Abstract
ABSTRACT Nitrogen (N) deficiency and water stress are major abiotic constraints upon the production of upland rice (Oryza sativa L.) in tropical Asia. It is, therefore, imperative to quantify the effect of N input on yield and to identify factors affecting the variability of yield response to N under various water supply conditions in order to develop efficient methods of N and crop management. Field experiments were conducted in Bihar, India, over four years to analyze the effect of N rate with split application of soluble urea, and a N sources, split application of soluble urea, and a single application of polyolefin resin-coated controlled-release urea (PCU) on the grain yield, apparent N recovery fraction (ANR), economic N use efficiency (grain yield per N uptake or GYNUE), and root growth. The yield responded linearly to increasing N rate in split urea, but along a different slope in each year. The yield response to N rate was variable among years due to variations in ANR and GYNUE. A significant relationship between the ANR and yield gain by N application across years indicated the importance of improving ANR to maximize the cost-benefit ratio. A comparison of split urea and PCU indicated that ANR could be improved more by the application of PCU than by split urea, especially under a high water supply from rainfall or irrigation. This is probably due to less N having been lost due to runoff and leaching when PCU was used. GYNUE was relatively stable across N treatments, but showed significant year-to-year variation, caused by variations in both the biomass N use efficiency (BNUE) (aboveground dry weight per N uptake) and harvest index (HI) as affected by rainfall conditions. The application of N increased root length from the surface to a below-45 cm depth, which may have contributed to the water exploitation under water stress.
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Claims 7
Claim · model-written summary
Grain yield increased linearly with split urea rate, with a slope varying by year.
- Taxon
- upland rice
Oryza sativae0 - Treatment
- increasing N rate in split ureae1
- Outcome
- yielde1
- Direction
- responded linearlye1
- Qualifier
- different slope in each yeare1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“upland rice (Oryza sativa L.)”
e1“yield responded linearly to increasing N rate in split urea, but along a different slope in each year”
Claim · model-written summary
Yield response to nitrogen rate varied among years with ANR and GYNUE.
- Taxon
- upland riceOryza sativae0
- Treatment
- N ratee1
- Outcome
- yield response to N ratee1
- Direction
- variablee1
- Qualifier
- variations in ANR and GYNUEe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“upland rice (Oryza sativa L.)”
e1“yield response to N rate was variable among years due to variations in ANR and GYNUE”
Claim · model-written summary
ANR and nitrogen-induced yield gain were significantly related across years.
- Taxon
- upland riceOryza sativae0
- Treatment
- N applicatione1
- Outcome
- yield gain by N applicatione1
- Qualifier
- ANRe1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“upland rice (Oryza sativa L.)”
e1“significant relationship between the ANR and yield gain by N application across years”
Claim · model-written summary
Controlled-release urea improved apparent nitrogen recovery more than split urea, especially with high water supply.
- Taxon
- upland riceOryza sativae0
- Treatment
- application of PCUe1
- Outcome
- ANRe1
- Direction
- improved moree1
- Qualifier
- high water supply from rainfall or irrigatione1
- Comparator
- split ureae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“upland rice (Oryza sativa L.)”
e1“ANR could be improved more by the application of PCU than by split urea, especially under a high water supply from rainfall or irrigation”
Claim · model-written summary
GYNUE was relatively stable across nitrogen treatments.
- Taxon
- upland riceOryza sativae0
- Treatment
- N treatmentse1
- Outcome
- GYNUEe1
- Direction
- relatively stablee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“upland rice (Oryza sativa L.)”
e1“GYNUE was relatively stable across N treatments”
Claim · model-written summary
GYNUE varied significantly among years.
- Taxon
- upland riceOryza sativae0
- Outcome
- GYNUEe1
- Direction
- variatione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“upland rice (Oryza sativa L.)”
e1“GYNUE was relatively stable across N treatments, but showed significant year-to-year variation”
Claim · model-written summary
Nitrogen application increased root length through depths below 45 cm.
- Taxon
- upland riceOryza sativae0
- Treatment
- application of Ne1
- Outcome
- root lengthe1
- Direction
- increasede1
- Qualifier
- from the surface to a below-45 cm depthe1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“upland rice (Oryza sativa L.)”
e1“application of N increased root length from the surface to a below-45 cm depth”
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