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Article

Experimental Warming Reduces the Grain Yield and Nitrogen Utilization Efficiency of Double-Cropping indica Rice in South China

by
Taotao Yang
1,
Jixiang Zou
1,
Longmei Wu
1,
Xiaozhe Bao
1,
Yu Jiang
2,
Nan Zhang
2 and
Bin Zhang
1,*
1
Rice Research Institute, Guangdong Academy of Agricultural Sciences, Guangdong Key Laboratory of New Technology in Rice Breeding, Guangdong Rice Engineering Laboratory, Key Laboratory of Genetics and Breeding of High-Quality Rice in Southern China (Co-Construction by Ministry and Province), Ministry of Agriculture and Rural Affairs, Guangzhou 510640, China
2
Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University, Nanjing 210095, China
*
Author to whom correspondence should be addressed.
Agriculture 2024, 14(6), 921; https://doi.org/10.3390/agriculture14060921
Submission received: 9 April 2024 / Revised: 30 May 2024 / Accepted: 5 June 2024 / Published: 11 June 2024
(This article belongs to the Special Issue Rice Ecophysiology and Production: Yield, Quality and Sustainability)
Browse Figure
Versions Notes

Abstract

:
The effect of climate warming on rice production in China is profound, yet there has been limited research on how it affects the grain yield, nitrogen (N) uptake, and N utilization efficiency (NUtE) of the double-cropping indica rice in South China. To address this gap, we conducted a free air temperature increase (FATI) experiment in Guangdong province during 2020 and 2021. Our findings revealed that warming led to a significant reduction in grain yield, with early rice (ER) and late rice (LR) experiencing average decreases of 5.2% and 6.3%, respectively, compared to control treatments. This decline was primarily attributed to the reduced grain weight of ER and the fewer spikelet numbers per panicle of LR under warming conditions. Although the dry matter translocation, harvest index, and N translocation efficiency of ER remained unchanged under warming conditions, these of LR decreased by an average of 58.1%, 8.8%, and 22.3%, respectively. Additionally, while warming did not affect the N uptake in ER at maturity, it significantly increased the N uptake in LR by an average of 11.0%. Therefore, under warming conditions, the NUtE of both ER and LR was markedly decreased by 6.9% and 15.5% over the two years. These results indicate that climate warming may have significant negative impacts on the grain yield and the NUtE of indica rice within double-rice cropping systems in South China. Understanding these dynamics is vital for maintaining the stability of rice yields in anticipation of future climate warming.

