Effect of Soil Mulches & Herbicides on Production Economics of Warm Season Vegetable Crops in a Cool Climate

8/9/2019 Effect of Soil Mulches & Herbicides on Production Economics of Warm Season Vegetable Crops in a Cool Climate

1/6 January–March 2000 10(1)154

RESEARCH REPORTS

Effect of SoilMulches andHerbicides onProductionEconomics of Warm SeasonVegetable Cropsin a Cool Climate

D .R. Waterer1

ADDITIONAL INDEX WORDS. muskmelon,Cucum i s melo , pepper, Capsi cum annuum , sweet corn, Zea mays , weed

control

SUMMARY. The efficacy and costefficiency of using various plastic soilmulches in the production of pepper(Capsi cum an nu um L.), corn (Zea mays L.) and muskmelon (Cucumis melo L.) were examined over fourgrowing seasons in Saskatchewan,Canada. Clear mulch with or withoutpreemergent herbicides was comparedwith black or wavelength selectivemulches. In all three crops, mulchesenhanced yields relative to bareground in most site–year combina-tions. Clear mulch usually producedthe highest yields. Herbicides appliedunder the clear plastic providedeffective weed control with noobservable changes in product efficacyor toxicity to the crop. The weedcontrol provided by the herbicideshad no effect on yields in the clearmulch treatments. Consequently, clearmulch without added herbicideusually represented the most cost-effective production option for allthree crops.

The use of plastic (polyeth-ylene) films as soil mulchesis widespread in horticultural

production and is especially commonin the production of high value veg-etable crops. The impact of mulcheson yields and production economicsvary with the crop, mulch type usedand prevailing environmenta l and mar-ket conditions. B enefits cited from theuse of mulches include increased earlyand to tal yields (Bo nanno and Lamo nt,1987; Schales and N g, 1978), reducednutrient leaching (Jo nes et al., 1977)and moisture loss (Bhella, 1988) andimproved quality (Sanders et al., 1986).H owever, mulches represent a signifi-cant additional input in terms of boththe materials and the labor required fortheir installation and removal (Gerberet al., 1983). Therefore growers mustselect the mulch type appropriate foreach crop and market situation.

Mulches are available in a rang e ofcolors, altho ugh clear, black and w hite

represent the most common choices.Clear, and to a lesser extent blackmulches, increase soil temperatureswhile white mulches keep the soil coo l(Ashwo rth and H arrison, 1983). Soilwarming is important when w arm sea-son crops are being grown in areaswith a short growing season or whenprice premiums for an early crop ne-cessitate planting into cold soil. Al-thoug h clear plastic is superior to blackin terms of enhancing soil tempera-tures, w eeds tend to proliferate und erthe clear plastic, whereas, black plastic

provides effective weed control. Anyweeds grow ing und er the clear mulchcompete with the crop for nutrients,moisture and space. The potential forcompetition w ith t he crop is greatestearly in the season, as the warm, moistenvironment provided by the mulchpromotes rapid growth of the weeds(Ricketson and Thorpe, 1983). Even-tua lly grow th o f the weeds is restrictedby the limited space available underthe mulches or by the shade cast b y thedeveloping crop (Ricketson andThorpe, 1983). Information on the

impact of t he weed grow th und er clearmulches on crop performance is lim-ited. Ricketson and Thorpe (1983)found that clear mulch produced su-perior yields than black plastic in atransplanted tomato (Lycopersi cum es- culentum L.) crop despite extensiveweed growth under the clear plastic.H ow ever, in a direct-seeded cucum-ber (Cucum is sati vus L.) crop, weedsgrowing under a clear plastic mulchchoked out the seedlings (Waterer,1993).

Problems with weed grow th un-der clear plastic are largely eliminatedwhen fumigants are applied in advanceof planting. Although the primary func-tion of fumigat ion is to control nema-to des and persistent soilbo rne diseases,they also kill or suppress most weeds.At $CD N 800 to 1700/ha ($U S 225to 480/acre) (H amm et al., 1997),fumigation represents an expensivemeans of weed control. Further, me-thyl bromide, w hich is the most popu-lar fumigant for vegetable crop pro-duction, is suspected as an ozone de-pleting substance and its use is beingcurtailed.

