Growth and yield of muskmelon in response to
plastic mulch and row covers
Luis Ibarra
a, Juanita Flores
a, Juan Carlos DõÂaz-PeÂrez
b,* aCentro de InvestigacioÂn en QuõÂmica Aplicada. 25100, Saltillo, Coah, Mexico
b
Department of Horticulture, Coastal Plain Experiment Station, University of Georgia, PO Box 748, Tifton, GA 31793-0748, USA
Accepted 8 May 2000
Abstract
The objective of this study was to determine the effect of plastic mulch alone or in combination with row covers on plant biomass, growth analysis parameters, and yield of muskmelon plants (Cucumis melo L.). The design was a randomized complete block with four replications. The treatments were: (1) no mulch, no row cover (control); (2) black plastic mulch (BPM); (3) BPM plus row cover removed 10 days after seeding (das) (BPMCE); (4) BPM plus row cover removed 20 das (BPMCI); (5) BPM plus row cover removed 32 das (BPMCL). Plants grown using soil mulch plus row cover presented higher values of plant biomass, speci®c leaf area (SLA), relative growth rate (RGR), and net assimilation rate (NAR) compared to control plants. Early and total yield were highest in plants grown under row covers. In non-covered plants, early and total yield were both higher in BPM plants relative to the control. Heat accumulation by the crop measured as soil degree-days showed a higher correlation with early and total yield compared to heat accumulation measured as air degree-days.#2001 Elsevier Science B.V. All rights reserved.
Keywords: Muskmelon (Cucumis meloL.); Plastic mulch; Row covers
1. Introduction
The use of plastic mulches for muskmelon (Cucumis meloL.) production is a popular cultural practice in Mexico. Mulched plants commonly show signi®cant
*
Corresponding author. Tel.:1-912-391-6861, fax:1-912-386-3356. E-mail address: jcdiaz@tifton.cpes.peachnet.edu (J.C. DõÂaz-PeÂrez).
increases in yield and fruit quality. Row covers and ¯oating covers have been used in Mexico to a limited extent to protect the plants against insect attack (RamõÂrez, 1994). However, the use of row covers under Mexican conditions has often resulted in yield reductions of muskmelon and other cucurbits (Ibarra and Flores, 1997).
Several environmental factors in¯uence plant growth and development, with temperature having one of the largest effects on plants. Mesophytes grow and develop at 10±308C and are heat stressed at 35±458C (Eastin and Sullivan, 1984).
Within the 10±308C range, the rate of plant growth usually increases with
temperature. One way to measure the effect of temperature on plants is by determining the degree-days or heat accumulated by the crop. The amount of degree-days accumulated by a crop has been used to predict plant growth rates and harvest date (Boswell, 1929; Perry et al., 1986).
Row covers increase air temperature around the crop and their usage has been associated with increased plant growth, yield and earliness (Wells and Loy, 1985; Bonanno and Lamont, 1987; Teasdale and Abdul-Baki, 1995). One objective of this study was to determine the effect of plastic mulches alone or in combination with row covers on muskmelon plant growth, early yield and total yield. Another objective was to determine the heat accumulated by the crop measured as either air degree-days or soil degree-days, and determine the relationship of both measurements with plant growth and yield.
2. Materials and methods
The study was conducted at the Center for Research on Applied Chemistry (CIQA), in Saltillo, Coahuila, Mexico. The experiment station is located at an altitude of 1610 m, 258270N and 1018020W. Muskmelon cv. `Crusier' was direct-seeded in the spring of 1996. The mulch used was a 1.2 m wide, caliper 130
(32.5mm thick), black polyethylene ®lm. The row cover was made of a
non-perforated polypropilene (Agribon, 17 g mÿ2) and was placed in the ®eld
immediately after seeding. Wire arches placed 1.2 m apart were used to support the cover. Plants were drip-irrigated and fertilized with 100N-60P-00K kg haÿ1. Half of N and all P were applied before seeding. The remaining N was applied through the drip system during the growing season.
2.1. Measurement of air and soil temperatures
Air and soil temperatures were measured with thermocouples connected to a data logger (LICOR, LI-1000 Lincoln, Nebraska). The data logger was programmed to make hourly measurements and store daily values of maximum, mean and minimum temperatures. To measure air temperature, a thermocouple was located 15 cm above the soil surface and was kept inside a wooden shelter. To determine soil temperature, thermocouples were inserted 10 cm below the soil surface.
