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AN EVALUATION CF PLASTIC AND ALUMINUM NULCHES IN RELATION
TO SOIL TITT‘IPE'LfiTURES, WEED CONTROL PRACTICE. , AND THE YIELD

OF MUSKMELONS AND TOMATOES

By

AN ABSTRACT

Submitted to the College of Agriculture, Michigan State
University of Arriculture and Applied Science in
partial fulfillment of the requirements for
the degree of

MASTER OF SCIENCE
Department of Horticulture

1960

1 3" C
Approved @af (Wmcj‘VL,//

 

JTPAID ”ANNE RIEKELS ABSTRACT

The effects of clear, black, and aluminum coated poly-
ethylene films on soil and air temperatures were measured
with thermocouples placed at depths of one and four inches
in the soil and four inches above the surface of the films.
Temperatures were recorded for forty—five days during July,
August, September, and October with unshaded plots during
warm and cold weather, shaded plots, and plots with windbreaks.
Moisture levels in four plots were increased by watering, and
one moist plot and a drv plot were covered with black plastic.
Tie use of windbreaks and shading was of little value as the
temperature relationships between the plots were essentially
the same as those observed for unshaded plots.

./ A‘—‘ 7

Clear plastic resulted in the warmest soil temperatures

-—~-. “

\.

during the day with maximum increases in soil temperature

\ __.._—-—— --‘

that averaged 13.5°F and 8.9°F greater than the temperatures
of bare soil at depths of one and four inches, respectively.
The lowest soil temperatures during the warmest part of the
day occurred under\aluminum mulch and averaqed 1.80F lower
than bare soil at one inch and 0.70F lower at four inches.
The daytime soil temperatures under black plastic were
warmer than-those of bare soil but were not as warm as those
under clear plastic. Black plastic over moist soil resulted
in temperature increases that averaged 10.60F greater than

bare soil temperatures at one inch and 7.0°F greater at four

inches. The dry soil under black plastic did not become as

JERALD VAYNB RIFLKRLS ABST‘

tun
fV

ACT - 2

warm as the moist soil under black plastic as the average
temperature increases were only 8.2°F and 5.h°F over bare
soil temperatures at the respective depths of one and four
inches.

The spil temperatures during the night under all the
films were approximately the same and averaged about 50F
warmer than bare soil at both depths. The average air temper-
atures above the plastic films for twenty-four hours were
O.7°F warmer than those above bare soil while the temperatures
above aluminum averaged 1.00? higher than those ahove bare
soil durinq the six—hour period before noon, but the average
was O.6°F cooler for the rest of the day.

Additional soil temperature measurements were made at
one and one-half inch depths in soil in flats. The flats
were covered with various plastic films, and soil temperatures
were recorded with the films in direct contact with the soil
and with a one-inch air space between the films and the soil.
The results showed that soil temweratures under films in
direct contact with the soil averaged 30F to 50F higher than
those obtained with an air space below the film.

Yulching experiments were conducted to determine the
effects of black plastic, hot tents, and chemical weed control
used with black plastic on the yields of muskmelons and

tomatoes. Nuskmelons and tomatoes showed definite responses

to plastic mulching which can be partially attributed to the

TERA?“ "AYN’E‘, ‘2I"‘}"1?.S ARS'FPACT - 3

higher soil temperatures under black plastic. An experiment

with seven varieties of muskmelons showed that Spartan Rock

‘ __I

responded the most to black plastic, and Honey Rock and
Nichiéan Honey Rock responded the least. Delicious, Harvest
Queen, Rurpee Hybrid, and Narpers Hybrid showed intermediate
resnonses to black plastic.

The use of hot tents with direct se ding produced definite

(D

increases in the yield of musknelons. Melons seeded with
cultivatinn and covered with hot tents resulted in yields
that were equivalent to those obtained from transplanting
melon plants through plastic. Hot tents used with melons
seeded through plastic produced the hinhest yields.

The use of simazine pellets and spray at two pounds per
acre between the rows of black plastic did not markedly affect
the yields of muskmelons and tomatoes even though some plants

were injured by the chemical.

AN EVALUATION OF PLASTIC AND ALUMINVM MULCHES IN RELATION
TO SOIL TEMPTCTL\TURES, WEED CONTROL PRACTICES, AND THE YIELD

OF NUSKMSLONS AND TOMATOES

BY

JERALD WAYNE RITKELS

A THESI 8

Submitted to the College of Agriculture, Michigan State
University of Agriculture and Applied Science in
partial fulfillment of the requirements for
the degree of

MASTER OF SCIENCE

Department of Horticulture

1960

ACKNOWLEDGMENTS

The author is grateful to Dr. Robert L. Carolus for
his valuable assistance and guidance in conducting these
investigations.

Special thanks are due the author's wife, Marva, for
her encouragement and assistance in preparing data and
typing the manuscript.

Sincere thanks are also extended to the Doctors
George P. Steirbauer, Sylvan H. Wittwer, and Stanley K.
Ries for their participation as members of the wuidance
committee.

Recopnition is also given to Dr. Donald Dewey for
providing the temperature recorder and to the U.S.D.A.
Hydrologic Research Station for providing the location
and solar radiation data used in the temperature study.

The author appreciates the partial financial support
afforded by the Union Carbide Plastics Company, a division

of Union Carbide and Chemicals Corporation.

TABLE OF CONTENTS

Page

INTRODUCTION . o . o o o . o o o o o o . . . . o a o . l
RDVIET‘I OF IITER'XT‘TRE . . . . . . . . . o o . o . . . . 2
METHODS AND NATICVIALS. . o . . . . . . . . . . . . o . 10
Temperature Studies . . . . . . . . . . . . . . . . 10
Muskmelon Yield Tests . . . . . . . . . . . . . . . 12
Nuskmelon Variety Test . . . . . . . . . . . . . 13
Nuskmelon Seeding and Transplant Test. . . . . . 13
Chemical Weed Control . . . . . . . . . . . . . . . 1h
Muskmelons . . . . . . . . . . . . . . . . . . . 1“
Tomatoes . . . . . . . . . . . . . . . . . . . . 1%
RESULTS. . . . . . . . . . . . . . . . . . . . . . . . 16
The Influence of Film Mulches on Temperature. . . . 16
Soil Temperature . . . . . . . . . . . . . . . . 16

Air Temperature. . . . . . . . . . . . . . . . . Bl1t

Soil Temperature as Affected by Film Placement . 3h

The Influence of Black Plastic on Huskmelon
PrOCIUCtionO O O O O O O O O O O O O O O O O O O O O 37

VariPt}r rFeSt O O O O O O O O O O O O O O O O O O 7
Feeding with Hot Tents and Transplanting Test. . 37

The Influence of Chemical Weed Control on Muskmelons
and Tomatoes Mulched with Black Plastic . . . . . . “O

Nuskmelons . . . . . . . . . . . . . . . . . . . “0
Tomatoes . . . . . . . . . . . . . . . . . . . . “2
TKIscussION . . . . . . . . . . . . . . . . . . . . . . #5
SUI'T'I‘IARY AND CONCLUSIONS. . . . . . . . . . . . . . . . 50

LITERgxrrUTI‘L-C CITED 0 o o a o o o o o o o o o o o o o o o 51"

INTRODUCTION

One of the primary purposes of mulching is to regulate
the temperature of the soil. Different mulching materiaIS'
have varied effects on soil temperature. Materials that
reflect solar radiation reduce the absorption of heat by
the mulched soil. Other materials absorb or transmit solar
energy which tends to increase soil temperatures above those
of unmulched soil. Mulches that warm the soil can be used
to improve the growth of warm season crops in cool climates
or during cool weather. A mulch that cools the soil can be
used in hot climates to lower the soil temperature for a
more favorable production of cool season crops.

In this study the influence of various films as mulches
on soil and air temperature relationships were evaluated.
Transparent, black, and aluminum coated transnarent poly-
ethylene films were utilized to measure the effect of
transmission, absorption, and reflection of solar energy
on the underlying soil.

