Volume XXIX |
By Darbie Granberry
University of Georgia
The plastic strips are almost paper thin. They may be as narrow as 12 inches or as wide as 32, depending on the crop. Plastic film mulch is very helpful in commercial vegetable production. It:
- Reduces weed problems, because most weed seeds don't germinate under black plastic.
- Reduces fertilizer leaching by limiting the amount of water moving through the soil.
- Reduces the need for irrigation because it helps hold moisture in the soil.
- Helps protect roots, because there's no need to hoe or cultivate near plants.
- Results in more vigorous plant growth and higher yields.
- Warms the soil and accelerates maturity so vegetables are ready to be harvested sooner.
Installation. To get the most benefits from plastic mulch, you have to install it right.
It's especially important to bury 8 to 10 inches on each side of the plastic strip under about 6 inches of soil to hold the plastic in place. Otherwise, the first gusts of wind will blow your plastic away. That can make your neighbors quite unhappy.
For plastic to effectively warm the soil, it must be the right type, installed on raised beds and "tight," so it remains in close, continuous contact with the soil surface.
A number of good plastic-laying machines are out there for large-scale production. Unfortunately, the equipment for gardeners is very limited and costly.
Because of that, gardeners who use plastic may have to install it by hand. That requires muscle and a lot of stamina. Manual plastic installation is definitely not for everyone.
Colors. Several colors of plastic are available. Clear is best for warming the soil. But it doesn't keep weed seeds from germinating. Use black plastic in the spring. It keeps weed seeds from sprouting and warms the soil, too.
Because black plastic may warm the soil too much during the summer, white plastic is better then.
Irrigation. Getting enough water from rainfall or sprinklers to plant roots under the plastic can be difficult, sometimes impossible. The best solution is to install drip irrigation hose or tape under the plastic so you can apply water directly to the soil near the plant rows.
Disposal. A few types of "degradable" plastic are supposed to self-destruct at the end of the season. However, because they cost more and sometimes break down too fast, not many gardeners use them.
After the gardening season is over, nondegradable plastic mulch must be removed and legally disposed of. Burning is not an option. Most of the time it goes to the landfill. Removing it can be quite a chore, and disposing of it is a considerable inconvenience.
Garden options
After some serious thought, if you feel the benefits of plastic are worth the extra cost, time and effort, try it.If you'd rather avoid plastic costs or feel you're not up to the hard labor required, don't feel bad. There's an excellent alternative: organic mulch, such as aged pine bark, grass clippings, straw or hay.
Except for warming the soil, organic much has all the benefits of plastic film mulch, with a bonus: you don't need to remove and dispose of it. Just till it into the soil at the end of the season and it will help build a better soil for next year's garden.
(Darbie Granberry is an Extension Service horticulturist with the University of Georgia College of Agricultural and Environmental Sciences.)
