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

2005 Annual 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

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


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 will evaluate two planting densities in combination with three mulching practices on the yield and quality of bell pepper. Detailed records will be maintained on all aspects of each treatment in-order to create enterprise budgets that will be used to make final determinations of treatment effectiveness.

Objectives/Performance Targets

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 (Bellvue 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.


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 This seems to indicate that interplant competition between pepper plants within the bed was minimal.

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 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.

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 the 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.

Impacts and Contributions/Outcomes

Results from the experiments founded 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.


Rick Belanger

Belanger and Sons Farm
3072 Cotton Road
Lewiston, ME 04240
Office Phone: 2075765845
Andrew Files

Associate Scientist of Resource Economics
University of Maine
Office Phone: 2075813108
David Handley

Small Fruit and Vegetable Specialist
University of Maine Cooperative Extension
Highmoor Farm
P.O. Box 179
Monmouth, ME 04259
Office Phone: 2079332100
Bryan Baggott

Bell Vue Farms
P.O. Box 306
Manchester, ME 04351
Office Phone: 2077243520