High Tunnel Project (Page 1)

Since 1998 we have been evaluating the potential for using high tunnels to enhance productivity and profitability of producing vegetable crops in Saskatchewan. High tunnels are similar to low tunnels in design and function, except that;

1. one high tunnel covers several rows,
2. the high tunnels are wide enough to allow crop growth to full maturity under the tunnels and
3. the tunnels are tall enough to allow spraying, cultivation and harvesting to occur with the tunnels intact.

Rolling up the sides and/or opening the end doors of the high tunnels provide both ventilation and access to the crop by pollinating insects.

The initial costs of materials and installation of high tunnels are considerably higher than traditional low tunnels. However, the economics of production with high tunnels may still be favourable if;

1. they increase yields,
2. they enhance earliness resulting in greater market access at a time when prices are at a premium,
3. the high tunnels are durable enough to be used for several seasons, thereby amortizing the costs of materials and installation over a greater length of time.

• Visit the High Tunnel Photo Gallery

Below is a collection of articles on high tunnel research written since 1998. The articles are available in HTML or as PDF files.

Yields and Economics of High Tunnels for Production of Warm Season Vegetable Crops PDF

2006 Growing Season PDF
Crops evaluated in 2006 were sequentially planted romaine lettuce and peppers.

2005 Growing Season PDF
Crops evaluated in 2005 were sequentially planted romaine lettuce, broccoli, peppers, cantaloupe, strawberries, and raspberries.

2004 Growing Season PDF
Vegetable crops evaluated in 2004 were cucumber, lettuce, tomato, pepper, muskmelon (cantaloupe), and watermelon.

2003 Growing Season PDF
Vegetable crops evaluated in 2003 were cucumber, tomato, pepper, and muskmelon (cantaloupe).

2002 Growing Season PDF
Vegetable crops evaluated in 2002 were muskmelon (cantaloupe) and pepper.

2001 Growing Season PDF
Vegetable crops evaluated in 2001 were muskmelon (cantaloupe), tomato, and pepper.

2000 Growing Season PDF
Vegetable crops evaluated in 2000 were muskmelon (cantaloupe), tomato, and pepper.

1999 Growing Season PDF
Vegetable crops evaluated in 1999 were muskmelon (cantaloupe), tomato, and pepper.

1998 Growing Season PDF
Vegetable crops evaluated in 1998 were muskmelon (cantaloupe), tomato, and pepper.

Temperature Comparison PDF
Temperature observations from 1998 - 2000 have been analyzed and compared.

Powerpoint Presentation High Tunnel Technology - Taking the Next Step (3.2 MB)
The risks and benefits of high tunnels are discussed High tunnel technology is compared with low tunnels and other crop covering technology.

 

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2006 Growing Season

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In 2006, we looked at the potential to use high tunnels to increase yields and/or quality of romaine lettuce and bell pepper. Performance of plants in the high tunnels was compared to standard production techniques - otherwise similar crop management procedures were used inside and outside the high tunnel. The lettuce crop was harvested at maturity, weighed and graded. Harvesting of the bell peppers continued until the first killing frost.

 

Results

Except for the month of June, temperatures in 2006 were above normal. Heavy rainfall events in June and mid September flooded the plot area. Problems with flooding stress were exacerbated in the high tunnels as the boards at the base of the tunnels kept the flood water from effectively draining away. Flooding compromised the vigour, yield and quality of the test crops both inside and outside the high tunnels. The first killing frost occurred September 19 in the open field. Pepper plants in the high tunnels were also extensively damaged by this frost.

 

Sequential Lettuce Crops

Previous trials had indicated a potential for lettuce production in the high tunnels if problems with crop emergence and overheating could be overcome. In 2005 transplants were used to establish sequential lettuce crops ie; late May - early July, early July to mid-August, mid-August to freeze up. Lettuce in the high tunnels developed more rapidly than the crop under standard field conditions. The 3rd planting under standard field conditions failed to mature prior to killing frost, but the 3rd crop inside the high tunnels was completely harvested by late September. For all three planting dates, yields of both lettuce cultivars from inside the high tunnel were higher than outside - largely because of reduced loss to disease inside the high tunnel. The quality of lettuce from inside the high tunnel was also superior to outside - although the crop inside the high tunnel seemed more susceptible to bolting.

In 2006, the 1st lettuce crop was transplanted out in late May and was ready for harvest by July 5 both inside and outside the high tunnel. Crop health and quality were excellent both inside and outside the high tunnels and the tunnel treatment had no impact on any aspect of yields for the 1st crop. 'Green Forest' had slightly lower yields but better head quality and flavor than 'Conquistador'.

