Different colors of mulch films being used at the Noble Foundation Horticulture Center

Plastic mulches have been available since the early 1960s and their popularity has continued to grow. In addition to commercial growers, countless numbers of backyard gardeners have come to appreciate the many advantages plastic mulch provides.

Some of these advantages include the following:

Earlier crops. Most experts consider this to be the single greatest benefit from using plastic mulch. When combined with raised bed culture, plastic mulch acts to raise soil temperature, thereby promoting faster crop development and earlier yields, up to two weeks in some conditions.

Weed control. I consider this to be the second greatest benefit of plastic mulch. For a mulch to be effective, enough light must be blocked to prevent weed growth. An exception is nutgrass, where the nutlike tubers provide enough energy for the seedling to puncture the mulch and emerge.

Reduced evaporation. Soil water loss is reduced under plastic mulch. While mulching insures greater irrigation efficiency, it also necessitates the need for drip irrigation as all moisture falling on the mulched bed, be it from overhead irrigation or rainfall, is shed from the bed.

Reduced fertilizer leaching. Because water runs off the mulch, plant nutrients are not lost through leaching. While plastic mulch does insure greater nutrient use efficiency, it also limits application of dry fertilizer materials, whether processed or natural (organic), prior to applying mulch. Any additional nutrients the crop receives must be applied via the drip system.

Cleaner product. The edible product from a mulched crop is cleaner and less subject to rot because mud from rainfall or irrigation is not splashed on the plants or fruit.

Plastic film mulch is available in several styles and widths. Black plastic is the most popular because it retards weed growth, warms the soil and is relatively inexpensive. White on black mulch provides a cooler soil temperature and is commonly used for establishing such crops as fall tomatoes or cole (cabbage, broccoli, etc.) crops under hot summer conditions.

Clear mulch provides the greatest soil warming potential of any mulch. A drawback of clear mulch is that it promotes weed growth because the plastic is transparent to sunlight. At the Noble Foundation, clear plastic mulch is used religiously during July and August in fallow beds to control weeds and soil-borne pathogens using heat, in a process known as solarization.

The best qualities of both clear and black plastic are available with IRT (infrared transmitting) mulch. IRT mulch transmits infrared radiation to warm the soil similar to clear mulch, but blocks most visible radiation, as does black mulch. IRT mulches are typically translucent green or brown.