Plastic Mulches and Row Covers on Growthand Production of Summer Squash

Garry G. GordonWheeler G. Foshee, III

Stewart T. ReedJames E. BrownEdgar Vinson

Floyd M. Woods

ABSTRACT. Row covers and colored plastic mulch are used routinelythroughout the United States to grow vegetables but are rarely used inconjunction to produce a crop. Summer squash (Cucurhita pepo L.). cv,Prelude 11, was grown on an Orangeburg sandy loam soil in Shorter, AL.The summer squash was direct seeded in single rows. The experimentconsisted of 12 treatments including: (1) black plastic mulch (BPM)+spun-bonded row cover (RC). (2) BPM alone. (3) white plastic mulch (WPM)+RC,(4) WPM alone. (5) red plastic mulch (RPM)+RC, (6) RPM alone. (7) bare

Garry G. Gordon is affiliated with the USDA-ARS Subtropical HorticultureResearch Station, 13601 Old Cutler Road, Miami, FL 33158 (E-mail: Gary.Gordon@ars.usda.gov).

Wheeler G. Foshee III is affiliated with the Department of Horticulture, 101Funchess Hall. Auburn University, AL 36849.

Stewart T. Reed is affiliated with the USDA-ARS Subtropical HorticultureResearch Station, 13601 Old Cutler Road, Miami, FL 33158.

James E. Brown is affiliated with the Department of Horticulture, 101 FunchessHall, Auburn University, AL 36849.

Edgar L. Vinson Ill is affiliated with the Department of Horticulture, 101Funchess Hall, Auburn University, AL 36849.

Floyd M. Woods is affiliated with the Department of Horticulture, 101 FunchessHall, Auburn University, AL 36849.

Address correspondence to Garry G. Gordon at the above address.

International Journal of Vegetable Science, Vol. 14(4) 2008Available online at http://www.haworthpress.com© 2008 by The Haworth Press. All rights reserved.

322 doi: 10.1080/19315260802215830

Gordon et al. 323

soil (BS)+RC, (8) BS alone, (9) silver plastic mulch (SPM)+RC. (10) SPMalone, (II) blue plastic mulch (BLUPM)+RC, and (12) BLUPM alone.Year and mulch color affected all variables, row cover affected plant heightand stem diameter, and the mulch color x row cover interaction affectedyield variables. Mulch color and year significantly affected air and soiltemperatures and row cover significantly affected air temperature. Soiltemperatures were more than 5°C lower than air temperatures in all treat-ments and air temperatures were 2-5°C higher with row covers than with-out. Increased soil and air temperatures did not always result in yieldincreases. Colored plastic mulch with or without row covers did notincrease early fruit yield in squash. Lack of a mulch/row cover inducedtemperature effect on yield was attributed to the relatively high mean airtemperatures that may have masked treatment temperature effects.

KEYWORDS. Cucurbita pepo, air temperature, earliness, soil temperature,stem diameter

INTRODUCTION

The main polyethylene used in mulches is low-density polyethylene,which is created by polymerization of ethylene under high pressure(Lamont, 1993). The typical plastic mulch used in the United States is1.25 mm thick and 122 to 152 cm wide and comes in rolls of 608 to1216 m long. It is used with raised beds that are 10.2 to 15.2 cm high and76.2 cm wide, depending on crop and cropping system (Lamont et al.,2005). Numerous additives are incorporated into plastic to improvespecific properties of the finished product and can include antiblockagents (a substance added to the plastic solution that acts as a barrier toprevent adhesion of surfaces of films made from the plastic to each other[www.patentstorm.us ]), antioxidants, pigments for color, flame retar-dants, and photodegradable additives (Wright, 1968).

Polyethylene mulch was first noted for its ability to increase soil tem-perature in the 1950s (Emmert, 1957). Due to the monetary value of manyhorticultural crops, it is beneficial to adjust the soil's microclimate toprolong the growing season and increase plant growth (Tarara, 2000). Theeffect of plastic mulch on soil surface temperature is determined by theoptical properties of the plastic material (Ham et al., 1993). Black plastichas intense shortwave transmittance and high shortwave absorptance,which causes soil temperatures to be quickly raised (Dodds et al., 2003;

324INTERNATIONAL JOURNAL OF VEGETABLE SCIENCE

HeiBner et al., 2005). Beneath black plastic mulch, soil temperature maybe 10-15°F hotter than bare soil (Splittstoesser, 1990; Stevens et al.,1991). Black mulch usually produces the hottest soil temperaturecompared to other colored mulches (DIaz-Perez and Bata], 2002; Infanteet al., 1998; Jiménez et al., 2003; Lira-Saldivar et al., 2000).

Other mulch colors have been used in vegetable production. Whiteplastic mulch usually generates cooler soil temperatures than black plastic(DIaz-Perez and Batal, 2002; Lamont, 1993). White plastic is preferredduring the summer growing season in warmer regions compared to blackbecause it can maintain soil moisture while providing cooler tempera-tures. Use of silver plastic mulch has been reported to result in lessdisease and reduce stress from silverleaf whitefly (Ber,nisia argentifolii)and aphid (Aphididae) in certain vegetable crops (Csizinszky et al., 1995;Lamont et al., 1990). Red plastic mulch is associated with increased yieldin tomato (Lvcopersicon esculentuin Mill.; Decoteau et al., 1989) andother crops (Decoteau et at., 1990; Kasperbauer, 1992). It is believed thatred plastic mulch generates a positive phytochrome response. A greateryield was found for some vegetable crops using blue plastic mulch(Csizinszky et al., 1995).

