Abstract
For five years experiments were performed in which lettuce (Lactuca sativa capitata L.) was grown in recirculating nutrient solutions. Both in winter and in summer, ammonium/ nitrate ratios and total nitrogen concentration were varied so as to lower the nitrate content of the lettuce heads. Fresh weight of the heads was mainly determined by global radiation during growth. In winter, when light was poor, the nitrate concentration of lettuce was considerably higher than in summer. Nitrate accumulation by lettuce was reduced when 20% of the total nitrogen in the solution, present as N03-N, was replaced by NH4-N. A further increase in the amount of NH4 in the nutrient solution a few weeks before harvest decreased the nitrate concentration of lettuce even more, while fresh weight of the heads was unaffected. Temporarily omitting all nitrogen resulted in the lowest nitrate concentrations, but also in a sharp decrease in fresh weight. When the N concentration of the solution was decreased in winter from 10 to 2.5 mmol I“1, growth and the nitrate concentration of lettuce were scarcely affected. In spring and summer, however, growth was severely reduced, while the nitrate concentration of the heads decreased. Addition of chloride decreased the nitrate concentration of lettuce only when NH4 was present in the nutrient solutions. With a view to minimizing energy consumption, the effect of a simultaneous increase in temperature of the nutrient solutions and a decrease in temperature of the glasshouse air on the growth and nitrate concentration of lettuce was investigated. Raising the temperature of the nutrient solution and lowering the air temperature resulted in better growth, but increasd the nitrate concentration of the lettuce, partially nullifying the effect of ammonium in the nutrient solution.
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Claims 14
Claim · model-written summary
Head fresh weight was mainly determined by global radiation.
- Taxon
- lettuce
Lactuca sativae1 - Outcome
- Fresh weight of the headse0
- Setting
- global radiation during growthe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Fresh weight of the heads was mainly determined by global radiation during growth”
e1“lettuce (Lactuca sativa capitata L.)”
Claim · model-written summary
Lettuce nitrate concentration was higher in winter than summer.
- Taxon
- lettuceLactuca sativae0
- Outcome
- nitrate concentration of lettucee0
- Direction
- highere0
- Comparator
- summere0
- Setting
- wintere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In winter, when light was poor, the nitrate concentration of lettuce was considerably higher than in summer”
Claim · model-written summary
Replacing 20% of solution nitrate nitrogen with ammonium nitrogen reduced lettuce nitrate accumulation.
- Taxon
- lettuceLactuca sativae0
- Treatment
- 20% of the total nitrogen in the solution, present as N03-N, was replaced by NH4-Ne0
- Outcome
- Nitrate accumulation by lettucee0
- Direction
- reducede0
- Comparator
- N03-Ne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrate accumulation by lettuce was reduced when 20% of the total nitrogen in the solution, present as N03-N, was replaced by NH4-N”
Claim · model-written summary
Increasing ammonium before harvest further decreased lettuce nitrate concentration.
- Taxon
- lettuceLactuca sativae0
- Treatment
- further increase in the amount of NH4 in the nutrient solution a few weeks before harveste0
- Outcome
- nitrate concentration of lettucee0
- Direction
- decreasede0
- Comparator
- 20% of the total nitrogene1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A further increase in the amount of NH4 in the nutrient solution a few weeks before harvest decreased the nitrate concentration of lettuce even more, while fresh weight of the heads was unaffected”
e1“20% of the total nitrogen”
Claim · model-written summary
Increasing ammonium before harvest left head fresh weight unaffected.
- Taxon
- lettuceLactuca sativae0
- Treatment
- further increase in the amount of NH4 in the nutrient solution a few weeks before harveste0
- Outcome
- fresh weight of the headse0
- Direction
- unaffectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A further increase in the amount of NH4 in the nutrient solution a few weeks before harvest decreased the nitrate concentration of lettuce even more, while fresh weight of the heads was unaffected”
Claim · model-written summary
Temporarily omitting all nitrogen yielded the lowest nitrate concentrations.
- Taxon
- lettuceLactuca sativae1
- Treatment
- Temporarily omitting all nitrogene0
- Outcome
- nitrate concentrationse0
- Direction
- loweste0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Temporarily omitting all nitrogen resulted in the lowest nitrate concentrations, but also in a sharp decrease in fresh weight”
e1“lettuce (Lactuca sativa capitata L.)”
