^ acid rain treatment but not at other pH values. In
contrast, in 1981, there was much less effect of acid rain on plot grain
yields. However, there was a significant effect of pH 4.0 rain on grain
yield of single-eared plants. When all plants were included in the
analysis, the effect was not statistically significant (P = .08).
However, there was a decrease of 16% in stover yield at pH 4.0 and a
smaller decrease in the more acidic treatments.
Since an effect of pH 4.0 rain on corn grain or stover yield was
observed in two years, the final year of these studies was devoted only
to corn.
-------
29
1982 MATERIALS AND METHODS
In 1982, experiments concentrated on the response of corn (Zea mays
L.) to acid precipitation. Three studies were conducted. Experiment
one examined the response of two early maturing cultivars, 'Pioneer
3992' and 'Northrup King PX39' to HgSO^-HNOg rain. Experiment two
studied the response of 'Pioneer 3992' to acid rain of varying H+
equivalent ratios of H2S04:HN03. The third experiment exposed 'Pioneer
3992' to treatments in which pH varied from event to event, but the
season-long average pH was the same for all treatments.
The background ion concentrations for all experiments were based on
weighted average ion concentrations for National Atmospheric Deposition
Program sites in New York, Pennsylvania, and Ohio from June 1 to Sep-
tember 30, 1979 (P. Irving, personal communication). Rain simulants
were prepared from a stock solution of deionized water with 0.165 mg/1
Ca2+, 0.169 mg/1 Na+, 0.031 mg/1 K+, 0.035 mg/1 Mg2+, 0.258 mg/1 NH4+,
1.114 mg/1 S042", 0.457 mg/1 N03~, 0.107 mg/1 CI", and 0.007 mg/1 PO^3"
added. The control rain consisted of stock solution in equilibrium with
atmospheric COg resulting in a pH of approximately 5.4.
Rain treatments were applied through stainless steel spraying
nozzles calibrated for uniform distribution over the calibrated spray
area at a rate of 1.4 cm/hr. During each rain event, rain was on for
five minutes and then off for five minutes, giving a total delivery
equal to 0.7 cm/hr. Rain events were 100 minutes/day, 2 days/week for a
total rainfall of Z.Z cm/week. A sample of rain solution was collected
for each treatment throughout each rain event (Table 16). The pH was
then checked using an Orion 901 Research Microprocessor Ionalyzer
calibrated to standard pH buffer solutions of 4.01 and 7.00.
Twenty-four portable exposure chambers were placed over the plots
to apply the simulated rain. Each chamber consisted of a closed top
polyvinyl chloride framework 4.6 m in diameter and 2.5 m tall (see
Appendix for details of chamber construction). This framework was
covered with woven polypropylene fabric to reduce disturbance of the
rain distribution by wind. This cover allowed free air exchange and
-------
Table 16. Summary of amount and acidity of natural and simulated rainfall and irrigation for the 1982 corn
experiments
Natural rainfall
Experi-
ment
No.
from
emergence
to harvest
on same day
as simulated
rainfall
Total
simulated
rainfall
Average pH of simulated
plus natural rainfall
treatment pH
Total
irri-
gation
3.5
3.7
3.9
4.1
4.3
5 4
—cm—
" """"" Llfl
#1
West block
'Pioneer 3992'
12.0
3.0
33.0
3.68
3.88
4.04
4.26
4.45
5.27
30.2
East block
'Pioneer 3992'
12.0
3.0
33.0
3.65
3.87
4.05
4.26
4.44
5.44
29.5
West block
'Northrup King PX39'
15.8
3.0
33.0
3.72
3.91
4.07
4.29
4.48
5.27
30.2
East block
'Northrup King PX39'
15.8
3.0
33.0
3.68
3.91
4.09
4.29
4.47
5.43
29.5
4.0
5.4
2:1
3:1
1:1
1:0
0:1
'Pioneer 3992'
11.6
1.9
30.8
4.12
4.15
4.13
4.11
4.12
5.40
29.4
4.0SV
4.0HV
4.0C
5.4
'Pioneer 3992'
11.6
1.9
30.8 4.16
4.25
4.34 5.50 29.9
1. Includes all natural rain from the date seedlings emerged from soil until harvest (simulated rainfall did not
begin until after emergence).
2. Includes only natural rain which fell on days when simulated rain was applied.
3. Volume weighted average (computed using emergence to harvest natural rainfall).
-------
31
simulated clcw*d cover so that rain was not applied in direct intense
sun. For a rain event, a chamber was placed upon a base consisting of a
4.6 m-diameter tubular steel ring and eight 1.8-m tubular aluminum
uprights. The chamber base was raised on the uprights as necessary as
the corn grew to keep the calibrated spray area always at the top of the
crop canopy. Chambers were placed over the plots by hand until August
3, then a mechanical crane was used for chamber placement and removal.
The chambers were rotated among treatments for successive rain events to
eliminate systematic variability contributed by chambers and nozzles. A
chamber was on a plot only during the rain event and then was removed.
Thermocouples, protected from rain contact, were suspended below
the rain delivery nozzles in four randomly selected chambers. Tempera-
tures from these four chambers and two ambient locations were recorded
before, during, and after each rain event (Table 17). The temperature
within the chambers was about 4°C cooler than the ambient during the
rain events, as one would expect.
