Articles
Productivity of winter vegetables in high tunnels with single or double plastic covering in the southeastern United States
Article number
1437_44
Pages
343 – 350
Language
English
Abstract
In the southeastern US, cool-season vegetables can grow through winter in high tunnels (HT). Farmers in the region tend to use inflated double plastic covering, hoping for better protection against cold temperatures.
This practice, however, has no research support in the mild Southeast and unavoidably adds extra cost.
This research aimed to test if double plastic covering is necessary for HT in the Southeast.
Conducted in 2019/20 and 2020/21 winters in North Carolina (plant cold hardiness zone 8, with -6.7 to -12.2°C average lowest temperatures), we tested Swiss chard (Beta vulgaris), kale (Brassica oleracea var. sabellica), collard (B. oleracea var. viridis), lettuce (Lactuca sativa) and bok choi (Brassica rapa subsp. chinensis) in six organically-managed HT, with which three had double-layer cover and another three had single-layer cover.
Each species had three cultivars.
All vegetables thrived in HT during winter.
There were no significant differences in HT with single or double covering in terms of harvest time and marketable yield for all vegetable species.
For example, collard produced 26.4/23.3, Swiss chard 21.2/18.6 and kale 18.3/18.1 leaves plant‑1, bok choi yielded 19.1/20.1 kg plot‑1, and lettuce weighed 105.7/92.4 g head‑1, in HT of single/double covering, respectively.
Double-layer covering had less solar radiation than single covering (306.2 vs. 333.6 W m‑2), resulting in lower daily light integral (55.9 vs. 58.8 mol m‑2 d‑1) but slightly higher lowest temperatures (-4.4 vs. -6.2°C) due to better insulation.
The growing degree days at 4.4°C were similar between HT with single (2109) or double (2195) covering.
Our research suggests that HT in the Southeast can and should use single plastic covering for winter vegetable production.
This practice, however, has no research support in the mild Southeast and unavoidably adds extra cost.
This research aimed to test if double plastic covering is necessary for HT in the Southeast.
Conducted in 2019/20 and 2020/21 winters in North Carolina (plant cold hardiness zone 8, with -6.7 to -12.2°C average lowest temperatures), we tested Swiss chard (Beta vulgaris), kale (Brassica oleracea var. sabellica), collard (B. oleracea var. viridis), lettuce (Lactuca sativa) and bok choi (Brassica rapa subsp. chinensis) in six organically-managed HT, with which three had double-layer cover and another three had single-layer cover.
Each species had three cultivars.
All vegetables thrived in HT during winter.
There were no significant differences in HT with single or double covering in terms of harvest time and marketable yield for all vegetable species.
For example, collard produced 26.4/23.3, Swiss chard 21.2/18.6 and kale 18.3/18.1 leaves plant‑1, bok choi yielded 19.1/20.1 kg plot‑1, and lettuce weighed 105.7/92.4 g head‑1, in HT of single/double covering, respectively.
Double-layer covering had less solar radiation than single covering (306.2 vs. 333.6 W m‑2), resulting in lower daily light integral (55.9 vs. 58.8 mol m‑2 d‑1) but slightly higher lowest temperatures (-4.4 vs. -6.2°C) due to better insulation.
The growing degree days at 4.4°C were similar between HT with single (2109) or double (2195) covering.
Our research suggests that HT in the Southeast can and should use single plastic covering for winter vegetable production.
Publication
Authors
S. Gu
Keywords
cool season vegetables, hoophouse, microclimate, season extension
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