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Article

Effects of Winter Green Manure Incorporation on Grain Yield, Nitrogen Uptake, and Nitrogen Use Efficiency in Different Ratoon Rice Varieties

by
Qiwen Hou
1,†,
Pufan Shao
1,†,
Sheng Chen
1,
Zhangzhen Yang
1,
Zhixiong Yuan
1,
Liusheng Zhong
1,
Ziyuan Zhao
1,
Yu Wang
1,
Cuo Ga
1,
Jiarui Tang
1,
Yaoyun Xu
1,
Yanfu Zeng
1,
Cong Yu
1,
Cheng Huang
1,2 and
Ying Xu
1,2,*
1
College of Agronomy, Hunan Agricultural University, Changsha 410128, China
2
Yuelushan Laboratory, Changsha 410128, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Agriculture 2025, 15(17), 1801; https://doi.org/10.3390/agriculture15171801
Submission received: 29 July 2025 / Revised: 20 August 2025 / Accepted: 21 August 2025 / Published: 22 August 2025
(This article belongs to the Special Issue Innovative Conservation Cropping Systems and Practices—2nd Edition)
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Abstract

This study evaluated the effects of winter green manure incorporation on grain yield, nitrogen uptake, and use efficiency in ratoon rice production. A two-year field experiment (2019–2021) was conducted using a split-plot design, with main plots comprising three cropping systems: fallow–ratoon rice (FA), rapeseed–ratoon rice (RA), and milk vetch–ratoon rice (MV). In the RA and MV systems, green manures were incorporated in situ, while subplots featured two ratoon rice varieties (Yliangyou 911, YLY911; Liangyou 6326, LY6326). Compared to FA treatment, RA and MV treatments significantly increased main crop yields by 16.37% and 9.31%, respectively, with corresponding annual total yield improvements of 11.34% and 7.78%. Under RA treatment, LY6326 achieved significantly higher yields than YLY911. Biomass accumulation analysis revealed that RA and MV treatments enhanced plant dry matter by 24.40% and 5.63% at heading stage, and 9.83% and 7.47% at maturity, respectively, relative to FA treatment. Green manure incorporation improved plant nitrogen content at maturity (9.42% and 10.29% for RA and MV, respectively) and panicle nitrogen accumulation (11.73% and 38.26%, respectively) compared to fallow treatment. Nitrogen use efficiency metrics demonstrated that RA and MV treatments enhanced nitrogen harvest index by 1.54% and 5.65%, respectively, while nitrogen partial factor productivity increased by 11.34% and 7.78%. Varietal comparison confirmed that LY6326 exhibited superior nitrogen accumulation and utilization compared to YLY911. These findings demonstrate that winter green manure incorporation significantly enhances grain yield and nitrogen use efficiency in ratoon rice systems, providing a scientific foundation for developing sustainable and productive rice cropping practices.

1. Introduction

Rice is one of China’s most important staple crops, serving as the primary food source for approximately two-thirds of the population [1,2]. The stability and enhancement of rice yields are strategically crucial for ensuring national food security. The middle reaches of the Yangtze River, as one of China’s major rice-producing regions, have long shouldered critical grain production responsibilities. In recent years, driven by escalating demands for national food security and evolving agricultural socioeconomic conditions, rice cropping systems in this region have undergone substantial optimization, demonstrating a clear trajectory toward simplified, efficient, and sustainable development [3,4].
Ratoon rice represents a cultivation system that harnesses dormant buds on rice stubble to regenerate and produce a second harvest following the main crop through strategic cultivation management [5]. Given that the growth period of ratoon crop is considerably shorter than that of the main crop, this system is particularly well suited for regions where light and temperature resources are adequate for single-season rice but insufficient to support double-season rice cultivation [6]. Compared to conventional single-season and double-season rice systems—the two predominant cropping patterns in central China—ratoon rice eliminates costs associated with land preparation, seeds, seedling cultivation, and transplanting, thereby substantially improving net profitability and enhancing farmers’ economic returns [7,8]. Moreover, ratoon rice reduces annual carbon footprint by 27.37% compared to double-season rice, owing to the lower carbon emissions during the ratoon season [9]. Through its integrated advantages of superior resource use efficiency, enhanced economic viability, and reduced environmental impact, ratoon rice has gained rapid adoption across China, emerging as a promising cultivation system with considerable development potential.
Winter green manure refers to the agricultural practice of cultivating leguminous or other green manure crops during the winter fallow period following rice harvest, with subsequent soil incorporation in spring [10]. This practice constitutes a fundamental sustainable soil management strategy in traditional agriculture. In conventional single-season and double-season rice systems, winter green manure has demonstrated multiple beneficial effects. These include significant improvements in soil physical and chemical properties, enhanced soil organic matter content and nitrogen supply capacity [11,12], increased soil microbial activity and biodiversity with concomitant optimization of soil ecological conditions [13], reduced chemical fertilizer requirements and agricultural non-point source pollution [14], and effective control of winter weed growth while minimizing pest and disease incidence [15]. Extensive research has confirmed that incorporation of common winter green manure crops—including milk vetch, ryegrass, and broad bean—significantly enhances subsequent rice yields [11,12,14]. However, research examining winter green manure effects in ratoon rice systems remains limited. Ratoon rice exhibits distinctive physiological and ecological characteristics, with notable differences in growth and development processes, nutrient demand patterns, and soil–plant interactions compared to traditional rice systems [16,17]. Consequently, the applicability of research findings from conventional rice systems to ratoon rice production requires thorough verification and refinement through comprehensive scientific investigation.
Nitrogen represents one of the most critical nutrients for rice growth and development, with its uptake and utilization efficiency directly influencing yield and quality formation [18]. Comprehensive understanding of rice nitrogen uptake and utilization characteristics not only facilitates optimization of cultivation management and fertilization strategies but also provides valuable insights for improving nitrogen nutrition traits [19]. In the middle reaches of the Yangtze River, rapeseed and milk vetch serve as prevalent winter green manure crops. Previous studies have revealed significant differences between rapeseed and milk vetch in straw and root residue carbon-to-nitrogen ratios and chemical composition [20]. Under ratoon rice systems, different preceding crop types generate varying quantities and chemical compositions of organic matter inputs from roots and straw, consequently altering soil microbial activity and community structure. These changes modify carbon and nitrogen cycling in paddy fields, subsequently affecting nitrogen uptake and utilization efficiency of ratoon rice and ultimately influencing yield performance. Furthermore, different ratoon rice varieties demonstrate variations in growth duration, root activity, and nitrogen assimilation capacity, potentially resulting in differential nitrogen uptake and utilization efficiency and yield formation [21].
This study systematically investigated nitrogen accumulation, translocation, and utilization in ratoon rice under different winter cropping systems. The goal was to elucidate how winter green manure incorporation affects grain yield and nitrogen use efficiency. The findings provide valuable theoretical insights and practical guidance for improving ratoon rice cultivation and promoting sustainable agricultural development in the middle reaches of the Yangtze River.