Poor seed germination in the greenhouse delayed the second lettuce planting to August 16th. Wet weather in September followed by frost resulted in no 2nd lettuce harvest.

2005 and 2006 Lettuce yields

	Planting 1 (late May)				Planting 2 (early July)				Planting 3 (late August)
	Green Forest (kg/m2)		Conquistador (kg/m2)		Green Forest (kg/m2)		Conquistador (kg/m2)		Green Forest (kg/m2)		Conquistador (kg/m2)
	2005	2006	2005	2006	2005	2006	2005	2006	2005	2006	2005	2006
High Tunnel	3.9	1.0	3.9	1.1	6.3	n/a	5.8	n/a	2.0	n/a	2.0	n/a
Standard	2.8	1.0	2.5	1.2	4.0	n/a	3.4	n/a	0	n/a	0	n/a

 

 

Peppers

In previous trials, peppers in the high tunnels had appeared to suffer from heat stress resulting in poor vigor and low fruit yields. In 2005, yields of bell peppers (cv. King Arthur and Redstart) in the high tunnels were comparable to peppers covered with a low tunnel until early July - but there were more mature red fruit in the high tunnel than outside.

2005 Pepper yields

	King Arthur			Redstart
	Red (kg/m2)	Mature Green (kg/m2)	Immature (kg/m2)	Red (kg/m2)	Mature Green (kg/m2)	Immature (kg/m2)
High Tunnel	0.1	2.9	0.2	0.3	2.2	0.2
Low Tunnel	0	2.7	0.1	0.1	2.2	0.2

 

In the 2006 trial, the plants in the high tunnels were much larger than those protected with a low tunnel until early July. Yields of mature green fruit of both cultivars tested were substantially greater in the high tunnels than for the standard production system. Yields of mature red fruit of cv. Redstart were also much greater in the high tunnel than outside. ‘Whopper Improved’ produced few mature red fruit irrespective of the production conditions. Grade out rates were similar inside and outside the high tunnels.

2006 Pepper yields

	Whopper Improved			Redstart
	Red (kg/m2)	Mature Green (kg/m2)	Immature (kg/m2)	Red (kg/m2)	Mature Green (kg/m2)	Immature (kg/m2)
High Tunnel	0.05	2.54	0.12	0.91	1.87	0.20
Low Tunnel	0.07	0.52	0.39	0.12	0.54	0.34

 

Conclusion

High tunnels have the potential to accelerate growth of vegetable crops but this does not necessarily result in earlier or higher yields. In previous years problems with overheating have reduced yields of crops like peppers and lettuce in the high tunnel, while pollination and fruit rot have been problematic for melons and tomatoes. The 2006 trials again illustrated the variability in growth and yield responses that occur in the high tunnels. Under near-ideal growing conditions the cool season lettuce crop did not benefit from the high.tunnel environment, but production in the high tunnels enhanced yields and crop value of the warmer season pepper crop.

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2005 Growing Season

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In 2005, we looked at increasing both the diversity of crops tested in the high tunnels and the intensity of production. Performance of plants in the high tunnels was compared to standard production techniques - otherwise similar crop management procedures were used inside and outside the high tunnel. The crops were harvested at maturity, weighed and graded. Harvesting continued until the crop was finished or the first killing frost. The date by which 50% of the crop had matured was calculated as an indicator of the rate of crop development.

 

Results

April through late June of 2005 were fairly cool, but from July onwards temperatures were near normal. Heavy rainfall events in early July and early September flooded (image) the plot area and the soil in the test area remained effectively saturated from July onwards. Problems with flooding stress were exacerbated in the high tunnels as the boards at the base of the tunnels kept the flood water from being effectively draining away. Flooding compromised the vigor, yield and quality of the test crops both inside and outside the high tunnels. The first killing frost occurred September 28 in the open field. Plants in the high tunnels survived through until mid-October but little in the way of yields were obtained after late September.

Sequential Lettuce Crops

Previous trials had indicated a potential for lettuce production in the high tunnels if problems with crop emergence and overheating could be overcome. In 2005 transplants were used to establish the lettuce crops during three different cropping periods. Four week old seedlings of romaine lettuce (cvs Conquistador and Green Forest) were transplanted into the high tunnels on May 26, July 8 and August 23. The crops were planted in twin rows 30 cm apart with 30 cm between plants within a row. The first planting was ready for harvest crop on July 7th both inside and outside the high tunnel. The second planting was harvested on Aug 17th in the high tunnels and 5 days later outside the tunnels. The 3rd planting was harvested on Sept 30 in the high tunnels but failed to mature prior to killing frost outside the tunnels.

