Gordon Johnson, Extension Vegetable & Fruit Specialist; firstname.lastname@example.org
I spent 5 years working as an Extension agent in a tropical country with small scale vegetable growers and teaching agricultural students at a technical school. One of the most interesting production practices that I was exposed to was the use of shadecloth. We grew a wide range of vegetables under shade including lettuce, cabbage, tomatoes, cucumbers, beans, peppers, and many others. Being a tropical environment, the shadecloth reduced solar radiation and created a cooler environment for production. A simple system using metal poles and wire was used to support the shadecloth above the growing crops at a height that allowed for access for all crop activities as well as for the use of a compact tractor for field operations.
The most common use of shadecloth in our area of the US has been for reducing greenhouse temperatures in the summer and in nurseries producing shade loving ornamentals. Very little work has been done with shadecloth for field production of vegetables.
As growers look to expand production or to manage production during the hot summers on Delmarva, shadecloth may have a fit for a number of crops. Certainly, leafy green production could benefit, potentially extending the production of lettuces through the summer. Day-neutral strawberry production in the summer may be another use. Tomatoes and peppers may benefit from some shading during hot periods. Research has shown the potential for shadecloth to improve quality in peppers and tomatoes, allow for the summer production of lettuce, and improve the production of repeat blooming strawberries in summer months. We have a few growers that have incorporated shade cloth into their production systems, especially in high tunnels where the shadecloth can be placed over the plastic cover in the summer.
There are a number of different types of shadecloth available. The most common colors are black and green. However, white or aluminized shadecloth may offer additional cooling. Other colors such as red may benefit specific crops by filtering different wavelengths of light. Using shadecloth is a balancing act. You want to shade enough to reduce heat loading on the crop. However, you do not want to cut down light to a level where it significantly impacts photosynthesis. Shadecloth come in various percent shading. For vegetable crops, choose a percent shade between 20 % and 40% with ~30% being the most common recommendation.
Shadecloth can be fitted over top of cold frames, high tunnels, low tunnels, or the post and wire support system mentioned above.