Plastic mulch reduces the weed population in comparison to bare soil.Plastic mulch creates a barrier against herbicide dissipation into the atmo-sphere rendering herbicides more effective (Clarkson and Frazier, 1957;Lourduraj et al. 1997; Rahman and Shadeque, 1999). It is this reduction inweeds and the cost associated with their eradication that helps make theuse of plastic mulch more economical.

One of the more popular reasons for using plastic mulch is its ability tomaintain soil moisture (Orzolek and Murphy, 1993; Lamont, 1996). Driptape is the preferred means of irrigating vegetables when using plasticmulch. The use of drip tape with plastic mulch allows crops to receiveadequate moisture and is more cost efficient than overhead irrigation(Berthelot and Robertson, 1990; Cooley et at., 2007). Studies haveconcluded that soil beneath plastic mulch and drip tape will have highersoil moisture than bare soil with drip tape (Alam and Zimmerman, 2001;Gough, 2001; Infante et al., 1998). Liakatas et at. (1986) documented theability of plastic mulches to alter the plant's microenvironment due in partto its ability to restrict soil water evaporation. Other advantages due to useof colored plastic mulches include improved fruit quality (Brown andChannel l-Butcher, 2001; Lamont, 1996), increased yield (Baker et at.,1999; Brown et at., 1995; Farias-Larios et at., 1999; Lamont et al., 2005;May et al., 2005), reduced fertilizer leaching (Alain and Zimmerman,

Gordon etal. 325

2006; Clarkson, 1960), and reduced soil compaction (Gough, 2001;Lamont, 1996).

Row covers act to protect seedlings from frost, heavy rains, periods ofdry weather, and cool winds without blocking needed moisture andsunlight (Jensen, 2000). Row covers are used to increase temperatureand promote earlier yield. Spunbonded polyester row covers were intro-duced in the early 1980s. Spunbonded polyester row covers are madefrom a thin mesh of white synthetic fibers. Heat is retained, but water canpenetrate the row cover, allowing for overhead irrigation, or rain, tohydrate plants and help to prevent soil compaction. The weight of polyes-ter row covers can range from 10 to 67+ g/m 2 (Penn State, 2003). Spun-bonded row covers in the 14.2 to 35.5 grange render a 1.1°C protectionagainst frost in the spring and even greater frost protection in the fall(Penn State, 2003).

Phytochrome is the photoreceptor responsible for light-regulatedgrowth responses. Research has documented a phytochrome response tocolored plastic mulch. Longer leaves and higher shoot/root ratios werefound in turnip plants grown on blue and green mulches that reflectedhigher Far Red:Red (FR:R) ratios than on white plastic mulches that gen-erated lower FR:R ratios (Antonious et al., 1996). These researchersbelieved the higher yields were due to the red plastic mulch's superiorability to produce a greater FR:R ratio compared to black plastic mulch.Blue light treatments have been shown to effect morphological, meta-bolic, and directional reactions in plants (Senger and Schmidt, 1994). Hart(1988) reported that blue light activates stomatal opening by promoting Kuptake and water movement into the plant's guard cells. Kadaman-Zahaviand Ephrat (1976) found that blue light would reduce stem elongation.Hatt et al. (1993) and Kasperbauer and Loughrin (2004) found that whiteplastic mulch reflected more blue light than other mulch colors used intheir experiments. Antonious et al. (1996) reported that white plasticmulch reflected the largest amounts of blue light. However, turnips grownon white plastic mulch had the least flavor among turnips grown on othermulch colors. Decoteau et al. (1988) believed that shorter stems and moreauxiliary growth could result from the blue light reflected by white plasticmulch to tomato plants.

There is little known on how colored mulch and row covers affectsummer squash (Cucurbita pepo L.). This project was undertaken toevaluate growth and yield, including earliness of yield, of summersquash produced on different colored plastic mulch, with or without arow cover.

326INTERNA TIONAL JOURNAL OF VEGETABLE SCIENCE

MATERIALS AND METHODS

The research was conducted at the E. V. Smith Research ExperimentStation in Shorter, Alabama. The soil type is an Orangeburg sandy loam,fine-loamy siliceous thermic Typic Kandiudult. A soil pH of 7 wasrecorded in 2003 and 6.1 in 2004. The summer squash, cv. Prelude II,was used.

Pre-plant fertilizers were applied in 2003 and 2004 in accordance withthe soil test recommendations from Auburn University Soil Testing Lab(Auburn, Ala.). Phosphorous was applied at the rate of 0.03 kgha 1 in2003 and 0.04 kg-ha-1 in 2004 (Table I). Potassium was applied at the rateof 0.08 k--ha-1 in both 2003 and 2004. The plots received 0.06 and

TABLE 1. Fertilizer and other chemicalamendments applied to squash plots in

2003 and 2004

Year

20032004

Preptant (kg.ha1)AmmendmentPhosphorus 0.030.04Potassium 0.080.08Magnesium 0.020.02Calcium 1.090.23Ammonium nitrate 197209Chloropicrin 336336

In season (kg.ha 1)

20-20-20 29.2

61.6Ca(NO3)2 20.5

zSeven 1.4Endosulfan 2.24

z

(L.ha1)Curbit (L.ha1) 4.674.67Round-up 2.344.67Asana 0.702.82Manex 3.73

15.00

Ambush 0.88 z

Bravo 100.762.34Topsin 0.58

zAsana 0.70

z

Z_not applied.

