Evaluation of silver reflective mulch, white inter-row mulch, and plant spacing for increasing yields of bell pepper

Final Report for ONE05-041

Project Type: Partnership
Funds awarded in 2005: $9,167.00
Projected End Date: 12/31/2005
Matching Non-Federal Funds: $6,540.00
Region: Northeast
State: Maine
Project Leader:
Dr. Mark Hutton
University of Maine Coope
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Project Information

Summary:

Pepper production in Maine and other northern regions is limited by the cool, short growing season. The reflective mulches are relatively new materials that make it possible to re-evaluate pepper production practices. Silver or white mulch used as inter-row mulch, or bed mulch has been demonstrated to allow changes in tomato plant density resulting in increases in yield per area and earliness. This study builds on previous work (2003, 2004) examining the effects of reflective and inter-row mulching on pepper production. In the proposed study we evaluated two planting densities in combination with three mulching practices on the yield and quality of bell pepper.
Double rows out performed the single rows and white inter-row mulch was better than reflective mulch and these both out yielded black plastic alone. Planting double rows on black plastic and then covering the inter-row area with white plastic obtained significantly greater yields than the other treatments evaluated. Plants grown in double rows on reflective mulch had the greatest number and weight of cull fruit. Sun burning followed by blossom end rot were the principle reasons for culling fruit harvested from the reflective mulch treatments. Blossom end rot was the primary defect resulting in culls in the other treatment plots. One of the more interesting findings in this study was the comparison of the control (double rows on black plastic) to single rows of peppers with the white inter-row mulch. While the control treatment had slightly more and larger fruit compared to the single row with white inter-row mulch the difference was quite small. More importantly, the single row with white inter-row mulch treatment produced a comparable yield with 25% fewer plants

Introduction:

In Maine, there is a consistent market for high quality local grown bell peppers. However in many years, pepper crop yields are disappointingly low. In some years pepper yields have averaged a single fruit per plant (2003 Highmoor Farm Pepper Variety Trial Report). Recent research in new mulch materials and techniques suggests more can be done in the cultural management of the crop to increase earliness and yields. Research at the University of New Hampshire has show that using white inter-row mulch between rows of high-density tomatoes (12” in-row spacing) can increase tomato yields 28-32% compared to tomatoes grown at standard density (18” in-row spacing) on back plastic mulched beds. Experiments in pepper production funded by the Maine Agricultural Center at the University of Maine, have shown a 28% increase in pepper yields by using white inter-row mulch and as much as a 90% increase in yields by growing peppers on silver reflective mulch compared to black plastic mulch alone (Hutton and Handley, 2003). Data from small plots in 2004, indicate that single rows of peppers grown on reflective mulch at 12” spacing produce yields equal to double rows on black mulch at 18” in-row spacing. This is very exciting in that the single rows have 22% fewer plants per acre. In an un-replicated experiment conducted in 2004 with Rick Belanger, Belanger and Sons Farm, white and silver inter-row mulch was compared to no inter-row mulch. Results from this experiment also indicated that white inter-row mulch increased yields of bell pepper over the no inter-row mulch check treatment. Inter-row mulch and reflective mulches reflect sunlight back into the plant canopy increasing the potential amount of photosynthesis. However, reflective mulches also reduce soil temperature. This is an undesirable side effect of covering planting beds and inter-row areas in Maine’s already cool soils. Additionally, the silver inter-row mulch appears to have resulted in a greater percentage of cull fruit (small size and sunburn).

Project Objectives:

This project will evaluate the use of inter-row mulches and reflective mulches for improving bell pepper production in commercial pepper fields. We will use black, white and silver mulches and two planting densities to determine how best to grow peppers in Maine. Particular attention will be give to the economics of each production system in terms of physical (mulches, seed/transplants) and cultural (weeding, harvesting) inputs and marketable output total i.e. un-graded yield, graded yield, and amounts and types of cull fruit.

Research plots will be established in commercial pepper fields on farms located in Lewiston (Belanger and Sons), Manchester (Bell Vue Farm) and the University of Maine Highmoor Farm, Monmouth, Maine. The experiments will be conducted in a split-plot design using three mulch treatments as the main plots: 1) Check treatment, black plastic; 2) Black plastic with white inter-row mulch; 3) Reflective silver plastic mulch (Repel Grow Heat-trap mulch). Plant density will be the split plots: 1) Standard high density, double rows at 18” in-row spacing (9,680 plants/acre); 2) Low density, single row at 12” in-row spacing (7,260 plants/acre). All beds will be on 6’ centers. One pepper variety will be grown at each location and each farm will grow or purchase their transplants. As fruit mature, one harvest crew will make bi-weekly harvests at each location. Harvested fruit will be graded by size and quality; cull fruit will be graded for the type and extent of the defect i.e. rot, sunburn, insect, etc. Records will be kept for time spent harvesting and grading each plot. All costs and time associated for each treatment will be collected. Economic data will be used to create an enterprise budget for these methods of pepper production. Yield will then be statistically analyzed to determine the optimum pepper production method.

