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Extending the Growing Season With the Use of Plastic Mulch

Steve Poppe

Extend the Growing Season With the Use of Plastic Mulch Topic Areas

• Review our past and current research

• How to extend the growing season

• Water conservation

• Weed reduction

• Different colored mulches

• Instructions for laying plastic mulch

• Biodegradable mulches

• How plastic mulch can save time for the busy gardener

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Strawberries in MN

• Short harvest season of 3‐weeks mid‐June to early July

• Inclement weather during harvest has significant impact

• Extending the season would alleviate many of these issues 

Extend the harvest season thus increasing:

• Fruit available during a non‐traditional time

• Financial stability 

• Supply of locally produced organic strawberries

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Why plasticulture? • Allowed under organic

certification

• Significantly reduces labor for weeding

• Allows for drip irrigation thus reducing water use

• Reduced incidence of diseases

• Reduce some insect pests

• Plastic recycling available?

Why low tunnels?• Allows for flowers and fruit

to remain dry reducing diseases

• Reduces fruit damage from weather events e.g. hail

• Newer systems easy to install

Day-neutrals + low tunnels can extend harvest from 3 weeks to 3½ months!

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Dubois Retractable Tunnel System Advantages

• Wind resistant

• Fast/simple to install as compared to our original system

• Less costly than original system

Concerns

• Slight tearing of hoop plastic

• Original system provided better heat retention in October

• Sides tend to roll down

www.duboisag.com

Tunnel flex‐retractable low tunnel system

50’ kit  $270.00

Albion Monterey Portola Seascape

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New Promising Day-neutral Variety

• Cabrillo from Planasa

• www.planasa.us

• Harvested about 3 weeks later than other varieties

• Continued strong harvest until Oct. 2nd

• Excellent uniform size and appearance, good flavor and held up well under refrigerated storage

• In a non-replicated trial - largest individual fruit size – 16.623 grams per individual fruit

Average Yields

Combined Low Tunnel YieldsMonterey: 20,224 lbs/acre/year

Albion: 18,240 lbs/acre/yearPortola: 23,985 lbs/acre/year

Seascape: 17,829 lbs/acre/year

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Mini Tunnels – Spotted Wing Drosophila in Raspberries

How to Extend the Growing Season

• Plastics, row covers and tunnels can speed up crop development and allow you to harvest earlier

• These systems raise soil temperatures and/or daytime air temperatures around the plant

• Has the potential for increased yields

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High Tunnel Raspberries

Drip Irrigation

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Drip Tape

Advantages of Drip Irrigation

• May require less than half of the water needed for sprinkler irrigation

• Disease pressure may be less because plant foliage remains dry

• Extensive automation is possible

• Water applications are made directly to the plant root zone

• No water splashing so cleaner product

• Harvesting, can continue during irrigation because the areas between rows remain dry

• Fertilizers can be applied efficiently through the drip system

• Compared to sprinkler irrigation, soil erosion can be reduced

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Disadvantages and Limitations of Drip Irrigation

• Initial investment costs may be higher than those of other irrigation options

• Rodent, insect, and human damage to drip lines are potential sources of leaks

• Water filtration is necessary to prevent clogging of the small emitter holes

• Compared to sprinkler irrigation, water distribution in the soil is restricted

Weed Reduction with Plastic Mulch

• Black Plastic will be most effective at weed reduction

• Can increase soil temp about 5 °F

• Clear plastic mulch-weeds can grow and flourish

• If hot and sunny it will solarize the weeds

• Will increase soil temp by as much as 14°F

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Plastic Mulch Advantages/Disadvantges

Advantages

• Reduced soil compaction

• Reduced fertilizer leaching

• Reduced drowning of crops

Disadvantages

• Possibly costly to remove

• Greater initial costs

• Increased moisture management

• Increased soil erosion between plastic-picture

• Weeds in holes close to crop-picture

Living Mulch in-between Rows

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Different Colored Mulches

Consider for:• Transplanted

vegetables• Clear has the highest

soil warming capacity-controls most weeds except for purslane

• Black doesn’t warm the soil as rapidly as clear

Clear Plastic Mulch

White on Black Plastic

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Low Tunnel Hoops

• Not only exclude rain, but can decrease the amount of ultraviolet light and infrared radiation

• This can reduce fungal spore germination as well as heat load on plants

• Also provide some protection from cold temperatures allowing for harvest well into October