1. Introduction

Compared to the timeframe spanning from 1850 to 1900, the global surface temperature is anticipated to rise by 1.6 °C to 2.5 °C between 2041 to 2060, as per the intermediate greenhouse gas emissions scenario [1]. It is crucial to note that China, being the world’s largest rice producer, is expected to face significant impacts on rice growth and production due to climate warming [2,3,4]. Hence, understanding these effects becomes imperative to ensure food security.
Traditionally, the prevailing method for assessing the influence of climate warming on rice production involves the use of open-top chambers (OTCs). While OTCs create a controlled environment, they simultaneously alter the paddy microenvironment, affecting factors such as light, solar radiation, and air flow [5,6]. In contrast, free-air temperature increase (FATI) facilities direct infrared radiation onto rice plants, providing a uniform and controlled warming environment under natural open-field conditions [7]. FATI facilities are thus better suited to simulate future global warming scenarios in field conditions, and have been widely used in warming experiments [8,9,10]. Previous studies utilizing FATI facilities have demonstrated that elevated temperatures significantly reduce grain yields for both indica rice and japonica rice in Jiangsu Province, China [9,11,12,13]. The adverse effects of elevated temperatures on grain yields can be attributed to changes in yield components [9,11,14]. In addition, the reduction in leaf area index, radiation-use efficiency, photosynthesis rate, and aboveground biomass under warming conditions further exacerbates unfavorable conditions for the formation of grain yield [8,11,14].
As one of China’s most vital rice cropping systems (CSs), double-rice CSs (which entails two rice crops per year) contribute approximately 27.5% of the country’s total grain yield [15]. Recent findings from a model ensemble approach suggest that under a warming scenario of 2.0 °C, the grain yields of early rice (ER) and late rice (LR) could decrease by 25.5% and 26.6%, respectively [3]. Conversely, a meta-analysis indicates a significant 6.2% decrease in the grain yield of ER and a 6.7% increase in that of LR under field warming conditions [16]. Notably, studies utilizing FATI facilities have shown no significant impacts on the grain yields of ER and LR in Jiangxi Province, China [17,18]. However, most previous warming experiments with FATI facilities were conducted in East China. Thus, urgent research is needed to understand the rice yield of double-cropping rice responses to experimental warming in South China, given the climate variations between the East and South China.
Nitrogen (N) is a fundamental nutrient for crop growth, and N uptake and utilization are pivotal abiotic factors influencing crop physiological function and production capacity [19,20,21]. In China, N fertilizer application constitutes approximately 35% of the total chemical fertilizer use, with a significant portion applied in rice cultivation [15]. Low N use efficiency of crops and high N loss rates from farmland contribute to severe environmental pollution [22]. Climate warming directly impacts crop growth and production and indirectly affects plant N concentrations, N uptake, and N utilization [23]. Changes in N concentrations, N uptake, and N use efficiency of rice plants have been observed using FATI facilities under field conditions in East China. For instance, Cai et al. (2016) and Wang et al. (2018) found that warming significantly decreased N uptake due to a reduced aboveground biomass at maturity [11,13]. Moreover, warming remarkably decreased grain yield, leading to no obvious changes in N utilization efficiency (NUtE) [13]. A recent study has shown differences in rice plant N uptake between seasons in response to warming in Central China. Elevated temperatures tend to decrease the N uptake in ER plants but increase it in LR plants using OTC systems [24]. Therefore, understanding the effects of experimental warming on the N uptake and NUtE of double-cropping rice in South China can provide valuable insights for effective N management under future climate warming conditions.
Furthermore, the ambient temperature remains relatively low during the vegetative growth period of the ER season but increases during the reproductive growth period. Conversely, the LR season experiences higher and lower temperatures during the vegetative and reproductive phases, respectively. Thus, we hypothesize that the impacts of warming on the growth of ER and LR during the vegetative and reproductive periods may differ, resulting in variations in grain yield, N uptake, and NUtE. To address these knowledge gaps, a two-year field warming experiment using FATI facilities was conducted in South China. The research aims to investigate the following: (i) the responses of grain yield, N uptake, and NUtE of double-cropping indica rice to experimental warming, and (ii) the differences between ER and LR in these responses.

2. Materials and Methods

2.1. Experimental Site

The experiment was carried out at a field experimental site belonging to the Guangdong Academy of Agricultural Sciences (113°22′ E, 23°09′ N), located in Tianhe, Guangdong, China. The climate of this region is marked by a lower subtropical climate, with an annual mean precipitation and temperature of 1694 mm and 21.8 °C, respectively. Figure S1 illustrates the daily rainfall and mean temperature recorded in 2020 and 2021. The basic soil properties (0–15 cm) at the site are as follows: pH 5.9, soil organic carbon content of 25.3 g kg−1, and total N content of 1.1 g kg−1.

2.2. Experiment Design and Crop Management

Two treatments were designed as follows: (1) elevated temperature of the rice canopy from transplanting to maturity (warming) and (2) ambient temperature conditions (control), with 3 replicates arranged in a completely randomized block design (Figure S2). Each plot measured 3.5 m long × 3.0 m wide. As described in our previous work, Yang et al. (2022), FATI facilities were used to elevate the canopy temperature in this study [18]. Briefly, an infrared heater was deployed at 75 cm above the midpoint of the last leaf in each subplot, with its height adjusted as the growth period progressed. Each subplot was equipped with two temperature sensors, one in the midpoint of last leaf and the other in the soil (8 cm depth). The rice canopy temperatures were continuously monitored at hourly intervals. The daily mean temperature of the rice canopy and soil of two temperature treatments for both ER and LR is summarized in Figure 1 and Table S1. Compared to control treatments, warming treatments demonstrated an elevation of 1.5–2.0 °C and 0.7–0.8 °C in the daily mean temperature of the rice canopy and soil, respectively.
The cultivars tested in the ER season were Hefengsimiao (HFSM, inbred indica rice) in 2020 and Yuehesimiao (YHSM, inbred indica rice) in 2021. In the LR season, the cultivar used was YHSM in 2020 and 2021. It should be noted that HFSM is not a high-quality rice cultivar. In order to meet the overall objectives of the warming experiment, we changed the cultivar to YHSM starting from the LR season in 2020, a second-level national standard high-quality rice cultivar. Pre-germinated rice seeds were sown in a seeding nursing paddy during the ER and LR seasons. Uniform rice seedlings were manually transplanted into subplots (25 and 15 days in the ER and LR seasons, respectively). The hill spacing was 19.8 cm × 16.5 cm, with three seedlings per hill in the ER season and two seedlings per hill in LR season. The rice phenologies in 2020 and 2021 are provided in Table S2.
Nitrogen fertilizer was supplied as urea (46% N) at 150.0 kg ha−1 in the ER and LR seasons. Nitrogen fertilizer was applied in three stages: 50% as basal fertilizer, 20% at early tillering, and 30% at panicle initiation. Phosphorus was applied as calcium magnesium phosphate (12.0% P2O5) at a rate of 48.0 kg ha−1, and all phosphorus fertilizer was utilized as basal fertilizers. Potassium was supplied as potassium chloride (60% K2O) at a rate of 188.0 kg ha−1, of which 70% of potassium fertilizer was utilized as basal fertilizer, and the remaining potassium was applied at panicle initiation. Diseases, insects, and weeds were managed through chemical spraying in accordance with the guidelines provided by the local department of plant protection.

