Abstract
Abstract Loss of soil‐water saturation may impair growth of rainfed lowland rice by restricting nutrient uptake, including the uptake of added phosphorus (P). For acidic soils, reappearance of soluble aluminum (Al) following loss of soil‐water saturation may also restrict P uptake. The aim of this study was to determine whether liming, flooding, and P additions could ameliorate the effects of loss of soil‐water saturation on P uptake and growth of rice. In the first pot experiment, two acid lowland soils from Cambodia [Kandic Plinthaqult (black clay soil) and Plinthustalf (sandy soil)] were treated with P (45 mg P kg−1 soil) either before or after flooding for 4 weeks to investigate the effect of flooding on effectiveness of P fertilizer for rice growth. After 4 weeks, soils were air dried and crushed and then wet to field capacity and upland rice was grown in them for an additional 6 weeks. Addition of P fertilizer before rather than after flooding depressed the growth of the subsequently planted upland rice. During flooding, there was an increase in both acetate‐extractable Fe and the phosphate sorption capacity of soils, and a close relationship between them (r2=0.96–0.98). When P was added before flooding, Olsen and Bray 1‐extractable P, shoot dry matter, and shoot P concentrations were depressed, indicating that flooding decreased availability of fertilizer P. A second pot experiment was conducted with three levels of lime as CaCO3 [to establish pH (CaCl2) in the oxidized soils at 4, 5, and 6] and four levels of P (0, 13, 26, and 52 mg P kg−1 soil) added to the same two acid lowland rice soils under flooded and nonflooded conditions. Under continuously flooded conditions, pH increased to over 5.6 regardless of lime treatment, and there was no response of rice dry matter to liming after 6 weeks' growth, but the addition of P increased rice dry matter substantially in both soils. In nonflooded soils, when P was not applied, shoot dry matter was depressed by up to one‐half of that in plants grown under continuously flooded conditions. Under the nonflooded conditions, rice dry matter and leaf P increased with the addition of P, but less so than in flooded soils. Leaf P concentrations and shoot dry matter responded strongly to the addition of lime. The increase in shoot dry matter of rice with lime and P application in nonflooded soil was associated with a significant decline in soluble Al in the soil and an increase in plant P uptake. The current experiments show that the loss of soil‐water saturation may be associated with the inhibition of P absorption by excess soluble Al. By contrast, flooding decreased exchangeable Al to levels below the threshold for toxicity in rice. In addition, the decreased P availability with loss of soil‐water saturation may have been associated with a greater phosphate sorption capacity of the soils during flooding and after reoxidation due to occlusion of P within ferric oxyhydroxides formed.
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Claims 16
Claim · model-written summary
Adding P before flooding gave lower growth of subsequently planted upland rice than adding P after flooding.
- Taxon
- upland rice
Oryza sativae1 - Treatment
- Addition of P fertilizer before rather than after floodinge1
- Outcome
- growthe1
- Direction
- depressede1
- Comparator
- after floodinge1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e1“Addition of P fertilizer before rather than after flooding depressed the growth of the subsequently planted upland rice”
Claim · model-written summary
During flooding, phosphate sorption capacity of the soils increased.
- Taxon
- RiceOryza sativat0
- Treatment
- floodinge0
- Outcome
- phosphate sorption capacitye2
- Direction
- increasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e0“During flooding, there was an increase in both”
e2“the phosphate sorption capacity of soils”
Claim · model-written summary
During flooding, acetate-extractable Fe and phosphate sorption capacity were closely related.
- Taxon
- RiceOryza sativat0
- Treatment
- floodinge0
- Outcome
- close relationship between theme3
- Value
- r2=0.96–0.98e3
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e0“During flooding, there was an increase in both”
e3“a close relationship between them (r2=0.96–0.98)”
Claim · model-written summary
Adding P before flooding depressed shoot dry matter and shoot P concentrations of rice.
- Taxon
- RiceOryza sativat0
- Treatment
- P was added before floodinge4
- Outcome
- shoot dry matter, and shoot P concentrationse4
- Direction
- depressede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e4“When P was added before flooding, Olsen and Bray 1‐extractable P, shoot dry matter, and shoot P concentrations were depressed”
Claim · model-written summary
Adding P before flooding depressed extractable P (Olsen and Bray 1) in the soil.
- Taxon
- RiceOryza sativat0
- Treatment
- P was added before floodinge4
- Outcome
- Olsen and Bray 1‐extractable Pe4
- Direction
- depressede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e4“When P was added before flooding, Olsen and Bray 1‐extractable P, shoot dry matter, and shoot P concentrations were depressed”
Claim · model-written summary
Under continuous flooding, lime raised soil pH above 5.6 with no rice dry matter response to liming.