Table 17. Air temperature (°C) for the 1982 simulated acid rain
2
events
Before
During
After
Ambient
20.3
22.1
22.8
Chamber 2
20.6
17.9
18.2
Chamber 10
19.9
17.3
17.8
Chamber 14
22.1
19.3
18.8
Chamber 18
24.8
18.8
19.9
1. Temperature probes suspended in the center of four randomly selected
chambers. Two ambient sites were measured using thermometers,
2. Mean of 116 rain events, ambient represents mean of two sites.
-------
32
Field preparation for the 1982 experiments consisted of plowing and
discing. Before the corn plots were established, the soil at the site
had a pH of 4.8 (Table 18). Therefore, an application of 4345 kg/ha
lime was plowed in and an additional 4345 kg/ha was disced in, as was an
application of 231, 101, 50, 30, and 9 kg/ha N, P2O5, an<*
The field was then cultivated with a rotary tiller and harrowed before
planting. Atrazine at 1 kg/ha and Lasso at 2.2 kg/ha active ingredient
were applied as pre-emergent herbicides after planting.
Corn was seeded by hand May 28 to June 1 in two blocks with 34
north-south rows per block. The rows were spaced at 50 cm with plants
within rows spaced at 30 cm. This planting arrangement provided a plant
population of approximately 67,000 plants per hectare. Each plot con-
sisted of 17 rows, with 20 plants per row. Eight rows to the outside of
the block and three to the inside served as east-west borders for the
3.35 m-diameter circular calibrated study area. Four rows served as
borders north and south. Within the calibrated rain area, 60 plants per
plot, in two rows each of 8, 10, and 12 plants, served as study plants
(Figure 1).
The first simulated rain events were applied June 14 and June 15.
Sprinkler irrigation (Table 16) was applied when the moisture in soil
cores from plot border areas indicated less than 50 percent field capac-
ity (Lorenz and Maynard, 1980).
The plots were harvested by hand. Single-eared plants per row were
harvested and informmation recorded together as one sample per plot.
All other plants within a plot were harvested and data were taken indi-
vidually on each plant. Fresh weights were taken for all mature ears.
All plant material was dried at 60°C for 48 hours. Dry weights were
taken for ears, kernels (grain dry weight), and stover. A 1,000-kernel
subsample from the single-ear plants of each plot was then counted and
the dry weight recorded. Leaf tissue from single ear plants of each
plot of Experiment 1 was selected at random, harvested, dried, ground,
and analyzed for concentrations of sulfur (S), potassium (K), phosphorus
(P), calcium (CA), magnesium (Mg), manganese (Mn), iron (Fe), copper
(Cu), boron (B), zinc (Zn), and aluminum (Al). The Plant Analysis
Laboratory, Oregon State University, determined total S using a Leco
-------
Table 18. Pre-study field soil characteristics for the 1982 corn experiments
Lime
pH req. P K B Na Zn Mn Cu S04 OM K Ca Mg Na CEC
m.t./ha ppm meg/100 g
4.8 11.5 32.9 148 0.92 98.9 0.97 31.1 0.98 4.90 3.31 0.38 4.11 0.58 0.43 20.7
aMean values for 35 field samples.
OJ
GJ
-------
34
oooooooooooooooooooooooo
oooooooooooooooooooooooo
o o o o
o o o o
o o o o
o o o o
o o o o
o o o o
o o o o
o o o o
o o o o
0 0 0 0
-PLOT BORDER*
o o o o o o
o o o o o o
O O OSD oooooooo
oooooooooooo
HARVEST AREA
oooooooo o/o o o
CHAMBER AREA
o o o o o
o o o o o
o o o o
o o o o
o o o o
o o o o
o o o o
o o o o
o o o o
o o o o
o o o o
o o o o
oooooooooooooooooooooooo
oooooooooooooooooooooooo
Figure 1. A sketch of the 1982 corn plots showing the location of the
acid rain chambers and the plot harvest areas.
-------
35
Sulfur Analyzer as described by Jones and Isaac (1972) and the 10 other
elements using direct reading emission spectrometry as described by
Chaplin and Dixon (1974).
Post-harvest soil samples were collected for analysis as shown in
Table 19.
A randomized complete block design was used for all three experi-
ments. A one-way analysis of variance (ANOVA) was used to compare
treatments in all three experiments. When the resulting pH-treatment F
test was significant (P s 0.05), two-sided t tests were used to deter-
mine which acid treatment means differed significantly (P £ 0.05) from
the control.
Experiment 1 consisted of 48 plots in two parallel north-south
strips, each strip being two plots wide and 12 plots long. In each
strip, there were 12 treatments - six pH levels for each of two culti-
vars, 'Pioneer 3992' and 'Northrup King PX 39'. Simulated rains were
applied to all plots in a strip at the same time. Then the chambers
were moved and rain applied to the second strip. Each variety in
Experiment 1 was exposed to rains of pH 3.5, 3.7, 3.9, 4.1, 4.3, and 5.4
(control). The pH levels 3.5 through 4.3 were attained by adding 3.6
NHgSO^ and 1.8 NHNOg to the control rain. All acid rain treatments had
an HgSO-HNOj ratio of 2.37:1. The 'Pioneer 3992' plots of Experiment 1
were harvested October 20, 21, and 22. The 'Northrup King PX39' plots
were harvested October 27, 28, and 29.
In Experiment 1, four plots, 'Pioneer 3992' block 3, pH 3.5, 4.1,
and 4.3, and 'Northrup King PX39' block 3, pH 4.1, were destroyed when a
heavy wind overturned a chamber. Data from those plots were not
included in the analysis.