Claim · model-written summary
Temporarily omitting all nitrogen sharply reduced head fresh weight.
- Taxon
- lettuceLactuca sativae1
- Treatment
- Temporarily omitting all nitrogene0
- Outcome
- fresh weighte0
- Direction
- sharp decreasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Temporarily omitting all nitrogen resulted in the lowest nitrate concentrations, but also in a sharp decrease in fresh weight”
e1“lettuce (Lactuca sativa capitata L.)”
Claim · model-written summary
Reducing solution nitrogen from 10 to 2.5 mmol I“1 scarcely affected winter growth.
- Taxon
- lettuceLactuca sativae0
- Treatment
- N concentration of the solution was decreased in winter from 10 to 2.5 mmol I“1e0
- Outcome
- growthe0
- Direction
- scarcely affectede0
- Comparator
- 10e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When the N concentration of the solution was decreased in winter from 10 to 2.5 mmol I“1, growth and the nitrate concentration of lettuce were scarcely affected”
Claim · model-written summary
Reducing solution nitrogen from 10 to 2.5 mmol I“1 scarcely affected winter lettuce nitrate concentration.
- Taxon
- lettuceLactuca sativae0
- Treatment
- N concentration of the solution was decreased in winter from 10 to 2.5 mmol I“1e0
- Outcome
- nitrate concentration of lettucee0
- Direction
- scarcely affectede0
- Comparator
- 10e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When the N concentration of the solution was decreased in winter from 10 to 2.5 mmol I“1, growth and the nitrate concentration of lettuce were scarcely affected”
Claim · model-written summary
The same nitrogen reduction severely reduced growth in spring and summer.
- Taxon
- lettuceLactuca sativae1
- Treatment
- N concentration of the solution was decreasede2
- Outcome
- growthe0
- Direction
- severely reducede0
- Setting
- spring and summere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In spring and summer, however, growth was severely reduced, while the nitrate concentration of the heads decreased”
e1“lettuce (Lactuca sativa capitata L.)”
e2“N concentration of the solution was decreased”
Claim · model-written summary
The same nitrogen reduction decreased head nitrate concentration in spring and summer.
- Taxon
- lettuceLactuca sativae1
- Treatment
- N concentration of the solution was decreasede2
- Outcome
- nitrate concentration of the headse0
- Direction
- decreasede0
- Setting
- spring and summere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In spring and summer, however, growth was severely reduced, while the nitrate concentration of the heads decreased”
e1“lettuce (Lactuca sativa capitata L.)”
e2“N concentration of the solution was decreased”
Claim · model-written summary
Chloride addition decreased lettuce nitrate concentration only when ammonium was in solution.
- Taxon
- lettuceLactuca sativae0
- Treatment
- Addition of chloridee0
- Outcome
- nitrate concentration of lettucee0
- Direction
- decreasede0
- Qualifier
- only when NH4 was present in the nutrient solutionse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Addition of chloride decreased the nitrate concentration of lettuce only when NH4 was present in the nutrient solutions”
Claim · model-written summary
Warmer nutrient solution and cooler glasshouse air improved lettuce growth.
- Taxon
- lettuceLactuca sativae0
- Treatment
- Raising the temperature of the nutrient solution and lowering the air temperaturee0
- Outcome
- growthe0
- Direction
- bettere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Raising the temperature of the nutrient solution and lowering the air temperature resulted in better growth, but increasd the nitrate concentration of the lettuce”
Claim · model-written summary
Warmer nutrient solution and cooler glasshouse air increased lettuce nitrate concentration.
- Taxon
- lettuceLactuca sativae0
- Treatment
- Raising the temperature of the nutrient solution and lowering the air temperaturee0
- Outcome
- nitrate concentration of the lettucee0
- Direction
- increasde0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Raising the temperature of the nutrient solution and lowering the air temperature resulted in better growth, but increasd the nitrate concentration of the lettuce”
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- no effect
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This paper is about lacking the nutrient, so it counts the other way round here.
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See all 248 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.