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9 pages, 564 KiB

Open AccessArticle

Delayed Sowing under the Same Transplanting Date Shortened the Growth Period of Machine-Transplanted Early-Season Rice with No Significant Yield Reduction Caused

by Xilin Fang, Peng Liu, Abdul Wahab, Yue Wang and Guanghui Chen

Agronomy 2023, 13(11), 2748; https://doi.org/10.3390/agronomy13112748 - 31 Oct 2023

Viewed by 743

Abstract

In early rice cultivation, the age of seedlings plays a crucial role in ensuring the annual safety production of double-cropping rice. When sowing staging and transplanting are performed simultaneously, it is still necessary to gather more data about the effects of seedling age [...] Read more.

In early rice cultivation, the age of seedlings plays a crucial role in ensuring the annual safety production of double-cropping rice. When sowing staging and transplanting are performed simultaneously, it is still necessary to gather more data about the effects of seedling age on the growth period and grain yield of early rice machines transplanted. Two years ago, field experiments were conducted on machine-transplanted rice seedlings in the early season to compare the growth duration, crop growth characteristics, and yield attributes between the 18-day-old seedlings (SA18) and 32-day-old seedlings (SA32) of two rice cultivars. As a result of the study, it was found that SA18 reduced the total crop duration by between 11 and 12 days but delayed the maturity date by 2–3 days compared to SA32. SA18 had 14.5% fewer panicles per m² and 3.6% less harvest index but 7.5% more spikelets per panicle higher than SA32. The grain yield of SA18 was 3.4% less than that of SA32, but there was no significant difference between the two seedling ages. The machine-transplanted seedlings for early rice production are more efficient in reducing seedling management time without affecting harvesting time and yields. The authors provide a new cultivation management scheme for farmers who are interested in planting double-cropping rice at the same time. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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14 pages, 2103 KiB

Open AccessArticle

Exogenous Application of Methyl Jasmonate Promotes Yield and Grain Quality of Rice under Terminal Drought Stress

by Yi Meng, Ping Liao, Yuqiong Chen, Wenan Weng, Le Chen, Fangfu Xu, Qun Hu, Zhipeng Xing, Haiyan Wei, Hui Gao and Hongcheng Zhang

Agronomy 2023, 13(7), 1903; https://doi.org/10.3390/agronomy13071903 - 19 Jul 2023

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Abstract

Exogenous application of methyl jasmonate (MeJA) improves rice drought tolerance, but its effects on rice yield and quality under drought stress during the reproductive phase remain unclear. A pot experiment was conducted to measure rice yield, grain quality, and starch physicochemical properties under [...] Read more.

Exogenous application of methyl jasmonate (MeJA) improves rice drought tolerance, but its effects on rice yield and quality under drought stress during the reproductive phase remain unclear. A pot experiment was conducted to measure rice yield, grain quality, and starch physicochemical properties under three treatments: continuous flooding irrigation throughout the whole growth season (CF), ten days of −40 kPa drought stress at the heading stage (DS), and foliar spraying 100 μmol L⁻¹ MeJA on the first three days of the ten-day −40 kPa heading stage drought stress (DM). An inbred japonica rice variety, Huaidao 5, was the experimental material, and each treatment had 11 replicates for sampling. The results indicated that DS significantly reduced rice yield and quality compared to CF. With increases in superoxide dismutase (+22.2%), peroxidase activities (+10.5%), catalase (+5.0%), and proline content (+5.7%), DM significantly increased 1000-grain weight (+8.6%), filled grain percentage (+3.6%), and yield (+11.1%) compared with DS. Regarding grain quality, DM significantly decreased the chalkiness degree (−12.3%) and protein content (−3.9%) but increased the amylose content (+17.2%) and taste value (+7.3%) relative to DS. In addition, DM improved breakdown viscosity (+17.8%), gelatinization enthalpy (+17.2%), retrogradation enthalpy (+28.0%), 1045/1022 cm⁻¹ ratio (+3.0%), and starch granule morphology compared to DS. In conclusion, exogenous application of 100 μmol L⁻¹ MeJA enhanced the antioxidant capacity of rice leaves, and thus improved starch physicochemical properties to increase grain yield and quality under terminal drought stress. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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13 pages, 1041 KiB

Open AccessArticle

Comparison of the Source–Sink Characteristics between Main Season and Ratooning in Rice (Oryza sativa L.)

by Xinjie Huang, Jing Yang, Wenxin Zhou, Guilian Zhang, Bin Liao, Abdul Wahab, Zhenxie Yi and Naimei Tu

Agronomy 2023, 13(7), 1731; https://doi.org/10.3390/agronomy13071731 - 28 Jun 2023

Cited by 1 | Viewed by 1070

Abstract

Objectives: In order to find out the differences in source–sink characteristics of ratooning rice and main season rice and find approaches to increase the grain yield of ratooning rice, a sowing-by-stage method was adopted to synchronize main season rice with ratooning rice and [...] Read more.