Experiment 2 consisted of 24 plots of 'Pioneer 3992' in one north-
south strip, two plots wide and 12 plots long. The treatments were
randomly assigned to six plots within each of four replicate blocks. In
addition to a control of pH 5.4, the plots received pH 4.0 simulated
rain treatments of H2S04 alone, HNOg alone, and HgSO^-NOg in ratios of
3:1, 2:1 and 1:1. Experiment 2 was harvested October 13, 14, and 15.
-------
Table 19. Soil
the conclusion of the 1982 corn experiment
Soil
—
ppm
— MEQ/100
g —-
h
Study
Treatment
pH
P
K
B
Zn
Mn
Cu
S
Ca
Mq
CEC
0M
Experiment 1
'Northrup
pH
King Px39'
3.5
6.2
35
123
.26
.49
.76
1.0
34.7
12.2
.62
17.3
3.7
3.9
5.9
34
131
.28
.37
17.4
.99
34.7
10.2
.35
16.4
3.5
4.3
6.3
53
201
.26
.33
9.6
.91
35.7
12.3
.83
17.3
3.8
5.4
5.7
33
86
.18
.34
11.4
.70
38.0
9.7
.40
15.6
3.1
1 Pioneer
3.7
6.4
42
158
.20
.41
9.5
.94
34.4
11.9
.57
16.8
3.6
3992'
4.1
4.7
29
100
.20
.50
28.6
.66
46.4
3.9
.30
14.3
3.0
Experiment 2
S-N
'Pioneer
PH
Ratio
3992'
4.0
3:1
5.2
29
101
.17
.58
24.0
.70
49.5
7.7
.47
15.7
3.2
4.0
2:1
4.7
31
90
.20
.80
32.0
1.0
34.3
4.5
.59
15.2
3.3
4.0
1:1
6.0
40
164
.20
.44
10.5
.86
29.9
11.5
.54
15.9
3.6
4.0
1:1
5.0
35
117
.17
.62
23.6
1.0
28.8
5.9
.51
15.7
3.4
4.0
0:1
5.0
38
105
.20
.58
27.4
.98
34.3
5.8
.50
15.7
3.4
5.4
2.37:1
5.7
49
191
.23
.44
11.6
1.3
29.4
9.4
.41
16.2
3.4
Experiment 3
r
'Pioneer
pH
VAR
3992'
4.0
0
5.1
24
86
.16
.82
35.0
.68
25.6
6.2
.78
15.2
2.5
4.0
2
5.0
28
86
.17
.82
40.6
1.1
26.7
5.8
.64
18.3
3.2
4.0
1
6.8
26
98
.20
.48
10.6
1.1
10.9
13.3
.67
16.6
3.0
5.4
0
4.9
21
78
.19
.84
43.0
1.0.
45.7
4.0
.69
14.8
2.6
CO
-------
37
Experiment 3 consisted of 24 plots of 'Pioneer 3992' in one north-
south strip, two plots wide and 12 plots long. Treatments were randomly
assigned to four plots within each of six replicate blocks. The
HgSO^HNOg acid ratio for Experiment 3 was 2.37:1. Two treatments, the
pH 5.4 (control) and the pH 4.0 (constant), were the same for all rain
events. The other two treatments received a rain of one pH at one event
and a rain of a different pH at the next event. In one variable pH 4.0
treatment, events ranged from pH 3.5 to 5.4 but averaged 4.0 for the
season. In a second, more variable pH 4.0 treatment, events ranged from
pH 3.1 to 5.4 and averaged 4.0 for the season. The variable pH treat-
ments were based on pH frequencies for events at University Park, Penn-
sylvania, and Champaign-Urbana, Illinois, from May 15 through October
15, 1981 (Dana and Rothert, 1983). Experiment 3 was harvested October
15, 19, and 20.
-------
38
1982 RESULTS AND DISCUSSION
'Pioneer 3992' and 'Northrup King PX391 field corn showed no signi-
ficant differences in response to any simulated acid rain treatment in
any of the three experiments conducted in 1982.
Seventy-eight percent of the 'Pioneer 3992' and 94 percent of the
'Northrup King PX391 plants in Experiment 1 produced single ears. Total
ear fresh weight, total ear dry weight, total grain dry weight, total
top dry weight, and total dry weight were not significantly affected by
simulated acid rain treatment for either variety (Tables 20 and 21).
Additional analysis for single-eared plants on a per plant basis did not
show any significant differences between treatments (Tables 22 and 23).
Tissue analysis of leaves from single-eared plants from each plot showed
no significant differences between treatments for S, K, P, Ca, Mg, Mn,
Fe, Cu, B, Zn, and A1 content (Table 24).
Table 20. The effects of 2:1 sulfuric-nitric simulated acid rain events
with different pH levels on ear fresh weight, ear dry weight,
top dry weight, and grain dry weight of 'Pioneer 3992' grown
in the field in 1982
Total ear weight Total stover Total grain
jdH fresh dry dry weight dry weight
g/m2 --
3.5
1,759
973
788
759
3.7
1,778
990
767
766
3.9
1,725
977
735
759
4.1
1,659
905
720
701
4.3
1,730
968
701
745
5.4
1,690
919
714
715
SEa
30.7
19.6
16.2
15.0
30
NS
32
NS
33
NS
32
NS
aStandard error of the mean.
Coefficient of variation of the mean (percent).
Significance level of the F-test.