Gordon etal. 327

0.02 kgha of Mg in 2003 and 2004, respectively. Liquid calciumwas applied through drip irrigation at a rate of 1.09 kg-ha' in 2003and 0.23 kg .ha7 l in 2004. No time was added to plots in either year.In 2003 and 2004 ammonium nitrate (34-0-0) was applied at 197 and209.44 kg-ha-1 , respectively. Prior to laying plastic mulch, Pic Brom 33®(Soil Chemicals Corporation, Hollister, Calif.; 67% CH 3 13r, 33% Chlorop-icrin (trichloro(nitro)methafle)) was applied at a rate of 336 kgha on 17April 2003 and on 27 March 2004, respectively. Fertilizers and pesticideswere also applied to developing plants (Table 1). Nitrogen, P, and K (20-20-20) were applied to the soil through drip fertigation tubes at the rate of29.2 kg-ha-1 (5.8, 2.6, and 4,8 kg of N-P-K) once a week from 30 May to8 July 2003. During 2004, 61.6 kg-ha of 20-20-20 was injected into thesoil once a week from 11 May to 25 June 2004. Liquid calcium nitrate,20.5 kg . ha', was applied to the soil through fertigation into the soil from6 June to 28 June 2003.

Pesticides were applied once a week according to label directions inMay 2003 and 2004. Curbit® herbicide (Loveland Products Inc., Greeley,

Cob.;benzenamine) was applied for weed control at a rate of 4.67 Lha1.Round_Up® herbicide (Monsanto Company, St. Louis, Mo.; isopropy-lamine salt of glyphosate) was applied between rows at 2.34 L'ha and4.67 Lha' in May 2003 and 2004, respectively. Asana XL® (DuPontCorporation, Wilmington, Del.; (S)-cyano (3-phenoxyphenyl) methyl (S)-4chloroalpha(1-methylethyl) benzene acetate) was applied at 0.70 and2.82 Lha in May 2003 and 2004, respectively, to control stink bugs(Halyornorpha hal ys) and squash hugs (Anasa tristis). Manex® (DuPontCorporation; Mn ethylenebisdithiocarbamate) was applied at 3.73 and15 L .W 1 in 2003 and 2004, respectively, to control diseases. In June of2003, a total of 0.88 Lha7 1 of Ambush® (Syngenta Crop ProtectionPty Limited, North Ryde, NSW; 3Phenoxyphenyl)rnethyl(±)2,2dimethylcyclopropane-carbOXY late) and 2.24 kg .ha (50 wp) of Endosulfan®(Bayer CropScience AG., Monheim am Rhein, Germany; 6,7,8,9, 10,10-hexachioro- I ,5 ,5a,6,9,9a-hexahydro-6, 9methano-2,4,3-beflZodiOXathiepine-3-oxide) were applied to plots for use as insecticides. In June of2003, three separate applications of 2.92 Lha of Bravo WS® (DuPontCorporation; tetrachloroisophthalOnitrile) and 0.58 L-ha7

i of Topsin M®(ATOHNA Chemicals Inc., King of Prussia, Pa.; dimethyl [(1,2-phenylene)bis-( iminocarbonothioyl)]bis[carbamatel) were applied to plots. On2 July 2003, 92 L-ha l Bravo WS and 0.70 L•ha 1 of Asana XL wereapplied as a fungicide and insecticide, respectively. In 2004, Sevin80S0

328INTERNATIONAL JOURNAL OF VEGETABLE SCIENCE

(Bayer CropScience AG., Monheim am Rhein, Germany; carbaryl(1 -naphthyl N-methylcarbamate) was applied on plots at a rate of 1.4 kg-ha-along with Bravo WS ® 2.34 Lha'.

Plastic drip irrigation lines (Toro Ag, El Cajon, Calif.), 10 mm thick,emitters spaced at 30.48 cm covered by six 111-rn-long strips of blackplastic were applied simultaneously over beds with a plastic mulch layermachine (Kenco Manufacturing Inc., Ruskin, Fla.). Seed were sown on8 May 2003 and 20 April 2004 into raised beds (15.24 cm in height)through holes created by the plastic mulch layer machine. Squash seedswere planted 30.48 cm apart within each row. Plots 6.08 x 1.52 m (L x W)were arranged in a randomized complete block design. Beds were 9.84 mapart.

