North Florida Research and Education Center - Suwannee Valley

Plasticulture Technology for Vegetable Production
Michael S. Sweat
Baker County Extension Director

    The term plasticulture generally describes a drip-irrigated production system using beds covered with a thin sheet of plastic mulch and in some cases the additional use of protective covers over the crop to allow for production of crops when production is not normally possible.  Information for this chapter comes from UF Extension Circular 805 "Polyethylene Mulching for Early Vegetable Production in North Florida" by G. J. Hochmuth.

Types of Mulch                                                                         
   Basically, three major colors of mulch are used commercially: black, clear, and white (or white-on-black). Black mulch is used most widely because it retards weed growth, resulting in less chemical usage. Black is popular for cool seasons because it warms the soil by contact. Clear polyethylene is used widely in the northern United States because it promotes warmer soil temperatures (by the greenhouse effect) than black mulch. White or white-on-black mulch is used for fall crops in Florida which are established under hot summer conditions. Soils under white mulch or white-on-black mulch remain cooler because less radiant energy is absorbed by the mulch. Some growers create their own "white" mulch by painting the surface of black-mulched beds with white latex paint. This technique also allows multiple cropping on the same mulch.

• Earlier crops. The greatest benefit from plastic mulch is raising the soil temperature in the planting bed, to promote faster crop development and earlier yields. Black plastic mulch can result in an earlier harvest (7 to 14 days).

• Soil water loss is reduced under plastic mulch. As a result, a more uniform soil moisture is maintained and irrigation frequency may be reduced. Plant growth on mulch can be twice that of unmulched soil. Because these larger plants will require more water, mulching is not a substitute for irrigation.

• Fewer weed problems. Black and white-on-black mulches will reduce light penetration to the soil. Weeds generally cannot survive under the mulch. An exception is nutsedge, where the nut-like tubers provide enough energy for the sharp pointed blades of the seedling to puncture the mulch and emerge through the plastic.

• Reduced fertilizer leaching. Excess water runs off the impervious mulch. Fertilizer beneath the mulch is not lost to leaching, so fertilizers are efficiently used and not wasted.

• Reduced soil compaction. Soil under the plastic mulch remains loose, friable and well-aerated. This provides for excellent root growth throughout the prepared bed.

• No cultivation. Cultivation is eliminated, except for the area between the mulched strips.

• Cleaner product. The edible product from a mulched crop is cleaner and less subject to rots because soil is not splashed on the plants or fruit. Note: This is accomplished by a bed that is firm and tapered away from the row center and plastic that is tight to encourage water run-off. There should be no puddles on the mulched bed.

• Aids fumigation. Mulches increase the effectiveness of soil fumigant chemicals. Because of the impervious nature of the plastic mulch, it acts as a barrier to gas escape.

• Bedding and pressing the soil. With some bedding machines, the soil is raised and then bedded in one operation ("super-bedders"). In other situations the soil is first raised in one operation with hilling discs or double disc hillers on a tool bar. The bed is then compressed to a uniform height and density using a bed press pan. All pre-plant fertilizer should be applied and incorporated into the bed before bedding. The width of the bed will depend on the crop and the number of rows desired per bed. For example, strawberries are traditionally planted in double rows and require a wider bed (28-36 inches).

• Application of the mulch and fumigation (if required). The soil must have adequate moisture (enough for seed germination) when laying plastic mulch. The soil should be rototilled or disked well and be free from undecomposed plant debris before applying the mulch. If fumigation is necessary, be sure to follow all label directions and application methods specified on the product label.

Drip Irrigation                                                                             
   Drip irrigation is an essential component of a plasticulture production system in the deep sands of North Florida. Drip irrigation allows for uniform watering of only the plant root zone, thus eliminating costly overhead systems which irrigate the entire field. A low pressure drip system allows for lower cost pumping equipment and reduced fixed costs of sprinklers and distribution systems.

• Drip tube placement. Drip irrigation tube should be applied at the same time as the mulch. For single-row crops such as tomatoes, cucumbers, muskmelons, honeydews, watermelons, and pumpkins a drip irrigation tube should be placed either in the center or 4 to 5 inches from the center of the bed with the emitters facing upward. On double-row crops of squash, eggplant, peppers and strawberries, the drip irrigation tube should be placed directly on the center of the bed. Placement of the drip tube in a shallow groove will aid in keeping it from shifting in the bed.

Planting the Crop                                                                        
    Vegetable crops can be established in mulch by transplanting or direct-seeding. Transplanting can be done by hand or by mechanical "pot" or "punch" planters or semi-automated transplanters. Direct-seeding through the mulch can be done by hand, with a "plug-mix" planter or "vacuum" seeder. With the "plug-mix" planter, seed is mixed with a peat-vermiculite (potting soil) material, wetted, and placed in the planter's hopper. The machine punches a hole in the plastic mulch and places a small amount of the "plug-mix" into the hole. The vacuum seeders will place individual seeds through the mulch. These machines are suggested for use in seeding large acreages but may be too expensive for a smaller grower.

Use of Row Covers                                                                      
   Row covers are another important component of a plasticulture production system. Row covers are flexible, transparent or semi-transparent materials used to cover or enclose a crop to enhance growth and yield by increasing soil and air temperature and reducing wind damage. Research has shown that row covers in conjunction with plastic mulch will allow for earlier yields and increased production.

Double Cropping                                                                         
   Plasticulture technology also affords the ability to double-crop on the same land and mulch. Once the first crop has been harvested, a second crop can be grown utilizing the same mulch and drip irrigation. This "intensive cropping" produces two crops from the same annual expenses. In addition, the second crop can be fertilized entirely through the drip system. Herbicides or hand removal may be needed to quickly eliminate the first crop before planting the second crop.

Source of Plasticulture Supplies

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