-------
39
Table 21. The effects of 2:1 sulfuric-nitric simulated acid rain events
with different pH levels on ear fresh weight, ear dry weight,
top dry weight, and grain dry weight of 'Northrup King PX391
corn grown in the field in 1982
Total ear weight Total top Total grain
jdH fresh dry dry weight dry weight
- g/mz
3.5
1,946
783
1,171
600
3.7
1,986
795
1,180
601
3.9
1,907
740
1,180
555
4.1
1,884
728
1,198
548
4.3
1,886
752
1,212
566
5.4
1,957
759
1,167
567
SEa
35.1
16.7
13.9
21.7
CVb
21
26
22
28
Fc
NS
NS
NS
NS
aStandard error of the mean.
^Coefficient of variation of the mean (percent).
Significance level of the F-test.
-------
40
Table 22. The effects of 2:1 sulfuric-nitric simulated acid rain events
of different pH levels on single-eared plant stover and grain
dry weight and kernel number per plant for 'Pioneer 3992'
corn grown in the field in 1982
PH
Stover weight
Grain dry weight
Kernel No.
g/plant
g/plant
kernel/plant
3.5
122
118
528
3.7
121
119
518
3.9
118
118
514
4.1
118
113
495
4.3
113
114
519
5.4
113
113
515
SEa
1.6
1.3
7.7
CVb
16
12
7
FC
NS
NS
NS
aStandard error of the mean.
^Coefficient of variation of the mean (percent)
Significance level of the F-test.
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41
Table 23. The effects of 2:1 sulfuric-nitric simulated acid rain events
of different pH levels on single-eared plant stover and grain
weight, and kernel number per plant for 'Northrup King PX39'
corn grown in the field in 1982
PH
Stover weight
Grain dry weight
Kernel No.
g/plant
g/plant
kernel/plant
3.5
185
95
478
3.7
186
95
511
3.9
184
88
469
4.1
190
88
460
4.3
185
90
432
5.4
182
89
474
SEa
2.3
1.6
8.6
cvb
15
21
9
Fc
NS
NS
NS
aStandard error of the mean.
^Coefficient of variation of the mean (percent)
Significance level of the F-test.
-------
Table 24. The concentrations of 11 mineral elements in leaves of two corn cultivars treated with
2:1 sulfuric-nitric simulated rain of two different pH levels. The corn was grown in the
field in 1982
Treatment Pioneer 3992
S
K
P
Ca
Mg
Mn
Fe
Cu
B
Zn
A1
3.5
.22
1.45
.26
.82
.23
172.5
319.3
7.75
ppm
7.25
29.0
298.3
5.4
.21
1.32
.25
.92
.18
240.3
373.5
8.50
7.75
23.5
382.0
CO
m
.02
.07
.02
.03
.02
17.3
40.1
.64
.42
1.9
51.3
cvb
21.7
14.8
20.5
8.6
28.5
23.7
32.7
22.3
16
20.3
42.7
FC
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
Treatment
Northrup King PX39
3.5
.22
1.45
.35
.85
.25
269.5
463.0
8.0
6.25
46.5
501.0
5.4
.21
1.57
.39
.91
.26
279.8
372.3
8.5
7.00
46.8
340.3
SEa
.01
.11
.02
.03
.01
27.8
51.8
.60
.37
3.2
78.8
SVb
7.1
19.7
12.7
9.5
10.7
28.7
35.1
20.6
16.0
19.7
53.0
Fc
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
aStandard error of the mean.
^Coefficient of variation for the mean (percent).
Significance level for the F-test with * denoting P s 0.05.
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43
'Pioneer 3992' was not significantly affected by the pH 4.0 rains
of differing nitric/sulfuric acid ratios in Experiment 2. Table 25
shows that yields per m2 of stover and grain were not affected by the
treatments. Table 26 shows that stover and grain yield per plant of
single-eared plants were likewise unaffected. Eighty-four percent of
the population produced single ears.
Variation in acidity of individual rain events in Experiment 3 did
not produce any significant differences in grain or biomass yield of
'Pioneer 3992' (Tables 27 and 28). Single ears were produced on 85
percent of the plants.
No foliar acid rain injury was observed in any of the three experi-
ments in 1982.
Table 25. The effects of pH 4.0 acid rain events having differing
nitric to sulfuric acid ratios on ear fresh weight and dry
weight, and stover and grain dry weight of 'Pioneer 3992'
corn grown in the field in 1982
Treatment Total ear weight" Stover Grain
pH N-S ratio" Fresh Dry dry weight dry weiq
—- g/m2 ------
4.0
0:1
1,744
945
808
740
4.0
1:0
1,709
885
741
687
4.0
1,743
911
775
708
4.0
2:1
1,708
913
779
711
4.0
3:1
1,690
901
725
724
5.4
0:0
1,733
926
764
741
SEa
30.3
17.2
15.5
14.1
CVb
21
23
24
24
Fc
NS
NS
NS
NS
aStandard error of the mean.
Coefficient of variation of the mean (percent).
Significance level of the F-test.
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44
Table 26. The effects of pH 4.0 acid rain events of differing nitric to
sulfuric acid ratios on single-ear plant stover and grain
dry weight and kernel number per plant of 'Pioneer 3992'
corn grown in
the field in 1982
Treatment
Stover
Grain dry
Kernel
pH
N-S ratio
weight
weight
No.
g/plant
g/pfant
kernels/plant
4.0
0:1
121.0
112.9
515.4
4.0
1:0
111.9
101.1
504.0
4.0
1:1
119.9
106.8
506.3
4.0
2:1
119.9
109.5
511.5
4.0
3:1
116.5
111.6
514.8
5.4
0:0
119.1
112.8
507.9
SEa
1.8
1.3
8.7
CVb
18.0
16.0
8.0
FC
NS
NS
NS
aStandard error of the mean.