2. Materials and Methods

2.1. Experimental Site

The experiment was conducted from October 2019 to October 2021 at the Teaching and Research Comprehensive Base of Hunan Agricultural University, located in Yanxi Town, Liuyang City, Hunan Province (28°30′ N, 113°83′ E). The region exhibits a subtropical monsoon humid climate characterized by abundant hydrothermal resources. Meteorological data including rainfall, daily maximum temperature, daily minimum temperature, and daily mean temperature during the experimental period are presented in Figure 1a. The experimental site was situated in a typical double-season rice cultivation area within the middle reaches of the Yangtze River, representing fields with long-term continuous double-season rice production. The soil was classified as red–yellow clay, with the following physicochemical properties in the topsoil layer (0–20 cm): bulk density 1.30 g cm−3, pH 4.92, total organic carbon 14.22 g kg−1, total nitrogen 1.03 g kg−1, nitrate nitrogen 0.62 mg kg−1, ammonium nitrogen 14.99 mg kg−1, total phosphorus 1.01 g kg−1, available phosphorus 131.56 mg kg−1, total potassium 17.53 g kg−1, and available potassium 89.88 mg kg−1.

2.2. Materials

The experiment involved two ratoon rice (Oryza sativa L.) varieties extensively cultivated in central China: Yliangyou 911 (YLY911) and Liangyou 6326 (LY6326). Both are two-line hybrid rice cultivars with strong ratooning ability and stable agronomic performance [9]. Rapeseed (Brassica napus L., cv. Xiangzayou 199) and milk vetch (Astragalus sinicus L., cv. Xiangzi 4hao) were used as green manure crops.

2.3. Experimental Design and Field Management

A split-plot design was adopted with cropping system as the main-plot factor and rice variety as the subplot factor. The three cropping systems were fallow–ratoon rice (FA, control), rapeseed–ratoon rice (RA), and milk vetch–ratoon rice (MV). The factorial combination of main plots and subplots yielded six treatments: FA–YLY911, FA–LY6326, RA–YLY911, RA–LY6326, MV–YLY911, and MV–LY6326, with each treatment replicated three times. Each main plot measured 61.60 m2 (11.00 m × 5.60 m), with raised ridges between main plots covered with plastic film to prevent cross-contamination of water and nutrients.
Rapeseed and milk vetch were broadcast seeded on 14 October 2019, and 12 October 2020, at seeding rates of 5.00 kg ha−1 and 62.50 kg ha−1, respectively. Green manure crops were harvested on 23 April 2020, and 23 April 2021, chopped to 5–10 cm segments, and subsequently incorporated into the soil using a rotary tiller at a plowing depth of 20 cm. The biomass production and nutrient composition of both green manure crops at the time of incorporation are illustrated in Figure 1b–e.
Ratoon rice was manually transplanted at a spacing of 13.3 × 30.0 cm with three seedlings per hill. Detailed information regarding sowing, transplanting, tillering, heading, and maturity dates for ratoon rice, along with fertilizer application rates, is provided in Table 1. For the main crop, nitrogen fertilizer was applied in a basal:tillering:panicle ratio of 5:2:3, phosphorus fertilizer was applied entirely as basal application, and potassium fertilizer was distributed in a basal: panicle ratio of 4:3. For the ratoon crop, nitrogen fertilizer was applied in a bud-promoting: seedling-promoting ratio of 1:1, with bud-promoting fertilizer applied 10 days after main crop heading and seedling-promoting fertilizer applied 10 days after main crop harvest. Water management for ratoon rice followed established protocols: shallow water transplanting followed by deep water for establishment during the main crop phase, field drying upon achieving adequate tiller numbers, then alternate wetting and drying management until heading, after which fields were drained. Immediately following main crop harvest, fields were re-flooded, followed by moist field management for the ratoon crop until heading, then water was withheld until harvest. The stubble height at main crop harvest was maintained at the penultimate leaf collar level. Pest, disease, and weed management adhered to standardized technical protocols for large-scale local production.

2.4. Plant Height, Biomass, and Ratoon Rice Yield

Representative plant samples (three hills) were selected based on average tiller number per plot and collected at the tillering, heading, and maturity stages of the main crop, and at the heading and maturity stages of the ratoon crop. Plant height was measured from the root collar at the base to the highest point of the plant. Following height measurements, plants were separated into stem-sheath, leaf, and panicle components (during heading and maturity stages), subjected to initial heat treatment at 105 °C for 30 min, then oven-dried at 80 °C to constant mass. Each component was weighed separately to determine biomass.
Effective panicle number was determined in each plot prior to rice harvest, and grain yield was assessed from a 3 m2 sampling area containing uniformly growing rice plants within each plot. Harvested panicles were threshed, sun-dried, and cleaned by winnowing to remove impurities. Total grain weight and moisture content were subsequently determined, with final yield calculated based on standardized 14% moisture content.

2.5. Plant Nitrogen Determination

Organ samples obtained from Section 2.4 were ground and sieved through a 60-mesh screen. Weighed dry samples were placed in digestion tubes, mixed gently with concentrated sulfuric acid, and heated to 350 °C in a far-infrared digestion furnace. Upon complete digestion to a uniform brown liquid, samples were removed and cooled slightly before hydrogen peroxide addition, followed by reheating to gentle boiling. After cooling, hydrogen peroxide addition was repeated until the digestion solution became colorless and transparent. Digestion tubes were then removed, cooled, and the digestion solution was quantitatively transferred to volumetric flasks using distilled water, cooled to ambient temperature, diluted to volume, and filtered. Nitrogen concentration in plant organs was determined using a San++ continuous flow analyzer. Calculation formulas for nitrogen uptake and utilization efficiency are presented below [22,23]:
D M p l a n t   ( k g   h a − 1 ) = D M s s + D M l + D M p
N C o r g a n   ( k g   h a − 1 ) = D M o r g a n × N o r g a n
N C p l a n t   ( k g   h a − 1 ) = N C s s + N C l + N C p
N T s s N T l   k g   h a − 1 = N C s s N C l   a t   f u l l   h e a d i n g − N C s s N C l at   maturity
N A p   k g   h a − 1 = N C p   a t   m a t u r i t y − N C p   a t   f u l l   h e a d i n g
N T R s s N T R l   ( % ) = N T s s N T l / N C s s N C l   a t   f u l l   h e a d i n g × 100
N H I   ( % ) = N C p / N C p l a n t   a t   m a t u r i t y × 100
N D M P E   ( k g   k g − 1 ) = N C p l a n t / D M p l a n t at   maturity
N G P E   k g   k g − 1 = G r a i n   y i e l d / N C p l a n t   at   maturity
P F P N F   ( k g   k g − 1 ) = G r a i n   y i e l d / N a r
where D M p l a n t : Plant dry matter; D M s s : Stem-sheath dry matter; D M l : Leaf dry matter; D M p : Panicle dry matte; N C o r g a n : Organ nitrogen content; D M o r g a n : Organ dry matter; N o r g a n : Organ nitrogen concentration; N C p l a n t : Plant nitrogen content; N C s s : Stem-sheath nitrogen content; N C l : Leaf nitrogen content; N C p : Panicle nitrogen content; N T s s : Stem-sheath nitrogen translocation; N T l : Leaf nitrogen translocation; N A p : Panicle nitrogen accumulation; N T R s s : Stem-sheath nitrogen translocation rate; N T R l : Leaf nitrogen translocation rate; NHI: Nitrogen harvest index; NDMPE: Nitrogen dry matter production efficiency; NGPE: Nitrogen grain production efficiency; PFPNF: Partial factor productivity of nitrogen fertilizer; N a r : Nitrogen application rate.