H erbicides represent an alterna-tive method for weed control underclear plastic mulch. To be used undermulches, a herbicide must be d esignedfor preplant incorporation and shouldprovide long-lasting control o f a b road

spectrum o f weeds. The activity of theherbicide and its impact on the cropmust not be adversely affected by t hechang es in soil temperature, moisture,wat er and air movement caused by t hemulch. Info rmation on the use of her-bicides in association with mulchesand particularly on the impact ofmulches on herbicide performance islimited. Some studies indicate thatmulches may increase the efficacy ofherbicides by reducing losses to vola-t i l i za t ion and photodegrada t ion(G orske, 1983; Jensen et al., 1985,

1989). H ow ever, if mulching increasessoil temperatures and moisture levels,there may be a corresponding reduc-tion in efficacy related to acceleratedbreakdown of the herbicide via bio-logical and nonbiological processes(Jensen et al., 1989; Savage, 1977).

Wavelength selective (WLS)mulches represent an alternative solu-tion to the weed control problemsexperienced with clear mulches. WLSmulches selectively absorb the pho to-synthetically active radiation requiredfor weed growth while allowing the

longer wavelengths responsible for soilwarming to pass. This produces a levelof weed control comparable to blackmulches but with a greater degree ofsoil warming . WLS mulches are pres-ently more costly than the standardblack and clear types.

This study compared the effec-tiveness and cost efficiency of varioussoil mulches for the production ofthree w arm-season vegetable crops ina cool, short season environment . Thepot ential for using preplant herbicides

This study was supported by funding from t he PAWBE Dagreement administered b y Saskatchewan Water C or-poration. Thanks to Manjula Bandara and AnnetteZatylny for reviewing the manuscript. The cost ofpublishing this paper was defrayed in part by the pay-ment of page charges. U nder postal regulations, thispaper therefore must be hereby marked advert i sement solely to indicate this fact.

1Associate professor, D epartment of Plant Sciences,U niversity of Saskatchewan, Saskatoo n, C anada, S7N5A8.


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155 January–March 2000 10(1)

for weed control under clear plasticmulch was also examined.

Materials and methodsThe test crops; muskmelon, pep-

per and sweet corn were selected fortheir high value and requirement forwarm g rowing conditions. Trials wereconducted in 1994 through 1997 on a

Bradwell series sandy loam soil nearOutlook, Saskatchewan (51°29’N,Lat.,107°11’W Long. , 541-m (1775-ft) elevation) and/or a Sutherland se-ries clay soil in Saskatoon, Saskatchewan(52°8’N Lat., 106°38’W Long., 515-m (1690-ft) elevation). The soil wasprepared before planting by discingand rot ot illing. Sufficient fertilizer wasincorporated d uring the tillage t o meetprovincial recommendations for eachcrop (pepper and melon = 100 kg·ha–1

(90 lb/ acre) of N , 52 kg·ha –1 (48 lb/

acre) of P and 166 kg·ha

–1

(150 lb/acre) of K; corn = 80 kg·ha–1 (70 lb/acre) of N, 17 kg·ha–1 (16 lb/acre) ofP and 166 kg·ha–1 of K.

The treatments were a) 1.0-milblack mulch (Market Farm Imple-ments, Friedens, Pa .), b ) 1.0-mil WLSmulch (IRT 76, Market Farm Imple-ments), c) 1.0-mil clear mulch (Bio-Way Inc., R ed D eer, Alta.), d) clearmulch and herbicide, and e) herbicidealone which represented the controltreatm ent. All mulches were 1.5 m (5ft) wide.

The herbicides were all preplantincorporated, with the m ulch appliedimmediately after incorporation o f theherbicide. The herbicides were selectedfor broad-spectrum activity and suit-ability for use before weed emergence.Rat es for each herbicide represent t hemidpoint of the recommended con-centration range. The herbicides testedand associated application rates wereas follows:

C orn = EP TC (S-ethyl dipropyl

carbamothioate) a.i. at 1 L·ha–1 (13.5oz/acre) was used in all trials. EPTCprovides short-term contro l of a rangeof grasses and broadleaf weeds. Lim-ited residual activity of this productallows unrestricted cropping in thenext season, w hich is desirable in mar-ket g arden production.