2.3. Plant Sampling and Measurement

At tillering, heading, and maturity stages, the tiller count of 20 hills was conducted in each subplot. According to the average value of tiller number, five representative hills were selected for sampling in each subplot. The rice samples were separated into straw (stems and leaves) and panicles, followed by oven-drying at 105 °C for 30 min and subsequently 75 °C until a constant weight was reached. The plant samples were weighed, ground, and filtered through a 0.25 mm sieve. Subsamples were analyzed using an N analyzer (Kjeltec 8400, FOSS, Hilleroed, Denmark), from which the aboveground total N uptake was calculated.
At maturity, five hills were sampled according to the mean value of the tiller number. Spikelet number per panicle, filled grain percentage, and grain weight were determined. A wind-selection instrument (FJ-1, Zhejiang Tuopu Yunnong Technology, Hangzhou, China) was used to separate the filled and unfilled spikelets. Lastly, 40 hills of rice plants were harvested and threshed using a portable thresher. The moisture content was measured from three randomly collected grain samples, and the grain yield was adjusted to a moisture content of 13.5%.
Dry matter translocation rate (DMT), harvest index (HI), N translocation efficiency (NTE), and NUtE were computed as follows:
DMT   ( % ) = straw   biomass   at   heading − straw   biomass   at   maturity straw   biomass   at   heading × 100
HI   ( % ) = grain   yield aboveground   biomass   at   maturity × 100
NTE   % = N   uptake   in   straw   at   heading − N   uptake   in   straw   at   maturity N   uptake   in   straw   at   heading × 100
NUtE   ( g   g − 1 ) = Grain   yield N   uptake

2.4. Statistical Analysis

All statistical tests were conducted with IBM SPSS v24.0. The grain yield, yield components, aboveground biomass, DMT, HI, N concentration, N uptake, NTE, and NUtE were subjected to two-way analyses of variance (ANOVA). Means were compared among treatments within the same season by the LSD test, and statistical significance was set at p ≤ 0.05.

3. Results

3.1. Grain Yield and Yield Components

For ER, obvious differences in grain yield were found between years (or cultivars) and treatments (Table 1). Early rice exhibited a significantly lower grain yield under warming conditions in both 2020 (−4.9%) and 2021 (−5.4%). The panicle number, spikelet number per panicle, and filled grain percentage (except 2020) of ER remained unaffected by warming, while the grain weight experienced a significant decrease due to warming in both years (Table 1). In addition, the yield components of ER displayed significant variations between the two years (or cultivars).
Similarly, the grain yield of LR was significantly influenced by years and treatments (Table 1). Warming led to a significant reduction in the grain yield of LR by 7.1% in 2020 and 5.6% in 2021. Interestingly, the filled grain percentage and grain weight of LR remained unaffected by warming, whereas the panicle number of LR increased, especially in 2020, and the spikelet numbers per panicle were significantly reduced by warming in both years (Table 1).

