Posted on January 7, 2014
TO BE MORE COMPETITIVE IN TODAY’S MARKETS, VEGETABLE GROW- T PRODUCE, SUPERIOR YIELDS, AND EARLY SPRING MARKETS. THE ERS ARE LOOKING FOR NEW WAYS TO ACHIEVE HIGHER-QUALITY PLASTICULTURE SYSTEM-WHICH COMBINES RAISED BEDS, PLASTIC MULCH, DRIP IRRIGATION, AND FUMIGATION-HAS HELPED AN IN- CREASING NUMBER OF PRODUCERS REACH THESE GOALS. GROWERS USING THE PLASTICULTURE SYSTEM HAVE DOUBLED AND TRIPLED YIELDS AND HARVESTED THEIR CROPS TWO TO THREE WEEKS EARLIER THAN IS POSSIBLE WITH TRADITIONAL GROWING PRACTICES.
Throughout this booklet we will emphasize that plasticulture is a system that cannot function optimally without all of its components. The benefits of these components are described below.
Raised beds help provide more uniform soil moisture and warmer growing conditions in the spring.
Plastic mulch, which gained wide acceptance in the early 1980s, helps warm the soil and reduces water loss. The mulch also protects fruits and leaves from disease by preventing direct contact with the soil.Black plastic mulch even helps control weeds.
Drip irrigation provides a uniform supply of water, which keeps the soil moist under the plastic. Soils in the Southeast, in particular, have limited water- holding capacity and do not re-wet easily once they have dried out. Drip irrigation helps eliminate this problem by frequently supplying small amounts of water to maintain a more constant moisture level.
Fumigation controls weeds, insects, and diseases. This control is an important element of plasticulture, because the high temperatures induced by plastic mulch stimulate pest activity. The success you can achieve with plasticulture depends on the specifics of your operation. This booklet provides information to help you decide if plasticulture is right for you, and if you decide it is, how to prepare your site and manage the system.
PLASTICULTURE’S ADVANTAGES AND DISADVANTAGES
Plasticulture is a management-intensive system that requires careful planning and close attention. Its benefits, however, can be many. Before you invest in plasticulture, you should carefully weigh the advantages and disadvantages of plasticulture versus traditional practices.
EARLIER PRODUCTION. Probably the greatest benefit of growing crops on plastic is earlier production.
Plastic mulch raises the soil temperature, which helps plants grow more quickly and mature earlier. Spring vegetables grown on black plastic can be harvested 7 to 21 days earlier than they can be on nonplastic mulch. Harvesting one to two weeks earlier often significantly increases market advantage and the prices growers
REDUCED LEACHING OF FERTILIZER. Because many fertilizer nutrients are not held tightly in the soil, rainfall and excessive irrigation may leach them below the roots of plants grown on bare ground. Nitrogen, potassium, magnesium, and some formulations of micronutrients are subject to leaching, especially in light, sandy soils. A plastic mulch covering the bed (or portion of it) prevents rainfall from percolating through the soil and moving nutrients beyond the reach of plant roots. Preventing leaching improves the efficiency of production by eliminating the need to make several trips through the field to resupply leached nutrients, thereby saving time, fuel, and fertilizer. In addition, it helps prevent reduced quality and lower yields resulting from
- hidden hunger – early stages of nutrient deficiency that may harm plants even before they begin to show symptoms and
- lag time – the time from when plants first show symptoms of a deficiency until nutrients are replenished in the plant tissues. Finally, minimizing the amount of leaching into the soil helps protect groundwater from fertilizer contamination.
FEWER WEEDS. Black plastic mulch prevents the growth of most weeds except nutsedge. Clear plastic, however, does not prevent weed growth because light can penetrate it. So if you are going to use clear plastic, you will also need to use a herbicide or soil fumigant. Herbicides also control weeds on bare ground between
the plastic-covered beds.
INCREASED PLANT GROWTH. Plants grow more with plastic mulch for two reasons. First, soil temperature at the 2-inch depth is increased by up to 10°F under black mulch and up to 15°F under clear mulch.
Second, during growth, plant roots take in oxygen and give off carbon dioxide (COJ. Plant leaves require CO, which they get from the atmosphere. When plants are grown on plastic, the CO, released from roots accumulates under the plastic and eventually escapes through the holes in which the plants are growing. This
“chimney effect” increases the concentration of CO, to the leaves and enhances plant growth.
REDUCED EVAPORATION. Because growth rate on mulch may be twice that on unmulched soil, plants
may require more water even though evaporation is reduced. Mulching cannot substitute for a sound irrigation program. However, less water evaporates from soil under plastic mulch, and soil moisture is maintained more uniformly. Therefore, you actually need less water per unit of production.
IMPROVED QUALITY. Vegetables grown on plastic mulch are cleaner and less subject to rots because soil has not been splashed on the plants or fruit.
REDUCED SOIL COMPACTION. Soil under plastic mulch remains loose, friable, and well aerated. Roots have access to adequate oxygen, and microbial activity is enhanced.
BETTER SURFACE WATER DRAINAGE. Excess water runs off the plastic-covered rows and out of the field, reducing drowning and other stresses related to waterlogged soil.
CULTIVATION ELIMINATED. There is no need for cultivation, except in the area between the mulched strips. Weed growth in these areas can be controlled with a labeled herbicide.
BElTER FUMIGATION. Plastic mulches increase the effectiveness of soil fumigation by retaining fumigants in the soil and providing better pest control.
REMOVAL AND DISPOSAL. A major problem with the plasticulture system is having to remove mulch and drip tubing from the field after cropping. Conventional black plastic mulch does not break down and should not be disked into the soil. It can, however, be recycled. Clear plastic does eventually break down, but small pieces may remain in the field for several years. In addition, there are photodegradable and biodegradable mulches, which break apart into the soil and do not have to be removed.
GREATER INITIAL COSTS. Because plasticulture requires an investment in specialized equipment including bed press, mulch layer, and mulch transplanter (or plug-mix seeder) – initial production costs are significantly higher than for traditional practices. Yearly costs of plastic and drip tubing further increase production expenses. These costs, however, should be offset by increased returns from earlier harvests, better quality, and higher yields.
INCREASED MANAGEMENT. Plastic mulch and drip irrigation must be monitored daily to be successful.
Although plasticulture technology offers several important advantages over conventional production practices, it is not necessarily for everyone. Whether plasticulture is right for your operation depends on
- are the vegetables you intend to grow suited to production on plastic,
- will the vegetables be intensely managed,
- are sufficient financial resources available or obtainable,
- do you have a good market, or prospects for one, and
- have you established a successful track record growing vegetables on bare ground?
If you answered “no” to one or more of these questions, then plasticulture might not be a good alternative for you now. However, if you answered “yes” to each of these questions, plasticulture may be profitable for you.