Muskmelons = napta lam (2-[(1-naphthalenylamino)carbonyl]benzoicacid) a.i. at 3 L· ha–1 (40 oz/acre) wasused in 1994 and 1995. Naptalamcontrols a range of broadleaf weeds.D ue to problems with availability ofnaptalam, D C PA (dimethyl 2,3,5,6-tetrachloro-1,4-benzenedicarbox-ylate) a.i. at 1.5 kg·ha–1 (1.3 lb/ acre)was used in the muskmelons in 1996and 1997. D C PA controls emerginggrasses and broadleaf weeds.

Peppers = t rifluralin (2, 6-dinitro-N,N-dipropyl-4-[trifluoromethyl]

benzenamine) a.i. at 0.5 L· ha–1

(6 oz/acre) was used in all trials. Trifluralincontrols emerging grasses and broad-leaf weeds.

Plots for each crop consisted of 3m (10 ft) long sections of each mulchtreatment laid out in a randomizedcomplete block design w ith four repli-cates. The rows were 2.5 m (8 ft) apart.Mulch treatments were applied oneweek before crop establishment to al-low for some soil warming. Trickleirrigation lines installed beneath themulch were used to maintain soil wa ter

potentials above –30 kPa throug houtthe growing season.

Pepper and corn trials were con-ducted at t he Outlook site in 1994 and1995 and at both sites in 1996 and1997. Six-week-old pepper seedlings(‘C alwond er 300’ in 1994, ‘Redstart’in 1995 and ‘Stadd on’ s Select’ in 1996and 1997) were transplanted into t hefield in late May or early June. P lantswere spaced 20 cm (8 inch) apart in t herow. Each row was covered with a

spunbonded polyester row covering(Reemay, Ken-Bar, Reading, Mass.)draped over 30-cm (12-inch) ta ll wirehoops. The row covers were removedin early July . A late-maturing,supersweet type corn (‘NorthernSupersweet’ in 1994, ‘C hallenger’ in1995 and ‘E agle’ in 1996 and 1997)was seeded by hand t hrough the mulchin late May. The seed was placed at 15cm (6 inch) intervals in twin rowsspaced 30 cm (12 inch) apart. Themuskmelon trials were conducted atthe Saskatoo n site in all test years andalso at O utlook in 1997. Fifteen-day-old melon seedlings (‘Earligold’)grown in peat pots (Jiffy Products,Batavia, Ill.) were transplanted intothe field in early June. Plants werespaced 20 cm (8 inch) apart in the row.The melon seedlings were covered withfloating row cover (Agryl P-17, Agri-

cultural Supply, E scond ido C alif.) un-til the onset of flowering in early July.Weed grow th under the different

mulch treatments w as estimated in eachcrop in July and again in August. Ateach sampling date, four 1000-cm 2

(155-inch2) quadrats were randomlyselected within the mulched area ofeach row . The quadrats were evalu-ated fo r the species compo sition o f theweed population and the proportionof the soil surface covered by weeds.

The corn was harvested twiceweekly at cob maturity until frost or

full harvest. Early yield for the corncrop was defined as yield t hrough thefirst week of September. Melons wereharvested tw ice weekly at full slip. P ep-pers were collected in a once overharvest just before the first fall frost.Marketab le yields were based on Agri-culture and Agri-food Canada specifi-cations. All yields reported representmarketable commo dity.

D ata w ere analyzed using t heanalysis of variance (ANOVA) pro-

T able 1. Gr owing season climatic characteristics for the Saskatoon and Outlook test sites from 1994–97.

C limate 1994 1995 1996 1997 30-Year avg

Saskatoon

Temperature (°C )z 15.7 15.3 15.5 16.2 15.6

Sunshine (h) 240 247 272 286 278

Fall frosty 13 O ct. 16 Sept. 10 Sept. 29 Sept. 20 Sept.

Outlook

Temperature (°C ) 16.7 16.3 16.2 17.0 16.7

Sunshine (h) 265 268 267 290 282

Fall frost 19 O ct. 19 Sept. 29 Sept. 5 O ct. 23 Sept.

zAverage from 15 May t o 15 Sept.; °F = 1.8(°C) + 32.yFirst occurrence of temperatures below –1°C (30 °F).