^Coefficient of variation of the mean (percent).
Significant level of the F-test.
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45
Table 27. The effects of variation in acidity of individual 2:1 sul-
furic-nitric simulated acid rain events, but averaging
pH 4.0, on stover and grain dry weights of 'Pioneer 3992'
corn grown in the field in 1982
Treatment Stover Grain
pH variation level dry weight ^ dry weight
4.0 constant 669 665
4.0 slight variation 708 685
4.0 high variation 693 727
5.4 constant 747 729
SEa 12.8 14.9
CVb 22 25
Ff ; NS NS
aStandard error of the mean.
^Ceofficient of variation of the mean (percent)
Significance level of the F-test.
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46
Table 28. The effects of variation in acidity of individual 2:1 sul-
furic-nitric simulated acid rain events, but averaging
pH 4.0, on single-eared plant stover and grain dry weight
and kernel number per plant of 'Pioneer 3992' corn grown in
the field in 1982
Treatment
pH variation
Stover
dry weight
Grain
dry weight
Kernel No.
g/plant
g/plant
kernels/plant
4.0 constant
109.8
113.6
513
4.0 slight
108.3
105.5
495
4.0 high
109.0
113.2
528
5.4 control
113.2
114.2
502
SEa
1.2
1.5
5.6
CVb
14
16
8
Fc
NS
NS
NS
aStandard error of the mean.
^Coefficient of variation of the mean (percent).
Significance level of the F-test.
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47
GENERAL DISCISSION
Two years of growing similar crops in pots in chambers (1979, 1980)
and in the field (Cohen et al., 1981, 1982) allow some general compari-
sons on crop responses to acid rain and on the responses of crops in
different environments.
'Vernal' alfalfa, 'Alta1 tall fescue, 'Russet Burbank' potato,
'Improved Thick Leaf' spinach, and 'Patio' tomato had no significant
yield response to acid rain in pot-grown studies in chambers. Field
studies of the same crops ('New Yorker' instead of 'Patio' tomato)
showed similar lack of response. Thus, it seems clear that in the
absence of other aerial pollutants, acid rain has little effect on yield
or quality of these crops.
'Southern Giant Curled' mustard greens exhibited significant
decreases in leaf weight at pH 3.0 and pH 4.0 in response to l^SO^
simulated rain when grown in pots in 1979. Field grown mustard greens
showed no response to HgSO^ rain in 1980. However, mustard greens
exposed to ^SO^-HNOg rain had decreases in yield at pH 3.0 and pH 4.0
in the field in 1980. Pot studies carried out in chambers showed
significant decreases in yield at pH 3.0 and pH 3.5 for 'Cherry Belle'
radish in the HgSO^-HNOg rain treatments and pH 3.0 in the HgSO^ rain
treatment. In contrast, a significant increase in yield was seen for
radishes exposed to pH 4.0 HgSO^ rain. These results on plants grown in
pots in chambers were contradicted by two years of field-grown radishes
with no significant differences in yield between treatments. The con-
trast in these comparisons suggests that great care is needed in inter-
preting results from plants grown in pots in chambers and those results
should not be used to estimate crop response under field conditions.
Comparison of foliar injury from acid rain on potted plants in
chambers versus that on field-grown plants indicates that the responses
are quite different in the two conditions. Alfalfa, barley, tall fes-
cue, potato, radish, tomato (leaves and fruit), and wheat all exhibited
some acid rain foliar injury at pH 3.0 in 1980 pot studies (Cohen et
al., 1982). In the field, only alfalfa exposed to HgSO^ rain had any
visible injury, and that was only on less than one percent of the leaf
-------
48
surface, at one harvest only, and in one year only. In 1981 field stu-
dies, we observed foliar acid rain injury to foliage in ^SO^-HNO^
exposed tomatoes in three plots and that was on less than 1 percent of
the leaf surface. Likewise, we observed some injury in a few tall
fescue plots on a few leaves. No tomato fruit exhibited acid rain
injury and the injury on tall fescue was not apparent after September
22. Radish cotyledons showed acid rain injury at pH 3.0 H2S04-HN03
treatment in 1981 in the field but no true leaves were injured. These
tiny flecks, which we scored as acid rain foliar injury, would likely
have gone unnoted in most experiments.
It is often assumed that foliar acid rain injury is an indication
of yield loss. This has not been true for field-grown crops exposed to
acid rain in these experiments in the few cases where there appeared to
be some foliar injury. Even in chamber studies where foliar injury was
more severe, the plant yields were seldom affected.
Among all the experiments in all crops during the several years of
simulated acid rain testing in the fields the only statistically clear
response was a reduction in corn stover weight in 1981. All acid
treatments (pH 4.0, 3.5, and 3.0) showed reduced stover production
compared to the control (pH 5.6) and the results were highly significant
(P s 0.01) for both the F test and for t tests for the means of the pH
4.0 and 3.5 treatments, compared to the control.
The response of corn to simulated acid rain has not been consistent
from year to year, however. Nevertheless, the results do suggest that,
among crop plants, corn may be particularly sensitive to acid rain. It
is of particular interest that the sensitivity appeared to be greater to
the mildly acidic rain of pH 4.0 than to the much more acidic rain of pH
3.5 and 3.0. Figure 2 shows the grain yield of 'Pioneer 3992' for the
three years in which acid rain was applied in the field. The yield data
for 1981 were quite variable so that the F test was not significant
(P=.08); however, the similarity of pattern of the response curves in
1980 and 1981 suggests that the response pattern shown in Figure 2 for
the two years was real. Although the results were not significantly
different, the same general response pattern was observed in the means
in 1982.