2.2. Degree days calculation
Air degree-days (DDair) and soil degree-days (DDsoil) (Jenni et al., 1996) were
calculated as:
DDair 12 TAMaxTAMin ÿTbase
DDsoil12 TSMaxTSMin ÿTbase
where TAMaxis the maximum daily temperature of the air, TAMinthe minimum
daily temperature of the air, TSMax the maximum daily temperature of the soil,
TSMin the minimum daily temperature of the soil, and T base is the base
temperature (108C) (Torres, 1995).
2.3. Plant biomass and yield
Two plants per experimental plot were sampled 10 and 32 das (the day when the ®rst row covers were removed). Fresh weight of leaves and stems was determined immediately after they were removed from the plant. Leaf area was measured with a leaf area meter (LI-3100, LI-COR, Lincoln, Nebraska). Leaves and stems were dried at 708C (until constant weight) and their dry weights were determined. Total fruit yield, early yield (1st and 2nd harvests) and culls (fruit lighter than 1 kg, rotten or with visual defects) were also determined.
2.4. Plant growth analysis
3. Results and discussion
Plastic mulches modify the amount of heat received and stored in the soil (Bonanno and Lamont, 1987). Mean daily values of air and soil temperature were higher under row covers compared to non-covered conditions (Table 1). Relative to control, air temperature was 4.7, 9.1 and 11.58C higher in BPMCE, BPMCI
and BPMCL treatments, respectively. These temperature differences were
because row covers retained an increased amount of heat radiating from both, the soil and the plants. In the absence of row cover, use of mulch alone resulted in increased soil temperature compared to the control, but it did not have a signi®cant effect on air temperature. Soil temperature was higher with mulched plants than with the control, which is consistent with previous reports (Bonanno and Lamont, 1987; Hemphill and Crabtree, 1988; Motsenbocker and Bonanno, 1989).
Time to anthesis (appearance of perfect ¯owers) was 45 and 55 das for BPM and control plants, respectively. The time plants remained under cover had no effect on time to anthesis. The time to anthesis in covered plants was 35 das. Fruit harvest of plants under cover was 24 days earlier than the control, while fruit harvest of BPM plants was 9 days earlier than the control. Thus, increases in air and soil temperatures under plastic mulch and row covers were probably responsible for the reduction in the time to anthesis and harvest, by increasing the rate of plant development. These results are consistent with previous reports that show the relationship of heat accumulation by the crop with growth rate and harvest date (e.g. Perry et al., 1986).
Plants under row covers had a faster rate of growth compared to BPM plants and the control. Plant biomass, leaf area, RGR and NAR were highest in covered
Table 1
Heat accumulation measured as air (DDair) or soil (DDsoil) degree-days, and maximum
temperatures during the ®rst 32 days after seeding
Treatmenta Degree-day Maximum temp. (
8C)
DDair DDsoil Air Soil
Control 442 408 37.5 32.1
plants, followed by BPM plants, and lowest in control plants (Table 2). Covered plants had increased RGR probably because they were exposed to higher air and temperature conditions than uncovered plants (Hemphill and Crabtree, 1988; Soltani et al., 1995). The RGR measures the ef®ciency of the plant as a producer of dry weight (NAR) or as a producer of leaf area (leaf area ratio, LAR) (Beadle, 1993). Plants under cover had higher values of NAR (Table 2), which indicates that they were able to produce more dry matter than uncovered plants. These higher NAR values were probably because plants under cover had a higher leaf area than uncovered plants. However, because LAR was not determined, it is not possible to know whether the increased leaf area in covered plants was due to a plant size effect or because covered plants allocated a relatively higher amount of biomass to leaf production compared to uncovered plants. Speci®c leaf area, which is a measure of the amount of carbon invested per unit of leaf area, was not affected by the presence of either row cover or mulch.
Early, marketable and total yields were highest for covered plants, followed by BPM plants and lowest for control plants (Table 3). Calculation of heat accumulated by the crop measured as air degree-days has often been used to predict plant biomass and yield (Wolfe et al., 1989). Plants under cover had the highest values of DDairand DDsoil. BPM Plants had a DDairvalue that was similar
to that of the control. However, BPM plants had a higher DDsoilvalue compared
to the control. This probably indicates that soil-accumulated heat might be more related to plant growth and yield than air-accumulated heat. Accumulation of DDairwas highly correlated with plant biomass (r0.94), and not correlated with
early yield (r0.67) or total yield (r0.77). However, heat accumulation measured as DDsoilwas correlated with plant biomass (r0.87) and tended to be
correlated with early (r0.89) and total yields (r0.93). Thus, muskmelon early
Table 2
Plant growth parameters of muskmelon plants, grown using plastic mulches and row covers for the period of 10 to 32 days after seeding
Treatment Plant
Control 0.59cd 27.7c 150.58 0.115c 7.5b
BPM 1.77c 195c 148.93 0.129c 8.3b
BPMCE 11.81b 1150b 149.97 0.242b 14.4a
BPMCI 22.95a 2284a 156.06 0.297a 17.4a
BPMCL 18.67a 2088a 160.65 0.279ab 15.2a
LSD (0.05) 3.13 439.9 N.S. 0.039 3.0
aSLA: speci®c leaf area.