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C lark, personal communication) Basiccosts include fertilizers, pesticides, seedor transplants, irrigation, taxes, over-head and labour. The costs for themulch and herbicide treatments in-clude the cost o f materials as well as thelabour involved in applying and re-moving t he mulches and applying t heherbicides. All material cost s are basedon 1997 commercial or bulk prices,freight on board Saskatchewan in$CD N. Lab our costs are based on awage of $CD N 5.50/h ($U S 3.68/h). Break-even prices for the variousmulch treatments were determinedbased on the average yield for eachtreatm ent over all site and year comb i-nations. The break-even price repre-sents the price per kilog ram that m ustbe ob tained to cover all costs and wascalculated by dividing the total costinto the marketable yields.

Results and discussionWEATHER CONDITIONS . Cloudier

than normal conditions slowed cropdevelopment in 1994 (Table 1), how -ever, the lateness of the first fall frostallowed the majority of the crops tomature. C ond itions in 1995 were simi-lar to 1994, but w ithout t he long openfall. I n 1996, unusually warm weather

Fig. 1. Percentage ground coverage by weeds for pepper, corn and melon cropsas influenced by plastic mulch and herbicide treatments. Data averaged for 1994–97. Bars represent L SD values at P = 0.05. W L S = wavelength selective.

T able 3. Early and total cob yields for corn pr oduced with different soil mulch and herbicide combinations.

1996

SaskatoonSoil mulch and 1994 1995 (kg·m–1 row) y Outlook

herbicide combination Early z T otal Early T otal Early T otal Early T otal

C lear 3.3 4.4 0.5 3.2 1.5 3.7 1.4 3.5

C lear + herbicide 3.7 4.6 1.2 1.3 1.5 4.0 0.6 3.3

Wavelength selective 2.2 3.8 0.3 0.9 0.5 2.7 0 2.7

Black 3.5 5.3 0.3 0.7 0.2 2.8 0 2.3

H erbicide only 1.7 3.3 0 0.2 0.3 2.8 0 2.8

LSD(0.05)

0.8 0.9 0.5 0.8 0.6 0.5 0.5 0.5

CV (%) 16 21 20 17 26 14 20

zEarly = before first w eek of September.y1.0 kg·m–1 = 0.67 lb/ft.

T able 2. Marketable fruit yields for peppers produced with dif ferent soil mulch and herbicide combinations.

Soil mulch and 1996 (kg·m–1 of row)z 1997 Mean

herbicide combination 1994 1995 Saskatoon Outlook Saskatoon Outlook 1994–97

C lear 0.9 5.1 4.5 3.1 6.2 6.4 4.4

C lear + herbicide 1.5 1.5 4.9 3.3 6.9 7.0 4.2

Wavelength selective 2.3 3.2 5.1 2.7 5.8 6.5 4.3

Black 2.2 4.1 3.7 2.2 6.0 6.6 4.1

H erbicide only 0.8 0.3 3.7 1.7 4.3 4.4 2.5LSD

(0.05)1.5 1.0 1.6 0.8 0.7 1.4

CV (%) 54 23 14 20 14 22

z1.0 kg·m–1 = 0.67 lb/ft.

gram of SAS (SAS Institute, 1990).D ata for percentage ground coverageby weeds were subject to arcsin con-version before analysis. Erro r variancesfor t he yield component s were highlyheterogeneous for sites and years;therefore those data were analyzedand presented separately. When the

analysis of variance indicated signifi-cant treatment effects, the treatmentmeans were compared using Fisher’sprotected LSD test.

Basic costs of production werecalculated for each crop along with t headditional costs associated with themulch and herbicide treatments (H .


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in August compensated for poo r con-ditions earlier in the year. Frost cameearly in Saskatoon in 1996. The 1997grow ing season was warmer than nor-mal, with abundant sunshine and along frost-free fall.