The experiment consisted of twelve treatments: (1) black plastic mulch(BPM)+spunbonded row cover (RC), (2) BPM alone, (3) white plasticmulch (WPM)+RC, (4) WPM alone, (5) red plastic mulch (RPM)+RC,(6) RPM alone, (7) bare soil (BS)+RC, (8) BS alone, (9) silver plasticmulch (SPM)+RC, (10) SPM alone, (11) blue plastic mulch (BLIJPM)+RC,and (12) BLUPM alone. Sections of black plastic (6.08 x 0.91 m) wereremoved and replaced with silver, white, blue, and red pieces of plastic. Theoriginal black plastic was retained in place for treatments requiring blackplastic mulch. For the control treatment, a black plastic section was notreplaced leaving exposed the bare soil. The silver, red, white, and blackplastic (Ken-Bar Inc., Reading, Mass.) was 1.5 mm thick and 91.44 cmwide. The blue plastic mulch (Pliant Corp., Schamburg, Ill.) and was1.25 mm thick and 152 cm wide.

Row covers, 170.18 cm wide, were established on 20 May 2003 and26 April 2004. Edges of row cover strips were tucked into the soil aroundthe edges of each plot and left to float loosely in an effort not to hinderplant growth as well as to prevent the loss of captured heat. Row coverswere removed from plots on 3 June 2003 and 24 May 2004, respectively.

Soil temperature was measured with a soil probe thermometer(Taylor® Switchable Digital Thermometer, Taylor Precision ProductsLP, Oak Brook, Ill.) from a depth of 10.16cm in each plot. Air temper-ature was recorded with an indoor/outdoor thermometer (TaylorPrecision Products LP) with sensors attached to the heat conductingwire (Toro Ag, Bloomington, Minn.) placed in the center of each plotat 12.7 cm above ground level. Soil and air temperatures were recordedfrom 27 May to 3 June 2003 and 20 to 27 May 2004, a time span longenough to demonstrate temperatures that occurred under the varioustreatments.

Gordon et al. 329

Stem diameters were measured with a 500-196 caliper (MitutoyoDigimatic Corp., Sakato Takatu-ku, Kawasaki-shi, Kanagawa 213, Japan)5 cm above ground level around bases of plants on 4 June 2003 and28 May 2004. Height measurements were taken with a meter stick bymeasuring from the base of the plant to the tip of the highest leaf. Plantheights and stem diameters were taken on the day row covers wereremoved. Squash fruit were considered either marketable or cull based onsize, shape, color, and presence of insect or disease damage in accordanceto the guidelines of the E.V. Smith Research Center.

Squash was harvested from 9 June to 14 July in 2003 and from25 May to 2 July in 2004. Harvest occurred every other day with week-ends being the exception. Yield differences among treatments weredetermined by weighing marketable and cull fruit at each harvest. Fruitcollected from 5 through 27 June 2003 and 25 May through 14 June2004 were considered early yield. All data were analyzed using SAS(SAS, 2003, ver. 9.1, Cary, NC.). Effects of mulch color, row cover,and year on selected plant physical characteristics and yield compo-nents were tested by ANOVA. If an interaction was present it was usedto explain results. For main effects, where appropriate, mean separationwas with the Fisher's least significant difference test. Temperature datawere analyzed using the GLM repeated measures procedure. Air andsoil temperatures were reported as means for values measured over therecording period during each year. Pearson correlation coefficientswere determined for air and soil temperatures versus total yield. Meanseparation for plant height, weight, and stem diameter was accom-plished using the Fisher's least significant difference test. Yield compo-nents, with mulch color x row cover interaction, were subjected to leastsquares analysis.

RESULTS

Year and mulch color affected all variables, row cover affected plantheight and stem diameter, and the mulch color x row cover interactionaffected yield variables (Table 2). The presence of a row cover had asignificant effect on stem diameter and plant height. Squash stem diam-eter, plant height, and fresh weight are shown in Table 3. Plants weresignificantly taller in 2004 than 2003. Treatments consisting of mulchplus row cover produced significantly taller plants than treatments with-out a row cover. Plants grown on BS were shorter than those grown

U -0

c::U)

CCUC-D

ca(U

CUDci)>E

.•I) (I) >>s—CU

co

o ca0U)

-C0Cd)

E C >U)

0C coU) (U

cDO CU

-CC

- 0(o .2 c- Co

(UCU

> -

zo<0

uJ---ix<2I-0

0

ci)

=Cci00iflCjo0)o

>000000

•5o D- 0) ,-0)-- Q0)0C•6 >• coocF-00000

II)-Q

!mci) 00)00r.-.000,-

-d00000I-

5OD

00)CO,-000QC)

OLUQW c000o

ci)0(cici)•-DC'JCci 0(000(DE> 0C'J00C\J

Cc\J 00) 0

-dddddCciLid

E ON- ON- CD-Eoc'jooj -i-

(/OOQL(D 00000

C)2fl- LO

LO co 00)0)OC')OODO)

-000)0000do

C)z

• a5.-.-,-0c\J

r000çc.i)0000)0)

CQOOCC

.000000

ci)>

-;-0

C C)

(1)O 0><c 0-

cci

330

Gordon et al. 33'

TABLE 3. Mian effects of year, mulch color and row coveron squash plant height, fresh weight and stem diameter

Source Plant Stem

Year20032004

Mulch colorBare soilBlackBlueRedSilverWhite

Row coverNoneYes

Height (cm)Freshweight (kg)

