Abstract
ABSTRACT The objective of this study was to investigate the possibility of predicting the concentrations of total nitrogen (N), nitrate-nitrogen, and ascorbic acid in spinach (Spinacia oleracea) leaves using the pocket chlorophyll meter SPAD-502 (Minolta, Japan) in a pot experiment in a greenhouse. Spinach plants were grown in plastic pots filled with 0.5 kg of brown soil per pot with urea as N fertilizer at 0, 30, 60, 120, and 240 mg N/kg soil. SPAD readings of the two uppermost fully expanded leaves were recorded 18, 25, and 32 d after sowing and at harvesting (34 d). Dry-matter biomass and total N concentrations in leaves and roots, and NO3-N, and ascorbic acid concentrations in leaves, were measured after harvesting. SPAD readings showed continuous reduction with increasing growth period irrespective of N applications. SPAD readings at harvest were significantly correlated with total N, leaf dry weight (DW), and NO3-N concentration. However, this correlation did not exist between SPAD readings and ascorbic acid concentrations in leaves. The above results suggest that it is possible to apply SPAD readings to estimate NO3-N concentrations in spinach plants, and that they may be applied for field assessments in decision-making and operational nutrient-management programs for the plant. Furthermore, the SPAD method may also be useful for ascertaining the harvest time. The results suggest that treatment with 120 mg N/kg significantly improved both leaf yields and leaf quality (i.e., leaf nitrate-N concentration and ascorbic acid). Too little and too much N fertilizer was not good for yield or spinach quality.
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Claims 10
Claim · model-written summary
SPAD readings fell as spinach growth progressed regardless of N application.
- Taxon
- spinach
Spinacia oleraceat0 - Organ / stage
- growth periode0
- Outcome
- SPAD readingse0
- Direction
- reductione0
- Qualifier
- irrespective of N applicationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SPAD readings showed continuous reduction with increasing growth period irrespective of N applications.”
t0“Spinach”
Claim · model-written summary
At harvest, SPAD readings were significantly correlated with total leaf nitrogen.
- Taxon
- spinachSpinacia oleraceat0
- Organ / stage
- leafe0
- Outcome
- total Ne0
- Qualifier
- SPAD readings at harveste0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SPAD readings at harvest were significantly correlated with total N, leaf dry weight (DW), and NO3-N concentration.”
t0“Spinach”
Claim · model-written summary
At harvest, SPAD readings were significantly correlated with leaf dry weight.
- Taxon
- spinachSpinacia oleraceat0
- Organ / stage
- leafe0
- Outcome
- leaf dry weight (DW)e0
- Qualifier
- SPAD readings at harveste0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SPAD readings at harvest were significantly correlated with total N, leaf dry weight (DW), and NO3-N concentration.”
t0“Spinach”
Claim · model-written summary
At harvest, SPAD readings were significantly correlated with nitrate nitrogen concentration.
- Taxon
- spinachSpinacia oleraceat0
- Organ / stage
- leafe0
- Outcome
- NO3-N concentratione0
- Qualifier
- SPAD readings at harveste0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SPAD readings at harvest were significantly correlated with total N, leaf dry weight (DW), and NO3-N concentration.”
t0“Spinach”
Claim · model-written summary
SPAD readings did not correlate with spinach leaf ascorbic acid concentration.
- Taxon
- spinachSpinacia oleraceat0
- Organ / stage
- leavese0
- Outcome
- ascorbic acid concentrationse0
- Qualifier
- SPAD readingse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“However, this correlation did not exist between SPAD readings and ascorbic acid concentrations in leaves.”
t0“Spinach”
Claim · model-written summary
The authors proposed SPAD readings to estimate spinach nitrate nitrogen.
- Taxon
- spinachSpinacia oleraceae0
- Outcome
- estimate NO3-N concentrationse0
- Qualifier
- field assessmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The above results suggest that it is possible to apply SPAD readings to estimate NO3-N concentrations in spinach plants, and that they may be applied for field assessments in decision-making and operational nutrient-management programs for the plant.”
Claim · model-written summary
The authors proposed SPAD readings as a guide to harvest timing.
- Taxon
- spinachSpinacia oleraceat0
- Outcome
- ascertaining the harvest timee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Furthermore, the SPAD method may also be useful for ascertaining the harvest time.”
t0“Spinach”
Claim · model-written summary
Treatment with 120 mg N/kg significantly improved spinach leaf yield.
- Taxon
- spinachSpinacia oleraceat0
- Treatment
- 120 mg N/kge0
- Outcome
- leaf yieldse0
- Direction
- improvede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The results suggest that treatment with 120 mg N/kg significantly improved both leaf yields and leaf quality (i.e., leaf nitrate-N concentration and ascorbic acid).”
t0“Spinach”
Claim · model-written summary
Treatment with 120 mg N/kg significantly improved spinach leaf nitrate nitrogen concentration and ascorbic acid quality.
- Taxon
- spinachSpinacia oleraceat0
- Treatment
- 120 mg N/kge0
- Outcome
- leaf nitrate-N concentration and ascorbic acide0
- Direction
- improvede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The results suggest that treatment with 120 mg N/kg significantly improved both leaf yields and leaf quality (i.e., leaf nitrate-N concentration and ascorbic acid).”
t0“Spinach”
Claim · model-written summary
Both insufficient and excessive nitrogen fertilizer were unfavorable for spinach yield and quality.
- Taxon
- spinachSpinacia oleraceae0
- Outcome
- yield or spinach qualitye0
- Qualifier
- Too little and too much N fertilizere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Too little and too much N fertilizer was not good for yield or spinach quality.”
The same questions in other papers
nitrogen · yield · Spinacia oleracea (spinach)Results differ
37 papers in the same direction as this paper · 4 in the opposite direction · 1 reporting no difference from an alternative
- no effect
- negative
- no effect
39 papers more in this group
See all 43 papers →nitrogen · quality: phytochemicals · Spinacia oleracea (spinach)Positive and negative results
5 papers in the same direction as this paper · 6 in the opposite direction · 1 reporting no difference from an alternative
- negative
- no effect
- negative
9 papers more in this group
See all 13 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.