WEE D CONTROL. Broadleaf annualweeds such as lambsquarters (Chenopo- dium album L.), red root pigweed(Amar ant hus retr oflexus L.) and pros-trate pigweed (A . graeci zans L.) werepredominant in terms of both speciesdiversity and plant numbers in the testplots. This is fairly typical of commer-cial vegetable fields as the herbicidesregistered for use in most vegetablecrops are more effective against grassesthan broadleaf weed species. The ex-tent of ground coverage by weeds inthe mulch and herbicide treatmentswas similar in t he various site and yearcombinat ions and the data were pooled

accordingly (Fig. 1). G round coverageby weeds was more extensive in thepepper plots than in the melon or cornplots. The peppers produced a muchsparser canopy than the melons orcorn, which allow ed estab lishment andgrowth of weeds. In the corn andpepper plots, weed growth under thenon treated clear plastic mulch was sub-stantially greater than any other treat-ment. Clear plastic mulches warm thesoil and conserve soil moisture whilealso transmitting light, resulting inconditions ideally suited for weed de-

velopment (Ricketson and Thorpe,1983). The shade produced by thesprawling melon crop appears to havereduced w eed g rowt h w hen clear plas-tic mulch was used without herbicides.Jensen et al. (1989) found that theweed species composition was influ-enced by the use of clear mulch. Spe-cies such as purslane (Por tul aca oleracea L.) which are adapted to high tem-peratures and have a relatively pros-

trate growth habit thrived under themulches while other species disap-peared. No such shift in weed speciesdiversity was noted under the clearplastic in this trial. In all three crops,applying herb icide under the clear plas-tic mulch provided a degree of weedcontrol equivalent to the black andWLS mulches. N o sing le weed speciesdominated t he population t hat d evel-oped in the herbicide treated areas.

PEPPERS. In 1994, variability incrop vigor and yields was high acrossthe trial (C V for yields of 54%) and nosignificant differences in yield poten-tial for the various mulch and herbi-cide combinations were apparent(Table 2). In 1995, plants in bothtreatments receiving the herbicide werestunted and chlorotic for the durationof t he grow ing season. The symptom swere characteristic of trifluralin dam-

age, yet the product, which is regis-tered for use on peppers, was appliedaccording to recommendations. Thedegree of damag e was not influencedby the presence of the clear mulch.This indicates the problem was notrelated to chang es in herbicide activityor crop t olerances caused by the mulchtreatment. Similar herbicide treatmentsproduced no crop damage in the othercropping seasons. Although weedgrowth was extensive under the clearmulch with no added herbicide, thattreatment prod uced the g reatest fruit

yields in 1995 followed by the blackand WLS mulch treatments (Table 2).Yields for the clear + herbicide andherbicide alone treatments lagg ed wellbehind the o ther treatments in 1995.In 1996, there were no significantdifferences in fruit yields between thevarious treatments at the Saskatoonsite (Table 2). In Outlook, the twoclear mulch treatments produced thehighest yields, while the nonmulched

control produced t he lowest yields. I n1997, the mulched treatments pro-duced grea ter y ie lds than thenonmulched controls at both sites(Table 2). I n Saskatoo n, t he combina-tion of clear mulch + herbicide in-creased yields relative to the othermulch treatments, b ut no correspond-ing response was ob served in O utloo k.

C ORN. Corn planted on the clearmulch treatments consistent ly emergedseveral days earlier than any of theot her treatments, but the final germi-nat ion percentages were uniformly highfor all treatments (data not shown).Yield responses to the mulch treat-ments varied between test years. In1994, all mulch treatment s except theWLS improved early and total cobyields relative to t he nonmulched con-trol (Table 3). In 1995, the comb ina-tion of herbicide with clear mulch en-

hanced early but not the final yields.The two clear mulch treatments pro-duced the best to tal yields at bot h testsites in 1996 and also enhanced earlyyields (Table 3). U sing the WLS andblack plastic mulches did no t improveyields relative to t he nonmulched con-trol in 1995 or 1996 (Table 3). In1997, the clear plastic mulch againenhanced early yields at both sites(Table 3). Total yields in Saskatoonwere higher on t he clear mulch with-out herbicide than w hen WLS or blackplastic was used. In Outlook, all

mulched treatments produced higheryields than the control.