Additional experiments were conducted with black poly-
ethylene to determine its effect on crop yields. Weed
control chemicals were applied between rows of black plastic
to investigate the effect of such chemicals upon the crop
and to determine if cultivation can be entirely eliminated

from a mulched field.

 

on:

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RVVI PM 0 T“ LITEQ.-\TURE

Many factors are resnonsihle for changes in soil tem-
perature. Bouyoucos (1916) listed these factors in two
separate cateoories: intrinsic and external. Intrinsic
factors are related to soil physical properties, including
specific heat, heat conductivity, radiation, water content,
evaporation of water, concentration of the soil solution,
topographic position, and condition of the surface. External
factors such as air temperature, sunshine, wind velocity,
barometric pressure, and rainfall are meteorological.

Soil color affects the absorntion of hen , but radi-
ation is affected more by the moisture content of the soil
(Bouyoucos, 1913). Bouyoucos (1916) further stated that
white surfaced sandy soils reflected heat and were cooler
than dark colored soils with the exception of peat which
has a high moisture content and is cooled by evaporation.
He also found that all soils, when covered with a layer of
sand, warmed up the same. He suggested covering the soil
with a layer of dark material to increase the rate of warm-
ing in the spring.

The application of such a covering layer of material
to the soil surface is defined as mulching by Rowe—Button
(1957). A wide range of materials can be used as mulches
which generally consist of natural suhstances, such as plant
residues, peat, manure, stones, straw, and sawdust, or

manufactured materials such as asphalt paper, glass wool,

aluminum foil, bituminous emulsion, and polyethylene plastic.
Mulching conserves moisture, controls weeds, provides winter
protection, and regulates soil temperatures. Rowe—Button
states that mulching with straw or sawdust tends to reduce
daily soil temperature fluctuation. Dark colored mulches,
such as asphalt paper and black polyethylene, tend to increase
soil temperatures during sunny periods by absorbing solar
radiation.

Smith (1927 and 1931) conducted soil temperature studies
with perforated and nonperforated black and gray paper. He
found that soil covered with nonperforated black paper
attained the highest average temperatures, between 5°F and
70F higher than those in cultivated soil. Soil temperatures
under the perforated black paper were slightly above those
of cultivated soil. The nonperforated gray paper resulted
in temperatures just below those of cultivated soil, and the
perforated gray paper gave the lowest temperatures.

Makarevskii, as cited by Jacks it 31 (1955), found that
the soil temperature under acetyl cellulose, bitumen, and
black paper was greater than that of cultivated soil. Under
white paper the soil temperature was lower than in cultivated
soil during the day and higher during the night. The tempera
ature differences between mulched and unmulched soils was
smallest under white paper and greatest under acetyl cellulose

film.

Flint (1928), Nagruder (1930), and Stewart 33 31 (1930)

all report that black paper mulch increased soil temperatures
with the greatest differences occurring on bright sunny days.
Flint stated that black paper increased the soil temperature

as much as 10°F on sunny days and 30F without solar radiation.
Mngruder found the daily mean temperature of soil mulched

with black paper to be 6.50F greater than the temperatures

of unmulched soil. Stewart 3: :1 found that the warmest months
produced the fireetest differences between mulched and unmulched
soil. The mulcbed soil showed differences that were 12-150F
areater during the day and h-SOF fireater at night. The corre-
sponding differences durinq the coldest months were S-ROF

and Z-MOP. During periods of heavy rains the differences

were not evident.

Shaw (1976) reported that covering the soil with black
paper hastened the rate of warming and retarded the rate of
cooling. A narrower ranne occurred between the maximum and
minimum temperatures to give a more uniform soil temperature
which was slightly higher under the black paper.

Honma et 31 (1959) studied muck soil temperatures beneath
black polyethylene mulch at a depth of five inches and found
that the average soil temperature was 2.5°F higher under the
black polyethylene than in bare soil. The maximum and minimum
soil temperatures were reached four and eight hours, respec-
tively, after the maximum and minimum air temperatures. The
mean soil temperatures for sunny days three inches below the

soil surface of bare and covered mineral soils were several

degrees higher during the night with covered soils than with
bare soils, but the day temperatures of covered soils were
lower than those of bare soils. The soil temperature under-
neath a black plastic hood, which was eight inches above the
soil surface, was 5°F lower than that of bare soil while
intermediate temperatures occurred beneath black, aluminum,
and white polyethylene in that order.

Heslip (1959), studyirg temperature effects of mulching,
found that temperatures at two inches generally exceeded
those at a four-inch depth. Black plastic increased the soil
temperature an average of 5°F above cultivated soil at the
two-inch depth and 30F at the four—inch depth. Aluminum
mulched soil warmed up similarly to cultivated soil but
stayed warm longer, and the soil terded to warm up and cool
more slowly than air temperature but did not become as low.

Gliniecki (1959) reported that black polyethylene raised
soil temperatures above those of unmulcbed soil while white
film produced lower soil temperatures than normal due to
reflected sunlight. Aluminum film tended to be similar to
white film. Clear film resulted in temperatures at least
29F higher than black film and had better heat storage.

Voth and Bringhurst (1959) found a high average temper-
ature under clear polyethylene and a low average temperature
under black polyethylene with the greatest differences occur-
ring in February, March, and April. During this time soils

covered with black plastic had lower temperatures at a three-

inch depth than bare soil, but in June and July black plastic
resulted in higher temperatures. Also, black and clear films
showed the smallest differences at this time.

Clarkson (1959) showed that median and average soil
temperatures are higher with black polyethylene mulch than
with unmulched soil and found that black film increases heat
accumulation during the early part of the growing season.
Downes gt_11 (1959) reported that temperatures under both
aluminum and black plastic mulches at a depth of four to five
inches were 3-50F higher than under cultivated soil.

Honma £3 31 (1959) found that temperatures one-fourth
inch above black plastic averaged 1°F warmer than those above
bare muck soil between four and six o'clock in the morning.
After sunrise the air temperature above these two surfaces
rose more rapidly than the air temperature twelve inches
above the soil. In another experiment, temperatures measured
one-half inch above bare mineral soil and the various plastic
mulches showed no differences during the early morning hours.
At noon temperatures were 3.60F higher over aluminum, 1.1°F
'higher over black plastic, and 7.60F lower over the black
hood than over bare soil.

Rowe-nutton (1957) stated that the purpose of any cultural
operation is to increase yields, earliness, or quality of
the crops by modifying environmental conditions. Many workers
have claimed these benefits from mulching, but others have

reported undesirable effects. Emerson (1903) listed crops

that responded favorably to mulching, but Shaw (1926) reported
adverse results from beans, milo, and potatoes mulched with
black paper. Flint (1998) found that mulching with paper
increased the yield of twelve crops over a four-year period.
Edmond (1929) reported increased yields and earliness with

six crops. He stated that mulching was best on warm season
crops. Magruder (1930) found that black asphalt paper mulch
gave off a soluble substance that depressed plant growth.
However, he also stated that mulching with black paper increased
the rate and percent of germination and early growth to give
earlier maturity and larger early yields. Nineteen vege-

tables responded favorably to mulching and were larger, cleaner,
and better in ouality. Smith (1931) found that nonperforated
black paper gave the highest yields and best growth of two
indicator crops while the poorest results were obtained on
unmulched soil.

Carolus and Downes (1058) and Carolus (1959) found that
mulching with black polyethylene resulted in greater total
yields and a greater percentage of the yield harvested early.
The greatest response to mulching was obtained from muskmelons
and squash while tomatoes, pepper, and eggplant gave favor-
able results but to a lesser extent. Heslip (1959) reported
that black plastic mulch increased the yields of cucumbers
28 percent, tomatoes 31 percent, squash 58 percent, and
muskmelons 81 percent above those of cultivated soil. The

cucurbits tended to respond more to mulching than tomatoes.

H:

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Muskmelons gave the best reSponse on plastic four feet wide,
but tomatoes produced satisfactory results on plastic three
feet wide.

Downes e3 :1 (1959) reported a #1 percent increase in
total yield of peppers mulched with black plastic over culti-
vated peppers. Voth and Bringhurst (1959) found that total
and early yields of strawberries were increased with clear
polyethylene mulch but not with black polyethylene mulch.
Emmert (1957) reported that aluminum plastic gave the best
results as black plastic became too warm and injured seed
germination.