2.6. Data Analysis

Statistical analyses were performed using SAS 9.4 for analysis of variance and multiple comparisons. Experimental results are presented as means ± standard errors of three replicates. Graphical representations were generated using R 4.2.3.

3. Results

3.1. Effects of Different Treatments on Ratoon Rice Grain Yield

Statistical analysis (Table 2) revealed that both green manure treatments and rice varieties significantly affected grain yield (p < 0.05), while their interaction was not significant. As shown in Figure 2, in 2021, LY6326 under RA treatment produced a significantly higher main crop grain yield than YLY911, with an increase of 11.66% (p < 0.05; Figure 2b). Moreover, LY6326 consistently outperformed YLY911 in annual total grain yield under both FA and RA treatments, showing increases of 9.02% and 7.62%, respectively (p < 0.05; Figure 2b). When averaged across years and varieties, RA and MV treatments markedly enhanced main crop yield by 16.37% and 9.31%, respectively, compared with FA (p < 0.05; Figure 2). In contrast, ratoon crop yield did not differ significantly among green manure treatments (Figure 2). Nevertheless, the annual total yield under RA and MV treatments exceeded FA by 11.34% and 7.78%, respectively (p < 0.05), with no statistical difference between RA and MV treatments (Figure 2).

3.2. Effects of Different Treatments on Ratoon Rice Plant Height

Green manure treatments and rice varieties significantly affected plant height across growth stages, with notable variations between cropping seasons (p < 0.05; Table 2, Figure 3). Main crop: LY6326 consistently exhibited significantly greater plant height than YLY911 under equivalent green manure conditions, except during heading and maturity stages in 2020 (p < 0.05; Figure 3). When averaged across years and varieties, RA and MV treatments generally promoted greater plant height (Figure 3). Relative to FA treatment, RA and MV increased plant height at heading by 6.56% and 3.27%, respectively, and at maturity by 4.37% and 1.97%, respectively (p < 0.05; Figure 3).
Ratoon crop: LY6326 consistently displayed greater plant height than YLY911 across all growth stages under identical green manure treatments (Figure 3). In 2021, when averaged across varieties, RA and MV treatments also produced greater plant height than FA treatment throughout ratoon crop development (Figure 3). Compared to FA treatment, RA and MV increased plant height at heading by 4.55% (p < 0.05) and 3.59% (p < 0.05), respectively, and at maturity by 7.26% (p < 0.05) and 2.51%, respectively (Figure 3).

3.3. Effects of Different Treatments on Ratoon Rice Dry Matter Accumulation

Green manure treatments and rice varieties significantly influenced dry matter accumulation in stem-sheath, leaf, panicle, and whole plant components across growth stages, with effects varying by developmental stage and plant organ (p < 0.05; Table 2, Figure 4). Main crop: At tillering, LY6326 exhibited significantly higher dry matter than YLY911 under specific conditions, including leaf and plant biomass under FA treatment in 2020, stem-sheath under FA treatment in 2021, leaf under all treatments, and plant under FA and RA treatments (p < 0.05; Figure 4a). Multi-year and variety-averaged analyses revealed that RA and MV treatments reduced stem-sheath dry matter by 6.09% and 18.38%, leaf dry matter by 2.15% and 2.28%, and total plant dry matter by 4.17% and 10.54%, respectively, compared to FA treatment (Figure 4a). At heading, YLY911 demonstrated significantly higher dry matter accumulation than LY6326 in multiple components: stem-sheath under all treatments in 2020, total plant under FA and RA treatments, stem-sheath under RA treatment in 2021, and panicle under all treatments (p < 0.05; Figure 4a). Multi-year and variety-averaged results showed that RA and MV treatments increased stem-sheath dry matter by 24.22% (p < 0.05) and 5.16%, leaf dry matter by 36.21% (p < 0.05) and 13.93% (p < 0.05), panicle dry matter by 21.58% and 10.28%, and total plant dry matter by 26.55% (p < 0.05) and 8.23%, respectively, compared to FA treatment (Figure 4a). At maturity, YLY911 maintained significantly higher dry matter than LY6326 across multiple organs and treatments (p < 0.05; Figure 4a). Multi-year and variety-averaged analyses demonstrated that RA and MV treatments enhanced stem-sheath dry matter by 8.33% (p < 0.05) and 7.63% (p < 0.05), leaf dry matter by 15.60% (p < 0.05) and 6.07%, panicle dry matter by 12.59% (p < 0.05) and 9.09% (p < 0.05), and total plant dry matter by 11.52% (p < 0.05) and 8.14% (p < 0.05), respectively, relative to FA treatment (Figure 4a).
Ratoon crop: At heading, YLY911 showed significantly higher stem-sheath and total plant dry matter than LY6326 under RA treatment in 2020 (p < 0.05; Figure 4b). Multi-year and variety-averaged results indicated that RA and MV treatments substantially increased dry matter accumulation compared to FA treatment: stem-sheath by 19.56% (p < 0.05) and 101.76% (p < 0.05), leaf by 33.79% and 123.37% (p < 0.05), panicle by 20.71% and 102.83% (p < 0.05), and total plant by 21.82% and 105.03% (p < 0.05), respectively (Figure 4b). At maturity, varietal differences were minimal except for panicle under FA treatment in 2021 (Figure 4b). RA and MV treatments increased stem-sheath dry matter by 7.27% and 2.47%, leaf dry matter by 11.45% and 5.49%, panicle dry matter by 7.51% and 11.60%, and total plant dry matter by 7.92% and 6.72%, respectively, compared to FA treatment (Figure 4b).
From an annual perspective, multi-year and variety-averaged analyses revealed that RA and MV treatments enhanced total plant dry matter by 24.40% (p < 0.05) and 5.63% at heading, and by 9.83% (p < 0.05) and 7.47% (p < 0.05) at maturity, respectively, compared to FA treatment (Figure 4c).

