Microclimate Modification with Plasticulture

 
 
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 Plastic mulches | Mini tunnels and floating row covers | Some suppliers of plastic mulch, tunnel and row cover material

The climate of the Canadian Prairies can make the production of warm season vegetable crops difficult. Early season soil and air temperatures are cool, slowing plant growth. This places limitations on growers, restricting them to varieties that will mature in a shorter time period. This results in a trade-off in overall quality and yield.

It is essentially impossible to modify a climatic area, other than by placing the whole growing system under cover. The modification of the environment around the roots and shoots of developing seedlings (microclimate) can extend the growing season slightly and provide many benefits, both in terms of yields and quality. Microclimate modification can be accomplished through the use of plastic mulches, mini-tunnels or floating row covers. Warm season crops respond the best to these practices.

Plastic Mulches

Plastic mulches are laid on a prepared soil surface that is free from trash and anchored using the weight of the soil on the edges. Mulch should be laid tightly, to ensure good heat transfer and prevent flapping and movement in the wind. Movement may cause the plastic to tear, eliminating the benefits. Plastic mulches are often used in conjunction with drip irrigation.


Photo Credit: Agricultural Research Institute of Northern Ireland.
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Photo Credit: Lane-Ag Center Lane, Oklahoma
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Physical Benefits of Plastic Mulch
  • Increased soil temperatures (degree depends on mulch type)
  • Reduced levels of weeds (depending on mulch type)
  • Reduction in contact with soil and decay organisms
  • Conserve soil moisture (less evaporation)
Disadvantages of Plastic Mulch
  • Plastic must be removed and disposed of
  • Greater initial costs
  • An increased level of management is required
Plastic mulches come in a variety of colours, with a range of qualities for each type. Common colours include:
Black plastic -does not increase soil temperature much (compared to bare soil) but provides excellent weed control. Black plastic is inexpensive.
Clear plastic - transmits light energy while preventing re-radiation, essentially forming a greenhouse above the soil. Clear plastic is inexpensive and can increase soil temperatures by 6-10C. Clear plastic does not provide any weed control unless used with a herbicide.
IRT or wavelength selective plastic - provides a compromise between clear and black plastic, for an additional cost. This plastic transmits only non-photosynthetic wavelengths of light, therefore providing weed control and an intermediate increase in soil temperature (4-6C).
Coloured plastics (red, silver, white, blue, etc.) - can have a variety of effects, ranging from improved fruit ripening, reduced soil temperature, weed control, insect management

Other Benefits of Mulches
  • Increased soil temperatures improves early season plant establishment
  • Increased soil temperatures accelerates early season plant growth, translating into earlier crop maturity and increased returns
  • Weed control reduces competition for water and nutrients
  • Increased plant vigour translates into increased final yields
  • U of Saskatchewan trials observed melon yield increases of up to 73% compared to bare soil controls.
  • The use of coloured mulches may improve fruit yield and quality of some vegetable crops, although results are variable
Mini Tunnels and Floating Row Covers

Mini tunnels involve the placement of plastic or spun-bonded fabric sheets on metal hoops over the developing crop, resulting in a mini-greenhouse effect. Plastic is usually clear and may be solid or perforated. This cover is left on for 3-4 weeks, depending on the crop. Mini tunnels are often used in conjunction with plastic mulches and drip irrigation.


Photo Credit: le cabanon

Benefits of Mini tunnels

  • Increased daytime air temperatures can enhance the growth rates of crops
  • Perforated covers can reduce the level of manual labour required for ventilation, but do not hold temperatures for as long as solid plastic
  • Covers can protect crops from insect pests
  • Spun-bonded fabric will allow passage of rain and irrigation
Disadvantages of Mini tunnels
  • High daytime temperatures in the spring can result in excessively high tunnel temperatures, impacting flower development and plant survival
  • Labour intensive to install
  • May require a lot of labour to ventilate
  • Can form a barrier to pollinating insects &/or precipitation (solid plastic)
Floating Row Covers are very large sheets of spun-bonded fabric (range of thicknesses available) that “float” over or lie on the developing crop. The material is anchored on the edges with soil, sandbags or rocks. Crops may be direct seeded or transplanted.


Photo Credit: Gathering Together Farm: September 17, 2002 Weekly Newsletter

Benefits of Floating Row Covers

  • Do not impede seedling emergence while increasing plant growth through soil and air temperature increases
  • Rain or irrigation can pass through the fabric freely
  • Finer weaves can prevent entry of some insect pests
  • Can provide some frost protection in the fall and spring
Disadvantages of Floating Row Covers
  • Movement in wind can damage some crops
  • High winds can be problematic
  • Cover must be removed to allow entry of pollinating insects = lots of labour
  • Can delay early fruit set in some crops (e.g. tomatoes)
  • Weed growth can be extensive
Some Suppliers of Plastic Mulch, Tunnel & Row Cover Material

Westgro Horticultural Supply Inc.
1557 Hastings Cresent S.E.
Calgary, AB T2G 4C8
Toll Free: 800-661-2991 Fax: 403-243-7470

The Professional Gardener Co. Ltd.
915-23 Ave S.E.
Calgary, AB T2G 1P1
Phone: 403-263-4200 Toll Free /Fax: 866-783-4038

Mechanical Transplanter Co.
1150 Central Ave.
Holland, MI 49423
Phone: 616-396-8738 Toll Free: 800-757-5268 Fax: 616-396-3619

Plastitech Inc.
478 Notre-Dame, C.P. 750
St-Remi, Quebec J0L 2L0
Toll Free: 800-667-6279 Fax: 877-667-1584

Pliant Corp.
1515 Woodfield Rd. Suite 600
Schaumburg, IL 60173
Toll Free: 866-878-6188

Rochelle Plastic Film
P.O. Box 606
Rochelle, IL 61068
Toll Free: 866-439-6121

Climagro Mulch Film
LECO Industries
3235 Sartelon
St-Laurent, Quebec H4R 1E9
Phone: 800-561-8029 Fax: 514-332-0406

Ken-Bar Inc.
25 Walkers Brook Drive
Reading, MA 01867-0704
Phone: 781-944-0003 Toll Free: 800-336-8882 Fax: 781-944-1055

Mulch Film

** This is not a comprehensive list of suppliers and does not represent any endorsement of any particular company **

References / Additional Resources:

Vegetable Cultivar and Cultural Trials 1996, 1997, 1998”, D. Waterer & J. Bantle, University of Saskatchewan, Dept. of Horticulture Science
Centre for Plasticulture – Penn State
American Society for Plasticulture

Prepared by Robert Spencer, Ag-Info Centre, Alberta Agriculture and Rural Development
 
 
 
 
For more information about the content of this document, contact the Ag-Info Centre.
This information published to the web on March 12, 2004.
Last Reviewed/Revised on November 26, 2013.