3.2. Aboveground Biomass, DMT, and HI

For ER, the aboveground biomass at tillering was significantly enhanced by 19.6% of warming treatments, while that of LR was significantly decreased by 10.1% over the years (Table 2). At the heading stage, the aboveground biomass of ER under warming conditions experienced a decrease, particularly in 2021 (−8.5%). Similarly, warming significantly reduced the aboveground biomass at heading for LR by an average of 6.5% over the two years. At the maturity stage, a significant reduction in the aboveground biomass of ER under warming conditions was observed only in 2021. Furthermore, there was a significant interaction between year and treatment for ER at tillering, and significant differences among years of ER at heading and maturity were observed. Warming did not significantly affect the DMT and HI of ER, but it significantly reduced the DMT and HI of LR, with an average reduction of 58.1% and 8.8%, respectively (Table 2). Additionally, the DMT of ER and LR showed significant differences among years.

3.3. N Concentration, N Uptake, NTE, and NUtE

Warming had no effects on the N concentration in ER straw and panicle, except for the panicle at maturity (Table 3). The N concentration in the ER panicle at maturity increased by an average of 10.5% under warming conditions. In contrast, the N concentration in LR straw and panicle at tillering, heading, and maturity tended to increase under warming conditions (Table 3). Compared to the control, warming elevated the N concentration in LR straw by an average of 7.6%, 10.5%, and 11.8% at tillering, heading, and maturity, and in the LR panicle by an average of 6.2% and 6.5% at heading and maturity, respectively. Furthermore, the N concentration in LR straw at heading and in both ER and LR panicles at maturity varied among years, and a significant interaction between year and treatment for LR straw was observed at heading.
At tillering, warming remarkably elevated the N uptake of ER by 14.4% over the two years, but it had no effect on that of LR (Table 4). At heading, the N uptake was only affected by years. At maturity, warming had no effect on the N uptake of ER, while the N uptake of LR increased significantly. Compared to the control treatments, the N uptake of LR was remarkably elevated by 9.8% and 12.3% in 2020 and 2021, respectively. Additionally, a significant interaction between year and treatment was observed at tillering for ER N uptake, as well as year variation in N uptake for ER and LR at maturity.
Compared to the control, the NTE of LR was decreased, especially in 2021 by 33.7%, while remaining unchanged in ER. Under warming conditions, the NUtE of ER remarkably decreased by 6.0% and 7.8% in 2020 and 2021, and that of LR remarkably reduced by 15.5% and 15.8% in 2020 and 2021, respectively.