3.4. Effects of Different Treatments on Ratoon Rice Nitrogen Content

Green manure treatments and rice varieties significantly affected nitrogen content across plant organs and growth stages, with variable effects depending on developmental timing and organ type (p < 0.05; Table 2, Figure 5). Main crop: At tillering in 2021, LY6326 exhibited higher nitrogen content in stem-sheath, leaf, and whole plant compared to YLY911 (Figure 5a). However, variety-averaged analyses showed no significant treatment differences in organ nitrogen content (Figure 5a). At heading in 2021, LY6326 displayed higher stem-sheath and leaf nitrogen content than YLY911, while showing lower panicle and whole plant nitrogen content (Figure 5a). Variety-averaged results demonstrated that RA and MV treatments increased leaf nitrogen content by 55.12% (p < 0.05) and 11.84%, respectively, compared to FA treatment, while other organs showed no significant treatment differences (Figure 5a). At maturity, YLY911 consistently maintained higher stem-sheath and leaf nitrogen content than LY6326 across all treatments and years, while exhibiting lower panicle and whole plant nitrogen content (Figure 5a). Multi-year and variety-averaged analyses revealed that RA and MV treatments enhanced stem-sheath nitrogen content by 12.33% and 1.04%, leaf nitrogen content by 13.68% and 0.20%, panicle nitrogen content by 14.63% (p < 0.05) and 9.35%, and total plant nitrogen content by 13.80% (p < 0.05) and 5.49% (p < 0.05), respectively, compared to FA treatment (Figure 5a).
Ratoon crop: At heading in 2021, YLY911 demonstrated significantly higher leaf nitrogen content than LY6326 under RA treatment (p < 0.05), while other organs showed no varietal differences under other treatments (Figure 5b). Variety-averaged results indicated that RA and MV treatments increased leaf nitrogen content by 66.41% (p < 0.05) and 32.78%, and total plant nitrogen content by 18.77% (p < 0.05) and 5.95%, respectively, compared to FA treatment, while stem-sheath and panicle showed no significant treatment effects (Figure 5b). At maturity, LY6326 exhibited significantly higher nitrogen content in specific organ-treatment combinations compared to YLY911 (p < 0.05; Figure 5b). Multi-year and variety-averaged analyses showed that RA and MV treatments enhanced stem-sheath nitrogen content by 2.29% and 6.73%, leaf nitrogen content by 0.58% and 8.74%, panicle nitrogen content by 5.19% and 24.95% (p < 0.05), and total plant nitrogen content by 3.69% and 16.56% (p < 0.05), respectively, relative to FA treatment (Figure 5b).
From an annual perspective, variety-averaged results at heading in 2021 showed that RA and MV treatments increased total plant nitrogen content by 31.83% (p < 0.05) and 8.89%, respectively, compared to FA treatment (Figure 5c). Multi-year and variety-averaged analyses demonstrated that RA and MV treatments enhanced total plant nitrogen content at maturity by 9.42% (p < 0.05) and 10.29% (p < 0.05), respectively, relative to FA treatment (Figure 5c).

3.5. Effects of Different Treatments on Nitrogen Translocation in Ratoon Rice

Green manure treatments and rice varieties significantly influenced nitrogen translocation dynamics, with organ-specific variations in response magnitude (p < 0.05; Table 2, Figure 6). Main crop: Using RA-LY6326 as the reference treatment, other combinations demonstrated substantial reductions in nitrogen translocation parameters. Specifically, FA-YLY911, FA-LY6326, RA-YLY911, MV-YLY911, and MV-LY6326 reduced stem-sheath nitrogen translocation by 89.43%, 87.36%, 80.38%, 81.00%, and 57.13%, respectively (p < 0.05; Figure 6a). Similarly, leaf nitrogen translocation was reduced by 93.40%, 59.16%, 65.98%, 90.90%, and 31.22%, respectively (p < 0.05; Figure 6a). Corresponding reductions in translocation efficiency were observed for both stem-sheath and leaf components (Figure 6a). Under equivalent treatment conditions, LY6326 consistently achieved significantly higher panicle nitrogen accumulation than YLY911 (p < 0.05), with peak values observed under RA treatment (Figure 6b).
Ratoon crop: RA and MV treatments enhanced nitrogen translocation parameters relative to FA treatment (Figure 6a). Although stem-sheath nitrogen translocation showed no significant treatment differences, leaf nitrogen translocation under RA-YLY911 was significantly higher than other treatments (p < 0.05) (Figure 6a). While MV treatment produced the highest panicle nitrogen accumulation for both varieties (33.81 kg ha−1 for YLY911 and 38.13 kg ha−1 for LY6326), treatment differences were not statistically significant (Figure 6b).
From an annual perspective, RA and MV treatments demonstrated superior nitrogen translocation performance compared to FA treatment across both stem-sheath and leaf components (Figure 6a). FA-YLY911 exhibited the poorest nitrogen translocation characteristics, while RA-LY6326 performed optimally (Figure 6a). Variety-averaged analyses revealed that RA and MV treatments increased panicle nitrogen accumulation by 11.73% and 38.26% (p < 0.05), respectively, compared to FA treatment (Figure 6b).

3.6. Effects of Different Treatments on Nitrogen Utilization Characteristics in Ratoon Rice

Green manure treatments and rice varieties significantly affected NHI and PFPNF (p < 0.05; Table 2 and Figure 7a,d). While effects on NDMPE and NGPE were generally not statistically significant (Table 2), discernible trends were observed (Figure 7b,c). Main crop: In 2021, LY6326 consistently demonstrated significantly higher NHI than YLY911 across all treatments (p < 0.05; Figure 7a). Under RA treatment in 2021, LY6326 also exhibited significantly superior PFPNF compared to YLY911 (p < 0.05; Figure 7d). Multi-year and variety-averaged analyses showed that RA and MV treatments enhanced NHI by 1.34% and 3.77%, NGPE by 2.02% and 3.42%, and PFPNF by 16.37% (p < 0.05) and 9.31% (p < 0.05), respectively, compared to FA treatment (Figure 7a,c,d).
Ratoon crop: No significant varietal differences were observed in nitrogen utilization parameters across years and treatments (Figure 7). Multi-year and variety-averaged results indicated that RA and MV treatments improved NHI by 1.41% and 8.03%, and PFPNF by 5.19% and 5.90%, respectively, relative to FA treatment (Figure 7a,d). Conversely, FA and RA treatments enhanced NDMPE by 10.41% and 14.05%, and NGPE by 12.33% and 11.82%, respectively, compared to MV treatment (p < 0.05; Figure 7b,c).
From an annual perspective, LY6326 maintained significantly higher NHI than YLY911 across all treatments in 2021 (p < 0.05; Figure 7a). Under RA treatment in 2021, LY6326 also exhibited significantly superior NGPE (p < 0.05; Figure 7c) and PFPNF under both FA and RA treatments (p < 0.05; Figure 7d). Multi-year and variety-averaged analyses demonstrated that RA and MV treatments enhanced NHI by 1.54% and 5.65% (p < 0.05), and PFPNF by 11.34% (p < 0.05) and 7.78% (p < 0.05), respectively, compared to FA treatment (Figure 7a,d). FA and RA treatments improved NDMPE by 2.64% and 2.82%, and NGPE by 4.80% and 3.42%, respectively, relative to MV treatment (Figure 7b,c).