Clarhson (1959) states that yield increases are not the
result of the plastic material but are due to the influence
of the plastic on the soils, microclimate, and diseases.
Carolus (1959) and Heslip (1959) reported that increased yields
from mulching are the result of conserving soil moisture,
increasing soil temperature, protecting the surface roots,
and increasing aeration of the soil surface. These factors
produce more benefits from mulching through increased nutrient
availability and the stimulation of microorganisms to increase
nitrification (Flint, 1928). weed control and reduced culti-
vation are other benefits of mulching that aid in preserving
soil moisture and fertility (Edmond, 1929).

Ries (1957) reoorted that herbicides and shallow culti-
vation used for weed control in pickling cucumbers resulted in

yields equal to those obtained with black plastic mulching.

He stated that black plastic had no additional advantage except

to keen the soil undisturbed.

10

FfUTHOTNF‘: ANT) M “iT‘SRI 113

Temperature Studies

 

Temperature measurements were made in 1959 at the
Hydroloric Research Station at East Lansing on a Hillsdale
fine sandy loam soil. A Brown Electronik sixteen point
strip chart temperature recorder was used to provide a
continuous twenty-four hour record of temperatures. Fifteen
thermocouples were placed at depths of one and four inches
in the soil and four inches in the air above the surface of
each of five plots, and the other thermocouple was placed
two and one-half feet above the soil to record the air
temoerature of the area.

Each thermocouple recorded one temperature reading every
four minutes for a total of 15 readings per hour or 360 read-
ings per day. The ex-eriment was conducted for forty—five
days under varying conditions providing a total of 259,200
temperature readings for all sixteen thermocouples. One
average reading was selected for each hour, a total of 17,280
values, and used in compiling the data reported in this study.

Moisture blocks were placed at a depth of four inches
in the plots and four of the plots were watered thoroughly
to raise the moisture content of the soil. Moisture read-
ings were taken approximately once a day during July and
August but were recorded less frequently in September and
0ctober. Dalapon was spread on the plots to prevent the

growth of ouacknrass, and simazine was applied later to

11

control broadleaf weeds. A snow fence was placed around the
entire area in an attempt to reduce the air movement over
the plots.

Sheets of polyethylene film, approximately four feet
square, were placed on four of the five plots in the follow-
ing manner:

1. Black polyethylene on dry soil.

2. A control plot of moist tare soil.

3. Clear polyethylene on moist soil.

. Black polyethylene on moist soil.
. Aluminum coated polyethylene on moist soil.

Temperatures were recorded under four different condi—
tions consistine of direct exoosure during warm and cold
weather, shading, and placina windbreaks around each plot.

Temperatures were recorded as follows:

July 22-27 “arm weather exposure
July 28—August 2 Shading

Aunust 2-0 Warm weather exposure
August 10-16 Shading

September 1—10 Windbreaks

October 11—12, 16-22 Cold weather exposure

The plots were shaded by monntinn a sinqle layer of
cheesecloth approximately twelve inches above the surface
of each plot. The reduction in sunlight intensity with
cheesecloth as measured with a foot-candle meter between

1:00 and 2:30 p.m. was approximately twenty—five percent or

2,200 foot-candles. The windbreaks consisted of sheets of
clear polyethylene that were supported approximately two and
one-half feet high around the border of each plot.

The days during which the temperatures were recorded
were classified as clear, partly cloudy, or cloudy. Pyrheli-
ometer readinws in gram-calories per square centimeter of
horizontal surface, supplied by the Hydrologic Research Station,
were used in making this classification. Records from the
Lansing weather bureau provided information as to the amount
of sky cover, hours of sunlight, and the percent of possible
sunlight and were also used in classifying the daily weather
conditions.

In another experiment, the effects of different plastic
covers on soil temperature were measured with the films in
direct Contact with the soil and one inch above the soil
surface. Clear, black, clear on black, and green polyethylene
films were placed over flats containing soil at two levels,
and thermocouples were placed at a depth of one and one-half
inches in the soil. The experiment was started in a green-
house during the winter months of 1960 and moved outside in
May to eliminate the effect of shading in the greenhouse.

Muskmelon Yield Tests

 

Mulching experiments were conducted in 1959 on the
horticultural farm at East Lansing. The effects of black
plastic mulch on muskmelon yields were compared with yields

from cultivated plots. The plastic was laid with a tractor

13

mounted attachment on soil which had been previously ferti-
lized and disced. The melons were harvested as they ripened
and records were kept of the number and weight of marketable
fruit.

Banded muskmelon plants were set in the field on June 3
in plots consistine of six hills, of two plants each, spaced
at five-foot intervals in rows six feet apart. Harvest was
started on August 12 and continued through September 18.
Muskmelon Variety Test: Cultivation was compared with four-
foot black plastic mulch in this experiment which consisted

of two replications of the following varieties:

1. Delicious 5. Narpers Hybrid
2. Harvest Queen 6. Spartan Rock
3. Honey Tlock 7. Michigan Honey Rock

h, Rurpee I’yhrid

Muskmelon Seeding and Transplant Test: Two replications

 

of the varieties, Delicious and Harvest Queen were used in
comparing the following treatments:

1. Handed plants - cultivated.

2. Banded plants — black plastic.

3. Seeded - cultivated.

A. Seeded thru black plastic.

5. Seeded - cultivated with hot tents.

6. Seeded thru black plastic with hot tents.
Seedinw was done on Nay 12 for the treatments with hot tents

and on May 22 for the other seeded treatments.

Chemical Weed Control

 

Experiments were conducted with tomatoes and muskmelons
utilizinn weed control chemicals on plots mulched with black
polyethylene. Fifty percent wettahle simazine and four per-
cent granular simazine were applied as a spray and as pellets
at the rate of two pounds per acre.

Muskmelons: Three replications of Delicious and Honey Rock
varieties were planted on June 10. llots consisted of seven
hills spaced at five-foot intervals with rows six feet apart.
The followinp treatments were compared:

1. Cultivated.

2. Four—foot black plastic.

3. Four-foot hlack plastic and sprayed simazine.

h. Four-foot black plastic and pelleted simazine.

The fruits were harvested from Auqust 12 through September 11.
Tomatoes: Two replications of Fireball and Noreton Hybrid
tomatoes were planted on May 30. The plots were thirty feet
long and five feet apart consisting of twelve Fireball plants
at two-foot intervals or ten Moreton Hybrid plants at two

and one-half foot intervals. Comparisors were made between
the fellowing treatments:

1. Cultivated.

2. Three—foot black plastic.

3. Four-foot black plastic.
h. Three-foot black plastic and sprayed simazine.

5. Four-foot black plastic and sprayed sinazine.

~.v

15

6. Three-foot black plastic and nelleted simazine.
7. Four-foot black plastic and pelleted simazine.

The tomatoes were harvested from July 17 through September 18.

16

ll T‘FITI 17?}

The Influence of Film flulohes on Temperature

 

 

 

Qoil Temperature: The effects of plastic and aluminum mulches

 

on soil temperature for unshaded plots durirg clear warm
weather are presented in Figure l as the hourly averages in
degrees F for July 26 and 27 and August 5 and 6. The warm-
est temperatures at the one-inch depth were under clear
plastic during the daytime between 10:00 a.m. and 7:00 p.m.
and under aluminum during the early morning hours between
1:00 a.m. and 8:00 a.m. The coolest soil temperatures at
both depths occurred in bare soil at night and under the
aluminum during the day. Black plastic over moist soil pro-
duced the warmest day temperatures at four inches in the soil
while the soil under clear plastic tended to he slightly
warmer at night. The greatest temperature fluctuations
occurred under the clear plastic at one inch and in the
moistenei soil under black plastic at four inches. The most
uniform temperatures were maintained under the alumixum at
both depths in the soil.

The minimum and maximum soil temperatures occurred from
6:00 to 7:00 a.m. and 3:00 to 4:00 p.m. at the one-inch

depth, and from 7:00 to 8:00 a.m. and hzoo to K:OO p.m.