Low Tunnel and Non-low Tunnel Temperatures

2016 Average Temperature at WCROC

Low Tunnel 62.6 F

Non-low Tunnel 60.8 F

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Red Plastic Mulch

Red Plastic Mulch for Tomatoes

• Has shown to increase yields up to 20%

• May not in the short MN growing season

• Reflects certain red shades of light back into the plant, accelerating fruit production

For best results …

• Allow several feet of the red showing on either side of the plant or row

• Use determinate tomato

• To obtain the maximum benefit of red mulch, tomato plants must be staked or trellised so that incoming sunlight can reach mulch and be reflected onto the plant

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Floating Row Covers

Floating Row Covers

• Fabrics laid directly on top of plants to protect against cold and insects

• Synthetic fabrics that are spun-bonded with varying degrees of light transmission

• Many different weights of row cover

• Allow rain to flow through them

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Floating Row Covers

• Lay down row cover over the row after planting

• Allow some slack so the plants have room to grow

• If the fabric comes loose in the wind, it can harm young plants

• Most gardeners use row covers for a month or less

• Plants that require insect pollination remove the cover once the plants start to bloom

• With care row cover can last more than one season

Green or Olive Wavelength-sensitive Plastic

• Usually green and somewhat transparent

• Prevents weeds similar to black plastic, but warms the soil as well as clear plastic

• Less common and more expensive

• Has increased yields of melons and squash-much earlier harvest

• Soil under green may become excessively hot as summer progresses

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Instructions for laying plastic mulch

• Put plastic in place one to two weeks before planting

• Make sure the soil is moist

• You may want to form raised beds

• Choose a calm day

• Lay the plastic in the heat of the day-mulch will shrink as temperatures drop

• Install drip tube irrigation

Instructions for laying plastic mulch

• Rain that falls on the soil not covered by plastic may move laterally and supply your plants with water or plan to water your plants at the holes

• Pull plastic as taut as possible and weigh the edges down with soil

• Smooth the soil evenly in the bed

• Plastic absorbs the sun’s energy and conducts to the soil touching the plastic

• If there are air pockets under the mulch, the plastic will not transfer heat

• Cut or burn planting holes in the plastic.

• Plant transplants or seeds through the holes

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Bio360 Biodegradable Mulch

Stated from the manufacturer’s website:

• Made of Mater-Bi®, a plastic that is completely biodegradable and compostable

• Temperature, humidity, and microorganisms in the ground transform Bio360 into water, carbon dioxide, and biomass

• No toxic residue left

Our Experiences:

• Had same mechanical and physical characteristics as white-on-black

• Installed on a 6” raised bed with a mulch machine

• Visibly, it didn’t have quite as tight a fit as white-on-black

• Without a tight fit, strawberry transplants initially appeared to have a more difficult time growing through the slit/opening

Bio360 Biodegradable Mulch

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Bio360 Biodegradable Mulch

• Starts to break-down near the end of the growing season

• Provided sufficient weed suppression in the plant row

• Breaks down along the edge, exposing the soil bed

• Creates a problem – as rain or water hits the exposed soil, it splashes onto the plants and fruit

• Not seeing this issue on the comparison white-on-black

Problems with Plastic Mulch

• Soil underneath plastic mulch is not as good a habitat for soil-dwelling organisms as soil under organic mulch such as composted leaves or straw

• Petroleum is a component of plastic mulch, so you must throw your plastic mulch away at the end of the season

• Biodegradable mulch solve some of these problems, but does not bring all the benefits of plastic mulch

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Solarization Technique

• Use sheets of clear plastic mulch to cover the soil and trap solar energy

• Intense heat and sunlight are required for effective solarization

• Moist soil conducts heat better than dry soil

• Minimum of 8 weeks or more is needed for effective control of weeds

• Length of solarizationdetermines the degree of weed seed depletion

Low Tunnel Installation Instructions

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Raised Beds

• 14” between rows, and 12”between plants staggered

• Wooden plant stake at the tip of the roots and insert the transplant

Raised Beds with Low Tunnels

Use pipe to anchor plastic hoop at the beginning and end of each row

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Raised Beds with Low Tunnels

Raised Beds with Low Tunnels

1.5 mil clear film roll

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Raised Beds with Low Tunnels

Thank you for Attending

Steven R. Poppe

University of Minnesota

West Central Research and Outreach Center

Horticulture Scientist

poppesr@umn.edu

320-589-1711 Ext. 2121http://wcroc.cfans.umn.edu

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