- Taxon
- riceOryza sativae5
- Treatment
- lime treatmente5
- Outcome
- pHe5
- Direction
- increasede5
- Value
- over 5.6e5
- Setting
- continuously flooded conditionse5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e5“Under continuously flooded conditions, pH increased to over 5.6 regardless of lime treatment, and there was no response of rice dry matter to liming”
Claim · model-written summary
Under continuous flooding, liming gave no response in rice dry matter.
- Taxon
- riceOryza sativae5
- Treatment
- liminge5
- Outcome
- rice dry mattere5
- Direction
- no responsee5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e5“Under continuously flooded conditions, pH increased to over 5.6 regardless of lime treatment, and there was no response of rice dry matter to liming”
Claim · model-written summary
Adding P substantially increased rice dry matter in both soils under continuous flooding.
- Taxon
- riceOryza sativae6
- Treatment
- the addition of Pe6
- Outcome
- rice dry mattere6
- Direction
- increasede6
- Qualifier
- substantially in both soilse6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e6“the addition of P increased rice dry matter substantially in both soils”
Claim · model-written summary
In nonflooded soil without P, shoot dry matter was reduced by up to one-half relative to continuously flooded plants.
- Taxon
- RiceOryza sativat0
- Treatment
- when P was not appliede7
- Outcome
- shoot dry mattere7
- Direction
- depressede7
- Value
- up to one‐halfe7
- Comparator
- plants grown under continuously flooded conditionse7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e7“In nonflooded soils, when P was not applied, shoot dry matter was depressed by up to one‐half of that in plants grown under continuously flooded conditions”
Claim · model-written summary
Under nonflooded conditions, adding P increased rice dry matter and leaf P, less than in flooded soils.
- Taxon
- riceOryza sativae1
- Treatment
- the addition of Pe1
- Outcome
- rice dry matter and leaf Pe1
- Direction
- increasede1
- Qualifier
- but less so than in flooded soilse1
- Comparator
- flooded soilse1
- Setting
- nonflooded conditionse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e1“Under the nonflooded conditions, rice dry matter and leaf P increased with the addition of P, but less so than in flooded soils”
Claim · model-written summary
Adding lime strongly changed leaf P concentrations and shoot dry matter of rice.
- Taxon
- riceOryza sativat0
- Treatment
- the addition of limee2
- Outcome
- Leaf P concentrations and shoot dry mattere2
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e2“Leaf P concentrations and shoot dry matter responded strongly to the addition of lime”
Claim · model-written summary
Lime and P application in nonflooded soil was associated with a significant decline in soluble Al.
- Taxon
- riceOryza sativae3
- Treatment
- lime and P applicatione3
- Outcome
- soluble Al in the soile3
- Direction
- declinee3
- Setting
- nonflooded soile3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e3“The increase in shoot dry matter of rice with lime and P application in nonflooded soil was associated with a significant decline in soluble Al in the soil and an increase in plant P uptake”
Claim · model-written summary
Lime and P application in nonflooded soil was associated with an increase in plant P uptake of rice.
- Taxon
- riceOryza sativae3
- Treatment
- lime and P applicatione3
- Outcome
- plant P uptakee3
- Direction
- increasee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e3“The increase in shoot dry matter of rice with lime and P application in nonflooded soil was associated with a significant decline in soluble Al in the soil and an increase in plant P uptake”
Claim · model-written summary
Loss of soil-water saturation may be associated with inhibition of P absorption by excess soluble Al in rice.
- Taxon
- RiceOryza sativat0
- Outcome
- inhibition of P absorptione4
- Qualifier
- excess soluble Ale4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e4“may be associated with the inhibition of P absorption by excess soluble Al”
Claim · model-written summary
Flooding decreased exchangeable Al in rice soils to below the toxicity threshold.
- Taxon
- riceOryza sativae5
- Treatment
- floodinge5
- Outcome
- exchangeable Ale5
- Direction
- decreasede5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e5“By contrast, flooding decreased exchangeable Al to levels below the threshold for toxicity in rice”
Claim · model-written summary
Decreased P availability may be associated with greater phosphate sorption capacity of soils during flooding and after reoxidation.
- Taxon
- RiceOryza sativat0
- Outcome
- P availabilitye6
- Qualifier
- greater phosphate sorption capacitye7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice Growth”
e6“the decreased P availability”
e7“may have been associated with a greater phosphate sorption capacity of the soils during flooding and after reoxidation due to occlusion of P within ferric oxyhydroxides formed”
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