29.8 by0.12 b20.0 a72.5 a0.79 a 17.8 b

33.7 b

0.17 b

27.2 b46.5 a0.46 a29.3 a

47.6 a0.51 a29.5 a

44.9 a0.47 a28.8 ab

43.9 a0.53 a29.8 a

44.9 a0.50 a29.4 a

37.9 b

0.44 a30.0 a

49.3 a0.45 a28.1 b

values within columns followed by the same letter are not significantlydifferent, P 0.05, Fisher's Least Significant Difference test.

diameter (mm)

under any of the plastic mulch treatments. Greater fresh weightsoccurred in 2004 than 2003. In addition, plants grown in BS and BS+RCtreatments consistently produced among the lowest squash freshweights. Stem diameters were smaller in 2004 than 2003 and smallerwith row cover than without. Bare soil produced the smallest stem diam-eters with the BS+RC treatment producing smaller diameters than BSwithout cover.

Early marketable and cull yields were lowest from plants grown onbare soil plus a row cover followed by bare soil alone (Table 4). In fact,early marketable yields from bare soil regardless of whether a row coverwas present or not were significantly lower than all but the black mulchwithout a row cover treatment. The highest early yield, marketable pluscull combined were from black mulch plus a row cover followed by bluemulch without a row cover. Early yields were between 59% and 65% ofoverall yields. Total yield followed the same trend as early yield, bare soilwith row cover, and bare soil without cover produced the lowest yields.Black mulch with a row cover and blue mulch without a row cover

332INTERNATIONAL JOURNAL OF VEGETABLE SCIENCE

TABLE 4. Interaction effects of mulch color and row cover on earlyand total marketable, cull and overall yield for summer squash

Source Early yield

Total yield

MarketableCullMarketableCullOverall(kg/plot)(kg/plot)(kg/plot)(kg/plot)(kg/plot)

Row cover x mulchBare soilBlueBlackRedSilverWhiteBare soilBlueBlackRedSilverWhite

3.7 dX10.0 ab11.9 a9.1 b8.6 bc9.9 ab6.5 c

12.1 a8.5 bc9.8 ab

10.0 ab10.2 ab

13.4 a4.9 b

3.0 e9.8 abc

11.1 a9.4 abc6.9 cd9.0 abc5.3 de9.9 ab7.4 bcd7.3 bcd8.7 abc8.0 bcd

8.9 a7.1 b

6.0 d14.1 ab17.9 a13.2 b12.8 bc14.2 ab9.0 cd

17.3 a12.8 bc14.3 ab14.2 ab14.6 ab

17.5 a9.2 b

5.3 d16.1 ab19.4 a16.Oab13.4 bc16.3 ab9.7 Cd

16.9 ab13.2 bc14.4 b14.7 b15.0 b

18.3 a10.2 b

11.3 e30.2 abc37.3 a29.2 bc26.3 Cd30.5 abc18.7 de34.2 ab26.0 cd28.7 bc29.0 bc29.5 abc

35.8 a19.4 b

Cover

None

Year20032004

'Mean separation within each column was determined by Least Squares Analysis. Valuesfollowed by the same letter are not significantly different at P!^ 0.05.

produced the highest overall yields. By the end of harvest the percent oftotal yield separated as cull increased over that found in early yield. Yearhad a significant effect on marketable yield (Table 2). Total yield in eachmulch/row cover treatment was lower in 2004 than 2003. This is likelydue to air temperatures in excess of 37°C for portions of the 2004 growingseason.

Mulch color and year significantly affected air and soil temperaturesand row cover significantly affected air temperature (Table 5). Air andsoil temperatures were higher in 2004 than 2003 (Table 6). Air tempera-tures as affected by mulch color followed the order: Silver ^! Blue ^! White= Red = Black = Bare soil. Soil temperatures as affected by mulch colorfollowed the order: Blue ^! Black ^! Red > White = Bare soil > Silver.Plots with row covers had significantly higher air temperatures than plotswithout row covers in 2003. Row cover did not affect soil temperature.There was no correlation between air or soil temperature and total yield(Table 5).

Gordon et al. 333

TABLE 5. ANOVA results for the effectsof treatments on air and soil temperatureand Pearson Correlation Coefficient for

temperature verses yield

TreatmentAir temperatureSoil temperature

Mulch color 0.0063** 0.0001"Row cover 0.0001 0.4311Year 0.0001*** 0.0001***

Rep O,326ns 0.1913nsMulch x Cover0334r 0.3227°r for Yield 049*** _0.31**

***significant at the 0.05 probability level.snot significant at the 0.05 probability level.

TABLE 6. Main effects of year, mulchcolor and row cover on summer squash

mean air and soil temperatures

Source

Year20032004

Mulch coverBare soilBlackBlueRedSilverWhite

Row coverNoneYes

Temperature (°C)

Air Soil

35.5 by27.3 b39.0 a29.3 a

36.6 b27.3 c36.6 b29.3 ab37.7ab29.6a37.0 b28.9 b38.6 a26.6 d37.3 b27.8 c

35.8 b28.2 a38.8 a28.3 a

'values within columns followed by the sameletter are not significantly different, P !^ 0.05,Fisher's Least Significant Difference test.