4. Discussions

4.1. Warming Reduced the Grain Yield of ER and LR in South China

Previous researchers have demonstrated that the grain yields of middle rice in East China decreased under warming conditions using FATI facilities [11,12]. In the present study, we found that warming significantly reduced the grain yields of ER and LR in South China (Table 1). These results are quite different from those of a study in East China by Wang et al. (2022), where experimental warming (FATI) showed no obvious effects on both ER and LR yields [17]. Generally, the reduction in grain yield by warming is attributed to decreases in spikelet number per panicle, filled grain percentage, and grain weight [9,11]. In this study, the decrease in the grain weight of ER and the spikelet number per panicle of LR were the main reasons accounting for lower grain yields under warming conditions in South China (Table 1). Therefore, the responses of grain yield to experimental warming cannot be generalized across rice CSs due to variations in rice growing-season temperatures between East and South China [16,25].
Rice growth is extremely sensitive to ambient temperature, which varies between the vegetative and reproductive growth periods [26]. The optimum temperature for indica rice is approximately 29.7 °C during tillering [27]. For ER, the average temperature from transplanting to panicle initiation was 28.5 °C (2020) and 25.1 °C (2021) (Table S1). Therefore, warming might be beneficial to the growth of tillers and increase their aboveground biomass of ER at tillering (Table 2). In addition, we observed that the increased aboveground biomass accumulation at tillering of ER was due to a higher tiller height rather than a high tiller number under warming conditions.
The maximum temperature for panicle initiation and anthesis of indica rice was 33.3 °C and 37.7 °C, respectively [27]. In this work, the average canopy temperature was 28.0 °C (2020) and 30.9 °C (2021) from panicle initiation to initial heading, and 29.7 °C (2020) and 29.3 °C (2021) from initial heading to full heading (Table S1). Thus, warming might not induce heat damage during panicle differentiation and flowering of ER, exerting no negative effects on spikelet number per panicle and filled grain percentage in our experiment. However, the ambient temperature rose after heading during the ER season (Figure 1A,B). Our findings indicated that warming accelerated the mean grain filling rate and reduced the grain filling period of ER (Table S3), leading to a decrease in grain weight (Table 1). Additionally, warming reduced the photosynthetic rate and increased the respiration rate of rice leaves, which was not conducive to the accumulation of photosynthetic products [8]. Such adverse changes directly impact grain filling and grain weight under warming conditions [8,10]. Furthermore, warming significantly decreased the aboveground biomass at the heading and maturity stages of ER in 2021 but had no effect in 2020 (Table 2). The early-season rice cultivar YHSM tested in 2021 might be more sensitive to experimental warming, which could be attributed to variety characteristics necessitating further research.
In contrast, warming decreased the aboveground biomass at the tillering and heading stages of LR (Table 2). During the pre-heading period of LR, the high ambient temperature led us to speculate that warming might cause heat damage and inhibit rice growth (Figure 1A,B). The lower aboveground biomass before heading to LR might adversely affect panicle differentiation, leading to a reduction in spikelet number per panicle [14]. In LR season, the average canopy temperature of warming treatments was 28.2 °C (2020) and 31.1 °C (2021) from initial heading to full heading (Table S1), which did not exceed the maximum temperature for the anthesis of indica rice [27]. Therefore, warming had no effect on the filled grain percentage of LR. The substances in rice endosperm during grain filling mainly come from carbohydrates stored in the straw before heading and photosynthetic products after heading [28,29]. Under warming conditions, the aboveground biomass matter of LR at the heading stage decreased, resulting in decreased DMT (Table 2). However, we observed that warming promoted aboveground biomass accumulation of LR after heading (Table 2), indicating that warming was beneficial to the accumulation of photosynthetic products of LR after heading [30]. In this study, although warming led to a decrease in the DMT of LR, it improved the dry matter production capacity after heading. Therefore, warming did not alter the grain filling parameters of LR and had no effect on its grain weight (Table 1 and Table S3).
Moreover, warming increased the aboveground biomass accumulation from heading to maturity, which differed significantly from ER (Table 2). The daily mean temperature of the ambient environment was lower during the post-heading period (Figure 1; Table S1), suggesting that warming could mitigate chilling damage in the LR season, especially during the late grain filling stage [30]. Consequently, warming had opposing effects on the aboveground biomass accumulation of LR before and after heading, leading to an obvious decrease in DMT (Table 2). In addition, the panicle number of LR was increased under warming conditions (Table 1). Thus, we speculate that warming may promote the growth and heading of ineffective tillers, thereby increasing panicle numbers and reducing spikelet numbers per panicle.
Consistent with previous research in East China [8,11], the HI of ER was not affected significantly under warming conditions in this study, probably due to the simultaneous decrease in grain yield and aboveground biomass (Table 2). However, warming had negative effects on grain yields and no effects on the aboveground biomass at maturity of LR, resulting in a decrease in HI, especially in 2020 (Table 2). Thus, warming reduced the ability of LR to transfer photosynthetic products into economic yields in this study.

