Abstract
Hydroponics has become a popular production technology for leafy greens in greenhouses. However, year-round production of cool-season leafy greens remains challenging due to costly heating and cooling during winter and summer seasons, depending on location. Therefore, the objective of this study is to investigate the effect of nutrient solution cooling and heating in deep-water hydroponic systems on the performance of several leafy green vegetables. Two experiments of nutrient solution cooling during the summer season and another two experiments of nutrient solution heating during the winter season were conducted in Texas, USA in 2020–2021. Lettuce (Lactuca sativa L.) ‘Bergams Green’ and ‘Red Mist’, Pak Choi (Brassica rapa subsp. chinensis) ‘Purple Magic’ and ‘White Stem’, and spinach (Spinacia oleracea L.) ‘Mandolin’ and ‘Seaside’ were grown in the summer experiments, and only the two lettuce cultivars were grown for the winter experiments. For both cooling and heating studies, six deep-water culture systems were used with two treatments: cooling (23 °C) vs. no cooling, and heating (22 °C) vs. no heating, with three replications in each experiment. In the nutrient solution cooling study, spinach was the most heat-sensitive species, and ‘Mandolin’ was more heat-tolerant than ‘Seaside,’ as evidenced by its lower mortality rate in both experiments. Lettuce and pak choi grew well and solution cooling increased shoot fresh weight in both lettuce cultivars and in ‘White Stem’ pak choi but not in ‘Purple Magic’ pak choi. Conversely, during the winter season, solution heating increased shoot fresh weight of both lettuce cultivars; however, ‘Red Mist’ was more responsive than ‘Bergams Green’ lettuce. These results indicate the potential to increase crop yield by controlling nutrient solution temperature throughout the year, depending on the season. Also, there were genotypic differences in both cooling and heating experiments, indicating that more research is needed to determine the species-dependent and even cultivar-dependent nutrient solution temperature control strategies to achieve optimum year-round production.
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Claims 13
Claim · model-written summary
Spinach was the most heat-sensitive species in summer cooling experiments.
- Taxon
- spinach
Spinacia oleraceae1 - Outcome
- most heat-sensitive speciese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“spinach was the most heat-sensitive species”
e1“spinach (Spinacia oleracea L.)”
Claim · model-written summary
Mandolin spinach had lower mortality than Seaside in both summer experiments.
- Taxon
- spinachSpinacia oleraceae1
- Material
- ‘Mandolin’e0
- Outcome
- mortality ratee0
- Direction
- lowere0
- Qualifier
- both experimentse0
- Comparator
- Seasidee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“‘Mandolin’ was more heat-tolerant than ‘Seaside,’ as evidenced by its lower mortality rate in both experiments.”
e1“spinach (Spinacia oleracea L.)”
Claim · model-written summary
Lettuce grew well during the summer experiments.
- Taxon
- Lettuce
Lactuca sativae1 - Outcome
- grew welle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Lettuce and pak choi grew well”
e1“Lettuce (Lactuca sativa L.)”
Claim · model-written summary
Pak choi grew well during the summer experiments.
Verbatim
e0“Lettuce and pak choi grew well”
e1“Pak Choi (Brassica rapa subsp. chinensis)”
Claim · model-written summary
Cooling increased shoot fresh weight in Bergams Green lettuce.
- Taxon
- LettuceLactuca sativae2
- Material
- ‘Bergams Green’e1
- Treatment
- solution coolinge0
- Outcome
- shoot fresh weighte0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“solution cooling increased shoot fresh weight in both lettuce cultivars”
e1“‘Bergams Green’ and ‘Red Mist’”
e2“Lettuce (Lactuca sativa L.)”
Claim · model-written summary
Cooling increased shoot fresh weight in Red Mist lettuce.
- Taxon
- LettuceLactuca sativae2
- Material
- ‘Red Mist’e1
- Treatment
- solution coolinge0
- Outcome
- shoot fresh weighte0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“solution cooling increased shoot fresh weight in both lettuce cultivars”
e1“‘Bergams Green’ and ‘Red Mist’”
e2“Lettuce (Lactuca sativa L.)”
Claim · model-written summary
Cooling increased shoot fresh weight in White Stem pak choi.
- Taxon
- pak choie0
- Material
- ‘White Stem’e0
- Treatment
- solution coolinge1
- Outcome
- shoot fresh weighte1
- Direction
- increasede1
Not reportedComparator
Verbatim
e0“in ‘White Stem’ pak choi but not in ‘Purple Magic’ pak choi.”
e1“solution cooling increased shoot fresh weight in both lettuce cultivars and in ‘White Stem’ pak choi”
e2“Pak Choi (Brassica rapa subsp. chinensis)”
Claim · model-written summary
Cooling did not increase shoot fresh weight in Purple Magic pak choi.
- Taxon
- pak choie1
- Material
- ‘Purple Magic’e0
- Treatment
- solution coolinge1
- Outcome
- shoot fresh weighte1
- Direction
- but note0
Not reportedComparator
Verbatim
e0“but not in ‘Purple Magic’ pak choi.”
e1“solution cooling increased shoot fresh weight in both lettuce cultivars and in ‘White Stem’ pak choi but not in ‘Purple Magic’ pak choi.”
e2“Pak Choi (Brassica rapa subsp. chinensis)”
Claim · model-written summary
Heating increased shoot fresh weight in Bergams Green lettuce.
- Taxon
- LettuceLactuca sativae2
- Material
- ‘Bergams Green’e1
- Treatment
- solution heatinge0
- Outcome
- shoot fresh weighte0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“solution heating increased shoot fresh weight of both lettuce cultivars”
e1“‘Bergams Green’ and ‘Red Mist’”
e2“Lettuce (Lactuca sativa L.)”
Claim · model-written summary
Heating increased shoot fresh weight in Red Mist lettuce.
- Taxon
- LettuceLactuca sativae2
- Material
- ‘Red Mist’e1
- Treatment
- solution heatinge0
- Outcome
- shoot fresh weighte0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“solution heating increased shoot fresh weight of both lettuce cultivars”
e1“‘Bergams Green’ and ‘Red Mist’”
e2“Lettuce (Lactuca sativa L.)”
Claim · model-written summary
Red Mist lettuce was more responsive to winter heating than Bergams Green.
- Taxon
- LettuceLactuca sativae1
- Material
- ‘Red Mist’e0
- Outcome
- more responsivee0
- Direction
- more responsivee0
- Comparator
- ‘Bergams Green’e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“‘Red Mist’ was more responsive than ‘Bergams Green’ lettuce.”
e1“Lettuce (Lactuca sativa L.)”
Claim · model-written summary
The authors concluded that seasonal control of solution temperature could increase crop yield.
Verbatim
e0“These results indicate the potential to increase crop yield by controlling nutrient solution temperature throughout the year, depending on the season.”
t0“Baby Leafy Vegetables”
Claim · model-written summary
The authors identified species and cultivar differences and called for further work on temperature control strategies.
Verbatim
e0“there were genotypic differences in both cooling and heating experiments, indicating that more research is needed to determine the species-dependent and even cultivar-dependent nutrient solution temperature control strategies to achieve optimum year-round production.”
t0“Baby Leafy Vegetables”
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See all 30 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.