334INTERNATIONAL JOURNAL OF VEGETABLE SCIENCE

DISCUSSION

Plants grown on BS with or without a row cover were smaller inheight, fresh weight, and stem diameter than those grown under any of theplastic mulch treatments. This is consistent with findings in other studies.For example, Brown et al. (1993) and Lopez (1998) found that squashwas taller with use of row covers plus plastic mulch than without rowcovers. Brown et al. also reported that bare soil resulted in a lower plantfresh weight than plastic mulch treatments. Row covers create anenclosed microenvironment for plants. The enclosed environment broughtplants close together and sometimes enabled individual plants to makecontact. Kasperbaur (1971, 1987) found the amount of far-red lightreflected from neighboring plants increased at higher planting densitiesaffecting assimilate partitioning. As a result, plants in dense populationswere taller than those at lower densities. The colored plastic mulches usedin our study may have contributed to the FR light reflected to the squashplants. A higher FR:R ratio due to light reflectance from the plastic mulchmay have activated the plants' phytochrome responses, signaling plants tocompete in an attempt to grow taller than their neighbors under the rowcover (Franklin and Whitelani, 2006). Competition between plants couldexplain why squash plants grown with plastic mulch and row covers weretaller than those grown with plastic mulch alone or on bare soil (Wilkinsonet. al., 1981). Studies with a spectroradio meter can measure the light spec-trum reflected from colored mulches. Further research is needed toconfirm possible benefits of colored mulch and row covers for productionof squash.

Air temperatures in plots with row covers were consistently higherthan in plots without row covers. Others researchers have reported higherair temperatures with use of plastic mulch plus row cover compared toplastic mulch alone or bare soil (Loy and Wells, 1975; Moreno et al.,2002; Rubeiz and Freiwat, 1999). In our study there was no correlationbetween air or soil temperature and total yield. The lack of a mulch/rowcover induced temperature effect on yield may be due to the relativelyhigh mean air temperatures during this study. Wien et al. (2004) founddelayed fruiting in certain pumpkin (Cucurbita sp.) cultivars at 28°C.In our study, mean air temperatures were above 33°C in every plot. Thismay have confounded temperature effects on yield. Plastic mulches couldhave a positive effect on growth and yield of vegetable crops as reportedby Decoteau et al. (1989) and Hatt et al. (1993) under more moderatetemperatures.

Gordon etal. 335

With increased earliness in squash fruit development, growers canpossibly generate greater revenue if a marketing opportunity exists.Brown et al. (1993) reported earlier squash yield with row cover plusplastic mulch compared to bare soil. Dickerson et al. (2003) found earlieryields under plastic mulch with or without row cover compared to baresoil. In our study, early yields were higher in mulched plots than on baresoil; however, there were no differences between bare soil and mulchedplots in the percentage of total yield produced early. High temperaturesduring the growing season likely masked effects of mulch colors onsquash yield.

The bare soil with a row cover and hare soil alone had the lowest totalmarketable yields. This is consistent with others who found that use ofplastic mulch with or without row covers generates greater squash yieldsthan that grown on bare soil (Bryan, 1966; Dickerson et al., 2003;Orzolek and Murphy, 1993; Orzolek et al., 2003). Total cull squash yieldwas similar to marketable yields.

LITERATURE CITED

Alam. M. and R. Zimmerman. 2001. Subsurface drip irrigation and plastic mulch effectson yield and brix levels of Kahocha squash. Cucurbita moschata. Dept. Biol. Agric.Eng., Kansas State Univ., Manhattan. Kan. (http://www.oznet.ksU.edU/SWaO/IrngationtKahocha%20Study%20repOrt%2OLateSt.Pdf).

Antonious, G.F., M.J. Kasperbauer, and M.E. Byers. 1996. Light reflected from coloredmulches to growing turnip leaves affects glucosinolate and sugar contents of edibleroots. Phytochem. Photohiol. 64(3):605-610.

Baker, L.B.B.. J.C. Henning, S. Jenni, E. Flava. and K.A. Stewart. 1999. An economic andenergy analysis of the number of pepper production systems using a range of nitrogenlevels plastic mulch and irrigation. Proc. Natl. Agr. Plast. Congr. 28:82-87.

Berthelot. P.B. and C.A. Robertson. 1990. A comparative study of the financial andeconomic viability of drip and overhead irrigation of sugarcane in Mauritius. Agric.Water Mgt. 17:307-315.

Brown, i.E., R.P.Yates, M.S. West, and C. Stevens. 1993. Effects of planting methods androw cover on summer squash production. Proc. Natl. Agr. Plast. Congr. 24:270-273.

Brown, J.E. and C. Channell-Butcher. 2001. Black plastic mulch and drip irrigation affectgrowth and performance of bell pepper. J. Veg. Crop Prod. 7(2):109-112.

Brown, J.E., S.P. Kovach, W.D. Goff, D.G. Himelrick, K.M. Tilt, W.S. Gazaway,L.M. Curtis, and T.W. Tyson. 1995. Fumigation and mulch affect yield, weight, andquality of 'Pimiento' pepper Capsicum nnnuuni L. J. Veg. Crop Prod. 1(2):71-80.

Bryan. H.H. 1966. Effect of plastic mulch on the yield of several vegetable crops in northFlorida. Fla. Agric, Expi. Sta. J. 2532:139-146.

