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Is There A Difference In Red Mulch?

M. D. Orzolek and L. Otjen
Department of Horticulture
The Pennsylvania State University, University Park, PA 16802


Abstract: The development of a red colored polyethylene mulch by various manufacturers in the last 5 years has resulted in the production of a product that appears to have many different characteristics of which no two are identical. Red polyethylene mulches were obtained from 5 different sources in 1995 and placed on raised beds with drip irrigation on May 16. Pepper and canteloupe were planted into the different mulches. Reflective wavelengths, soil temperature, color retention, and quality of the polyethylene differed among the 5 manufacturers.


Keywords: Polyethylene mulch, color, reflective light, peppers, cantaloupe


Introduction


In 1985, Michael J. Kasperbauer and Patrick G. Hunt (USDA-ARS Soil and Water Conservation Research Lab, Florence, SC) conducted a tomato production trial with plastic mulch in cooperation with Dennis R. Decoteau from Clemson. University (Kaplan, 1991). They painted black polyethylene mulch red, yellow, blue, orange and green with latex paint. Tomatoes grown on red mulch produced a 20% increase in number-one fruit compared to black mulch. However, over the years, tomato response to red plastic mulch has been variable and average yield increase is only about 10% greater than black. Kasperbauer and Hunt have evaluated several other vegetables and have concluded that different vegetable crops respond differently to the different colored mulches.


The change in vegetable crop yield in response to the different mulch colors is due in part to an increase in soil temperature and the range of reflected wavelengths produced by individual mulch colors. Different colors will absorb and reflect different wavelengths of light and plants are very sensitive to the color of light their leaves intercept from the sun and reflected surfaces. Red and far- red light (between 600 and 800 nanometers) produce the largest growth responses in plants. Light that has a lower far-red to red OT,/R) ratio will cause a plant to develop shorter stems and larger roots (Table 1). A higher FR/R ratio will cause a plant to direct more new growth into shoots, resulting in a taller plant with more leaves. Different mulch colors reflect different wavelengths and thus different FR/R ratios.


Materials and Methods


Five red mulches were placed in the field with a 'Rainflo' bedder/mulch layer on May 16, 1995 at the Horticulture Research farm, Russell E. Larson Research Center, Rock Springs, PA. The beds were placed on 7 foot centers and beds were formed to a height of 4 inches. Drip irrigation tubing was placed under the mulch (2"deep in the soil) at the same time the mulch was layed in the field. Red mulch treatments were replicated three times in a randomized complete block design. Red mulch film was received from: Bemis Plastics, Flemington, NJ; Four Seasons Agricultural Products, Atlanta, GA; Polyon Inc., Israel (US rep-PolyWest, San Diego, CA; Rochelle Plastic Film Inc. Rochelle, IL; and Sonoco Products Company, Hartsville, SC. Pepper transplants, cv 'Ranger', were planted on May 24 and cantaloupe transplants, cv 'Athena', were planted on June 1, 1995. The peppers were placed at 12 inch spacings in single rows (10 plants/plot) and cantaloupe at 24 inch spacing with 5 plants/plot. Oxyfluorfen (0.2 lbs/A) and metachlor (1.0 lb/A) were broadcast prior to laying the plastic in the field for weed control. Insecticides and fungicides were applied as warranted when either insect or disease pressure exceeded threshold levels. Water was applied through the drip irrigation system several times a week from June 2 to September 7, 1995. Reflected wavelength was measured with a LI-COR Ll- 1800 spectroradiometer with a light collector on a 1.5 rn fiber optic probe. The readings were taken on June 6 and August 17, 1995.


Results and Discussion


The red polyethylene films obtained from five manufacturers differed in their color retention and appearance characteristics (Table 2). The Sunoco and Polyon mulches were colorfast and opaque throughout the growing season. The Rochelle red plastic was initially dark red and opaque when applied in the field in May, but within 30 days, a visible change in color was evident, the red color was beginning to fade. The Four Seasons and Bemis red plastic mulches were initially translucent with a pale red color which had faded during the course of the growing season. There was little change in the temperature of the soil beneath the different red mulches (Table 2). The minimum soil temperature recorded on May 23, 1995 was not high but acceptable for plant establishment and early growth of both cantaloupe and pepper. Previous field studies which had recorded soil temperatures under colored mulches in 1992 and 1994 with an Omni data logger indicated that temperature under Rochelle's red mulch were equal to soil temperature under clear plastic mulch and higher than yellow, blue, black or grey colored mulch (Orzolek, 1993).


The peak waveband for Sunoco red was at 500 and 600 nanometers throughout the entire growing season with a slight shift to 650 nanometers in August (Figure 1). The red SLT mulch from Polyon had peak wavebands at 500 and 600 to 650 nanometers with a significant peak at 800 nanometers, (Figure 2). There was very little change in the spectral graph of reflected light from the red SLT at the end of August. The peak waveband for Rochelle red was at approximately 500 and 600 nanometers throughout the entire growing season with very little change in August even after the color had begun to fade (Figure 3). The other red mulch materials from Four Seasons and Bemis had similar spectral graphs as Sunoco, Polyon, and Rochelle with waveband peaks at around 500 and 600 nanometers. The 500 and 600 nanometer wavebands coinicide with the colors blue and red which have been implicated as promoters of photosynthesis, phototropism, seed germination, seedling and vegetative growth, photoperiodism and anthocyanin synthesis (Leopold, 1964).


There were significant differences in the yield of cantaloupes from the different red mulch materials (Table 3). Red mulch manufactured by Polyon had plants which produced more fruit compared to Four Seasons-degradable and Rochelle. Largest average fruit weight was produced from plants grown on the Sunoco red and Polyon brown mulches and the smallest average fruit size from the Four Seasons biodegradable red mulch. The percent marketable fruit harvested from the different mulch colors was relatively uniform except for the Four Season mulches which had plants that produced approximately 50% marketable fruit.. There was no difference in fruit soluble solids from melons gown on the different red colored mulches.