Cooperators

Click linked name(s) to expand
  • Bryan Baggott
  • Rick Belanger
  • Andrew Files
  • David Handley

Research

Materials and methods:

Research plots were established in commercial pepper fields on farms located in Lewiston (Belanger and Sons), Manchester (Bellevue Farm) and the University of Maine Highmoor Farm, Monmouth, Maine. The experiments were conducted in a split-plot design with three replications using three mulch treatments as the main plots: 1) Check treatment, black plastic; 2) Black plastic with white inter-row mulch; 3) Reflective silver plastic mulch (Repel Grow Heat-trap mulch). Plant density was the split plot: 1) Standard high density, double rows at 18” in-row spacing (9,680 plants/acre); 2) Low density, single row at 12” in-row spacing (7,260 plants/acre). All beds were on 6’ centers. One pepper cultivar, ‘King Arthur’ was grown at each location and each farm will grow or purchase their transplants. As fruit mature, one harvest crew made bi-weekly harvests at each location. Harvested fruit were graded by quality; cull fruit were graded for the type and extent of the defect i.e. rot, sunburn, insect, etc. Yields were then statistically analyzed to determine the optimum pepper production method.

Research conclusions:

Interestingly, there were no significant differences in the yield of individual pepper plants grown in single or double rows when averaged over all mulch treatments. However, when plants were grown in single rows they tended to be slightly larger and have slightly greater yields when compared to plants grown in double rows (Table 1.) This seems to indicate that interplant competition between pepper plants within the bed was minimal.

Table 1. Average total yield of individual ‘King Arthur’ pepper plants grown in single rows at 12” in-row spacing or double rows at 18” in-row spacing at three locations during the summer of 2005 z.

Plant Density Number of marketable fruit per row foot Marketable weight per row foot (kg) Number of Cull fruit per row foot Cull weight per row foot (kg) Average Plant Fresh Weight (g) Average Fruit Weight (g)
Single row 5.6 0.976 0.752 0.111 456 780
Double row 5.3 0.892 0.755 0.107 437 789
LSD (0.05) n.s. n.s. n.s. n.s. n.s. n.s.

zValues are means of data from 27 plots, nine plots on farms located in Lewiston, Monmouth and Readfield, Maine.

Plot size and corresponding number of plants per plot varied between treatments and between farms. Therefore, the data are reported on the basis of yield per row foot. We feel this not only makes it possible to compare the yields of plots with different plant densities but also makes it possible to easily extrapolate to yields on acre row foot basis.

Significant differences were observed among the three mulch treatments when the plant density sub-plots were combined. The white inter-row mulch treatments resulted in significantly greater yields compared to standard black mulch treatments. The yield increase of the inter-row mulch treatments over the standard production practice of black mulch was 23.6%. The magnitude of the yield increase due to the white inter-row much has been significant in each year of our experiments and is remarkably consistent with the yield 28-32% increases observed in tomato by Ouellette and Loy, 2000.

Results of the reflective silver mulch have not been consistent from year to year. In the first year of evaluation, 2003, the silver mulch increased weight of marketable pepper yield by 90% over black plastic alone (Hutton and Handley, 2003). However, in 2005 the yield in the reflective silver mulch plots were only 8.7% greater than the black mulch control plots.

Table 2. Average yields of ‘King Arthur’ pepper grown, in 2005, using three different much treatments z.
Mulch Type Number of marketable fruit per row foot Marketable weight per row foot (kg) Number of Cull fruit per row foot Cull weight per row foot (kg) Average Plant Fresh Weight (g) Average Fruit Weight (g)
Black Mulch with White Inter-row 16.684 a 2.964 a 2.13 b 0.368 a 499 776
Reflective Silver 14.304 b 2.606 ab 3.379 a 0.512 a 409 786
Black (control) 13.724 b 2.397 b 2.13 b 0.321 a 423 791
LSD (0.05) 2.073 0.4566 0.9666 0.1938 n.s. n.s.

zValues are means of data from 9 plots, three plots on farms located in Lewiston, Monmouth and Readfield, Maine.

Yield results for the various combinations of mulch treatments and plant densities are shown in Table 3. Double rows out performed the single rows and white inter-row mulch was better than reflective mulch and these both out yielded black plastic alone. Planting double rows on black plastic and then covering the inter-row area with white plastic obtained significantly greater yields than the other treatments evaluated. Plants grown in double rows on reflective mulch had the greatest number and weight of cull fruit. Sun burning followed by blossom end rot were the principle reasons for culling fruit harvested from the reflective mulch treatments. Blossom end rot was the primary defect resulting in culls in the other treatment plots. One of the more interesting findings in this study was the comparison of the control (double rows on black plastic) to single rows of peppers with the white inter-row mulch. While the control treatment had slightly more and larger fruit compared to the single row with white inter-row mulch the difference was quite small. More importantly, the single row with white inter-row mulch treatment produced a comparable yield with 25% fewer plants.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary

Education/outreach description:

Results from the experiments funded by this project were presented at the 2005 New England Vegetable and Fruit Conference to more than 75 growers from all areas of New England. Additionally, a written summary of the project was published in the conference proceedings and distributed to more than 1,000 conference attendees. The results were also discussed in a grower panel at the annual meeting of the Maine Vegetable and Small Fruit Growers Association attended by 80 growers and held in January 2006.

Results of these experiments are also being written for publication.

Project Outcomes

Project outcomes:

Economic analysis is still underway, though it looks as if the increase in pepper yields may not offset the increased costs associated with the inter-row mulch.

Farmer Adoption

More than 10 farmers have requested more information about this production practice, and four farms have committed to small scale testing in 2006.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

Additional information is needed on the economics of this production practice in order to help growers make decisions about the adoption of the practice.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.