Abstract
Sawah, an Indo-Malaysian word for rice paddy, is used in West Africa to refer to a lowland rice field that is bunded, puddled and levelled for ease of water control and management. There are insufficient data on lowland soil and rice responses to sawah preparation intensity, defined by relative completeness of these three land preparation activities (bunding + puddling + levelling). This study assessed soil physical properties and rice grain yield under sawah preparation intensities [complete (bunded, puddled, levelled), quasi-complete (bunded, slightly puddled, levelled) and incomplete (bunded, non-puddled/levelled) sawah, and control] and soil amendments [NPK, poultry droppings (PD), rice husk (RH), its ash (RHA) and control] in southeastern Nigeria for 3 years. At rice maturity, soil bulk density increased with decreasing intensity of sawah preparation and was lower with than without amendments, being lowest in RH-amended plots. Aggregate sizes were adversely affected in the three sawah plots and by soil amendments, mainly NPK. Mean-weight diameter of aggregates was always highest in complete sawah, while showing lowest and highest values in NPK and PD plots, respectively. Sawah bunding/puddling and amendments positively affected soil water content. Saturated hydraulic conductivity was always highest in complete sawah plus PD and lowest in the control. Rice grain yield did not always increase with sawah preparation intensity but all sawah plots out-yielded the control after the first year. All amended plots always out-yielded the control, with higher values due to PD/RH compared with RHA/NPK in the third year. Soil physical control of rice grain yield revealed strengths (R2, 0.847–0.420) in decreasing order of conductivity, bulk density/water content, <0.25-mm aggregates and mean-weight diameter. Only soil bulk density related inversely to grain yield up till a critical value of 1.05 g cm−3. Complete sawah or, where improved soil structure after rice is not desired, quasi-complete/incomplete sawah can be combined with organic amendments (PD/RH) to grow lowland rice.
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Claims 18
Claim · model-written summary
Soil bulk density increased as sawah preparation intensity decreased.
- Taxon
- lowland ricet0
- Treatment
- decreasing intensity of sawah preparatione1
- Outcome
- soil bulk densitye1
- Direction
- increasede1
Not reportedComparator
Verbatim
t0“grain yields of lowland rice”
e1“At rice maturity, soil bulk density increased with decreasing intensity of sawah preparation and was lower with than without amendments, being lowest in RH-amended plots”
Claim · model-written summary
Soil amendments lowered soil bulk density compared with no amendments.
Verbatim
t0“grain yields of lowland rice”
e1“At rice maturity, soil bulk density increased with decreasing intensity of sawah preparation and was lower with than without amendments, being lowest in RH-amended plots”
Claim · model-written summary
Soil bulk density was lowest in RH-amended plots.
Not reportedComparator
Verbatim
t0“grain yields of lowland rice”
e1“At rice maturity, soil bulk density increased with decreasing intensity of sawah preparation and was lower with than without amendments, being lowest in RH-amended plots”
Claim · model-written summary
Aggregate sizes were adversely affected in the three sawah plots.
- Taxon
- lowland ricet0
- Treatment
- three sawah plotse2
- Outcome
- Aggregate sizese2
- Direction
- adversely affectede2
Not reportedComparator
Verbatim
t0“grain yields of lowland rice”
e2“Aggregate sizes were adversely affected in the three sawah plots and by soil amendments, mainly NPK”
Claim · model-written summary
Aggregate sizes were adversely affected by NPK, mainly among the soil amendments.
Not reportedComparator
Verbatim
t0“grain yields of lowland rice”
e2“Aggregate sizes were adversely affected in the three sawah plots and by soil amendments, mainly NPK”
Claim · model-written summary
Mean-weight diameter of aggregates was highest in complete sawah.
- Taxon
- lowland ricet0
- Treatment
- complete sawahe3
- Outcome
- Mean-weight diameter of aggregatese3
- Direction
- higheste3
Not reportedComparator
Verbatim
t0“grain yields of lowland rice”
e3“Mean-weight diameter of aggregates was always highest in complete sawah, while showing lowest and highest values in NPK and PD plots, respectively”
Claim · model-written summary
Mean-weight diameter of aggregates was lowest in NPK plots.