For all three planting dates, yields of both lettuce cultivars from inside the high tunnel were higher than outside - largely because of reduced loss to disease inside the high tunnel. The quality of lettuce from inside the high tunnel was also superior to outside - although the crop inside the high tunnel seemed more susceptible to bolting.


	Planting 1 (May 26)		Planting 2 (July 8)		Planting 3 (August 23)
	Green Forest (kg/m2)	Conquistador (kg/m2)	Green Forest (kg/m2)	Conquistador (kg/m2)	Green Forest (kg/m2)	Conquistador (kg/m2)
High Tunnel	3.9	3.9	6.3	5.8	2.0	2.0
Standard	2.8	2.5	4.0	3.4	0	0

 

Broccoli

Three week old broccoli seedlings were transplanted out on May 4th. The crop in the high tunnel got off to a very quick start but -4 to -6C frosts on May 11 and 14 killed some of the plants in both the high tunnel and in the open. All the plants that survived were triggered to bolt, producing very small unmarketable heads.

 

Peppers

In previous trials peppers in the high tunnels had appeared to suffer from heat stress resulting in poor vigor and low fruit yields. In 2005, five week old pepper seedlings (cv. King Arthur and Redstart) were transplanted out on May 30. Plant spacing were very tight (15 cm) within the row to maximize productivity. The rows were 1.5m apart to allow for easy worker access. The crop growing outside the high tunnel was covered with row cover from the time of transplanting through to early July. Pepper plants in the middle rows of the high tunnel were far more vigorous and higher yielding than those at the edges of the tunnel. Overall yields in the high tunnels were comparable to the standard production method - but there were more mature red fruit in the high tunnel than outside.

	King Arthur			Redstart
	Red (kg/m2)	Mature Green (kg/m2)	Immature (kg/m2)	Red (kg/m2)	Mature Green (kg/m2)	Immature (kg/m2)
High Tunnel	0.1	2.9	0.2	0.3	2.2	0.2
Low Tunnel	0	2.7	0.1	0.1	2.2	0.2

 

Cantaloupe

Three week old seedlings of Earligold and Earliqueen melon were transplanted into the high tunnels on May 30. The seedlings were spaced 30 cm apart within the row, with 1.5 m between rows. The crop growing outside the high tunnel was covered with row cover from the time of transplanting through to early July. The melon crop inside the high tunnel was severely damaged by the flooding events - the vines died and the fruit rotted prior top maturity. The melon crop outside the high tunnel was less adversely affected - but the damage delayed maturity to the point where the crop was lost to frost.

 

Strawberry

Day neutral strawberries (cv. Ward 219) were transplanted into the high tunnels on May 6th - with 30 cm between plants in a row and 1.5 m between rows. In previous trials early productivity of day neutral strawberries had been enhanced in the high tunnels, but later in the season, the crop growing outside the high tunnel had more successful runnering and greater vigor with less fruit decay - resulting in substantially higher overall yields. In the 2005 trial, the strawberries in the high tunnel again developed more quickly than outside - with the first harvest occurring July 15. Marketable fruit yields in the high tunnel were 40% higher than outside. The strawberries were less affected by the flooding events than some of the other crops. Runnering was more successful in the high tunnel than in previous years and the incidence of fruit decay was comparable to outside the tunnels.

	Date of 50% harvest	Marketable fruit (g/m2)	Marketable %
High Tunnel	September 5	719	80
Low Tunnel	September 8	441	82

 

Raspberry

High tunnels are widely used in Europe to extend the fruiting season of bush fruit like raspberry. In 2005 rows of both primocane (cv. Red River) and floricane (Red Mammoth) raspberry were established in the high tunnels. Despite careful management, die back following transplanting was quite severe both in the open and in the high tunnel. The raspberry plants in the high tunnels were severely damaged by the flooding events and many will need to be replanted.

 

Conclusion

High tunnels have the potential to accelerate growth of vegetable crops but this does not necessarily result in earlier or higher yields. In previous years problems with overheating have reduced yields of crops like peppers and lettuce in the high tunnel, while pollination and fruit rot have been problematic for melons and tomatoes. The 2005 trials showed that cool season crops could be relay cropped in the high tunnels, providing problems with frost and crop establishment were managed. The high tunnel design and conditions appeared to exacerbate problems with crop health following flooding of the trial area.

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