Abstract
Abstract Although lowland soils in Asia are frequently fallowed between rice ( Oryza sativa L.) crops, little is known about the effects of fallow management on N cycling and growth of a subsequent lowland rice crop. A 2‐yr field study was conducted in the Philippines on a Typic Tropaquept to determine the interactive effects of pre‐rice land management and urea fertilization on rice growth, N uptake, and response to applied N. Management treatments before transplanting wet‐season rice were (i) weedy fallow (WF), (ii) weed‐free fallow (WFF), and (iii) Sesbania rostrata Bremek. & Oberm. grown in situ for either 45 or 60 d as green manure (SR). Weeds and S. rostrata were incorporated after soil flooding on 23 June of each year, and rice was transplanted on 30 June 1989 and 4 July 1990. Four rates of urea‐N (0, 40, 80, and 120 kg N ha ‐1 ) were applied to rice following each pre‐rice treatment. The efficiency of added N with respect to dry matter accumulation (kg dry wt. kg −1 N applied) was reduced following WF and SR compared with that following WFF at 45 d after transplanting (DAT), about 10 to 15 d after panicle initiation. Rice recovered from the initial adverse effect of incorporated plant residue, and growth rate after 45 DAT was greater following SR and WF than that following WFF. Grain yield without applied urea was 0.9 Mg ha ‐1 higher following WF than that following WFF. Incorporated weed‐N (35 kg N ha ‐1 ) substituted for 40 kg urea‐N ha ‐1 . High initial rice growth rate in the absence of incorporated plant residue (WFF) resulted in a lower rice N concentration at 45 DAT. Incorporated S. rostrata and weeds continued to provide N to rice after 45 DAT. When no plant residues were incorporated (WFF), the application of only one‐third of the total urea‐N at panicle initiation was insufficient to meet the N requirements of rice. Basal urea‐N (two‐thirds of the total urea‐N) failed to increase rice dry weight or N concentration at 21 DAT following all pre‐rice treatments. Results suggest that optimal distribution of urea among application timings might depend on whether plant residues are incorporated before transplanting.
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Claims 14
Claim · model-written summary
WF reduced added-N efficiency for dry matter accumulation relative to WFF.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“The efficiency of added N with respect to dry matter accumulation (kg dry wt. kg −1 N applied) was reduced following WF and SR compared with that following WFF at 45 d after transplanting (DAT), about 10 to 15 d after panicle initiation.”
Claim · model-written summary
SR reduced added-N efficiency for dry matter accumulation relative to WFF.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“The efficiency of added N with respect to dry matter accumulation (kg dry wt. kg −1 N applied) was reduced following WF and SR compared with that following WFF at 45 d after transplanting (DAT), about 10 to 15 d after panicle initiation.”
Claim · model-written summary
Rice recovered from an initial adverse effect of incorporated plant residue.
- Taxon
- Rice
Oryza sativat0 - Outcome
- recoverede0
- Direction
- recoverede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“Rice recovered from the initial adverse effect of incorporated plant residue, and growth rate after 45 DAT was greater following SR and WF than that following WFF.”
Claim · model-written summary
Rice growth rate after 45 DAT was greater after SR than WFF.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“Rice recovered from the initial adverse effect of incorporated plant residue, and growth rate after 45 DAT was greater following SR and WF than that following WFF.”
Claim · model-written summary
Rice growth rate after 45 DAT was greater after WF than WFF.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“Rice recovered from the initial adverse effect of incorporated plant residue, and growth rate after 45 DAT was greater following SR and WF than that following WFF.”
Claim · model-written summary
Without urea, WF increased grain yield over WFF by 0.9 Mg ha ‐1.
- Taxon
- RiceOryza sativat0
- Treatment
- WFe0
- Outcome
- Grain yielde0
- Direction
- highere0
- Value
- 0.9 Mg ha ‐1e0
- Comparator
- WFFe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“Grain yield without applied urea was 0.9 Mg ha ‐1 higher following WF than that following WFF.”
Claim · model-written summary
Incorporated weed N substituted for 40 kg urea N per hectare.
- Taxon
- RiceOryza sativat0
- Treatment
- Incorporated weed‐N (35 kg N ha ‐1 )e0
- Outcome
- substitutede0
- Direction
- substitutede0
- Value
- 40 kg urea‐N ha ‐1e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“Incorporated weed‐N (35 kg N ha ‐1 ) substituted for 40 kg urea‐N ha ‐1 .”
Claim · model-written summary
WFF produced lower rice N concentration at 45 DAT.
- Taxon
- RiceOryza sativat0
- Treatment
- WFFe0
- Outcome
- rice N concentratione0
- Direction
- lowere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“High initial rice growth rate in the absence of incorporated plant residue (WFF) resulted in a lower rice N concentration at 45 DAT.”
Claim · model-written summary
Incorporated S. rostrata continued to provide N after 45 DAT.
- Taxon
- RiceOryza sativat0
- Treatment
- S. rostratae0
- Outcome
- provide N to ricee0
- Direction
- continuede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“Incorporated S. rostrata and weeds continued to provide N to rice after 45 DAT.”
Claim · model-written summary
Incorporated weeds continued to provide N after 45 DAT.
- Taxon
- RiceOryza sativat0
- Treatment
- weedse0
- Outcome
- provide N to ricee0
- Direction
- continuede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“Incorporated S. rostrata and weeds continued to provide N to rice after 45 DAT.”
Claim · model-written summary
One third of urea N at panicle initiation was insufficient without incorporated residues.
- Taxon
- RiceOryza sativat0
- Treatment
- application of only one‐third of the total urea‐N at panicle initiatione0
- Outcome
- N requirements of ricee0
- Direction
- insufficiente0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“When no plant residues were incorporated (WFF), the application of only one‐third of the total urea‐N at panicle initiation was insufficient to meet the N requirements of rice.”
Claim · model-written summary
Basal urea N failed to increase rice dry weight at 21 DAT.
- Taxon
- RiceOryza sativat0
- Treatment
- Basal urea‐N (two‐thirds of the total urea‐N)e0
- Outcome
- rice dry weighte0
- Direction
- failed to increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“Basal urea‐N (two‐thirds of the total urea‐N) failed to increase rice dry weight or N concentration at 21 DAT following all pre‐rice treatments.”
Claim · model-written summary
Basal urea N failed to increase N concentration at 21 DAT.
- Taxon
- RiceOryza sativat0
- Treatment
- Basal urea‐N (two‐thirds of the total urea‐N)e0
- Outcome
- N concentratione0
- Direction
- failed to increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“Basal urea‐N (two‐thirds of the total urea‐N) failed to increase rice dry weight or N concentration at 21 DAT following all pre‐rice treatments.”
Claim · model-written summary
Optimal timing of urea application may depend on pretransplant residue incorporation.
- Taxon
- RiceOryza sativat0
- Outcome
- optimal distribution of urea among application timingse0
- Qualifier
- whether plant residues are incorporated before transplantinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Rice”
e0“Results suggest that optimal distribution of urea among application timings might depend on whether plant residues are incorporated before transplanting.”
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