/

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(1"

the four-inch depth, respectively. The magnitude of the
differences in soil temperature under mulches at these maxi-
mum and minimum points as compared with the uncovered soil

are indicated below:

7?

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mthrm Lou meLOHmOIEmhm H.Hmw I mhso£ :N Mom Seeuwmpnk kaHom etmho><
.Am mechmwc Cw mmLaLm>w kapsomv .m»0HQ pmcmfim2§ npw3 memo hwoao L509

acaHSU meanemeQEmv Hfiom Go mEHfiM anofihwb ho eomkho Omaho>w 038 .H casuah

 

    

 

29:2: :82 22:2: :82 22%.:
N. m. w .m N. m mw m N_Q mm m .m N. .w w m N.
_ 1 J _ a _ _ _ L. _ 4 _ a 1 a _ .. l 900
gamma socanpsom n.33. spawn nocanoco m.s;.
cos
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com
.09
e<.EE.
1 :Rwlll.
:35an II... A l
1 x5 «85 III 4,, \2 1 .0:
3: 32m I // ‘.
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T . l . 1 CON-
_ p b p _ p _ L4» _ p h b _ _ Fl _

 

 

18

 

Variflum Einimufl
l-inch h-inches l-inch h-inches

Bare Soil

Temperature: 105.30 96.50 6h.5° 60.5o
Clear: +16.7° +13.8° +6.50 +6.80
Black-Wet: +16.0° +14.5° +6.50 +6.00
Black-Dry: +13.5° +ll.0° +7.00 +5.80
Aluminum: -R.0° -2.5° +lO.3° +6.8°

Tables I and II present the average temperatures
recorded from unshaded plots during warm weather for partly-
cloudy days on July 22, 2h, and 25 and August h and 9 and
for cloudy days on July 23 and August 3, 7, and 8. The
results are the averages of the temperatures obtained during
six-hour intervals throughout the day. The relationship
between the various soil temperatures are the same as those
presented in Figure 1 except that the warmest temperatures
at the four-inch depth occur under the clear plastic instead
of in the moist soil under the black plastic. The temperature
differences between the various plots tended to decrease
as the amount of solar radiation decreased.

Figure 2 presents the hourly averages in degrees F
obtained from shading the plots during clear days on July 31
and August 1, 2, and 1h. A single thickness of cheesecloth
which reduced the light intensity approximately 2,200 foot-
candles, or 25 percent, was used to simulate the effect of
a plant growing on the plastic. The reduction in light

intensity was not Treat enough to exert much influence as

TABLE I

The Average Effect of Various Films on Soil Temperatures
During Five Partly-cloudy Days* with Unshaded Plots.
(Averages for Six-hour Periods in Degrees F)

19

 

 

 

piffereFé'és“?rom Bafé'S'Efi

 

 

 

 

 

Time Air Bare Black Black Clear Alum.
Soil Dry Wet Wet Wet
One-inch depth
Mid. to 6 a.m. 66.2 69.2 +5.8 +5.3 +6.h +6.6
6 a.m. to Noon 77.5 77.9 +5.2 +5.9 +6.7 +1.2
Noon to 6 p.m. 86.3 91.8 +1l.h +13.0 +15.5 -2.0
6 p.m. to Mid. 73.2 79.2 +10.5 +10.5 +11.l +5.h
Epur-inch depth
Mid. to 6 a.m. 66.2 73.0 +5.6 +5.7 +7.0 +h.2
6 a.m. to Noon 77.5 74.8 +h.6 +h.8 +5.3 +2.8
Noon to 6 p.m. 86.3 87.8 +6.6 +7.5 +8.9 -0.5
6 p.m. to Mid. 73.2 82.6 +9.0 +9.8 +10.8 +2.5

 

 

 

 

.—_.——_._ _.—_.

 

*Average solar radiation for 2h hours

calories per square centimeter.

h76.9 gram-

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TABLE II

The Average Effect of Various Films on Soil Temperatures

During Four Cloudy Days* with Unshaded Plots.
(Averages for Six-hour Periods in Degrees F)

 

 

20

 

 

Diffbrences from Bare Soil

 

 

 

 

 

Time Air Bare Black Black Clear Alum.
Soil Dry Wet Wet Wet
One—inch depth
Mid. to 6 a.m. 68.2 71.9 +7.0 +6.6 +7.7 +6.6
6 a.m. to Noon 73.3 75.9 +h.2 +4.8 +6.1 +2.0
Noon to 6 p.m. 75.6 81.6 +4.7 +5.3 +8.0 -l.0
6 Pom. to Mid. 69.1 73.9 +4.9 +5.0 +6.1 +2.8
Four-inch depth
Mid. to 6 a.m. 68.2 76.0 +6.6 +6.7 +8.0 +4.1
6 a.m. to Noon 73.3 74.9 +4.3 +4.6 +6.2 +2.9
Noon to 6 p.m. 75.6 79.9 +3.8 +h.3 +6.h +0.2
6 p.m. to Mid. 69.1 76.8 +h.5 +u.9 +6.5 +1.2

 

 

*Average solar radiation for 24 hours - 208.7 gram-
calories per square centimeter.

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the relationships between the plots are essentially the
same as in Figure 1 except that at the four-inch depth the
soil under the clear plastic was the warmest during the
entire twenty-four hour period.

The soil temperature differences at the maximum and
minimum points with shade are presented below usine the
temperatures of bare soil as reference points:

F'ajcinuinl lTiJiinElfll

l-inch 4—inches l-inch 4—inches

Bare Soil

Temperature: 98.3° 92.00 66.80 71.3°
Clear: +21.0° +l5.3° +7.7° +R,2°
Black—Wet: +18.0° +l4.5° +7.5o + .20
Black-Dry: +l6.0° +11.8° +7.50 +7.20
Aluminum: —2.5° ~0.2° +0.50 +6.20

These differences, as compared with those of Figure l, are
larger for the three plastic films and smaller for the
aluminum. This would indicate that shading had more influence
on the temperature of bare soil than on covered soil.

The soil temperatures of the shaded plots during eight
partly-cloudy days are shown in Table III as the averages
’of six-hour intervals for July 28, 29, and 30 and August 10,
ll, 12, 13, and 15. The temperature differences between the
plots are smaller than those occurring during clear weather
and except for the soil under clear plastic, which averaged
warmest during the eight day period at both depths, the rela-

tionships are the same as those presented in Figure 2 for clear

days.

93

TABLE III

The Average Effect of Various Films on Soil Temperatures
During Eight Partly-cloudy Days* with Shaded Plots.
(Averages for Six-hour Periods in Degrees F)

 

Differences from Bare Soil
Time Air Bare Black Black Clear Alum.
Soil Dry Wet Wet Wet

 

 

One-inch depth

 

Mid. to 6 a.m. 71.9 7h.l +6.3 +6.5 +7.1 +5.9
6 a.m. to Noon 81.2 80.5 +3.9 +6.3 +7.2 +0.7
Noon to 6 p.m. 91.3 9u.9 +9.0 +12.2 +1u.u -3.0
6 p.m. to Mid. 79.5 83.8 +8.0 +8.6 +9.7 +3.2

 

Four-inch depth

 

 

Mid. to 6 a.m. 71.9 77.1 +6.2 +7.1 +8.0 +4.1
6 a.m. to Noon 81.2 77.8 +4.1 +h.7 +5.7 +2.h
Noon to 6 p.m. 91.3 90.2 +6.0 +8.0 +8.7 -1.4
6 p.m. to Mid. 79.5 85.7 +7.3 +8.8 +10.0 +1.3
*Average solar radiation for 24 hours - h79.2 gram—

calories per square centimeter.

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The effects of shading on soil temperature cannot be
directly compared with that from unshaded plots as the
temperatures were recorded on different days. The differ—
ences between Figures 1 and 2 indicate that shading reduced
temperatures as the solar energy was greater when the plots
were shaded; but the air temperature was lower during this
time also, and the lower temperatures in Figure 2 way have
been due to the lower air temperature and not the reduced
light intensity. Tables I and III show a similar effect as
the soil temperatures with shading are greater than in
unshaded plots even though solar radiation wasrapproximately
the same for both periods.