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49
EFFECT OF ACID RAIN ON CORN YIELDS
108 -
106 -
104 -
102 -
100
98 -
96
94 -
92 -
90 -
88 -
86 -
84
3.8
4.2
3.4
4.8
5
5.4
3
~ 1980 ~ , e, « 1982
Figure 2. The grain yield of 'Pioneer 3992' at different pH of acid
rain in 1980, 1981, and 1982.
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50
In 1980, the effect of acid rain treatments on yield of corn
appeared to be an effect on the number of two-eared plants in the treat-
ments (Cohen et al., 1981). In 1981, there was no effect of acid rain
on the degree of prolificacy. Thus, these effects of acid rain on the
grain yield were dissimilar in the mechanism by which they were
expressed in the plant and would not be particularly noteworthy had the
yield of stover not been depressed in 1981. However, the depression of
the stover yields by 19% at pH 4.0, 10% at pH 3.5, and 1% at pH 3.0
indicated that the carbohydrate production of the corn was affected by
acid precipitation in 1981. This strenghtened the argument that the
corn yield depression in 1980 was real. No explanation is apparent of
why the depression in yield would have been greater at pH 4.0 than at
the more acidic levels.
These results on corn were surprising, given the fact that other
crops had shown no response to acid rain. Surprising, too, was the
particular sensitivity to mildly acidic rain. Therefore, in 1982, the
research concentrated on corn.
During the 1982 growing season, there were no significant effects
of any kind from treating field-grown corn with simulated acid rain.
The grain and biomass yields of all treatments were identical and there
was no foliar or compositional effects of acid rain on the corn. Yet in
1980 and 1981, there were significant effects on either biomass or grain
yield. Thus, these data support the conclusion that, under some condi-
tions, corn is particularly sensitive to acid precipitation.
This document constitutes a final report on the research on acid
rain by the Crop Science Department of Oregon State University. In
general, studies over the past several years have shown that crop plants
are amazingly tolerant of acid precipitation. Even repeated applica-
tions of precipitation of pH 3.0 throughout the entire growing season
had no effect on the yield or appearance of most crops. The only
exception was corn, as discussed above.
Perhaps we should not be surprised by these results. Plant foliage
is equipped well by nature to tolerate acid precipitation. The leaves
and stems are covered with wax (the cuticle) which excludes acid preci-
pitation from contacting living cells. The stomata, the route of entry
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51
arid egress of gases such as water vapor, oxygen, and carbon dioxide,
close in the presence of acids. If acid rain were to begin to penetrate
a stomatal opening, it would contact first a stomatal guard cell. Guard
cells can absorb acids and an increase in the acidity of the guard cell
contents causes water to be transported out of the cell, it loses tur-
gor, and the stoma closes. Thus, one would expect foliage to be rela-
tively tolerant of acids.
Plant roots, on the other hand, may readily absorb acids, and soil
acidity is a well known problem for plant growth. It is important to
realize, however, that agriculture, since its early inception, has been
managing soil aciditiy. In general, soils have a huge buffering capac-
ity compared to the quantity of hydrogen ions incident on a soil surface
from acid rain. Of much greater concern to soil managers is the normal
flux of acid generated in the soil each year by natural processes and by
the necessary applications of fertilizer. "Worst case" estimates
suggest that acid rain could supply only about \% of the normal hydrogen
ion flux that would be generated yearly in a fertilized agricultural
soil (Baham, John. Department of Soil Science, Oregon State University-
-private communication). Thus, agriculture has learned to manage soil
acid fluxes much larger than those threatened by acid rain. Acid rain
should not pose a serious problem for the soil manager because the soil
buffers the acid when it first contacts the soil and the slow changes
induced in the soil acidity by the precipitation are readily handled by
the application of lime.
From a soil management point of view, a far more important aspect
of acid rain may be the fertilizer value of the components of the rain.
Every year the progressive farmer spends a significant portion of his
budget on nitrogen fertilizer. The nitrate in acid rain provides part
of the essential nutrients that crop plants need. In many areas the
soils are also deficient in sulfur, and fertilizers must contain sulfur
for crops to yield well. Thus, any assessment of the impact of acid
rain on crop plants should consider the fertilizer value of the N and S
in acid rain to adequately assess the role that acid rain plays in crop
yields.
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52
RECOMMENDATIONS
We recommend to the U.S. Environmental Protection Agency that
further field tests should be performed on the response of corn to
controlled applications of simulated acid rain. Those tests should be
performed in an environment where corn is a major crop and where acid
rain occurs naturally, because the responses we observed were not
consistent from year to year. This suggests that the environment may be
important in determining any response. Therefore, the studies should be
conducted in an environment similar to that in which corn is grown as a
commercial crop.
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53
APPENDIX
This appendix describes the rain simulation chamber used in 1981
and 1982. Different designs were used each year to meet the needs of
the particular experiment.
Natural rainfall is highly variable in composition, distribution,
droplet size (Best, 1950), terminal velocity of the raindrops (Gunn and
Kinger, 1949), intensity (Laws and Parsons, 1943), and duration. Thus,
decisions had to be made as to the range for these factors in our
experiments. Many different rainfall simulators have been developed to
deal with specific traits of rainfall (Mutchler and Hermsmeier, 1965).
For these experiments, composition and distribution were primary
concerns. In the design, however, droplet size and terminal velocity
were also considerations.
Our exposure chambers were designed to meet four criteria:
1. The simulated rainfall should have a uniform distribution of
rain over the plot at an application rate of approximately 0.7
cm/hr.