336INTERNATIONAL JOURNAL OF VEGETABLE SCIENCE

Clarkson, V.A. 1960. Effect of black polyethylene mulch on soil microclimate tempera-ture and nitrate level. Agron. J. 52(6):307-309.

Clarkson, V.A. and W.A. Frazier. 1957. Effect of paper and polyethylene mulches andplastic caps on cantaloupe yields and earliness. J. Amer. Soc. Hort. Sci. 69:400-404.

Cooley, E.T., B.L. Lowery, K.A. Kelling. and S. Wilner. 2007. Water dynamics in dripand overhead sprinkler irrigated potato hills and development of dry zones. Hydrol.Proc. 21:2390-2399.

Csizinszky. A.A., D.J. Schuster. and J.B. King. 1995. Color mulches influence yield andpest populations in tomatoes. J. Amer. Soc. Hort. Sci. 120:778-784.

Decoteau, DR., M.J. Kasperhauer, D.D. Daniels. and P.G. Hunt. 1988. Plastic mulchcolor effects on reflected light and tomato plant growth. Sci. 1-lortic. 34:169-175.

Decoteau. DR., M.J. Kasperhauer. and P.G. Hunt. 1989. Mulch surface color affects yieldof fresh-market tomatoes. J. Amer. Soc. Hort. Sci. 114(2):216-219.

Decoteau, DR.. M.J. Kasperhauer. and P.G. Hunt. 1990. Bell pepper plant developmentover mulches of diverse colors. Hortsciencc 25(4):460-462.

Diaz-Perez. J.C. and D. Batal. 2002. Colored plastic film mulches affect tomato growthand yield via changes in root-zone temperature. J. Amer. Soc. Hort. Sci. 127(1):127-136.

Dickerson, G., S. Guldan, L.M. English. and P. Torres. 2003. Effects of woven, blackplastic mulch and row cover on winter squash and pepper production. Proc. Natl. Agr.Plast. Congr. 31:63-67.

Dodds, G.T., C.A. Madramootoo, D. Janik, E. Fava, and A. Stewart. 2003. Factorsaffecting soil temperatures under plastic mulches. Trop. Agric. (Trinidad) 80:6-13.

Emmert, E.M. 1957. Black polyethylene for mulching vegetables. Proc. Amer. Soc. Hurt.Sci. 69:464-469.

Farias-Larios, J., J.G. López-Auguirre. M. Orozco-Santos. C. Guerrero. and C. Sandoval.1999. Polyethylene and organic mulch for honey dew melon production in westernMexico. Proc. NatI. Agr. Plast. Congr. 28:128-133.

Franklin. K.A. and Whitelam. G.C. 2006. Improvement of horticultural and ornamentalcrops through transgellic manipulation of the phytochrome family of plant photorecep-tors. J. Crop Improvement. 17(1-2):263-278.

Gough, R.E. 2001. Color of plastic mulch affects lateral root development but not rootsystem architecture in pepper. Hortscience 36(1):66-68.

Ham. J.M., G.J. Kluitenherg. and W.J. Lamont. 1993. Optical properties of plasticmulches affect the held temperature regime. J. Amer. .Soc. Hort.Sci. 118(2):188-193.

Hart, J.W. 1988. Light and plant growth. Unwin Hyman, London.Hatt, HA.. M.J. McMahon. D.E. Linvill, and D.R. l)ecoteau. 1993. Influence of spectral

qualities and resulting soil temperatures of mulch films on bell pepper growth andproduction. Proc. NatI. Agr. Plast. Congr. 24:233-238.

Hei6ner. A., S. Schmidt. and B. Von Eisner. 2005. Comparison of plastic mulch films withdifferent optical properties for soil covering in horticulture: Test under simulatedenvironmental conditions. J. Sci. Food Agr. 85:539-548.

Infante, ML., S.A. Garrison, and S.A. Johnson. 1998. Influence of black plastic mulch,bare ground, and no-till systems on yield of summer squash. Proc. NatI. Agr. Plast.Congr. 27:178.

Gordon etal. 337

Jensen, M.H. 2000. Plasticulture in the global community-View of the past and future.Proc. Natl. Agr. Plast. Congr. 29: Appendix A: 1-10.

Jimdnez. L.L. M.R. Quezada. J. Mungufa. and B. Cedcno. 2003. Effect of color plastic mulchon photosynthesis. growth and yield of potato. Proc. Nail. Agr. Ptast. Congr. 31:95-99.

Kadaman-Zahavi. A. and E. Ephrat. 1976. Development of plants in filtered sunlight II.Effects of spectral composition, light intensity, day length. red and far-red irradiationsand long and short day grasses. Israel J. Bot. 25:11-23.

Kasperhauer. M.J. 1992. Phytochrome regulation of morphogenesis in green plants: fromBeltsville spectrograph to colored mulch in the field. Photochem. Phytohiol.56(5):823-832.

Kasperhauer, M.J. 1971. Spectral distribution of light in a tobacco canopy and effects ofend-of-day light quality on growth and development. Plant Physiol. 47:775-778.

Kasperhauer. M.J. 1987. Far-red light reflection from green leaves and effects onphytochrome-mediated assimilate partitioning under field conditions. Plant Physiol.85:350-354.