Windbreaks were olaced around each rlot to permit a
more eccurate measurement of the air temnerature above each
film, but the recorded differences were neither consistent
nor great enough to be of any importance. The average hourly
soil temperatures obtained by placing windhreaks around the
plots are shown in Figure 3 for six clear days on September

3. 1*.

‘J'l

, 6, 7, and 8. The soil temperatures in the different
plots are related in the same manner as in Figures 1 and 2.
The maximum soil temperatures at the one—inch depth were
reached hetween 2:00 and 3:00 p.m. which is one hour earlier
than those for shaded and unshaded plots. The daytime
differences in the soil temperatures beneath the clear and
black films tended to be greater than those recorded under

shaded or unshaded conditions. These differences, as they

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occur at the maximum and minimum points, are related to bare

soil temperatures as follows:

Tfaxinnnn Iiininunn
1-inch h-inches 1—inch h—inches

Bare Soil

Temperature: 103.5° 98.8° 73.7° 77.0°
Clear: +20.3° +15.7° +6.8° +7.2°
Black-Wet: +17.8° +1?.9° +5.10 +6.80
Black-Dry: +8.5o +6.h° +5.8o +5.3°
Aluminum: +0.20 -o.6° +9.00 +7.00

Table IV presents the average soil temperatures as they
were recorded with a windbreak around each plot during partly-
cloudy weather on September 1, 2, 9, and 10. The table shows
the aluminum covered soil to be slightly warmer than bare
soil; whereas, the reverse occurred with shaded and unshaded
plots. Clear plastic resulted in the warmest temperatures
throughout the entire day. The temperature differences and
fluctuations were not as great during partly—cloudy weather,
but the relatiorships are similar to those occurring in clear
weather 0

The data in Tables V, VI, and VII are the average soil
temoeratures of unshaded plots during cold weather for clear
days on October 18, 19, and 20, partly—cloudy days on
October ll, 16, 21, and 22, and cloudy days on October 12
and 17. The results, when compared with Figure l and Tables
I and II, indicate that the various covers have the same

relative effects on soil temperature in both cold and warm

TABLE IV

The Average Effect of Various Films on Soil Temperatures
During Four Partly-cloudy Days* for Plots with Windbreaks.
(Averages for Six-hour Periods in Degrees F)

27

 

 

 

 

Differences from Bare Soil

 

 

 

 

 

 

 

 

Time Air Bare Black Black Clear Alum.
Soil Drx, Wet Wet Wet
One-inch depth
Mid. to 6 a.m. 75.2 79.5 +6.1 +5.6 +7.6 +6.6
6 a.m. to Noon 80.2 82.2 +h.6 +6.8 +l0.0 +3.7
Noon to 6 p.m. 87.0 93.2 +8.2 +ll.h +l7.h +O.h
6 p.m. to Mid. 76.7 80.8 +8.7 +8.6 +11.8 +6.3
Four-inch depth
Mid. to 6 a.m. 75.2 83.1 +5.5 +5.9 +7.h +5.0
6 a.m. to Noon 80.2 81.h +h.7 +5.5 +7.h +h.l
Noon to 6 p.m. 87.0 90.6 +5.4 +8.0 +ll.6 +0.6
6 p.m. to Mid. 76.7 8h.h +7.7 +8.7 +11.7 +3.8
*Average solar radiation for 24 hours - 370.1 gram-

calories per square centimeter.

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28

TABLE V

The Average Effect of Various Films on Soil Temperatures
During Three Clear Days* with Unshaded Plots in Cold Weather.
(Averages for Six-hour Periods in Degrees F)

 

Differences from Bare Soil
Time Air Bare Black Black Clear Alum.
Soil Dry Wet Wet Wet_

 

One-inch depth

 

Mid. to 6 a.m. Ah.1 h5.0 +6.8 +5.0 +h.0 +9.6
6 a.m. to Noon 55.0 50.5 +5.0 +h.6 +h.8 +6.8
Noon to 6 p.m. 65.h 68.7 +h.5 +h.8 +8.0 +0.9
6 p.m. to Mid. h8.3 52.0 +8.0 +5.9 +6.h +8.5

 

Four-inch depth

 

Mid. to 6 a.m. uu.1 50.1 +2.5 +1.8 +0.6 +5.1
6 a.m. to Noon 55.0 51.9 +3.1 +1.9 +1.3 +5.0
Noon to 6 p.m. 65.u 65.6 +2.8 +3.0 +5.0 +0.5
6 p.m. to Mid. h8.3 57.8 +3.8 +2.8 +3.7 +3.9

*Average solar radiation for 24 hours - 365.6 gram-
calories per square centimeter.

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TABLE VI

The Average Effect of Various Films on Soil Temperatures
During Four Partly-cloudy Days* with Unshaded Plots in Cold

 

 

 

 

 

 

 

 

 

 

Weather. (Averages for Six-hour Periods in Degrees F)
__ Differences from Bare Soil
Time Air Bare Black Black Clear Alum.

Soil Dry Wet Wet Wet
One-inch depth
Mid. a.m. 39.3 hh.2 +6.5 +h.4 +h.5 +8.5
6 a.m. Noon 51.4 51.5 +3.h +3.2 +h.0 +h.0
Noon to 6 p.m. 6h.2 67.5 +3.2 +3.7 +6.6 -O.h
6 p.m. Mid. 51.2 54.9 +6.6 +h.8 +5.5 +6.2
Four-inch depth
Mid. a.m. 39.3 50.2 +h.6 +2.7 +3.0 +5.5
6 a.m. Noon 51.h 51.h +3.2 +2.0 +2.5 +h.3
Noon to 6 p.m. 6h.2 65.3 +2.2 +2.3 +h.2 -0.1
6 p.m. to Mid. 51.2 59.5 +3.9 +3.3 +h.2 +2.9
*Average solar radiation for 2h hours - 262.3 gram-

calories per square centimeter.

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TABLE VII

30

The Average Effect of Various Films on Soil Temperatures
During Two Cloudy Days* with Unshaded Plots in Cold Weather.
(Averages for Six-hour Periods in Degrees F)

 

Differences from Bare Soil

 

 

 

 

 

Time Air Bare Black Black Clear Alum.
Soil Dry Wet Wet Wet
One-inch depth
Mid. to 6 a.m. 50.8 53.6 +5.2 +3.9 +h.1 +5.6
6 a.m. to Noon 52.0 5u.7 +u.u +3.7 +3.8 +h.2
Noon to 6 p.m. 5h.7 59.8 +h.h +3.7 +h.8 +2.6
6 p.m. to Mid. h7.7 51.8 +6.2 +5.1 +5.1 +6.6
Four-inch depth
Mid. to 6 a.m. 50.8 56.7 +3.7 +3.0 +3.0 +3.5
6 a.m. to Noon 52.0 56.h +3.3 +2.9 +2.5 +3.1
Noon to 6 p.m. 5h.7 59.2 +3.3 +3.0 +3.0 +1.8
6 p.m. to Mid. #7.? 55.9 +2.8 +2.7 +2.h +2.3

’—
_....-_.

 

 

_’-—' m”

*Average solar radiation for 2h hours - l3h.5 gram-

calories per square centimeter.

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weather. Aluminum caused the greatest difference by keep-
ing the soil warmest throughout most of the night at both
soil depths. Cloudy weather resulted in similar soil
temperatures beneath the various covers, but all films
produced warmer soil temperatures than were recorded in
bare soil for the entire day.

Figure 4 summarizes the average hourly soil temperatures
obtained under all conditions for forty-five days. At both
depths the soil under clear plastic was warmer than the
moist soil under black plastic during the day. The next
highest day temperatures vere in the dry soil under black
plastic. The next in order was the bare soil followed by
the soil under aluminum.