4. Discussion

4.1. Effects of Winter Green Manure and Rice Varieties on Grain Yield and Dry Matter

This study found that RA and MV treatments significantly enhanced grain yield in main season rice and total annual yield, while exerting no significant effect on ratoon season rice yield (Figure 2). These results indicate that green manure treatments produced pronounced yield-increasing effects in main season rice but failed to demonstrate similar benefits in ratoon season rice. Both treatments enhanced dry matter accumulation in stems and sheaths, leaves, panicles, and whole plants at heading and maturity stages, with more pronounced effects at the heading stage (Figure 4). This phenomenon can be attributed to improved soil nutrient supply, enhanced root activity, and accelerated organic matter mineralization following green manure incorporation [24], thereby optimizing soil quality during critical growth stages of main season rice and promoting yield and dry matter accumulation. The limited effects of green manure on ratoon season rice likely reflect the dependence of ratoon rice on nutrients accumulated during the main season. Consequently, green manure effects are concentrated primarily on early-stage soil nutrient improvement, with minimal impact on ratoon rice tillering and growth [25]. This finding aligns with previous research indicating that green manure effects vary across seasons and growth stages, with more pronounced benefits in nutrient-poor soils [26,27]. Although RA and MV treatments showed no significant yield differences (Figure 2), subtle variations in stage-specific dry matter accumulation regulation were observed (Figure 4), offering new insights for future research on green manure regulatory mechanisms.
Varietal differences significantly influenced yield and dry matter accumulation in ratoon rice. LY6326 demonstrated superior grain yield in main season rice compared to YLY911 (Figure 2), potentially due to its higher photosynthetic efficiency and nutrient transport capacity. Conversely, YLY911 exhibited superior dry matter accumulation in certain organs and periods (Figure 4), possibly reflecting its enhanced adaptability and distinct resource allocation mechanisms. These inter-varietal differences in dry matter accumulation and distribution likely stem from genetic variations in regulatory mechanisms governing photosynthesis, nutrient absorption, and matter allocation [28,29]. These findings underscore the importance of selecting varieties suited to specific cultivation conditions for optimizing yield and dry matter accumulation in ratoon rice production [30,31].

4.2. Effects of Winter Green Manure and Rice Varieties on Nitrogen Uptake and Utilization

Further analysis revealed that RA and MV treatments significantly increased nitrogen content across rice plant organs and enhanced overall nitrogen accumulation, with more pronounced effects at heading and maturity stages (Figure 5). Additionally, these treatments significantly improved nitrogen transport to panicles, promoting panicle nitrogen accumulation and PFPNF (Figure 6b and Figure 7d). These effects likely result from organic matter inputs following green manure incorporation (Figure 1b–e), which improved soil carbon–nitrogen ratios and rhizosphere microecological environments, thereby enhancing nitrogen mineralization processes and rice nitrogen uptake and transport [32,33]. The substantial increase in nitrogen accumulation at the heading stage suggests that green manure provided a continuous, effective nitrogen source during critical growth periods while enhancing source–sink coordination [34,35]. Despite significant promotional effects on main season rice nitrogen uptake, green manure showed limited enhancement of ratoon season rice nitrogen uptake (Figure 5, Figure 6 and Figure 7). This outcome may be explained by the limited carryover of nutrients and the mismatch between nutrient release and crop demand. During the main season rice, most of the available nutrients released from green manure, particularly nitrogen, were absorbed by the main season rice, leaving only a small residual supply for the ratoon season rice. Furthermore, the decomposition and mineralization of green manure may not coincide with the peak nutrient requirements of ratoon season rice, thereby reducing its role as a nutrient source. Nutrient acquisition in ratoon season rice also relies more on carbon and nitrogen reserves stored in the root system and basal stems of the mother plants rather than on external soil-derived nutrients, which further accounts for the limited effect of green manure in the ratoon season. Overall, these findings indicate that the benefits of green manure are primarily concentrated on improving soil nutrient availability in the main crop, while its sustained contribution to tillering and nitrogen accumulation in ratoon season rice remains limited. Unlike some previous studies [27,36], this research observed no significant enhancement of ratoon season rice nitrogen accumulation by green manure, further emphasizing the differential effects across growth stages.
Varietal differences in nitrogen utilization were also evident. LY6326 exhibited higher NHI and PFPNF in main season rice (Figure 7a,d), indicating superior nitrogen use efficiency. This advantage may relate to stronger root absorption capacity, nitrogen assimilation potential, and higher photosynthetic efficiency, promoting grain filling and effective nitrogen allocation [37,38]. In contrast, while YLY911 performed better in nitrogen accumulation in certain organs, it showed lower overall PFPNF (Figure 5 and Figure 7d), possibly due to inferior source–sink transport efficiency and nitrogen allocation coordination. Varietal differences were most pronounced in main season rice but narrowed in ratoon season rice, suggesting reduced dependence of ratoon rice on varietal genetic characteristics [31,39,40]. These findings support the existence of genetic regulatory differences in nitrogen accumulation and distribution among varieties [41] and emphasize the importance of synergistic optimization between variety selection and cultivation management for efficient nitrogen fertilizer utilization.

4.3. Effects of Year and Multi-Factor Interactions

In this study, the main effect of year exhibited significant variations across multiple agronomic traits (Table 2), including grain yield, dry matter accumulation, nitrogen uptake, NHI, and PFPNF. These results emphasize the pivotal role of interannual climatic variability in shaping the performance of ratoon rice production. Overall, most traits performed better in 2021 compared to 2020, likely due to more favorable climatic conditions. Meteorological data from the experimental site indicate that the growth period of ratoon season rice in 2021 was characterized by relatively low rainfall and moderate temperatures (Figure 1a), which likely enhanced photosynthetic efficiency, promoted carbon and nitrogen metabolism, and facilitated dry matter accumulation, thereby improving plant growth and productivity [42]. It is important to note that climate effects are rarely isolated; they interact with varietal characteristics and management practices, collectively determining crop performance and resource use efficiency. Consequently, climatic fluctuations can modulate the responses of various treatment combinations, either enhancing or diminishing the effectiveness of green manure application and variety selection. Although soil physicochemical properties were not monitored during the two years of this study, the observed climatic differences alone were sufficient to induce substantial variations in system performance across years, underscoring the significant role of year effects in green cultivation systems. To better understand the potential coupling mechanisms among climate, soil, variety, and management practices, future long-term studies should not only continue monitoring meteorological factors but also include systematic soil data collection. This would provide a more comprehensive basis for optimizing green manure practices and evaluating their adaptability to different regions.
As shown in Table 2, the interaction terms Y × S × G, Y × S × V, S × G × V, and Y × S × G × V exhibited significant effects on traits such as plant height, dry matter accumulation, and nitrogen uptake, indicating that rice performance and nitrogen use efficiency are jointly influenced by year, cropping season, green manure treatment, and variety. While the significance of each interaction varied depending on the specific trait, these results highlight the complex interplay among multiple factors. For instance, the cultivar LY6326 under the RA treatment exhibited significantly higher grain yield, NHI, and PFPNF than YLY911 in the main season of 2021, whereas such differences were less pronounced in 2020 (Figure 2 and Figure 7a,d). This suggests that the positive effects of green manure are not consistently realized across all years and treatment combinations, but instead depend on the interaction between climatic conditions, varietal traits, and management strategies. These findings confirm the high sensitivity of ratoon rice systems to both environmental factors and agronomic practices, emphasizing the necessity to consider the stability and adaptability of treatment combinations under varying climatic conditions when designing optimized green cultivation strategies, ultimately enhancing the system’s overall productivity and resilience.