MELONS. In all test seasons, veg-etative growth (vine length) of thecrop was enhanced by the mulch treat-ments, with the clear mulch providingthe greatest benefit (data not show n).In 1994 and 1995, there were nosignificant differences in fruit yieldsamong the mulched treatments, butthe mulched treatments produced anaverage of 92%and 77%more fruitthan the nonmulched controls in thetwo seasons (Table 4). In 1996, the

two treatments with clear mulchyielded, on average, 63%more thanthe other treatments (Table 4). Theblack and WLS mulches did not im-prove yields relative to the control in1996. In 1997, there were again nosignificant differences in fruit yieldsamong the mulched treatments, butthe mulched treatments produced anaverage of 51%and 73%more fruitthan the nonmulched controls at thetw o t rial sites (Table 4).

E CONOMICS. The mulch and her-

1997 Mean

Saskatoon Outlook 1994–97

Early T otal Early T otal Early T otal

5.4 5.8 2.4 4.7 2.4 4.2

4.4 4.9 2.1 4.8 2.2 3.8

2.2 4.2 2.1 4.1 1.2 3.0

2.9 3.8 0.8 4.0 1.3 3.2

3.0 4.8 0.2 2.9 0.9 2.8

1.1 1.3 1.0 0.8

12 21 18 24 11


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RESEARCH REPORTS

bicide treatments represented a rela-tively minor component of the totalproduction cost for the pepper andmelon crops, b ut added considerablyto t he cost of producing the corn crop(Table 5). All the mulch treatmentsreduced t he b reak-even price requiredfor the pepper crop relative to produc-ing the crop without mulches (Table

6). D ifferences in cost per unit fruitproduction between the mulch treat-ments were small but based on theaverage for t he six site–year combina-tions, the clear mulch with no addedherbicide had the lowest cost per unitfruit production.

Based on t he six site–year comb i-nat ions, mulches of all types generallyimproved co rn yields and earliness rela-tive to the nonmulched control. The

T able 6. C rop cost, average yield and br eak even price for peppers, corn and melons as influenced by differin g soil mulch and herbicide combinations.

Pepper C orn Muskmelon

Soil mulch and C rop Break C rop Yield Break even C rop Break

herbicide cost z Yield y even x cost (kg·m–1) ($C DN/kg) cost Yield even

combination ( $C D N/m) w (kg·m–1) w ($C DN/kg) w ($C DN/m) Early T otal Early T otal ($C DN/m) (kg·m–1) ( $C D N/kg)

C lear 1.16 4.4 0.26 0.28 2.4 4.2 0.12 0.07 0.94 15.5 0.06

C lear + herbicide 1.17 4.2 0.27 0.29 2.2 3.8 0.13 0.08 0.95 15.0 0.06

Wavelength selective 1.25 4.3 0.29 0.37 1.2 3.0 0.31 0.12 1.02 13.7 0.07

Black 1.16 4.1 0.28 0.28 1.3 3.2 0.21 0.09 0.94 12.0 0.08

H erbicide only 1.12 2.5 0.45 0.24 0.9 2.8 0.27 0.09 0.89 8.1 0.11

zBased on calculations presented in Table 5.yAverage over all site year combinations.xCrop cost/yield.w $CD N 1.00/m = $U S 0.20/ft, 1.0 kg·m–1 = 0.67 lb/ft, $CD N 1.00/kg = $U S 0.30/lb.

T able 5. Basic cost of production for drip irr igated pepper, corn and meloncrops and cost of associated mulch and herbicide treatments.

Basic cost Mulch/herbicide cost C rop ($C DN/m of row)z Mulch tr eatment ( $C D N/m r ow)

Pepper $1.11 C lear $0.05

C orn $0.23 Black $0.05

Melon $0.88 Wavelength selective $0.14H erbicide alone $0.01

z$CDN 1.00/m = $US 0.20/ft.

T able 4. Marketable fruit yields for muskmelons produced with different soil mulch and herbicide combinations.