The early morning soil temperatures at one inch were
warmest under aluminum and coolest in bare soil. The dry
soil beneath the black film is similar to that under clear
film, but both soils were warmer than the moist soil under
the black film. The early morning temperatures at four
inches were warmest in the soil beneath clear plastic and
coolest in bare soil. The black and aluminum covers resulted
in similar soil temperatures with the aluminum covered soil
slig-jhtly lower than that under the two black films between
midnight and 5:00 a.m. The greatest and smallest soil
temoerature fluctuations occurred beneath the clear and
aluminum films, respectively.

The average minimum and maximum soil temperatures during
(__‘0 t.

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the forty-five day period occurred from 6:00 to 7:00 a.m.
and 2:00 to 3:00 p.m. at the one—inch depth and from 7:00
to 8:00 a.m. and 3:00 to #:00 p.m. at the four—inch death,
respectively. The soil temperatures at these maximum and

minimum points vary from bare soil temperature as follows:

”aximum Minimum
l-inch h—inches l-inch h-inches

Pare Soil

Temperature: 87.l° 83.5° 6h.6° 68.0o
Clear: +l3.5° +8.9° +5.1° +5.0O
Black-Vet: +lO.6° +7.0o +8.6° +h.0°
Black—Dry: +8.2o +5.h° +5.h° +h.h°
Aluminum: —l.8° -0.7° +7.2° +4.5O

The averages of twenty-four soil moisture readines
indicating the percentage of field capacity are presented

as follows:

Clear: 93.8 Aluminum: 811.5
Qlack—Wet: 91.3 Bare Soil: 83.0
Black-Dry: 89.3

5

A possible effect of these differences in soil moisture
on soil temperatures beneath black plastic is sugeested by
the data in Figure A. The soil with the highest moisture
content showed a greater fluctuation in temperature through-
out the twenty-four hour period and was lower at night and
higher in the daytime. The differences were more evident

at one inch than at four inches with very little difference

occurring during the night at four-inch depths.

3h

Air Ter‘ferature: "x sumrrmry of the air temoeratures during

 

the forty—five day period four inches above the different
surfaces is presented in Table VIII. The data indicate that
temperatures above the black and clear films were between
one-half to one degree warmer than those above bare soil

and aluminum. The black and clear films both tend to radiate
more heat to the air than does bare soil, but this could be
the natural result of the warmer soil temperatures under the
films. The air temperatures above aluminum were slightly
cooler than those above bare soil which shows that less

heat escapes from the soil with an aluminum cover. Between
6:00 a.m. and nooi the air above aluminum averaged one degree
warmer than that above bare soil which could be attributed

to the reflection of heat from the surface of the film.

l§oil Temperature as Affected by Film placement: The data

in Table IX indicate that the presence of an air space
beneath the plastic films will result in lower soil temper-
atures than when the film is in direct contact with the soil.
The clear plastic and transparent green plastic produced the
warmest soil temperatures while the soil temperatures under
the translucent green plastic were sli htly cooler. The soil
temperatures under the black plastic and the combination of
clear on black were cooler than under the green plastic but
were warmer than bare soil. The transparent green and clear
plastics had similar effects on soil temperature as did the
black and the clear on black combination. The clear on black
combination tended to increase the soil temperature when the

films were in contact with the soil surface.

TABLE VIII

Average Air Temperatures Four Inches Above Various Films.
(Averages in Degrees F During a Forty-five Day* Period at

Six-hour Intervals)

35

 

 

 

 

Differences from Dare Soil

 

 

 

Time Air Bare Black Black Clear Alum.
Soil Dry Wet Wet

Mid. to 6 a.m. 62.8 62.2 +0.7 +0.6 -0.2
6 a.m. to Noon 72.h 71.0 +0.9 +1.3 +1.0
Noon to 6 p.m. 80.6 80.9 +0.7 +0.5 -0.3
6 p.m. to Mid. 68.7 67.9 +0.9 +0.h -O.7
Averages 71.1 70.5 +0.8 +0.7 -0.1

 

“-

*Average solar radiation for 24 hours - h51.l gram-
calories per square centimeter.

Vt

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TABLE IX

The Effects of Various Plastic Films on Soil Temperatures

at One and One-half Inch Depths.

36

 

 

 

 

 

 

Type °f Film “$32.2” 33522. ”$122.21:
Outdoor Measurements
Bare Soil (2h)* 87.“ 87.4 — -
Black (12) +2.0 +8.3 _ _
Clear on Black (12) +2.0 +11.7 _ _
Translucent Green (12) +9.1 +1h.9 - -
Transparent Green (12) +17.6 +18.6 - -
Clear (12) +15.u +19.h - -
Average +9.2 +1h.6
greenhouse Measurements
Bare Soil - - — - 72.7
Black (5)* 73.0 75.8 72.5
Translucent Green (5) 75.2 77.5 76.8
Transparent Green (5) 76.0 79.5 79.3
Average 7h.7 77.6

 

 

 

 

*Number of readings averaged.

**Average of seven readings made with dial thermometers.

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37

The Influence of Black Plastic an Huskmelon Production

 

 

 

Variety Test: The effects of mulching and cultivation on

 

the yields of seven different muskmelon varieties is shown
in Table X. Mulching with black plastic resulted in a
total yield of 780 bushels per acre which is significantly
greater than the H97 bushels per acre obtained with culti-
vation. There was no significant differential variety effect
from treatment. Spartan Rock showed the greatest response
to mulching with an increased yield of 95 percent while
Nichigan Honey Rock responded the least with a 21 oercent
increase.

The number of melons per slot was significantly greater
in the mulched plots, but the size of the fruit was approx—
imately the same. Spartan Rock and Vichigan Honey Rock

showed the larg.st and smallest respective increases in the

l

number of melons produced.

’J}

eedin.

0‘
LL

With Pot Tents and Transplanting Test: Table XI
shows the effect of using black plastic mulch and hot tents
with direct seeding and plants. All treatments except that
of melons seeded thru plastic produced yields that were
significantly greater than those obtained from melons seeded
with cultivation. Helons seeded through plastic and covered
with hot tents produced the hifihest yield of 835 bushels per
acre which was significantly greater than the yields obtained
from melons transplanted with cultivation and melons seeded

through plastic. Iulcking with black plastic resulted in

38

 

 

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melon yield increases of 163 bushels with direct seeding,
158 bushels with nlants, and 10? bushels With direct seeding
and hot tents. The yield of 733 bushels per acre obtained
from the melons seeded with cultivation and covered with

hot tents was essentially the same as the 798 bushels per
acre harvested from the melons transplanted on plastic. A
similar relationship occurred between the 6&0 bushels per
acre obtained from melons transplanted with cultivation and
the 620 bushels per acre produced from melons seeded through
plastic.

The treatments producing the largest yields also produced
the largest number of melons per plot, but the largest fruit
occurred on the plots with the smallest number of melons
and the lowest yields. This indicates that yield increases
are primarily due to increases in the number of fruit and
not the size of the fruit.

Both varieties had the lowest yields on plots with
direct seeding and cultivation, but the highest yields were
obtained from melons planted with plastic for Delicious and
from direct seeding with plastic and hot tents for Harvest
Queen. Delicious showed more response to the various treat-
ments than Harvest Queen.

The Influence of Chenical Weed Control on Muskmelons and
Tomatoes Hulched with Black Plastic

 

 

 

 

Iuskrelons: iuskmelon yields of 5H7, #70, and hh9 bushels

 

per acre, as shown in Table XII, were obtained from plastic,

plastic with granular simazine, and plastic with sprayed

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simazine, respectively, all of which were significantly
greater than yields from the cultivated plots. Black plastic
resulted in yields that were larrer than those obtained from
black plastic with simazine, and larger yields were also
obtained with granular simazine than with sprayed simezine.
The lower yields that occurred with the use of simazine
could be attributed to the washint of treated soil into the
holes with the plants which resulted in severe injury in a
few cases. The yield reduction that occurred with sprayed
sima7ine may have been caused by injury to the melon plants
during the application of the chemical.

The largest yields were obtained with the treatments
)rodncing the lorfiest number of melons per plot except for
the oelleted treatment which produced fewer melons than the
spray treatment. However, the fruit size was the largest
in the pelleted treatment and resulted in the increase in
yield over the spray treatment. The larre fruit size with
the pelleted treatment was consistent for both varieties
which indicates that the pellets may have increased the size
of the melons. Delicious responded more to the various treat—
ments ban Honey Rock, but both varieties showed the highest
yields on plots with black plastic and the lowest yields on
cultivated plots.