4.4. Research Significance, Limitations, and Future Directions

This study systematically explored the regulatory effects of green manure treatments and rice variety configurations on nitrogen uptake, transport, and use efficiency in ratoon rice. Results demonstrated that both green manure treatments and variety configurations play significant roles in enhancing nitrogen accumulation and transport efficiency while optimizing nitrogen fertilizer utilization. Theoretically, this research expanded understanding of nitrogen spatial–temporal distribution and dynamics in crop nutritional ecology, addressing the knowledge gap regarding green manure effects on full-season nitrogen metabolism in ratoon rice production systems [43]. These findings provide important evidence for developing efficient planting theories based on “variety-nutrient regulation” models [40]. Practically, RA and MV treatments significantly improved PFPNF and nitrogen harvest capacity in main season rice, while the high nitrogen use efficiency potential of LY6326 during the main season (Figure 6 and Figure 7) offers feasible pathways for sustainable ratoon rice production. These results provide theoretical and practical guidance for establishing efficient rice production systems without significantly increasing nitrogen fertilizer inputs.
However, several limitations warrant consideration. First, the relatively homogeneous ecological environment of the research site limits the generalizability of findings across different regional soil and climatic conditions [44,45]. Second, this study focused primarily on plant nitrogen content and organ transport characteristics, lacking in-depth exploration of underlying physiological mechanisms and molecular regulatory processes, particularly nitrogen transport protein expression and key enzyme activities [46,47]. Finally, comprehensive evaluation of green manure effects on rice quality, nitrogen losses, and environmental impacts remains insufficient, with carbon–nitrogen synergistic regulatory mechanisms requiring further investigation [48]. Future research should conduct long-term experiments across multiple ecological regions, integrating 15N isotope tracing, rhizosphere process monitoring, and multi-omics analyses to elucidate the eco-physiological basis of efficient nitrogen utilization under green manure-variety interactions. Additionally, comprehensive evaluation of synergistic benefits across yield, quality, and environmental parameters is essential for developing sustainable ratoon rice production systems.

5. Conclusions

Field experiments demonstrated that, compared with the fallow control, the incorporation of rapeseed and milk vetch significantly enhanced main crop yields and total annual ratoon rice productivity, with rapeseed showing superior performance, while LY6326 exhibited greater responsiveness. In contrast, neither type of green manure significantly affected the ratoon-season yield, suggesting that the yield benefit was mainly confined to the first-season crop. Green manure incorporation substantially increased plant dry matter accumulation, elevated plant nitrogen content at maturity, enhanced nitrogen accumulation in panicles, and improved both NHI and PFPNF. LY6326 showed superior nitrogen accumulation and utilization capacity. These findings indicate that incorporating rapeseed and milk vetch can significantly improve ratoon rice yield and nitrogen efficiency, offering key insights for developing sustainable rice cropping systems. To sustain these benefits, catch crops should be incorporated into the system annually, and strategic selection of compatible green manure species together with ratoon rice varieties is essential for maximizing agronomic returns. Nevertheless, this study was conducted in a single location without cross-regional validation and did not investigate the physiological or molecular mechanisms of nitrogen utilization. Future research should therefore involve long-term, multi-site trials and employ 15N isotope tracing to elucidate the regulatory pathways underlying green manure–cultivar interactions in improving nitrogen use efficiency.

Author Contributions

Conceptualization, Q.H. and Y.X. (Ying Xu); methodology, Q.H., P.S., S.C., and Y.X. (Ying Xu); software, Q.H. and Y.X. (Ying Xu); formal analysis, Q.H. and Y.X. (Ying Xu); investigation, Q.H., P.S., S.C., Z.Y. (Zhangzhen Yang), Z.Y. (Zhixiong Yuan), L.Z., Z.Z., Y.W., C.G., J.T., Y.X. (Yaoyun Xu), Y.Z., and C.Y.; resources, C.H.; data curation, Q.H., P.S., S.C., and Y.X. (Ying Xu); writing—original draft preparation, Q.H., P.S., and S.C.; writing—review and editing, C.H. and Y.X. (Ying Xu); visualization, Q.H., P.S., and S.C.; supervision, Y.X. (Ying Xu); project administration, Y.X. (Ying Xu); funding acquisition, C.H. and Y.X. (Ying Xu). All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the National Key Research and Development Program of China (2024YFD2300301), the National Natural Science Foundation of China (32372237, 31801319), the Science and Technology Innovation Program of Hunan Province (2023RC3153), the Natural Science Foundation for Distinguished Young Scholars of Changsha City (kq2209016), and the Key Scientific Research Project of the Hunan Provincial Department of Education (24A0160).

Institutional Review Board Statement

Not applicable.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
YLY911Yliangyou 911
LY6326Liangyou 6326
FAfallow–ratoon rice
RArapeseed–ratoon rice
MVmilk vetch–ratoon rice
NHINitrogen harvest index
NDMPENitrogen dry matter production efficiency
NGPENitrogen grain production efficiency
PFPNFPartial factor productivity of nitrogen fertilizer