4.2. Effects of Warming on the N Uptake, NTE, and NUtE of ER and LR in South China

Nitrogen utilization efficiency reflects the quantity of grain produced per unit of N absorbed by the rice plant until harvest [13]. In our study, warming significantly decreased the NUtE of ER and LR, which differs from the findings in East China [13]. Under warming conditions, the decrease in the NUtE of ER was attributed to the reduction in grain yield, while the decrease in the NUtE of LR was determined by both the reduction and elevation in grain yield and N uptake, respectively. In addition, warming had no effect on the NTE of ER, while it decreased the NTE of LR (Table 4), indicating that a lower proportion of N stored in straw before heading transferred to the grain [31]. In this study, the decrease in NTE of LR under warming conditions was mainly attributed to the increase in N uptake at maturity stage (Table 4).
The response of N uptake in ER and LR varied across different growth stages in our study. At tillering, we observed that warming increased N uptake in ER but had no effect on LR (Table 4). In contrast, Wang et al. (2020) reported that warming increased the N uptake at jointing in both ER and LR using OTCs in Central China [24]. Nitrogen uptake is associated with N concentration and aboveground biomass and strongly influenced by ambient temperature at different growth stages [24,32]. As discussed earlier, the average canopy temperature from transplanting to panicle initiation of ER remained at a lower level (25.1–28.5 °C) (Table S1). Thus, warming was beneficial to the growth of ER at the tillering stage, leading to higher N uptake. Conversely, warming increased the N concentration but decreased the aboveground biomass of LR (Table 2 and Table 3), resulting in no changes in N uptake at tillering and heading stages (Table 4). In addition, the decrease in aboveground biomass at tillering and heading of LR was associated with a higher canopy temperature under warming conditions, but further study is needed to understand how warming increases its N concentration.
At maturity, warming significantly increased N uptake in LR but had no effect on N uptake in ER (Table 4). Inconsistent results have been reported regarding elevated temperature-decreasing N uptake in rice plants at maturity in East China [11,13]. For LR, the increase in N concentration in both straw and panicle under warming conditions resulted in higher N uptake at maturity (Table 3 and Table 4). In contrast, for ER, warming increased N concentration in panicle at maturity, but reduced aboveground biomass at maturity, thus having no effect on N uptake (Table 2, Table 3 and Table 4). We observed that warming increased N concentration in panicle, possibly because warming had positive effects on plant N assimilation after heading in both ER and LR. First, elevated temperature increased the activities of glutamate synthase and glutamine synthetase in rice grains, promoting N accumulation in rice grains [33]. Second, warming increased soil temperature in the experiment (Figure 1; Table S1), potentially increasing N mineralization from soil organic N, N supply, and N uptake from soil, especially for LR due to the lower ambient temperature [23,24,34]. In addition, warming decreased the sink capacity (less spikelet number per panicle) and NTE from straw to grains, leading to higher N concentrations in LR plants. Third, the decrease in grain weight of ER was observed (Table 1), indicating that elevated temperatures are unfavorable for starch accumulation in grains, leading to an increase in relative protein content [35,36].
In this study, we must acknowledge a limitation. The effect of experimental warming on rice yield formation is influenced by ambient temperature and verity characteristics [16,32]. We observed differences in grain yield, N uptake, and NUtE between years, seasons, and varieties. Therefore, multi-year field experiments with various rice cultivars are essential to elucidate the effects of climate warming on grain yield and NUtE in South China. Additionally, both negative and positive influences of warming on the growth of ER and LR were noted. Some agronomic practices may help attenuate the effects of climate warming on grain yield and NUtE. For ER, warming led to a decrease in grain weight and aboveground biomass. We suggest increasing N fertilizer application rates at panicle initiation and heading stages to enhance source vitality and grain weight under warming conditions [10,36]. For LR, warming significantly reduced spikelet numbers per panicle. To counteract this, increasing plant density and panicle number may prevent yield decline [37]. Moreover, adapting to climate warming could involve adjusting sowing dates or selecting more heat-tolerant varieties [38,39].

5. Conclusions

In conclusion, our two-year experiment revealed that warming decreased the grain yield of both ER and LR in South China, attributed to lower grain weight and spikelet number per panicle, respectively. In addition, under warming conditions, N uptake in LR at maturity increased while that in ER remained unchanged, resulting in a decrease in NUtE for both ER and LR. These adverse changes may be attributed to the variable effects of warming on ER and LR growth during the vegetative and reproductive growth periods, along with source-sink imbalance. Our findings offer valuable insights into grain yield and NUtE responses to experimental warming. In the near future, innovative climate-smart strategies should be established to mitigate the negative influence of warming on double-cropping rice production in South China.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/agriculture14060921/s1, Figure S1: Daily mean temperature and daily precipitation during rice growing season in 2020 (A) and 2021 (B); Figure S2: Schematic diagram of free air temperature increase facilities (A) and field actual photography (B, Control; C, Warming) in a double-rice CS; Table S1: Effect of warming on average temperature (°C) at specific rice growth stages of ER and LR in 2020 and 2021; Table S2: Effects of warming on phenology of ER and LR in 2020 and 2021; Table S3: Effect of warming on grain-filling parameters of ER and LR in 2021.

Author Contributions

Conceptualization, T.Y. and Y.J.; methodology, T.Y.; investigation, J.Z. and N.Z.; writing—original draft preparation, T.Y.; writing—review and editing, L.W., X.B., Y.J. and B.Z.; visualization, T.Y.; funding acquisition, T.Y. and Y.J. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the National Natural Science Foundation of China (32201900), the Guangdong Basic and Applied Basic Research Foundation (2022A1515011279), and the National Natural Science Foundation of China (31601263).