2. The mean volume raindrop size and drop size distribution should
be within the range ordinarily observed for natural rain.
3. The chambers should simulate cloud cover by reducing light
intensity about 75 percent (Welch et al.).
4. The chambers should be portable and adaptable to plants of
different heights.
The exposure chambers were designed in two basic parts, the struc-
ture and the rain delivery system. The rain delivery system delivered
the rainwater to the plots, formed the raindrops, and distributed the
raindrops uniformly over the harvest area. The structure provided
support for the rain delivery system, shelter from the wind (required
for uniform distribution of the rain over the study area), and support
for the simulated cloud cover (shade cloth).
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54
The 1981 Simulator
In 1981, the rain was provided by Oelevan type R-D spray nozzles.
They gave hollow cone spray patterns. We used a combination of an RD-1
cap, a #23 disc and a #2 cone, which gave us the desired rate of appli-
cation. However, this combination gave patterns that were inconsistent
from nozzle to nozzle and many nozzles were tested to find sufficient
similar nozzles for our studies. The best results were obtained when
the nozzles were operated at a pressure of 40 pounds per square inch.
Pairs of nozzles provided coverage of a 2 m x 2 rh calibrated spray
area. The enclosures were circular. The nozzles were located 2 m apart
and 0.7 m into the chamber from the sides. The nozzles were held by a
"hanger" that allowed adjustment of the nozzle to any orientation. The
nozzles were oriented to deliver the simulated raindrops with an upward
velocity. The rain then fell by gravity upon the plants (Figure Al).
Distribution was checked by collecting rain in containers placed at
the intersections of a 0.3 m grid laid out over a 2 x 2 m area. Distri-
bution for a pair of nozzles was accepted if no values were below 3.7
mm/hr or greater than 12.3 mm/hr. The coefficient of variation for
raindrop distribution over the plot area was less than 25 percent and
the average rate over the area fell between 5.9 mm/hr and 7.4 mm/hr.
The distribution pattern for pairs of nozzles was adjusted by turning,
tilting, and tipping the nozzles until an acceptable pattern was
achieved. This was a difficult, time-consuming process.
The exposure chambers were 3.3 m in diameter with 2 m vertical
walls plus an additional 0.6 m wall extension at the top which tapered
inward to a diameter of 2 m (Figure Al). Extensions were added at the
bottom of the chamber to adjust the height so that the top of the crop
canopy was in the vertical zone where the spray distribution pattern was
uniform. The tapered top of the chamber helped reduce wind turbulence
in the chamber. The sides of the chamber were covered with clear poly-
ethylene film. The top 2 m diameter circle was left open for ventila-
tion. The entire chamber was then covered with a shade cloth. The
cloth was sufficiently porous to allow ventilation through the opening
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55
©
Figure Al. A sketch of the construction details for the exposure
chambers used in 1981.
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56
at the top of the chamber. The total weight of the chambers was
approximately 20 kg.
The frame of the enclosure was made from 1.9 cm polyvinyl chloride
(PVC) pipe and fittings (Figure Al). Hoops were made of class 1120 PVC
pipe and the uprights and all the fittings, crosses, tees, and 45-degree
elbows were schedule 40 PVC pipe. All joints were either glued or
secured with a short section of hardwood dowel inserted both into the
end of the pipe that goes into the fitting and into the fitting itself.
These dowels were secured by a machine screws and nuts. Wires were
strung diagonally across the frame to prevent it from flexing exces-
sively in the wind.
The frame was covered with 6 mil polyethylene film (Monsanto 602).
The film was held in place by Monsanto clear plastic tape.
The shade fabric was a black, woven polypropylene material (Chicko-
pee brand) that provided 73 percent shade. It was porous enough to
allow sufficient ventilation so that interior temperatures were close to
ambient.
Mobile home anchors were screwed into the ground at the corners of
the field plots. Tether lines attached to the middle hoop of the cham-
ber were tied to the anchors when the chambers were on the plots. These
tethers stabilized the chambers in wind.
The raindrops coming from the nozzles initially had a horizontal
component to their trajectory. Therefore, distribution and density of
rain drops changed with distance fallen. A uniform distribution
occurred about 0.3 m below the nozzles (about 0.6 m above the bottom of
the chamber). As crops grew taller, extensions were added at the base
of the chamber to assure that the distribution of the rain was uniform
at the top of the crop canopy. These extensions were circular frames of
PVC pipe identical in construction to the sidewalls of the chamber
proper. They consisted of two 3.1-m diameter, class 1120, PVC pipe
hoops, supported by struts of schedule 40 PVC pipe of an appropriate
length. For corn, a 1.1-m extension was used. These extensions were
not covered in any fashion. Border rows of the crop provided a wind
break and shade. When the crop was tall enough to begin to interfere
with the spray pattern, the extensions were placed permanently in the
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57
crop. The chambers were then set on the extensions rather than on the
soil.
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58
The 1982 Simulator
The rain in 1982 was applied by a Spraying Systems 1/4 GG 10W
spraying nozzle. This nozzle had a wide angle, solid cone spray pat-
tern. The drop size and drop size distribution compare favorably with a
moderately heavy natural rain (Best, 1976). Less than 2 percent of the
drops were less than 700 microns in diameter, and less than 2 percent of
the drops were greater than 5,500 microns in diameter. The mean volume
diameter was 2,910 microns (Spraying Systems, Wheaton, IL). The best
performance occurred at operating pressure of 8 to 10 pounds per square
inch.