Tomatoes: Title XTII indicates that plastic mulch signifi-

 

cantly increased the early and total yields and numbers of

tomatoes. The four-foot plastic resulted in yields that

#3

TABLE XIII

Effect of Black Plastic and Chemical Weed Control on the
Average Yield of Fireball and Moreton Hybrid Tomatoes.
(Marketable Yields in 56 Pound Bushels per Acre)

 

 

 

 

 

 

 

 

 

Average
Yield Number
glPlot
Early Yield (July 17 to Aug. 12)
Cultivated 156 106
3 ft. Plastic 282 191
4 ft: Plastic 28h 193
3 ft. Plastic + Simazine 278 193
h ft. Plastic + Simazine 28h 205
L.S.D. .05 32 bu. 24
L.S.D. .01 #3 bu. 33
Total Yield (July 17 to Sept. 18)
Cultivated SH? 378
3 ft. Plastic 980 628
h ft. Plastic 1,066 688
3 ft. Plastic + Simazine 1,010 612
h ft. Plastic + Simazine 1,081 713
L.S.D. .05 160 bu. 65

L.S.D. .01 216 bu. 88

 

 

 

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were slightly greater than those

three-foot olastic.

yields also resulted in the
rilot, anrl'the
for all treatments which indicates that

ttua rernllt rfif
Both varieties showed
resnonse to the various

showed a

81 if'htlv

l

Moreton Hybrid.

The use of simazine with black plastic

on the eerly yield of

increases in the total yield that
These increases in total yield on
olots night have been fireater but

injured by the simazine which was

with the nlants.

ohtained

The treatments

size of the fruit was aparoximately the

treatments

greater resoonse to

the tomatoes but resulted in

11h

from plots with

nroducing the largest

larrest numher of melons per

yield ircreases are

increases in the number of fruit nroduced.

approximately-tflwggymne relative

except that Fireball

mulching than did

had no effect
Slijfldt
were not significant.

the chemically treated
some plants were

s everelv

washed into the holes

“5

DISCUSSION

The data obtained in these studies indicate that cover-
ing the sail with a plastic or aluminum mulch will result
in distinct changes in soil temjeratures. Mulches that tend
to increase the soil temperature in cool climates make condi-
tions more favorable for warm weather cr0ps and increase
earliness while mulches that reduce soil temperatures are
important in warm climates in the production of cool season
crops (Rowe-Dutton, 1957).

The warmest soil temneratures in this study were measured
under clear plastic and are similar to those reported by Voth
and Bringhurst (1959) and Gliniecki (1959). The soil temper-
atures under black plastic were also warmer than those of
bare soil and agree with the results obtained by Heslip (1959),
Gliniecki (1959), and Clarkson (1959), but are contrary to
those reported by Honma gt a; (1959) for Mineral soils and
by Voth and Pring-jhurst (1959). Aluminum mulches resulted in
soil temperatures that were approximately tte same as or
lower than bare soil tenperatures during the day and warmer
than bare soil at night. Feslip (1959) ohtained similar
results in soil mulched with aluminum. These results indicate
that clear and black plastic would be most useful as mulches
in cool climates with warm—season crops while aluminum mulches
might be more effective in warm climates with cool season crops.

The differences observed in the air temperature above

the plastic films are similar to those recorded by Honma 33 a1

1&6

(1959) as both studies showed that temperatures above the
films are slightly greater than those above bare soil. The
temperatures in this study were recorded four inches above
the surface of the films. Greater differences probably
occurred closer to the films.

Soil tenoeratures measured under various films in direct
contact vith the soil surface and with an air space between
the film and the soil surface indicate that a film should
be laid in direct contact with the soil to obtain the warm-
est soil temperatures. These conditions can be attained by
smoothing the soil surface before apnlying the film and then
stretchinw the film tightly over the surface while it is
being laid. Paper mulches tear easily and cannot be pulled
or stretched as tipht to the soil as plastic mulches. This
indicates that more air space occurs under paper mulches and
the resultine soil temperatures would tend to be lower than
those under plastic mulches.

The use of black plastic and aluminum mulches with
various warm-season crops in Michigan has resulted in larger
early and total yields, and such increases can be partly
a tributed to the warmer soil temperatures that were attained
with these mulches (Carolus and Downes, 1058, and Ueslip,
1959). The effect of increasing soil temperatures on the
arowth of tomato plants was investigated by Tiessen (1956)
who found that increasing the soil temperature from h6°F to

70°F resulted in larae increases in plant growth. He also

14,7

observed that there was a larger number of flowers and fruit
on the vlants nrown at the higher soil temperatures than on
plants grown at lower temperatures. Roberts (1053) reported
similar results obtained by increasins the soil temperature
of strawberry nldnts from 45°F to 75°F. These observations
indicate that the increase in soil temperatures obtained
with black plastic could be a very imoortant contributing
factor to the hirher yields and better plant nrowth.

The effect of increases in soil tewperature on the
absorption of water was studied by Schroeder (1039). He
found that an increase in root temnerature of cucumbers caused
an increase in the rate of absorption of water by the plant
and reduced wilting. He attributed the increase in absorp-
tion to the reduced viscosity of water and colloidal cellular
material and to the increased metabolic activity which occurs
at the higher temneratures. Such an increase in the rate
of absorbtion will not brevent a plant from wiltinv if condi-
tions are such that the rate of transpiration exceeds the
rate of absorntion, but the increased absorption will reduce
anv injury from wi ltinfr and result in a duicker recovery.

$hort periods of wiltina will occur in many plants in
the late afternoon as a result of a temporary excess in the
rate of transpiration over that of absorption. The stomates
of a plant generally close during wilting which results in
a reduction of photosynthesis. The combined effect of these
occurrences may be sufficient to decrease the growth and yield

of the plant.

The higher crop yields that have been obtrined from
black plastic can be attributed to the increase in soil
temperature which increases the rate of absorption of water
and prevents the plant from wilting. The yield increases
that occur with plastic mulch are due mainly to increases
in tle number of fruit and not the size of the fruit. Such
results may be due to the improved absorption of water by
the plant which may result in the development of more flowers
and definitely in greater fruit set.

Vulching with black polyethylene has resulted in definite
yield increases with muskmclons and tomatoes (Carolus and
Downes, 1958, and TIeslip, 1959). Similar results have been
observed in the various mulching experiments conducted in
this investigation. The results obtained with the different
melon varieties are comparable to those reported by Heslip
(1059). The greatest increases were obtained with Spartan
Rock in both studies while Honey Rock and Michigan Honey Rock
showed the least response. These differences indicate that
Honey Rock and Michigan Honey Rock may be more adapted to
the climate in Michigan and receive less benefit from mulch-
ing with black plastic than Spartan Rock.

{uskmelons covered with hot tents showed larfie increases
in yield as compared to those without hot tents. Heslip
(1959) also reoorted yield increases on muskmelcns covered
with hot tents, but the differences were not as great as

those observed in this study. Melons seeded through black

h9

plastic and covered with hot tents resulted in the highest
yields, however, this practice could be costly.

Nelons transplanted on plastic produced the second high-
est yiel’s which were approximately the some as those obtained
from melons seeded with hot tents and cultivated. The cost
considerations between these two treatments are quite compli-
cated as the expense of raisin? plants to be transplanted
with the plastic may exceed the cost of seedinr, cultivating,
and using hot tents; but the reverse can also be true as
these expenses tend to vary from year to year. The yields
of melons seeded thru plastic and of melons transplanted and
cultivated were also similar and the costs of these treatments
would determine which practice to employ. However, one of
the above practices may be economic as the yields obtained
from seeding with cultivation tended to be the lowest.

The use of chemical weed control between the rows of
mulched tomatoes and muskmelons did not affect the yield of
either crop significantly. Such results indicate that chemical
weed control in combination with black plastic would be
practical only when the cost of such a practice is less than
mechanical weed control and trere is no injury or significant

reductions in crop yield.