Kasperhauer. M.J. and J.H. Loughrin. 2004. Butterhean seed yield, color and proteincontent are affected by photomorphogenesis. Crop Sci. 44:2123-2126.

Lamont. W.J. 1993. Plastic mulch for the production of vegetable crops. HortTechnology3:35-39.

Lamont, W.J. 1996. What are the components of a Plasticulture vegetable system? Hort-Technology 6(3):150-154.

Lamont. W.J., M.D. Orzolek. and B. Dye. 2005. Production of early specialty potatoesusing Plasticulture. Proc. Nat]. Agr. Plast. Congr. 32:7-10.

Lamont. Wi., K.A. Sorensen, and C.W. Averre. 1990. Painting aluminum strips on blackplastic mulch reduces mosaic symptoms on summer squash. Hortscience 25:1305.

Liakatas, A., J.A. Clark, and J.L. Monteith. 1986. Measurements of heat balance underplastic mulches. Agric. Forest Meteorol .36.227-239.

Lira-Saldivar. RH., R. Quezada. and J. MuoguIa. 2000. Soil temperature under differentphotodegradable plastic mulches and its relationship with earliness and yield ofcantaloupe. Proc. Nail. Agr. Plast. Congr. 29:315-320.

Lopez. M.V. 1998. Growth, yield and leaf NPK concentrations in crop-covered squash.J. Sustain. Agr. 12(4):25-38.

Lourduraj. C., A.K. Padmini. R. Rajendran, V. Ravi, T. Pandiarajan. and V.V. Sreenarayanan.1997. Effect of plastic mulching on hhendi Abelinoschus esculenius (L.) Moench.South Indian Hurt. 45(3&4): 128-133.

Loy. J.B. and O.S. Wells. 1975. Response of hybrid muskmelons to polyethylene row cov-ers and black polyethylene mulch. Sci. Hortic. 3(3):223-230.

May, D., B. Hanson. and R. Molinar. 2005. Plastic color and composition effect onearliness, yield. and quality of cantaloupe and bell pepper in central California. Proc.Natl. Agr. Plast. Congr. 32:136-141.

Moreno, D.A., G. Vullora. J. Heniández, N. Castilla. and L.R. Monreal, 2002. Yield andchemical composition of Chinese cabbage in relation to thermal regime as influencedby row covers. I. Amer. Soc. Hort. Sci. 127(3):343-348.

Orzolck. M.D. and J.H. Murphy. 1993. The effect of colored polyethylene mulch on yieldof squash and pepper. Proc. Natl. Agr. Plast. Congr. 24:157-161.

338INTERNATIONAL JOURNAL OF VEGETABLE SCIENCE

Orzolek, M.D., J. Murphy. and J. Ciardi. 2003. The effect of colored polyethylene mulchon the yield of squash, tomato and cauliflower. Penn State Center for Plasticulture.31 January 2006. (http://plasticulture.cas. psu.edul cmulch-93.1-itm).

Patentstorm. 2007. U.S. patent 5491013-Static-dissipating adhesive. (http://www.patentstomi .us/patetits/5491013-description.htm]).

Penn State. 2003. Row Covers. ( http://www.pliisticulture-cas.psu.edLi/RowCovel-S.Iltil)l). N. and A. Shadeque. 1999. Comparative efficacy of mulches with or without a

herbicide on growth and yield of lady's finger [Abelmoschus esculentus (L.) Moench(var. Vijaya)]. J. Agr.Sci. Soc. NE India, 12(1):123-127.

Ruheiz, I.G. and M.M. Freiwat. 1999. Row cover application duration effects on field andlong shelf-life tomato in a dry temperature climate. Proc. Natl. Agr. Plast. Congr. 28:100-104.

Senger. H. and W. Schmidt. 1994. Diversity of photoreceptors. p. 301-324. In: R.E. Kendrickand G.H.M. Kronenherg (eds.). Photomorphogenesis in plants. Kluwer AcademicPublishers. Dordrecht.

Splittstoesser. W.E. 1990. Vegetable growing handbook. 3rd ed. Van NorstrandReinhold, New York.

SAS. 2003. Statistical Analysis System. Version 9.1. SAS Institute Inc., Cary, N.C.Stevens. C., V.A. Khan, J.E. Brown. G.J. Hochmuth, W.E. Splittstoesser, and

D.M. Granberry. 1991. Plastic chemistry and technology as related to plasticulture andsolar heating of soil. p. 141-158. In: J. Katan and J.E. Devey (eds.). Soil solarization.CRC Press, Boca Raton, Fla.

Tarara, J.M. 2000. Microclimate modification with plastic mulch. HortScience. 35(2):169-180.

Wien. H.C., S.C. Stapleton, D.N. Maynard. C. McClurg. and D. Riggs. 2004. Flowering,sex expression, and fruiting of pumpkin (Cucurbita sp.) cuttivars under varioustemperatures in greenhouse and distant field trials. HortScience 39:239-242.

Wilkinson. RE.. M.J. Kasperhauer. and C.T. Young. 1981. Free amino acid content ofburley tobacco leaves developed under different light and temperature conditions.J. Agric. Food Chem. 29:658-660.

Wright. J.C. 1968. Production of polyethylene film. Proc. Natl. Agr. Plast. Congr. 8:72-79.