Southeastern U.S. Vegetable Crop Handbook - 2021 - 36

Double cropping
Growers frequently grow two crops on black plastic mulch to get
the most out of their investment. The spring crop is killed and removed,
and then a second crop is planted through the mulch. The
new crop should be planted into new holes and fertilizer added
based on soil test results and the new crop's nutrient requirements.
Plastic Mulch Removal and Disposal
Commercial mulch lifters are available. Plastic can be removed by
hand by running a coulter down the center of the row and picking
the mulch up from each side. There are many types of plastic
mulch removal equipment that can be used to reduce the cost of removal.
Following the list of best management practices below for
plastic mulch retrieval is imperative if the plastic mulch will be recycled.
Make sure a viable recycling market exists for mulch film
in your region. If there is a viable market, the following BMP's
will help you prepare your material in a way that is desirable to
the recycler. Even if there is not a viable recycling market, the best
management practices, if implemented, have shown as much as a
$125 per acre savings in some areas. Transportation logistics and
costs should be considered when deciding the process to be used.
Sanitary landfills may accept plastic mulch in some areas. There
are a few recycling projects which accept plastic mulch. Some
states allow burning of mulch with a permit.
Plastic Mulch Retrieval Best Management
Practices
- Remove all top vegetation: Mowing down the existing
crop to eliminate debris on the plastic. Reel mowers seems
to remove the debris better when compared to rotary types.
Plant debris is difficult to remove in the recycling process
and tends to remain with the plastic causing a " forest fire
smell " and moisture retention, both of which are undesirable
in the recycling process.
- Remove as much soil as possible: Soil adds weight making
transport to the landfill or recycling plant more expensive.
Proper soil conditions for the timing of removal is as
dry a day as possible with a few days of soil drying underneath
the plastic mulch before the retrieval process.
- Keep it dry: Pull film on dry days and keep it under cover.
Water adds weight to the shipment and is the nemesis of the
shredding and prime cleaning operation. Make sure when
bundling that there are no pockets of water in the folds of
the plastic.
- Roll it tight: The bundles should be tight, solid, and no
longer than 24 " long. The tight bundles will allow for more
plastic per load and the bundles will fit better on the conveyors
inbound to the shredder. Loading the conveyor is likely
to be a manual activity so 25 to 50 pounds should be the target
weight of each bundle.
- Consider thicker films: Increasing the film thickness aids
retrieval plus we can get higher plastic recovery rates in the
recycling process. Use 1.5 mil or thicker plastic. Using the
appropriate width of plastic on the bed so that no more than
6 " of plastic is buried on both sides of the bed reduces the
soil and debris.
36
- Proper retrieval equipment: Adjustments to removal
equipment might be required to optimize debris removal as
well as tightness of bundles.
Row covers
Row covers are used to hasten the maturity of the crop, exclude
certain insect pests, and provide a small degree of frost protection.
There are two main types of row covers: vented clear or translucent
polyethylene and floating row covers. Polyethylene types
are supported by wire hoops placed at regular (5 to 6 ft) intervals.
In addition, plastic can be placed loosely over the plants with or
without wire supports. Floating row covers are porous, lightweight
spunbonded materials placed loosely over the plants.
Floating covers are more applicable to the low-growing vine
crops. Upright plants like tomatoes and peppers have been injured
by abrasion when the floating row cover rubs against the plants or
excess temperatures build-up. Erratic spring temperatures require
intensive management of row covers to avoid blossom shed and
other high-temperature injuries. In particular, clear plastic can
greatly increase air temperatures under the cover on warm sunny
days, resulting in a danger of heat injury to crop plants. Therefore,
vented materials are recommended. Even with vents, clear plastic
has produced heat injury, especially when the plants have filled a
large portion of the air space in the tunnel. This has not been observed
with the translucent materials. Usually, row covers are combined
with plastic mulch.
High Tunnels
High tunnels are unheated, polyethylene-covered structures that
provide a larger degree of frost protection than row covers. A properly
built high tunnel with one or two layers of plastic, should afford
5-8 °F of frost protection. As with row covers, high tunnels require
intensive management to ensure that they are vented properly
when warm spring temperatures can cause excessive heat to build
up in tunnels, resulting in damage to the crop. Tomatoes are commonly
produced in high tunnels as well as a variety of leafy greens
crops, due to the premium prices obtained. Row covers are often
combined with the use of high tunnels and plastic mulch.
High tunnels can provide 3-4 weeks or more of season extension
for spring and fall crops such as tomatoes as well as yearround
production of Cole crops and lettuce. High tunnels can reduce
the incidence of certain diseases and insects due to protection
from rain and changes in light interception, respectively, inside the
tunnel; however, traditional greenhouse pests, such as leaf mold,
aphids, spider mites, and whiteflies may be more prevalent in high
tunnels. In many states, high tunnels are considered a greenhouse
structure for the application of pesticides, which may reduce the
number of chemicals available compared to field production. Be
sure to determine if the pesticides you are applying are acceptable
for use in high tunnels in your state.
Extensive information regarding construction, specifics of
crop production, soil management, and economics of production
for many fruits, vegetable, and cut flowers grown in high tunnels
can be found at http://www.hightunnels.org/.
2021 Vegetable Crop Handbook for Southeastern United States
http://www.hightunnels.org/
Southeastern U.S. Vegetable Crop Handbook - 2021

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