Not reportedComparator
Verbatim
t0“grain yields of lowland rice”
e3“Mean-weight diameter of aggregates was always highest in complete sawah, while showing lowest and highest values in NPK and PD plots, respectively”
Claim · model-written summary
Mean-weight diameter of aggregates was highest in PD plots.
Not reportedComparator
Verbatim
t0“grain yields of lowland rice”
e3“Mean-weight diameter of aggregates was always highest in complete sawah, while showing lowest and highest values in NPK and PD plots, respectively”
Claim · model-written summary
Sawah bunding and puddling with amendments positively affected soil water content.
- Taxon
- lowland ricet0
- Treatment
- Sawah bunding/puddling and amendmentse4
- Outcome
- soil water contente4
- Direction
- positively affectede4
Not reportedComparator
Verbatim
t0“grain yields of lowland rice”
e4“Sawah bunding/puddling and amendments positively affected soil water content”
Claim · model-written summary
Saturated hydraulic conductivity was highest in complete sawah plus PD.
- Taxon
- lowland ricet0
- Treatment
- complete sawah plus PDe5
- Outcome
- Saturated hydraulic conductivitye5
- Direction
- higheste5
Not reportedComparator
Verbatim
t0“grain yields of lowland rice”
e5“Saturated hydraulic conductivity was always highest in complete sawah plus PD and lowest in the control”
Claim · model-written summary
Saturated hydraulic conductivity was lowest in the control.
Verbatim
t0“grain yields of lowland rice”
e5“Saturated hydraulic conductivity was always highest in complete sawah plus PD and lowest in the control”
Claim · model-written summary
Rice grain yield did not always increase with sawah preparation intensity.
- Taxon
- lowland ricet0
- Treatment
- sawah preparation intensitye6
- Outcome
- Rice grain yielde6
- Direction
- did not always increasee6
Not reportedComparator
Verbatim
t0“grain yields of lowland rice”
e6“Rice grain yield did not always increase with sawah preparation intensity but all sawah plots out-yielded the control after the first year”
Claim · model-written summary
All sawah plots out-yielded the control after the first year.
Verbatim
t0“grain yields of lowland rice”
e6“Rice grain yield did not always increase with sawah preparation intensity but all sawah plots out-yielded the control after the first year”
Claim · model-written summary
All amended plots out-yielded the control in grain yield.
Verbatim
t0“grain yields of lowland rice”
e7“All amended plots always out-yielded the control, with higher values due to PD/RH compared with RHA/NPK in the third year”
Claim · model-written summary
In the third year, PD/RH amendments gave higher grain yields than RHA/NPK.
Verbatim
t0“grain yields of lowland rice”
e7“All amended plots always out-yielded the control, with higher values due to PD/RH compared with RHA/NPK in the third year”
Claim · model-written summary
Soil physical properties explained rice grain yield with R2 values from 0.847 to 0.420 in decreasing order of conductivity, bulk density/water content, aggregates and mean-weight diameter.
- Taxon
- rice
Oryza sativat0 - Treatment
- Soil physical controle7
- Outcome
- rice grain yielde7
- Value
- R2, 0.847–0.420e7
- Qualifier
- in decreasing order of conductivity, bulk density/water content, <0.25-mm aggregates and mean-weight diametere7
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“grain yields of lowland rice”
e7“Soil physical control of rice grain yield revealed strengths (R2, 0.847–0.420) in decreasing order of conductivity, bulk density/water content, <0.25-mm aggregates and mean-weight diameter”
Claim · model-written summary
Soil bulk density was inversely related to grain yield up to a critical value of 1.05 g cm-3.
- Taxon
- riceOryza sativat0
- Treatment
- soil bulk densitye6
- Outcome
- grain yielde6
- Direction
- inverselye6
- Value
- 1.05 g cm−3e6
- Qualifier
- up till a critical valuee6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“grain yields of lowland rice”
e6“Only soil bulk density related inversely to grain yield up till a critical value of 1.05 g cm−3”
Claim · model-written summary
Complete sawah or quasi-complete/incomplete sawah can be combined with organic amendments (PD/RH) to grow lowland rice where improved soil structure after rice is not desired.
Verbatim
t0“grain yields of lowland rice”
e5“Complete sawah or, where improved soil structure after rice is not desired, quasi-complete/incomplete sawah can be combined with organic amendments (PD/RH) to grow lowland rice”
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