One nozzle was used in each enclosure to provide coverage for the
calibrated spray area, a circle 3.4 m in diameter (about 9 m2). A
nozzle was suspended at the center of each chamber by a harness that
allowed us to adjust the nozzle to the appropriate position and orien-
tation. Nozzles were selected which gave uniform spray patterns and
adjustments were not required to get uniform distribution over the
harvest area.
Spray patterns were checked by collecting rain in containers placed
at the intersections of a 0.3-m grid laid out over the 3.6-m diameter
circular area. No values were below 7.4 mm per hour or greater than
24.6 mm per hour. The coefficient of variation was less than 25 per-
cent, and the average rate over the harvest area was 13.3 mm per hour.
This rate was twice as great as the desired application rate. An
appropriate application rate was achieved by simulating rain for 5
minutes, then turning off the rain for 5 minutes, then back on for 5
minutes and so on.
As with the Delevan nozzle used in 1981, this nozzle gave each
raindrop a horizontal velocity component. Density and distribution of
drops were functions of the distance the drops had fallen. In this
application a desirable rain pattern was developed as the drops were
falling through the vertical interval 1 to 1.5 m below the nozzle when
the nozzle was oriented upward. To keep the top of the plant canopy
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S9
within this interval from the nozzle, the chamber was adjusted verti-
cally as the plants grew. This adjustment was achieved by adding
extensions to the base on which the spray chamber rested. This proce-
dure allowed us to vary the height of the nozzle, relative to the
ground, from about 1.5 to 4.5 m and allowed for a plant height to 3.5 m.
The adjustable chambers consisted of two cylinders, one inside the
other (Figure A2). The nozzle was fixed at the center near the top of
the inner cylinder. The nozzle did not move relative to this part of
the chamber. The two cylinders were attached to each other by snap-
bolts at the bottom of the inner cylinder that hooked to eyebolts on the
frame of the outer cylinder. When the snap-bolts were not connected to
the eyebolts, the inner cylinder was free to move vertically within the
outer cylinder. Sets of eyebolts were spaced at one-foot intervals
vertically on the outer frame. By attaching the snap-bolts to a set of
eyebolts, the height of the nozzle relative to the ground could be
adjusted.
The inner cylinder was 5 m in diameter (Figure A2). Initially the
cylinder had a 2-m side-wall consisting of three hoops and two sets of
struts. The shade cloth covered the chamber to the bottom of this side-
wall. After the corn had exceeded 1 m in height, another 1 m of side-
wall was added. This gave a total side-wall height of 3 m. The shade
cloth did not cover this addition. All structural members were schedule
40 PVC 1.9-cm diameter pipe and fittings except the small hoop 1n the
roof of the inner cylinder. This was made of class 1120 PVC 1.9 cm
pipe. All joints were doweled and bolted as described for 1981 cham-
bers.
The outer cylinder was slightly more than 5 m in diameter (Figure
. A2). The bottom hoop was constructed of rectangular steel (2.5 x
1,2 cm). This rigid hoop maintained the shape of the structure. The
uprights of the outer cylinder were constructed of 2.5-cm tube drawn
from 0.15-cm aluminum (6061-46). Each was 2 m long. The eyebolts were
attached to these uprights. The uprights were supported by a zigzag
frame of schedule 40 PVC 1.9-cm diameter pipe and fittings. The shade
cloth was a woven polypropylene fabric (Chicopee brand). It provided
about 90 percent shade. The fabric was porous and allowed ventilation
-------
nozzle location
(top view)
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61
Figure A3. A sketch of the mechanical crane placing a chamber upon a
plot in 1982.
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62
enough that inside temperatures were close to ambient (Table 17), but
provided an adequate wind shelter for the spray pattern. When the cham-
bers were raised to accommodate the growing crop, there was a gap
between the shade cloth and the ground. It was assumed that the crop
provided the shade and the wind break in this gap. The shade cloth
covering the chamber walls always extended at least one foot below the
top of the crop canopy.
The nozzle was suspended in the center of the chamber by #40 braid-
ed Dacron line (Fig. A2). These lines were attached to the nozzles with
springs which helped to dampen any vibrations in the structure that
would tend to disturb the spray pattern. The springs were attached to,
and the nozzle supported by, a stainless steel washer. At points of
adjustment, the lines were run through electrical solderless butt
connectors (#10-12 AGW). After adjustments were made and the nozzle was
centered and leveled at the proper height the connectors were crimped to
hold the lines in place.
The chambers were secured on the field plots during rain events to
mobile home anchors by tether lines from the top of the chamber. After
the corn was four feet in height, a mechanical crane was used to lift
the chambers onto the plots (Figure A3).
The rain making and rain delivery to the plots were similar for
both years. Rain was delivered to the plots by various pipes, tubing
and other plumbing. Because of the corrosive nature of the rain solu-
tions, and a desire to apply nothing to the study plants but the for-
mulated rains, great care was used in selecting appropriate materials to
be in contact with the rain solutions. With one exception, there was no
evidence that any of them corroded or leached anything into the rain
solutions. The following materials were used.
Of the plastics, polyvinyl chloride types I and II, polyethylene
and polypropylene were all excellent. (Handbook of Plastics and Elasto-
mers). Other polymers used were Teflon, as a coating on some parts, and
viton, as "0" rings in the compression fittings (vendor recommendation).
Where metal fittings or parts were required, only 316 stainless steel
was used (Source Book on Stainless Steel). In 1981, the Delevan nozzles
were 306 stainless steel. Some corrosion was observed on those nozzles.
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63
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