Regulating Temperatures in a High Tunnel Environment

Category: Education

Presentation Description

Horticulture Specialist James Quinn presents on temperature regulations of high tunnel systems on January 28, 2013.


Presentation Transcript

Regulating Temperatures in a High Tunnel Environment:

Regulating Temperatures in a High Tunnel Environment By James Quinn Regional Horticulture Specialist East Central Region- MU Extension 2436 Tanner Bridge Road Jefferson City 65101 573-634-2824

Side ventilation is essential in Missouri:

Side ventilation is essential in Missouri Roll up sides Drop down sides Drop down sides have a number of advantages. They do take more materials. Cannot use a single sheet of plastic for ‘ground to ground’ cover

PowerPoint Presentation:

60” HIGH SIDEWALLS Bigger is Better!

Ventilation Basics:

Ventilation Basics It heats up quicker than you’d think, especially if sunny One vent open ‘downwind’ is good for when for less cooling Both sides open for greater cooling A breeze makes a big difference Get a thermometer! A max/min is quite helpful

Ventilation Basics- continued :

Ventilation Basics- continued Try and keep crop within its preferred growing temperatures Can push a little warmer at beginning and end of day For variable weather periods (e.g. April) one may have to adjust 3 times per day!

PowerPoint Presentation:

Barn curtains used for side walls: Roll-up crank

Ventilation and row covers:

Ventilation and row covers Row covers can be taken off or left on during venting Be conscious of the temperature ‘under’ the row cover if left on, about 5 F warmer Usually not held down, so wind may blow off

Ventilation and humidity control:

Ventilation and humidity control More plant vegetation will increase condensation- look up Higher humidity increases diseases Venting during some cloudy and rainy weather may be necessary to reduce Observe how long dew takes to evaporate Humidity is higher under row covers

Ventilation as the season progresses:

Ventilation as the season progresses Leave the sides open all the time Open up the end walls Add shade cloth A 50% shade cloth will improve quality of tomatoes and NOT reduce yield. Typically used from end of May/early June until early to mid Sept.

Peak ventilation is good:

Peak ventilation is good Relieves the heat out of the peak, if small Creates a ‘chimney’ effect if large; this is very helpful during stagnant weather Full ridge vents are the ‘deluxe’, but are a substantial added expense and complication to install

Cold weather & cold spells:

Cold weather & cold spells Frost damaged tomatoes can recover quickly Temporary heat can come to the ‘rescue’ in extreme situations Lettuce, salad greens and spinach can survive a LOT if protected with low tunnels inside a high tunnel


Summary Get started Consider an automated drop down curtain if you can’t tend your tunnel sufficiently There’s lots of hit and miss advice for regulating the temperature Highly variable and dependent on a grower’s specific situation

Climatic Factors--Outside:

Climatic Factors--Outside Air Temperatures Soil Temperatures Sun light Wind

Air Temperature Profile (Versailles, 2008):

Air Temperature Profile (Versailles, 2008)

Radiation Profile at Versailles (2008):

Radiation Profile at Versailles (2008)

Changes in light over a year:

Changes in light over a year Courtesy of Dr. Robert Anderson, University of Kentucky, Department of Horticulture

Tomato Production Overview:

Tomato Production Overview Planning Take a soil test Determine spacing- 2 ft by 4 ft is popular Transplants take about 5 to 7 weeks in optimum conditions; place order or grow them. What variety? Work up soil Order & pick up supplies Most good field varieties will work just fine* * To grow a determinate or indeterminate? The determinate ‘system’ is easier

Tomato Production Overview:

Tomato Production Overview Preparation Add required fertilizer (if using) Apply compost at 300 to 400 LBS per 1,000 sq ft* Make raised beds and apply drip tape & plastic mulch 1 week in advance Warm up environment Harden off transplants * Assumes 2% N compost

Tomato Production Overview:

Tomato Production Overview Planting (about 3/22) Irrigate before planting After planting, water with dilute fertilizer solution Irrigate thru drip system when needed Put up wire hoops and cover with row cover, if using Ventilate as needed Ideal soil temperature for transplanting tomatoes is 60 °F at the 2-3” dept h.

Supplemental heat for an earlier start very popular with many growers:

Supplemental heat for an earlier start very popular with many growers Set plants in February Many are training on a string (Trust, Big Beef, & Goliath are common varieties) Need to pay attention to foliar diseases and pollination Proper ventilation is critical Note strings Heat source can be as simple as a radiant furnace

Tomato Production Overview:

Tomato Production Overview Up until flowering Put up wire hoops and cover with row cover, if using, until training is required Train with appropriate system- ‘stake & weave’, cage, or string & clip Irrigate when needed Ventilate as needed Establish fertilization schedule Sucker prune Row covers can be left unused but handy in case they are needed

Tomato Production Overview:

Tomato Production Overview Flowering until picking Continue training Ventilate to facilitate pollination Consider fruit thinning to 4 per cluster Eventually will be able to leave vented all the time (about mid-May) Leave vents open if it stays above 60F overnight

Tomato Production Overview:

Tomato Production Overview Picking & thereafter Continue training Pick, irrigate and fertilize Consider fruit thinning to 4 per cluster Ventilate as needed Prune out lower foliage to improve airflow Keep environment as sanitary as possible (e.g. weed free) Typical yields? Modest- 10 lbs/plant Good job- 15 lbs/plant Top notch!- 20 lbs/plant

Tomato Production Overview:

Tomato Production Overview The END! Keep them going thru the fall? It’s profitable Or rip out and start over? Turn off water, dry ‘ em ’ up and deal with it later (when it cools off) Put in a cover crop Or a fall crop? Or another crop of tomatoes? Cover crop is a mix of buckwheat, oats & soybeans

Two tomato revenue examples:

Two tomato revenue examples ‘By the book’ (from 2004) 170 plants per 1,000 sq ft Mid yield- 10 lb/plant Mid price- $2 per lb Mid gross revenue- $10,200 Production costs- $3,000 Fixed costs- $1,000 a year, given only a single crop of tomatoes grown. Assumes 10 year life on structure. 2009 real world Put up a 3,000 sq ft tunnel Sold all product at the Clark Produce Auction Gross revenue about $12,000 Structure about $6,000 All other supplies about $2000 to $3000 Typical price range per pound- $0.75 to $2.50 Average- $1.50 to $2

A comprehensive resource:

A comprehensive resource Addresses Site selection Production- including fertility, varieties and temperature management Economics Marketing Pest control Harvest and handling

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