Winter Broccoli and Cauliflower under Organic High Tunnels in a Humid, Subtropical Climate

Abstract

Abstract. There is a lack of information related to adapting high tunnel systems to humid, subtropical climates in the Southeastern United States, resulting in a disadvantage for their use to extend growing seasons and meet the increasing demand for local horticulture products. This research project explored the possibility of growing organic broccoli and cauliflower (Brassica oleracea L.) under high tunnels during two consecutive fall/winter seasons in northeast Georgia (USDA plant hardiness zone 8a), particularly evaluating questions related to crop feasibility, planting dates and cultivar choices. Marketable yields for high tunnel broccoli ranged from ' '11,800 to 15,800 kg · ha L1 and were not consistently affected by either planting date or cultivar type. Broccoli required an additional 8-45 days to reach maturity compared with seed catalog estimates with harvesting occurring during mid-December to mid-January. Marketable yields for high tunnel cauliflower ranged from ' '8600 to 26,000 kg · ha L1 and were affected primarily by the cultivar type. Cauliflower required an additional 19-56 days to mature with harvesting occurring during the entire month of January. The first season was cooler than the second with the lowest growing degree days (GDD) units accumulated during the months of January and February. Differences in air temperature at the crop canopy between the high tunnel system and open field were largely related to high tunnel ventilation protocols that changed as the season progressed. An average heat gain of 7 to 8 8C under the high tunnels at crop canopy height was documented on the coldest days and an average of 1 8C gain on the warmest days compared with the open field. Overall, winter broccoli appeared more adaptable to high tunnels than cauliflower but production of both crops may be possible if planting dates and cultivar types are taken into account for the region.

Miniature Head Lettuce Yield and Anthocyanin Concentration under High Tunnels and the Field in Georgia

“…In 2015, the mini-lettuce yield (i.e., mean marketable head weight) was similar between the high tunnels and the field, but in 2016, the yield was greater under the high tunnels. Our results are similar to other studies that have found high tunnels can boost yields but that biotic or abiotic variables can affect crop yields in any given year (Jayalath et al, 2017;O'Connell and Tate, 2017;O'Connell et al, 2012;Rho et al, 2020;Wallace et al, 2012). It is unclear why the high tunnel system had yield increases in 2016, while overall the field system had yield decreases compared with 2015.…”

Impact of Shade and Fogging on High Tunnel Production and Mineral Content of Organically Grown Lettuce, Basil, and Arugula in Georgia

“…In is also noteworthy that the non-shaded high tunnel had a reduction in PPFD of 30.3% compared to outdoor ambient conditions. Other studies have reported similar effects of plastic deterioration on shading in high tunnels [22]. The combination of shading from both plastic and the shade cloth, resulting in a reduction in PPFD of 51% in the shaded high tunnel compared to outdoor conditions.…”

“…Although well documented for use in greenhouses, less information is available evaluating the effectiveness of shade cloth and fogging/misting systems in passively cooled structures such as high tunnels in hot humid climates, such as the Southeastern United States, is limited. Research is needed to develop cultural practices that can be used to mitigate heat stress, which often limits production in regions of the world with similar climates to the Southeastern United States [22]. The objectives of this study were to determine the impact of fogging systems and shade cloth on high tunnel microclimates and growth of fall planted, high tunnel-grown basil, lettuce, and arugula.…”

Spectrophotometric Method for Determination of Nitrite and Nitrate Levels in Broccoli and Cauliflower with Different Fertilization Treatment

“…Broccoli and cauliflower are not native plants in Indonesia, but are widely cultivated and widely consumed by people in Indonesia. Broccoli and cauliflower are harvested at 7 weeks to 8 weeks after planted 5 . Several analytical methods have been discovered for analysis of Nitrite and Nitrate, such as high performance liquid chromatography 6 and spectrophotometric 7 .…”