There were significant differences in the yield of peppers from the different red mulch materials (Table 4). Red mulch manufactured by Sunoco and Polyon had plants with higher yields (weight) compared to Four Season and Rochelle mulches. Largest average fruit weight was produced from plants grown on the Bemis red mulch and the smallest average fruit size from the Four Seasons biodegradable red mulch. Hatt et al (1993) reported the highest yield of pepper from plants grown on white mulch because it had the greatest reflection of red and blue light. They also reported that Polyon's brown SLT had the greatest FR/R ratio (730-740/640-650 nm). Larger early pepper yields were reported from plants grown on either clear or red plastic mulch with no difference in total yields (Begin, 1995). In our study, peppers grown on brown SLT did yield (weight) significantly more than the Four Season, Rochelle, and Bemis red, but no significant difference in yield compared to the Sunoco red or Polyon red SLT.


Conclusions


There was a difference in color retention and film appearance of the different red plastic mulches currently on the market. This difference in film characteristics affected plant responses. In general, the red polyethylene mulches manufactured by Sunoco, and Polyon resulted in higher plant yields than the mulch material from Four Seasons, Rochelle and Bemis. Since soil temperature and reflected light were similar for all the red mulch formulations evaluated, color retention during the growing season, film appearance, and film longevity appear to have been the key characteristics responsible for the change in crop yield when both cantaloupe and pepper plants were grown on these mulches. The Four Seasons photodegradable red film broke down within 4 to 6 weeks of application in the field and Rochelle's red turned translucent within 30 days after application in the field.


Literature Cited


Begin, S., J. Calandriello, and P. A. Dube. 1995. Influence of the color of mulch on development and productivity of peppers. HortScience 30(4):883.


Hatt, H. A., A J. Mcmahon, D. E. Linvil, and D. R. Decoteau. 1993. Influence of spectral qualities of mulch film on bell pepper growth and production. Proc. Natl. Ag. Plastics Cong. 24:233-239.


Kaplan, J. K. 1991. Dress-for-Success Mulch. Ag. Research. 39(9): 10-13.


Leopold, C. A. 1964. Plant growth and development. McGraw-Hill Book Co. pp466.


Orzolek, M. D. 1993. The effect of colored polyethylene mulch on the yield of squash and pepper. Proc. Natl. Ag. Plastics Cong. 24:157-161.

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Table 1. The effect of different colors of light on plant response.

Color Wavelength band Response
Violet 380 - 440 nm no reported
Blue 440 - 495 nm phototropism, photosynthesis
Green 495 - 570 nm none
Yellow 570 - 595 nm insect attraction
Orange 595 - 625 nm none
Red 625 - 800 nm photosynthesis, seed germination, seedling and vegetative growth, and anthocyanin synthesis.

Table 2. Characteristics of the different red colored plastic mulches, Horticulture Research Farm, Rock Springs, PA - 1995.

Mulch X Source Soil TemperatureZ °C Color Retention Film appearance
. 5/23 5/31 . .
Sunoco 23.0 15.5 colorfast opaque
Four Seasons-ND 22.5 15.0 faded translucent
Four Seasons-PD 23.5 13.5 faded translucent
Rochelle 24.0 14.5 faded opaque/translucent
Bemis PlasticsY 23.5 15.0 faded translucent
Polyon brown SLT 22.5 15.0 colorfast opaque
Polyon red SLT 23.5 14.5 colorfast opaque

X-Four Season plastic mulch: ND= non-degradable and PD= photodegradable
Y- Bemis Plastics no longer manufacturers agricultural plastic products.
Z- Soil temperature taken with soil thermometer to a depth of 8 cm at 9:00 am on May 31 and at 3:00 pm on May 23, 1995.
Translucent- permitting light to pass through so diffusedly that objects cannot be clearly seen.
Opaque- not transparent or translucent.

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Table 3. Yield and quality of 'Athena' muskmelon harvested from different red colored plastic mulches, Horticulture Research Farm, Rock Springs, PA - 1995.

Mulch Source Marketable yield
no. wt. (lbs)
Total fruit
number
Avg fruit
weight (lbs)
Percent marketable % Percent soluble solids %
Sunoco 12.3 55.8 18.0 4.54 75.5 13.6
Four Season ND 9.7 40.4 18.7 4.16 55.8 13.8
Four Seasons 5.0 16.0 10.3 3.21 50.0 14.5
Rochelle 8.0 29.3 12.0 3.66 82.5 14.3
Bemis Plastic 12.3 52.6 16.7 4.28 80.4 14.1
Polyon br 10.0 45.0 16.7 4.50 63.7 13.8
Polyon red 13.7 54.7 18.3 3.99 76.2 13.9
LSD .05 4.6 17.8 6.6 0.72 8.0 NS

Table 4. Yield and quality of 'Ranger' pepper harvested from different red colored plastic mulches, Horticulture Research Farm, Rock Springs, PA 1995.

Mulch Z source Marketable Yield no. wt. (lbs) Avg fruit weight (oz)
Sunoco 51.0 15.0 4.70
Four Seasons-ND 37.7 10.5 4.46
Four Seasons-PD 25.3 6.8 4.28
Rochelle 24.0 6.5 4.36
Bemis Plastics 29.7 9.0 4.87
Polyon brown SLT 45.7 13.4 4.69
Polyon red SLT 62.3 17.6 4.51
LSD 23.06.8 NS

Z-Four Season plastic mulch: ND=non-degradable and PD=Photodegradable