Abstract
To evaluate the influence of reducible iron (Fe) on the availability of silicon (Si) by rice (Oryza sativa L.), (1) relationships between the available Si content in soil (successive water elution method), the Si content in rice shoots and ears, and the levels of oxalate-extractable Si (Sio), Fe (Feo), and aluminum (Alo) in 13 paddy soils were analyzed; and (2) the Si concentration in soil solution following sequential flooding/drainage was traced in soil microcosm experiments. Both the available Si and Feo contents in soil were positively correlated with the Si content in rice shoots, while a similar correlation was not observed between the available Si, Sio and Feo. These results suggest that the Sio adsorbed to Feo is not necessary to determine the pool size of the Si available to plants. In microcosm experiments, intermittent drainages decreased Fe concentration in soil solutions by 83–96% compared to that in the continuous flooding treatment. The oxidation of Fe2+ resulted in the co-precipitation of Si with Fe. However, the decrease of Si in a soil solution following drainage was 22% or less, which were smaller than the values observed when solutions containing various ratios of metasilicic acid and Fe2+ were mixed under oxic conditions (24–97%). In addition, as the Si concentrations in soil solutions in the intermittent flooding treatment increased to the levels similar to those in the continuous flooding treatment after re-flooding before Fe was re-reduced, the effect of reduction/oxidation of Fe on the dissolved Si concentrations was small. Thus, the reducible Fe is not a major factor in rice-available Si in paddy soil.
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Claims 10
Claim · model-written summary
Available soil Si was positively correlated with Si content in rice shoots.
- Taxon
- rice
Oryza sativae0 - Compound
- available Sie0
- Outcome
- Si content in rice shootse0
- Direction
- positively correlatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both the available Si and Feo contents in soil were positively correlated with the Si content in rice shoots”
Claim · model-written summary
Soil Feo content was positively correlated with Si content in rice shoots.
- Taxon
- riceOryza sativae0
- Compound
- Feoe0
- Outcome
- Si content in rice shootse0
- Direction
- positively correlatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both the available Si and Feo contents in soil were positively correlated with the Si content in rice shoots”
Claim · model-written summary
Available Si, Sio, and Feo in soil did not show a similar correlation.
- Taxon
- riceOryza sativae1
- Compound
- Sio and Feoe0
- Outcome
- correlatione0
- Direction
- not observede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a similar correlation was not observed between the available Si, Sio and Feo”
e1“Si content in rice shoots, while a similar correlation”
Claim · model-written summary
The authors inferred that Sio adsorbed to Feo is unnecessary for determining plant-available Si pool size.
Not reportedTaxon
Verbatim
e0“the Sio adsorbed to Feo is not necessary to determine the pool size of the Si available to plants”
Claim · model-written summary
Intermittent drainage lowered soil solution Fe concentration by 83–96% versus continuous flooding.
- Treatment
- intermittent drainagese0
- Outcome
- Fe concentration in soil solutionse0
- Direction
- decreasede0
- Value
- 83–96%e0
- Comparator
- continuous flooding treatmente0
Not reportedTaxon
Verbatim
e0“intermittent drainages decreased Fe concentration in soil solutions by 83–96% compared to that in the continuous flooding treatment”
Claim · model-written summary
Oxidation of Fe2+ led to coprecipitation of Si with Fe.
Not reportedTaxon
Verbatim
e0“The oxidation of Fe2+ resulted in the co-precipitation of Si with Fe”
Claim · model-written summary
Drainage decreased soil solution Si by 22% or less.
Not reportedTaxonComparator
Verbatim
e0“the decrease of Si in a soil solution following drainage was 22% or less”
Claim · model-written summary
Si declines after drainage were smaller than 24–97% declines in mixed oxic solutions.
- Outcome
- decrease of Si in a soil solutione1
- Direction
- smallere0
- Qualifier
- 24–97%e0
- Comparator
- solutions containing various ratios of metasilicic acid and Fe2+e0
Not reportedTaxon
Verbatim
e0“which were smaller than the values observed when solutions containing various ratios of metasilicic acid and Fe2+ were mixed under oxic conditions (24–97%)”
e1“the decrease of Si in a soil solution following drainage was 22% or less”
Claim · model-written summary
After reflooding, intermittently flooded soil solution Si reached levels similar to continuous flooding before Fe was reduced again.
- Treatment
- intermittent flooding treatmente0
- Outcome
- Si concentrations in soil solutionse0
- Direction
- increasede0
- Qualifier
- after re-flooding before Fe was re-reducede0
- Comparator
- continuous flooding treatmente0
Not reportedTaxon
Verbatim
e0“the Si concentrations in soil solutions in the intermittent flooding treatment increased to the levels similar to those in the continuous flooding treatment after re-flooding before Fe was re-reduced”
Claim · model-written summary
The authors concluded that reducible Fe has little effect on dissolved Si and is not a major determinant of rice-available Si.
- Taxon
- riceOryza sativae0
- Compound
- reducible Fee0
- Outcome
- rice-available Sie0
- Qualifier
- effect of reduction/oxidation of Fe on the dissolved Si concentrations was smalle1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the reducible Fe is not a major factor in rice-available Si in paddy soil”
e1“the effect of reduction/oxidation of Fe on the dissolved Si concentrations was small”