Objectives: In order to find out the differences in source–sink characteristics of ratooning rice and main season rice and find approaches to increase the grain yield of ratooning rice, a sowing-by-stage method was adopted to synchronize main season rice with ratooning rice and induce their key growth stages under similar environmental conditions. The source–sink characteristics of four varieties under similar ecological conditions of main and ratooning rice were examined in 2019 and 2020. Results: The main results were: (1) The leaf area index (LAI) of the ratooning rice ranged from 0.54 to 1.44, while that of the LAI of main season rice was 4.67–7.71. The LAI of ratooning rice was much smaller than that of the main season rice; the former was only approximately 1/7–1/5 of the latter. (2) The photosynthesis (Pn) and net assimilation rate (NAR) of the ratooning rice were significantly higher than those of the main season rice before the milking–maturing stages. Still, at the late maturing stage, no definite tendency existed. (3) Ratooning rice transported ¹⁴C-assimilate from the flag leaf to the panicle at an estimated 81.43%, while main season rice transported 63.95%. The main stem’s top first and second internodes have been observed to be a major location for the ¹⁴C-assimilate in main season rice. (4) The grain yield of main season rice was 6029–7929 kg ha⁻¹ while the grain yield of ratooning rice ranged from 2363–3297 kg ha⁻¹. The sink capacity of the main season rice was approximately 2.4–3.6 times that of ratooning rice. The catalase activity of the rachis branches of the ratooning rice was higher than that of the main season rice. (5) The grain/leaf area (sink/source) ratio in the ratoon season rice was 1.69–2.46 times higher than that of the main season rice. Conclusions: The grain yields of ratooning rice were determined by the interaction of source and sink capacity while those of main season rice were mainly increased by enhancing sink capacity. Choosing varieties with heavier 1000 grain weight, exerting the advantages of higher photosynthetic rate and net assimilation rate of ratooning rice, promoting leaf area, and improving the transportation capacity of carbohydrate are the main approaches to increase the grain yield of ratooning rice. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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12 pages, 2123 KiB

Open AccessArticle

Optimum Cultivation Model Increased the Grain Yield of Ratoon Rice and Nitrogen Agronomic Efficiency by Improving Root Morphological Traits and Stubble Character of the Main Rice

by Huabin Zheng, Shanzhen Liu, Dan Zou, Zaizhou He, Yuanwei Chen, Panpan Gai, Weiqin Wang and Qiyuan Tang

Agronomy 2023, 13(7), 1707; https://doi.org/10.3390/agronomy13071707 - 26 Jun 2023

Cited by 1 | Viewed by 926

Abstract

The present study investigated the effects of different integrated cultivation treatments on the yield, nitrogen agronomic efficiency (AE_N), and growth performance of a ratoon rice system. A two-year field experiment was carried out during 2021–2022 using a randomized block design. Cultivation [...] Read more.

The present study investigated the effects of different integrated cultivation treatments on the yield, nitrogen agronomic efficiency (AE_N), and growth performance of a ratoon rice system. A two-year field experiment was carried out during 2021–2022 using a randomized block design. Cultivation treatments included the farmers’ practice model (control, CK), high-yield and high-efficiency model (T1), enhanced-high-yield and high-efficiency model (T2), and the no-N model (N0). The grain yield, yield components, root traits, and stubble characteristics were determined. The results showed that T2 treatment significantly increased the grain yield and AE_N by 53% and 236%, respectively, compared with CK. Similarly, the stubble weight, non-structure carbohydrate contents, and the root attributes were significantly improved under T2 treatment. The correlation analysis suggested that ratoon rice yield and AE_N was significantly and positively correlated with root weight (p < 0.01) and the stubble parameters including stubble weight (p < 0.01), starch content (p < 0.01), and soluble sugar content (p < 0.01). Additionally, a significant and positive correlation between root weight and stubble weight (p < 0.05) was determined in our study. Consequently, our work highlights the benefits of integrating planting density, nitrogen/water management, and other practices to achieve high AE_N and grain yield of the ratoon rice by improving root trait and stubble characteristics of the main rice. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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15 pages, 937 KiB

Open AccessArticle

Agronomic and Physiological Performances of High-Quality Indica Rice under Moderate and High-Nitrogen Conditions in Southern China

by Gangqiang Duan, Jiale Wu, Renwei Que, Yanhua Zeng, Yongjun Zeng, Xiaohua Pan and Xiaobing Xie

Agronomy 2023, 13(6), 1617; https://doi.org/10.3390/agronomy13061617 - 15 Jun 2023

Viewed by 916

Abstract

High-quality (i.e., higher appearance and eating quality) rice (Oryza sativa L.) is being increasingly and widely planted in China with the improvement of people’s living standards and the achievement of rice breeding efforts in recent years. However, the agronomic and physiological performances [...] Read more.