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Figure 1. Meteorological conditions and characteristics of the incorporated green manure at the experimental site (2019–2021): (a) daily rainfall and maximum, minimum, and mean temperatures, with the left y-axis representing rainfall and the right y-axis representing temperature; (b) biomass of the incorporated green manure; (c) carbon content of the incorporated green manure; (d) nitrogen content of the incorporated green manure; (e) carbon-to-nitrogen ratio of the incorporated green manure. Different lowercase letters in the figure indicate statistically significant differences between rapeseed and milk vetch at the p < 0.05 level.
Figure 1. Meteorological conditions and characteristics of the incorporated green manure at the experimental site (2019–2021): (a) daily rainfall and maximum, minimum, and mean temperatures, with the left y-axis representing rainfall and the right y-axis representing temperature; (b) biomass of the incorporated green manure; (c) carbon content of the incorporated green manure; (d) nitrogen content of the incorporated green manure; (e) carbon-to-nitrogen ratio of the incorporated green manure. Different lowercase letters in the figure indicate statistically significant differences between rapeseed and milk vetch at the p < 0.05 level.
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Figure 2. Grain yield of ratoon rice under different treatments in (a) 2020 and (b) 2021. Columns bearing different lowercase letters differ significantly within the same season (p < 0.05). Lowercase letters positioned above each column represent annual grain yield and likewise indicate significant differences among treatments (p < 0.05).
Figure 2. Grain yield of ratoon rice under different treatments in (a) 2020 and (b) 2021. Columns bearing different lowercase letters differ significantly within the same season (p < 0.05). Lowercase letters positioned above each column represent annual grain yield and likewise indicate significant differences among treatments (p < 0.05).
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Figure 3. Plant height of ratoon rice under different treatments. The top and bottom edges of the box plot represent the 75th and 25th percentiles, respectively; the horizontal line within the box indicates the median. Dots represent individual measurements (n = 9). Different lowercase letters within the same panel indicate statistically significant differences among treatments at the p < 0.05 level.
Figure 3. Plant height of ratoon rice under different treatments. The top and bottom edges of the box plot represent the 75th and 25th percentiles, respectively; the horizontal line within the box indicates the median. Dots represent individual measurements (n = 9). Different lowercase letters within the same panel indicate statistically significant differences among treatments at the p < 0.05 level.
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Figure 4. Dry matter accumulation dynamics in ratoon rice under different treatments during the main season (a), ratoon season (b), and throughout the annual cycle (c). Different lowercase letters within bars indicate significant differences among treatments within the same growth period at p < 0.05. Different lowercase letters above bars indicate significant differences in total plant dry matter accumulation (a,b) and annual dry matter accumulation (c) among treatments at p < 0.05.
Figure 4. Dry matter accumulation dynamics in ratoon rice under different treatments during the main season (a), ratoon season (b), and throughout the annual cycle (c). Different lowercase letters within bars indicate significant differences among treatments within the same growth period at p < 0.05. Different lowercase letters above bars indicate significant differences in total plant dry matter accumulation (a,b) and annual dry matter accumulation (c) among treatments at p < 0.05.
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Figure 5. Changes in nitrogen content of ratoon rice under different treatments during the main season (a), ratoon season (b), and throughout the annual cycle (c). Different lowercase letters within bars indicate significant differences among treatments at the same growth stage at p < 0.05. Different lowercase letters above bars indicate significant differences in plant nitrogen content (a,b) and annual nitrogen content (c) among treatments at p < 0.05.
Figure 5. Changes in nitrogen content of ratoon rice under different treatments during the main season (a), ratoon season (b), and throughout the annual cycle (c). Different lowercase letters within bars indicate significant differences among treatments at the same growth stage at p < 0.05. Different lowercase letters above bars indicate significant differences in plant nitrogen content (a,b) and annual nitrogen content (c) among treatments at p < 0.05.
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Figure 6. Nitrogen translocation dynamics from stem-sheath and leaves (a) and panicle nitrogen accumulation (b) in ratoon rice under different treatments post-heading. In panel (a), data in the heatmap represent mean values; different lowercase letters indicate significant differences among treatments within the same season and plant organ at p < 0.05. In panel (b), different lowercase letters above bars indicate significant differences among treatments at p < 0.05.
Figure 6. Nitrogen translocation dynamics from stem-sheath and leaves (a) and panicle nitrogen accumulation (b) in ratoon rice under different treatments post-heading. In panel (a), data in the heatmap represent mean values; different lowercase letters indicate significant differences among treatments within the same season and plant organ at p < 0.05. In panel (b), different lowercase letters above bars indicate significant differences among treatments at p < 0.05.
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Figure 7. Nitrogen harvest index (a), nitrogen dry matter production efficiency (b), nitrogen grain production efficiency (c), and partial factor productivity of nitrogen fertilizer (d) in ratoon rice under different treatments. Different lowercase letters above the columns indicate significant differences among treatments within the same season at p < 0.05.
Figure 7. Nitrogen harvest index (a), nitrogen dry matter production efficiency (b), nitrogen grain production efficiency (c), and partial factor productivity of nitrogen fertilizer (d) in ratoon rice under different treatments. Different lowercase letters above the columns indicate significant differences among treatments within the same season at p < 0.05.
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Table 1. Growth stages and fertilizer application of main and ratoon crops in 2020 and 2021.
Table 1. Growth stages and fertilizer application of main and ratoon crops in 2020 and 2021.
YearCrop SeasonVarietiesSowing DateTransplanting DateTillering StageFull Heading StageMaturity StageGrowing PeriodChemical Input (kg ha−1)
(Day/Month)(Days)NP2O5K2O
2020Main crop YLY911 120-March27-April26-May14-July9-Auguest14220090120
LY6326 220-March27-April26-May5-July9-Auguest14220090120
Ratoon crop YLY911///12-Sepember9-October6115000
LY6326///14-Sepember9-October6115000
2021Main crop YLY91123-March30-April26-May18-July9-Auguest13920090120
LY632623-March30-April26-May6-July9-Auguest13920090120
Ratoon crop YLY911///14-Sepember9-October6115000
LY6326///14-Sepember9-October6115000
1 YLY911, Yliangyou911; 2 LY6326; Liangyou6326.
Table 2. Analysis of variance for plant height, dry matter weight, and nitrogen accumulation, yield, nitrogen harvest index (NHI), nitrogen dry matter production efficiency (NDMPE), nitrogen grain production efficiency (NGPE), and partial factor productivity of nitrogen fertilizer (PFPNF) as affected by year (Y), crop season (S), green manure (G), rice variety (V), and their interactions.
Table 2. Analysis of variance for plant height, dry matter weight, and nitrogen accumulation, yield, nitrogen harvest index (NHI), nitrogen dry matter production efficiency (NDMPE), nitrogen grain production efficiency (NGPE), and partial factor productivity of nitrogen fertilizer (PFPNF) as affected by year (Y), crop season (S), green manure (G), rice variety (V), and their interactions.
Growth StageIndicatorFactorYSGVY × SY × GY × VS × GS × VG × VY × S × GY × S × VY × G × VS × G × VY × S × G × V
Tillering stagePlant heightPlant0.54 ns 1/2.38 ns103.16 ***/3.73 *0.83 ns//0.38 ns//2.59 ns//
Dry matter weightStem-sheath6.32 2,*/4.49 *6.28 */2.60 ns2.64 ns//2.62 ns//0.38 ns//
Leaf19.62 ***/0.10 ns29.65 ***/2.39 ns0.69 ns//1.04 ns//0.87 ns//
Plant19.62 ***/0.10 ns29.65 ***/2.39 ns0.69 ns//1.04 ns//0.87 ns//
Nitrogen
accumulation		Stem-sheath//0.06 ns10.10 **/////0.98 ns/////
Leaf//1.09 ns18.40 **/////0.09 ns/////
Plant//0.30 ns22.36 ***/////0.28 ns/////
Full
heading stage		Plant heightPlant226.76 ***769.05 ***25.02 ***37.80 ***17.74 ***7.96 ***3.63 ns1.83 ns1.91 ns0.27 ns2.49 ns6.56 *1.34 ns2.45 ns3.24 *
Dry matter weightStem-sheath0.10 ns22.11 ***20.21 ***0.77 ns0.25 ns2.68 ns25.29 ***0.45 ns2.77 ns0.56 ns5.66 **14.55 ***1.52 ns1.95 ns0.72 ns
Leaf20.78 ***384.82 ***25.08 ***2.18 ns0.01 ns9.62 ***2.23 ns3.44 *2.21 ns0.35 ns1.20 ns16.53 ***0.37 ns0.63 ns1.57 ns
Panicle36.74 ***0.26 ns4.77 *17.02 ***0.05 ns2.61 ns7.83 **0.25 ns8.98 **0.03 ns0.47 ns11.58 **0.64 ns0.36 ns1.99 ns
Plant12.88 ***62.63 ***24.80 ***7.13 *0.18 ns5.99 **5.24 *0.85 ns0.02 ns0.21 ns2.83 ns3.92 ns1.05 ns0.79 ns0.23 ns
Nitrogen
accumulation		Stem-sheath/8.19 **6.40 **0.95 ns///4.99 *0.98 ns0.25 ns///0.98 ns/
Leaf/116.08 ***21.49 ***0.07 ns///2.42 ns18.28 ***2.96 ns///3.86 */
Panicle/0.09 ns1.96 ns14.05 **///0.15 ns13.03 **0.08 ns///1.43 ns/
Plant/20.59 ***11.72 ***1.55 ns///2.44 ns0.00 ns0.04 ns///0.97 ns/
Maturity stagePlant heightPlant194.40 ***741.68 ***18.18 ***51.22 ***2.43 ns5.12 **9.14 **1.74 ns2.40 ns4.01 *2.54 ns7.05 **1.36 ns1.57 ns0.57 ns
Dry matter weightStem-sheath8.77 **68.53 ***4.86 *8.16 **13.11 ***0.68 ns4.53 *0.56 ns3.91 ns1.29 ns1.22 ns0.16 ns0.70 ns1.84 ns0.63 ns
Leaf141.27 ***843.75 ***9.84 ***28.54 ***34.22 ***5.75 **15.16 ***2.32 ns48.94 ***2.37 ns1.57 ns1.87 ns0.71 ns1.51 ns3.13 ns
Panicle1.25 ns155.69 ***9.50 ***13.71 ***5.65 *5.15 **11.94 **1.28 ns7.17 *0.67 ns0.42 ns2.91 ns0.75 ns0.50 ns1.56 ns
Plant12.14 **104.54 ***17.19 ***0.02 ns7.44 **4.32 *0.18 ns0.94 ns0.50 ns1.37 ns0.87 ns0.52 ns0.46 ns0.39 ns0.99 ns
Nitrogen
accumulation		Stem-sheath9.93 **0.53 ns1.69 ns1.22 ns0.56 ns1.41 ns1.60 ns2.00 ns19.49 ***2.23 ns1.35 ns1.81 ns0.07 ns0.59 ns0.90 ns
Leaf30.83 ***743.37 ***3.37 *36.53 ***36.50 ***1.56 ns19.80 ***5.20 **50.03 ***1.12 ns3.51 *0.95 ns0.55 ns0.03 ns2.15 ns
Panicle82.71 ***119.82 ***10.90 ***17.32 ***0.00 ns0.80 ns1.00 ns5.40 **12.94 ***0.13 ns0.65 ns0.93 ns0.80 ns0.12 ns0.83 ns
Plant19.79 ***220.09 ***12.10 ***2.32 ns2.69 ns0.16 ns0.67 ns9.97 ***1.14 ns0.46 ns1.61 ns1.87 ns0.22 ns0.07 ns0.05 ns
After full heading stageNitrogen translocationStem-sheath/8.28 **5.24 *4.25 ns///1.59 ns5.74 *1.68 ns///2.68 ns/
Leaf/16.72 ***12.16 ***10.50 **///1.15 ns40.04 ***1.30 ns///5.35 */
Panicle/51.10 ***4.62 *42.87 ***///4.94 *36.58 ***0.56 ns///1.27 ns/
Nitrogen translocation rateStem-sheath/8.52 **5.02 *4.05 ns///0.99 ns6.69 *1.17 ns///2.59 ns/
Leaf/0.40 ns3.03 ns8.47 **///0.13 ns24.00 ***2.55 ns///2.44 ns/
Maturity stageYieldActual yield21.33 ***264.02 ***17.50 ***7.57 **52.49 ***0.93 ns4.13 *5.89 **0.44 ns0.41 ns0.36 ns0.07 ns0.06 ns1.58 ns0.13 ns
Nitrogen use efficiencyNHI102.85 ***2.25 ns4.27 *16.48 ***10.93 **2.74 ns7.72 **0.61 ns39.98 ***1.12 ns0.35 ns0.04 ns0.46 ns0.17 ns2.17 ns
NDMPE36.22 ***46.95 ***2.20 ns3.41 ns6.54 *1.75 ns1.64 ns8.33 ***0.93 ns0.00 ns0.56 ns1.16 ns0.16 ns0.20 ns1.20 ns
NGPE32.25 ***1.18 ns1.18 ns0.09 ns12.10 **0.53 ns3.26 ns2.73 ns0.94 ns0.36 ns0.49 ns0.88 ns0.19 ns0.38 ns0.10 ns
PFPNF27.92 ***6.48 *13.00 ***6.14 *54.52 ***0.75 ns3.50 ns3.09 ns0.07 ns0.36 ns0.27 ns0.00 ns0.05 ns1.37 ns0.11 ns
1 Data are F-values; ns denotes not significant. 2 p < 0.001 (***), 0.001 ≤ p < 0.01 (**), 0.01 ≤ p < 0.05 (*).
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Hou, Q.; Shao, P.; Chen, S.; Yang, Z.; Yuan, Z.; Zhong, L.; Zhao, Z.; Wang, Y.; Ga, C.; Tang, J.; et al. Effects of Winter Green Manure Incorporation on Grain Yield, Nitrogen Uptake, and Nitrogen Use Efficiency in Different Ratoon Rice Varieties. Agriculture 2025, 15, 1801. https://doi.org/10.3390/agriculture15171801