and total yield were more related to DDsoilthan to DDair. Jenni et al. (1996) found
that DDsoilis a good predictor of muskmelon yield (Jenni et al., 1996).
In summary, use of row covers and plastic mulch resulted in earlier harvests and higher yields compared to plants grown using no row cover. In plants grown with no row cover, the presence of plastic mulch resulted in higher plant biomass and yield relative to plants grown in bare soil (control). Heat accumulation by the crop measured as soil degree-days showed a higher correlation with early and total yield compared to heat accumulation measured as air degree-days.
References
Beadle, C.L., 1993. Growth analysis. In: Hall, D.O., Scurlok, J.M.O., BolhaÁr-Nordenkampf, H.R., Leegood, R.C., Long, S.P. (Eds.), Techniques in Bioproductivity and Photosyntesis, 2nd Edition. Chapman & Hall, London, pp. 36±46.
Bonanno, A.R., Lamont Jr., W.J., 1987. Effect of polyethylene mulches, irrigation method, and row covers on soil and air temperature and yield of muskmelon. J. Am. Soc. Hort. Sci. 112, 735±738. Boswell, V.R., 1929. Factors in¯uencing yield and quality of peas, Maryland. Agric. Exp. Sta. Bull.
306.
Eastin, J.D., Sullivan, C.Y., 1984. Environmental stress in¯uences on plant persistence, physiology, and production. In: Tesar, M.B. (Ed.), Physiological Basis of Crop and Development. American Society of Agronomy, Madison, WI, USA, pp. 201±236.
Evans, G.C., 1972. The Quantitative Analysis of Plant Growth. Blackwell Scienti®c Publications, Oxford, 734 pp.
Hemphill Jr., D.D., Crabtree, G.D., 1988. Growth response and weed control in slicing cucumbers under row covers. J. Am. Soc. Hort. Sci. 113, 41±45.
Ibarra, L., Flores, J., 1997. Acolchado plaÂstico, cubiertas ¯otantes, y desarrollo y rendimiento de sandõÂa y calabacita. Agrociencia 31, 9±14.
Jenni, S., Cloutier, D.C., Borgeois, G., Stewart, K.A., 1996. A heat unit model to predict growth and development of muskmelon to anthesis of perfect ¯owers. J. Am. Soc. Hort. Sci. 121, 274±280. Motsenbocker, C.E., Bonanno, A.R., 1989. Row cover effects on air and soil temperatures and yield
of muskmelon. HortScience 24, 601±603. Table 3
Yield of muskmelon plants grown using plastic mulches and row covers
Treatment Early
Control 13.125ba 14.317 34.133b 48.450b
BPM 48.042a 12.160 59.022a 71.182a
BPMCE 60.198a 13.023 65.710a 78.733a
BPMCI 59.842a 8.530 78.572a 87.102a
BPMCL 57.530a 12.853 68.703a 81.555a
LSD (0.05) 12.749 NS 21.07 19.66
a
Perry, K.B., Wehner, T.C., Johnson, G.L., 1986. Comparison of 14 methods to determine heat unit requirements for cucumber harvest. HortScience 21, 419±423.
RamõÂrez, V.J., 1994. Cubiertas ¯otantes para desarrollar cultivos hortõÂcolas y controlar virosis. Universidad AutoÂnoma de Sinaloa.
Soltani, N., Anderson, J.L., Hamson, A.R., 1995. Growth analysis of watermelon plants with mulches and row covers. J. Am. Soc. Hort. Sci. 120, 1001±1009.
Teasdale, J.R., Abdul-Baki, A.A., 1995. Soil temperature and tomato growth associated with black polyethylene and hairy vetch mulches. J. Am. Soc. Hort. Sci. 120, 848±853.
Torres, R.E., 1995. AgrometeorologõÂa. Trillas, Mexico, DF.
Wells, O.S., Loy, J.B., 1985. Intensive vegetable production with row covers. HortScience 20, 822± 826.