Institutional Review Board Statement

Not applicable.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Conflicts of Interest

The authors declare no conflicts of interest.

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Agriculture 14 00921 g001
Figure 1. Daily mean temperature of rice canopy (A,B) and soil (C,D) during rice growing seasons in 2020 (A,C) and 2021 (B,D). The temperature values displayed in figure stand for the average temperatures of the whole growth period. Mean ± standard deviation (n = 3).
Figure 1. Daily mean temperature of rice canopy (A,B) and soil (C,D) during rice growing seasons in 2020 (A,C) and 2021 (B,D). The temperature values displayed in figure stand for the average temperatures of the whole growth period. Mean ± standard deviation (n = 3).
Agriculture 14 00921 g001
Table 1. Effects of warming on grain yield and yield components of ER and LR in 2020 and 2021.
Table 1. Effects of warming on grain yield and yield components of ER and LR in 2020 and 2021.
SeasonYear/CultivarTreatmentGrain Yield
(g m−2)		Panicle Number
(m−2)		Spikelet Number
(panicle−1)		Filled Grain
Percentage
(%)		Grain Weight
(mg)
ER2020 (HFSM)Control661.3 c211.2 b156.2 b86.8 a26.23 a
Warming628.9 d215.3 b166.9 ab80.6 b25.17 b
2021 (YHSM)Control750.2 a255.1 a174.2 a91.4 a23.56 c
Warming709.4 b249.0 a174.7 a89.7 a22.02 d
LR2020 (YHSM)Control766.3 a232.6 b180.9 a92.2 a23.16 ab
Warming711.7 bc271.4 a144.2 b91.6 a23.56 a
2021 (YHSM)Control729.3 ab236.7 b179.4 a80.6 b22.95 b
Warming688.7 c244.9 ab152.3 b80.5 b23.34 ab
Analysis of variance
ERYear (Y)*********
Treatment (T)**nsnsns**
Y × Tnsnsnsnsns
LRYear (Y)*nsns**ns
Treatment (T)*****nsns
Y × Tnsnsnsnsns
ER, early rice; LR, late rice. HFSM, Hefengsimiao; YHSM, Yuehesimiao. Different letters indicate significant differences among treatment within the same season at p < 0.05 by LSD test. *, p ≤ 0.05; **, p ≤ 0.01; ns, not significant.
Table 2. Effects of warming on aboveground biomass, DMT, and HI of ER and LR in 2020 and 2021.
Table 2. Effects of warming on aboveground biomass, DMT, and HI of ER and LR in 2020 and 2021.
SeasonYear/CultivarTreatmentAboveground Biomass (g m−2)DMT
(%)		HI
(%)
TilleringHeadingMaturity
ER2020 (HFSM)Control151.0 d1045.1 a1375.2 bc31.0 a41.6 a
Warming198.2 a1017.7 a1361.9 c28.9 a40.0 a
2021 (YHSM)Control166.3 c944.7 b1574.2 a13.7 b41.2 a
Warming179.6 b864.3 c1450.5 b14.0 b42.4 a
LR2020 (YHSM)Control230.0 a1051.8 a1361.4 a26.9 a48.7 a
Warming206.2 ab982.3 bc1432.3 a12.8 bc43.0 b
2021 (YHSM)Control214.6 ab1036.9 ab1375.8 a20.2 ab45.9 ab
Warming193.4 b971.3 c1379.3 a7.3 c43.2 b
Analysis of variance
ERYear (Y)ns******ns
Treatment (T)****nsns
Y × T**nsnsnsns
LRYear (Y)nsnsns*ns
Treatment (T)***ns***
Y × Tnsnsnsnsns
ER, early rice; LR, late rice. HFSM, Hefengsimiao; YHSM, Yuehesimiao; DMT, dry matter translocation rate; HI, Harvest index. Different letters indicate significant differences among treatment within the same season at p < 0.05 by LSD test. *, p ≤ 0.05; **, p ≤ 0.01; ns, not significant.
Table 3. Effects of warming on N concentration (g kg−1) of ER and LR in 2020 and 2021.
Table 3. Effects of warming on N concentration (g kg−1) of ER and LR in 2020 and 2021.