Soil mulch and Fruit yield (kg·m–1 of row)z

herbicide 1997 Mean

combination 1994 1995 1996 Saskatoon Outlook 1994–97

C lear 10.9 7.2 9.5 26.3 23.7 15.5

C lear + herbicide 8.5 7.5 9.1 27.2 22.9 15.0

Wavelength selective 10.6 7.1 6.8 22.9 21.3 13.7

Black 10.8 5.8 4.8 20.1 18.6 12.0H erbicide alone 5.3 3.3 3.9 15.8 12.5 8.1

LSD(0.05)

2.5 2.5 4.5 4.5 4.5

C V (%) 14 17 26 12 12

z1.0 kg·m–1 = 0.67 lb/ft.

clear plastic mulch with or withoutherbicide usually produced superiorearly and total yields and thereforerepresented the most cost effectiveproduct ion option (Table 6). The clearmulch was particularly cost effectivewhen the objective was early produc-tion. The wavelength selective mulchrepresented a less cost effective pro-

duction o ption for corn than growingwithout mulch.

Over the 4 years of testing, themulches increased m elon yields by anaverage o f 73% rela t ive to thenonmulched controls. There was noconsistent difference in melon yieldsamong the various mulch treatments.All mulches reduced cost per unit f ruitproduced relative to t he nonmulchedcontro ls (Table 6), with the clear mulch

with or without herbicide having thelowest cost per unit of fruit yield.

This study demonstrated that intemperate production zones with ashort growing season, clear plasticmulches generally represented the mosteffective means for enhancing yields

and profitability of production o f warmseason veget able crops. The enhance-ment in yields is likely due to thehigher soil temperatures produced bythe clear mulches. Soil warming asso-ciated w ith t he use of clear mulches isparticularly important when slow-ma-turing warm-season crops such as mel-ons and peppers are grown in regions,such as Saskatchew an, as the brevity o fthe growing season necessitates earlyplanting. Soil warming by clear mulchesis also valuable in crops, such as corn,where earliness in prod uction brings a

substantial price premium.The potential for excessive weed

growth is a concern whenever clearplastic mulches are used on nonfumi-gated soils. This study showed thatherbicides applied under the clearmulch at standard recommended ratesprovided effective weed control withno observable changes in herbicideefficacy or crop toxicity relative tononmulched areas. This indicates that


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herbicides may represent a cost effec-tive and environmentally sound alter-native to fumigants where weeds rep-resent t he primary pest prob lem in thecrop. The weed control provided bythe herbicides or by the mo re opaquemulches did not improve yields rela-tive to clear mulch with no herbicide inthis stud y. Intensive irrigation and fer-tility management may have reducedthe potent ial for competition betweenthe crop and the weeds growing und erthe clear mulch for these productionfactors. Weed growth under clearmulches may be more of a concern inless intensively manag ed situat ions es-pecially if the initial weed populat ion islarger or comprised of more competi-tive species. In this study, establish-ment and early growth of the pepperand melon crops was promot ed by theuse of transplants and field covers.

Similarly, seeding of the corn was de-layed until air and soil temperatureswere conducive to rapid grow th. Thesemanagement factors provided the cropswith an early competitive advantageover any emerging weeds. Weed con-tro l via the application of herbicides orthe use of opaque mulches may bemore important when slow develop-ing crops are direct seeded or whenadverse cond itions retard developmentof the emerging crop relative to theweeds.

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Bonnano, A.R. and W.J. Lamont. 1987.Effect of polyethylene mulches, irrigationmethod, and row covers on soil and airtemperatures and yield of muskmelon. J.Amer. Soc. H ort. Sci. 112:735–738.

Gerber, J.M., J.E. Brown, and W.E.

Splitt stoesser. 1983. E cono mic evaluationof plastic mulch and row t unnels for use inmuskmelon production. P roc. N atl. Agr.Plastics Congr. 17:46–50.

G orske, S.F. 1983. C hemical weed controlprograms for selected vegetables. Proc.Natl. Agr. Plastics Congr. 16:142–148.

Hamm, P.B., R. Ingham, and D. Hane.

1997. The econo mics of soil fumigat ion inpotato production in the C olumbia Basin.Proc. 36th Ann. Wash. State Po tato C onf.,Moses Lake, Wash. p. 155–159.

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Documents

Effect of Soil Mulches & Herbicides on Production Economics of Warm Season Vegetable Crops in a Cool Climate