Studies Show Colored Mulches Outperform Traditional Black Plastic Mulch

By Trish Svoboda

Studies have demonstrated benefits of using colored mulches as compared to the conventional black plastic mulch. The benefits of colored mulches over traditional black plastic mulch, as revealed by research, might seem minor but are worth considering for home gardeners who prefer to use plastic mulch.

Cynthia Domenghini, a horticulture specialist at Kansas State University, stated that plastic mulches are recognized for their benefits to vegetable growers, such as earlier fruiting, improved yields, and weed management.

Studies indicate that certain crops perform even better with colored plastic mulches. For tomatoes, a favorite among Kansas gardeners, the preferred color is 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 (weather) we have,” Domenghini said. “There may be no increase during years of near-perfect weather, or up to a 20% increase with less favorable growing conditions. An average expected increase is about 12%.”

Domenghini suggests the following procedure for applying plastic mulch:

1. Prepare the soil.

2. Position a trickle irrigation line near the center of the intended mulch area. This is crucial as the plastic will block rainwater or overhead irrigation from reaching the plants.

3. Create trenches for the outer six inches of the plastic mulch. This ensures the center of the bed remains undisturbed, with the mulch edges hanging into the trench.

4. Cover the mulch edges by filling the trenches. This step prevents the wind from lifting and blowing away the mulch. If the soil has been tilled, a hoe can be used to prepare the trenches.

While commercial growers utilize a mulch-laying machine that simultaneously applies the trickle irrigation line and mulch, home gardeners are required to perform this task manually.

Domenghini also points out that the disposal of plastic mulch presents a challenge.

“Availability of biodegradable plastic mulches will likely increase in years to come,” Domenghini said. “Some gardeners are able to re-use their plastic mulch for multiple years but as soil covers the top it reduces the efficacy of weed prevention.”

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