SeasonYear/CultivarTreatmentTilleringHeadingMaturity
StrawStrawPanicleStrawPanicle
ER2020 (HFSM)Control25.4 a13.8 a14.4 a9.9 a11.8 b
Warming24.7 a14.8 a13.9 a9.9 a12.2 b
2021 (YHSM)Control27.0 a14.4 a14.7 a10.1 a12.8 b
Warming25.3 a15.0 a14.3 a10.2 a15.1 a
LR2020 (YHSM)Control23.7 b14.2 bc12.0 b9.7 b12.3 a
Warming25.2 a16.3 a12.9 a10.3 ab12.9 a
2021 (YHSM)Control23.7 b13.7 c12.0 b9.4 b11.4 b
Warming25.8 a14.6 b12.6 ab11.0 a12.3 a
Analysis of variance
ERYear (Y)nsnsnsns**
Treatment (T)nsnsnsns*
Y × Tnsnsnsnsns
LRYear (Y)ns**nsns*
Treatment (T)*********
Y × Tns*nsnsns
ER, early rice; LR, late rice. HFSM, Hefengsimiao; YHSM, Yuehesimiao. Different letters indicate significant differences among treatment within the same season at p < 0.05 by LSD test. *, p ≤ 0.05; **, p ≤ 0.01; ns, not significant.
Table 4. Effects of warming on N uptake and NUtE of ER and LR in 2020 and 2021.
Table 4. Effects of warming on N uptake and NUtE of ER and LR in 2020 and 2021.
SeasonYear/CultivarTreatmentN Uptake (g m−2)NTE
(%)		NUtE
(g g−1)
TilleringHeadingMaturity
ER2020 (HFSM)Control3.83 b14.50 ab15.03 b50.7 a44.0 a
Warming4.89 a14.95 a15.20 b52.2 a41.4 b
2021 (YHSM)Control4.48 a13.61 bc18.25 a39.3 b41.1 b
Warming4.54 a12.89 c18.72 a41.6 ab37.9 c
LR2020 (YHSM)Control5.46 a14.60 ab15.08 bc50.1 a50.9 a
Warming5.19 a15.53 a16.56 a44.7 a43.0 b
2021 (YHSM)Control5.08 a13.98 b14.23 c45.4 a51.3 a
Warming4.98 a13.95 b15.97 ab30.1 b43.2 b
Analysis of variance
ERYear (Y)ns*******
Treatment (T)**nsnsns**
Y × T**nsnsnsns
LRYear (Y)ns****ns
Treatment (T)nsns******
Y × Tnsnsnsnsns
ER, early rice; LR, late rice. HFSM, Hefengsimiao; YHSM, Yuehesimiao; NET, N translocation efficiency; NUtE, N utilization efficiency. Different letters indicate significant differences among treatment within the same season at p < 0.05 by LSD test. *, p ≤ 0.05; **, p ≤ 0.01; ns, not significant.
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Yang, T.; Zou, J.; Wu, L.; Bao, X.; Jiang, Y.; Zhang, N.; Zhang, B. Experimental Warming Reduces the Grain Yield and Nitrogen Utilization Efficiency of Double-Cropping indica Rice in South China. Agriculture 2024, 14, 921. https://doi.org/10.3390/agriculture14060921

AMA Style

Yang T, Zou J, Wu L, Bao X, Jiang Y, Zhang N, Zhang B. Experimental Warming Reduces the Grain Yield and Nitrogen Utilization Efficiency of Double-Cropping indica Rice in South China. Agriculture. 2024; 14(6):921. https://doi.org/10.3390/agriculture14060921

Chicago/Turabian Style

Yang, Taotao, Jixiang Zou, Longmei Wu, Xiaozhe Bao, Yu Jiang, Nan Zhang, and Bin Zhang. 2024. "Experimental Warming Reduces the Grain Yield and Nitrogen Utilization Efficiency of Double-Cropping indica Rice in South China" Agriculture 14, no. 6: 921. https://doi.org/10.3390/agriculture14060921

APA Style

Yang, T., Zou, J., Wu, L., Bao, X., Jiang, Y., Zhang, N., & Zhang, B. (2024). Experimental Warming Reduces the Grain Yield and Nitrogen Utilization Efficiency of Double-Cropping indica Rice in South China. Agriculture, 14(6), 921. https://doi.org/10.3390/agriculture14060921

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