AMA Style

Hou Q, Shao P, Chen S, Yang Z, Yuan Z, Zhong L, Zhao Z, Wang Y, Ga C, Tang J, et al. Effects of Winter Green Manure Incorporation on Grain Yield, Nitrogen Uptake, and Nitrogen Use Efficiency in Different Ratoon Rice Varieties. Agriculture. 2025; 15(17):1801. https://doi.org/10.3390/agriculture15171801

Chicago/Turabian Style

Hou, Qiwen, Pufan Shao, Sheng Chen, Zhangzhen Yang, Zhixiong Yuan, Liusheng Zhong, Ziyuan Zhao, Yu Wang, Cuo Ga, Jiarui Tang, and et al. 2025. "Effects of Winter Green Manure Incorporation on Grain Yield, Nitrogen Uptake, and Nitrogen Use Efficiency in Different Ratoon Rice Varieties" Agriculture 15, no. 17: 1801. https://doi.org/10.3390/agriculture15171801

APA Style

Hou, Q., Shao, P., Chen, S., Yang, Z., Yuan, Z., Zhong, L., Zhao, Z., Wang, Y., Ga, C., Tang, J., Xu, Y., Zeng, Y., Yu, C., Huang, C., & Xu, Y. (2025). Effects of Winter Green Manure Incorporation on Grain Yield, Nitrogen Uptake, and Nitrogen Use Efficiency in Different Ratoon Rice Varieties. Agriculture, 15(17), 1801. https://doi.org/10.3390/agriculture15171801

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