50

SU} 3‘ {ANY AN”) C ("ll-7.91 ,U R I (“ NS

The effects of various films on soil and air temper—
atures were recorded at deaths of one and four inches in the
soil and four inches above the films durina forty—five days
in July, Ausust, September, and October in 1959. The temper—
atures as affected by clear, black, and aluminum coated
polyethylene were compared with those of bare soil.

Clear plastic resulted in the warmest soil temperatures
durinw the day at both one and four inches in the soil. The
maximum increases in soil temperature under the clear plastic
averaged 13.50? and 8.90F greater than the temperatures of
bare soil at depths of one inch and four inches, respectively.

he daytime soil temperatures under black plastic were
warmer than those of bare soil but were not is warm as those
under clear plastic. The black plastic over moist soil
resulted in temperature increases that averaged 10.6°F
greater than bare soil temperatures at one inch and 7.0°F
breater at four inches. The dry soil under black plastic
did not become as warm as the moist soil under black plastic
as the average temperature increases were only 8.2°F and
5.h°F over bare soil temperatures at the respective depths
of one and four inches.

-he lowest soil temperatures during the warmest part of
the day occurred. under aluminum mulch and averaged 1.80F
lower than the temperature of bare soil at the one-inch depth

and 0.70F lower at four inches.

The soil temperatures under all the films were approxi-
mately the same during the night and averajed about 5°F
warmer than bare soil at both denths.

The average air temneratures above the plastic films
were 0.70F warner than those above bare soil. The air temper-
atures above the aluminum averaged l.O°F Fisher than those
above hare swil during the six—hour period before noon, but
the average temperature throughout the rest of the day was
0.60F Cooler.

The effects of various plastic covers on soil temper-
atures were also measured at one and one-half inch depths
with the films in direct contact with the soil surface and
one inch above the surface. The results showed that soil
temperatures under films in direct contact with the soil
surface averaged from 3°F to 5°F higher than soil temper-
atures under films with an air space between the film and
the soil surface.

Mulching experiments were conducted in 1959 to measure
the effects of black plastic, hot tents, and chemical weed
control used with black plastic on the yields of muskmelons
and tomatoes.

Nuskmelons and tomatoes showed definite responses to
plastic mulching. The results indicated that fruit size was

not influenced by plastic mulch and that increases in yield

. ,-
,..-..

are primarily due to increases in the number of fruit nroduced.

The use of hot tents nroduced definite increases in the

yield of muskmelons. Melons seeded with cultivation and
covered vith hot tents resulted in yields that were eouivalent
to those ohtained from melons transplanted on plastic. Hot
tents used on plastic with direct seedine rroduced the hiah-
est yields.

The use of simazine pellets and Spray between the rows
of black olastic did rot markedly affect the yields of musk—
melons and tomatoes even though some plants were seriously
injured by the chemical.

The results obtained in these studies seem to warrant
the following conclusions:

{,m}
\kyfl Black plastic and clear plastic mulches increase
soil temperatures throushout the entire day.

2. Clear plastic results in warmer daytime soil temper-
atures than hlrck plastic.

3. Aluminum mulches result in the least fluctuation
in soil temperature and tend to keep the soil cool during
the warmest part of the day.

RA; The higher soil temperatures ohtained with black
plastic are imwortant contributing factors to the higher yields

and better plant growth.

. 5. The yield increases obtained with plastic mulch are

I

‘\...-

nrimarily due to increases in the numher of fruit produced.
6. The use of hot tents result in yield increases of
seeded muskmelons.

7. The use of chemical weed control with black plastic

53

did not affect the yields of tomatoes and muskmelons and can
be recommended for use with these crows providinq the chemicals

have been approved for use by the Food and Drug Administration.

51+

LITICR.-‘LTURE CITED

Bouyoucos, G. J. 1913. An investigation of soil temper-
ature and some of the most important factors
influencing it. Mich. Arr. Exp. Sta. Tech.
Bul. 17: 1-196.

. 1916. Soil temperature. Mich. Agr. Exp.

 

Carolus, R. L. 1959. Now northern prowers can grow vine
crops at a profit. Amer. Veg. Grower. Karch.

, and J. D. Downes. 1959. Studies on
muskmelon and tomato responses to polyethylene
mulching. Mich. Agr. Exp. Sta. Quart. Bul. #0:
770-785.

 

Clarkson, V. A. 1959. Sail temperatures and nitrogen
level as affected by polyethylene mulches. Paper
presented at Southern Region of Amer. Soc. Fort.
Sci.

Downes, J. D., R. Heslip, and S. Honma. 1959. Effect of
polyethylene mulches, starter solution, and kind
of transplant on yields of sweet peppers.

Mich. Afir. Exp. Sta. Quart. Bul. M1: 6M1-6h7.

Edmond, J. D. 1929. hulch paper for vegetable crops is
tested. Mich. Afr-r. Exp. Sta. Quart. Bul. 11:
115—117.

Emerson, R. A. 1903. Experiments in mulching garden

vegetables. Neb. Agr. Exp. Sta. Bul. 80. 26 pp.

1‘

Emmert, a. H. 1957. Black polyethylene for mulching vege-
tables. Proc. Amer. Soc. Vort. Sci. 69: MAM-h69.

Flint, L. W. 1929. Crop—plant stimulation rith paper
mulch. U. 8. Dept. Anr. Tech. Bul. 75: 1—20.

Cliniecki, V. I. 1059. E alueting polyethylene films for
agriculture. Down to Earth 15 (3): 7-9.

Heslip, R. P. 1959. The influence of mulching on several
vegetable crops with special reference to black
polyethylene. M. S. Thesis. Michigan State
University.

Honma, S., F. McArdle, J. Carew, and D. H. Dewey. 1959.
Soil and air temperature as affected by polyeth-
ylene film mulches. Mich. Agr. Exp. Sta. luart.
Bul. Ml: BBQ-9&2.

\J!
\H

Jacks, H. V., 9. Brind, and Robert Smith. 1955. Fulching.
Coruvvrxealtli‘hireowllof Skyil SciINice. ’Fech. (low.
1‘?“ o h()0

Uefiruder, Roy. 1039. Paper mulch for the veactable warden.
Ohio Aer. on. Sta. Pul. ”47.

Dies, 9. V. 1°57. Chemical and cultural methods of
controlling weeds in pickling cucumbers.
Mich. Agr. Exp. Sta. Quart. Bul. ho: 503-514.

Roberts, A. N. 1953. Growth and composition of the straw-
berry plant in relation to root temperature.
Ph. D. Thesis. Michigan State University.

Rowe-Button, Patricia. 1957. The mulching of vegetables.
Commonwealth Bureau of Hort. and Plant Crops.
Tech. Com. No. 2h.

Schroeder, R. A. 1939. The effect of root temperature upon
the absorption of water by the cucumber.
'Vnivu (of Ho. 'Tfr. Vbqv. Stad lies. Thnl. 309.

Shaw Charles P. 1926. The effect of a taper mulch on

i .1. 1
soil temperature. Cal. Aer. Exp. Sta. Nilaardia
1: 3H1—36h.

Smith, fllfrcd. 1927. Effect of mulches on soil tewoeratures
durinrj' the warvrlest weeks in July, 1925. Cal. Aer.
Exo. Sta. Vilarrdia 2: 395-397.

 

. 1931. Effect of paper mulches on soil tem-
perature, soil moisture, and yields of certain
crops. Cal. \Fr. Exp. Sta. Vilmardia 6: 159—291.

Stewart, G. R., J. C. Thomas, and John Horncr. 1926. Some
effects of paper mulching on Hawaiian soils.
Soil Science 22 (1): 37-59.

Tiessen, Herman. 1956. The effects of high analysis soluble
fertilizers as interrelated with environmental
conditions and cultural practices on the growth
and yield of vegetables with special reference to
the tomato. Ph. D. Thesis. Fichinan State
University.

Voth, Victor, and R. S. Rrinwhurst. 1959. Polyethylene over
strawberries. California Arriculture l3 (5): 5-1h.

{If}? Z}! ‘3: E C211]

IQU’U