Abstract
1. High seeding density combined with a short transplanting age synergistically enhances seedling vigor and chlorophyll concentration, thereby improving early-stage photosynthetic efficiency. 2. Early transplanting extends the effective thermal time window, promoting early nitrogen assimilation and late-stage remobilization of non-structural carbohydrates (NSC) under ultra-high planting density. 3. High seeding density and reduced transplanting age increase leaf area index and post-transplantation dry matter accumulation. 4. An optimized tillering architecture under these conditions contributes to higher nitrogen use efficiency (NUE). 5. Accelerated translocation of NSC from vegetative tissues to grains enhances grain yield formation. Ultra-high-density rice seedling cultivation using crop straw boards provides a labor-saving method for mechanized transplanting, yet frequently triggers early physiological aging and depletes internal nutrient reserves, thereby impairing post-transplant carbon-nitrogen (C–N) metabolic efficiency. This study examined whether optimizing transplanting age could alleviate these constraints and enhance C–N coordination and yield formation. A three-year field experiment (2021–2023) conducted in Sihong, Jiangsu, China, applied five nursery-stage seeding densities (D1–D5, 150–350 g/tray) and three transplanting ages (A1–A3, 10–20 days). Early transplanting extended the post-transplant thermal duration, promoting greater nitrogen uptake predominantly during vegetative and early reproductive phases. This facilitated enhanced leaf area expansion, increased dry matter accumulation, and higher photosynthetic assimilate production. Subsequently, improved sink strength—manifested as greater numbers of productive tillers and larger panicles—supported increased pre-heading non-structural carbohydrate (NSC) storage and enabled more efficient remobilization of stem NSC to grains during grain filling. Thus, nitrogen assimilation and NSC translocation were temporally distinct but metabolically synergistic, contributing to superior source–sink coordination. Notably, the optimal treatment, D4A2 (300 g/tray, 15-day-old seedlings), designed under labor-saving and high-efficiency nursery conditions, achieved a grain yield 2.91% higher than the conventional D1A3 treatment, demonstrating that enhanced C–N metabolism can maintain or slightly increase yield while reducing nursery labor input and tray usage. These findings indicate that aligning high seeding density with moderately early transplanting improves post-transplant C–N metabolism and presents a practical strategy for enhancing yield stability in mechanized rice production systems.
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Claims 9
Claim · model-written summary
The D4A2 treatment (300 g/tray, 15-day-old seedlings) gave a 2.91% higher grain yield than the conventional D1A3 treatment.
- Taxon
- rice
Oryza sativat0 - Treatment
- D4A2 (300 g/tray, 15-day-old seedlings)e1
- Outcome
- grain yielde1
- Direction
- highere1
- Value
- 2.91%e1
- Comparator
- conventional D1A3 treatmente1
- Setting
- Sihong, Jiangsu, Chinae2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mechanically transplanted rice”
e1“Notably, the optimal treatment, D4A2 (300 g/tray, 15-day-old seedlings), designed under labor-saving and high-efficiency nursery conditions, achieved a grain yield 2.91% higher than the conventional D1A3 treatment”
e2“A three-year field experiment (2021–2023) conducted in Sihong, Jiangsu, China”
Claim · model-written summary
High seeding density combined with a short transplanting age enhanced seedling vigor and chlorophyll concentration.
- Taxon
- riceOryza sativat0
- Treatment
- High seeding density combined with a short transplanting agee3
- Outcome
- seedling vigor and chlorophyll concentratione3
- Direction
- enhancese3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mechanically transplanted rice”
e3“High seeding density combined with a short transplanting age synergistically enhances seedling vigor and chlorophyll concentration”
Claim · model-written summary
Early transplanting promoted early nitrogen assimilation under ultra-high planting density.
- Taxon
- riceOryza sativat0
- Treatment
- Early transplantinge4
- Outcome
- early nitrogen assimilatione4
- Direction
- promotinge4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mechanically transplanted rice”
e4“Early transplanting extends the effective thermal time window, promoting early nitrogen assimilation and late-stage remobilization of non-structural carbohydrates (NSC) under ultra-high planting density”
Claim · model-written summary
Early transplanting promoted late-stage remobilization of non-structural carbohydrates under ultra-high planting density.
- Taxon
- riceOryza sativat0
- Treatment
- Early transplantinge4
- Outcome
- late-stage remobilization of non-structural carbohydrates (NSC)e4
- Direction
- promotinge4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mechanically transplanted rice”
e4“Early transplanting extends the effective thermal time window, promoting early nitrogen assimilation and late-stage remobilization of non-structural carbohydrates (NSC) under ultra-high planting density”
Claim · model-written summary
High seeding density and reduced transplanting age increased leaf area index and post-transplantation dry matter accumulation.
- Taxon
- riceOryza sativat0
- Treatment
- High seeding density and reduced transplanting agee5
- Outcome
- leaf area index and post-transplantation dry matter accumulatione5
- Direction
- increasee5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mechanically transplanted rice”
e5“High seeding density and reduced transplanting age increase leaf area index and post-transplantation dry matter accumulation”
Claim · model-written summary
An optimized tillering architecture was associated with higher nitrogen use efficiency in rice.
- Taxon
- riceOryza sativat0
- Treatment
- An optimized tillering architecturee6
- Outcome
- nitrogen use efficiency (NUE)e6
- Direction
- highere6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mechanically transplanted rice”
e6“An optimized tillering architecture under these conditions contributes to higher nitrogen use efficiency (NUE)”
Claim · model-written summary
Accelerated translocation of NSC from vegetative tissues to grains enhanced grain yield formation.
- Taxon
- riceOryza sativat0
- Treatment
- Accelerated translocation of NSC from vegetative tissues to grainse7
- Outcome
- grain yield formatione7
- Direction
- enhancese7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mechanically transplanted rice”
e7“Accelerated translocation of NSC from vegetative tissues to grains enhances grain yield formation”
Claim · model-written summary
Early transplanting increased photosynthetic assimilate production in rice.
- Taxon
- riceOryza sativat0
- Treatment
- Early transplantinge1
- Outcome
- photosynthetic assimilate productione2
- Direction
- highere2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mechanically transplanted rice”
e1“Early transplanting extended the post-transplant thermal duration”
e2“This facilitated enhanced leaf area expansion, increased dry matter accumulation, and higher photosynthetic assimilate production”
Claim · model-written summary
Improved sink strength was associated with increased pre-heading non-structural carbohydrate storage in rice.
- Taxon
- riceOryza sativat0
- Treatment
- improved sink strengthe3
- Outcome
- pre-heading non-structural carbohydrate (NSC) storagee3
- Direction
- increasede3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“mechanically transplanted rice”
e3“Subsequently, improved sink strength—manifested as greater numbers of productive tillers and larger panicles—supported increased pre-heading non-structural carbohydrate (NSC) storage”
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