Increasing Tomato Yields with Red Plastic Mulch
By Ron Honig
Most gardeners employ some type of mulch system in their gardens to control weeds and conserve moisture. Research has shown certain vegetables may gain an advantage by using varying colors of plastic mulch. Kansas State University Horticulture Expert Ward Upham provided the following report on the use of red plastic mulch under tomato plants.
Upham says plastic mulches have long been known to provide advantages for the vegetable grower including earlier fruiting, increased yields and weed control. More recently, advantages have been noted for colored mulches over the more traditional black plastic mulch.
With tomatoes, the color of choice has been red. Though normally there is an increase in production of marketable fruit with red mulch over black mulch, the amount of the increase varies with the type of year we have. There may be no increase during years of near-perfect weather or up to a 20% increase with less favorable growing conditions. A good average expected yield increase is about 12%.
How to Apply Plastic Mulch
Upham says commercial growers have a mulch-laying machine that applies the trickle (drip) irrigation line and the mulch in one operation. Home gardeners must do this by hand. The first step after soil preparation is to place a trickle line near the center of where the mulch will lay as the plastic will prevent rainwater or overhead irrigation from reaching the plants.
Then, Upham recommends to construct trenches for the outer 6 inches of the plastic mulch. This allows the center of the bed to be undisturbed with the edges of the mulch draping down into the trench. Fill the trenches to cover the edges of the mulch. This will prevent wind from catching and blowing the mulch. Upham states, if the soil has been tilled, a hoe is all that is needed to prepare the trenches.
It is important to remember that the red plastic sheet must be on top of any other mulch so it can reflect the light back to the tomato plants. Placing an additional organic mulch such as straw on top of the plastic in an attempt to hold the plastic sheets down, will negate the benefit received from the light reflection.
The red plastic mulch is available from a number of sources. Check with your local garden supply store, but an online search will also provide a number of vendors offering the red plastic sheets.
The use of red plastic mulch has shown an average tomato produce yield increase of approximately 12 percent. (Photo courtesy of Ward Upham, Kansas State University).