High-quality (i.e., higher appearance and eating quality) rice (Oryza sativa L.) is being increasingly and widely planted in China with the improvement of people’s living standards and the achievement of rice breeding efforts in recent years. However, the agronomic and physiological performances of high-quality indica rice (HQIR) under different nitrogen (N) application conditions in southern China are little known. Two-year consecutive field experiments were conducted with two HQIR and two ordinary-quality indica rice (OQIR) varieties under moderate and high-N application rates, with yield and yield components, biomass, N uptake, and their related traits, being investigated. We found that grain yields of HQIR were slightly decreased, but grain yields of OQIR were significantly increased by 7.0–9.6% under a high N rate, compared with a moderate N rate within two years. Thereby, OQIR produced a 5.7–14.7% and 18.7–25.6% higher grain yield than HQIR under moderate and high N rates, respectively. The different responses of grain yield to N application rates were mainly due to a decreased grain setting rate in HQIR and increased spikelets m⁻² in OQIR under a high N rate. Furthermore, a high N rate significantly reduced pre-anthesis AE (apparent exportation of pre-anthesis stem and leaf blade dry matter) and improved the grain-leaf area ratio, while it did not increase post-anthesis dry matter, compared with a moderate N rate in HQIR, which might result in carbon-metabolic deterioration, an imbalance of the source–sink relationship and, subsequently, a lower supply of carbohydrate in panicle. Our results suggest that a moderate N rate (165 kg N ha⁻¹) is beneficial for the HQIR varieties to balance the maximum grain yield and high quality in southern China. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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13 pages, 4186 KiB

Open AccessArticle

Increasing Nitrogen Fertilizer Application Is a Feasible Strategy to Mitigate Rice Yield Reduction in Wet Year

by Bin Liao, Omar Aziz, Yangbo He, Xue Yang, Qianan Yu, Yufeng Luo, Guoan Lu and Yuanlai Cui

Agronomy 2023, 13(6), 1536; https://doi.org/10.3390/agronomy13061536 - 31 May 2023

Cited by 1 | Viewed by 1248

Abstract

Rice production is intimately related to water and nitrogen management, whereas rice yield inevitably decreases with extreme rainfall. Optimization of water and nitrogen management may mitigate the degree of rice yield reduction. Hence, we conducted a field experiment in a normal and wet [...] Read more.

Rice production is intimately related to water and nitrogen management, whereas rice yield inevitably decreases with extreme rainfall. Optimization of water and nitrogen management may mitigate the degree of rice yield reduction. Hence, we conducted a field experiment in a normal and wet year to investigate suitable water and nitrogen management that could reduce the risk of rice yield reduction. The field experiment comprised six water and nitrogen management methods, which included two irrigation methods (CF: continuous flooding; AWD: alternating wet and dry) and three nitrogen fertilizer levels (N0, N90, and N180: 0, 90, and 180 kg N ha⁻¹, respectively). The results showed an average yield reduction of 23.5% in the wet year compared to normal year. The nitrogen rate of N0, N90, and N180 resulted in a 36.9%, 24.8%, and 11.0% of yield reduction in the wet year, which presented a decrease in yield reduction with the increase in nitrogen rate. Panicle contributed over almost 60% and 75% on average to biomass and total nitrogen uptake, but both the total amount and proportion of nitrogen uptake in panicle showed a decrease in the wet year. In addition, the rice yield showed a significant positive correlation with nitrogen uptake both in the normal and wet year. Therefore, in the wet year, the decrease in nitrogen uptake in panicle results in a yield reduction. With the increase in nitrogen rate, the nitrogen internal use efficiency (IE_N) was significantly decreased in the normal year, while it increased in the wet year, and the nitrogen recovery use efficiency (RE_N) and nitrogen harvest index (HI_N) were not affected by nitrogen rate. Therefore, these results suggested that increased nitrogen rate in a wet year could improve rice nitrogen uptake to reduce the risk of yield reduction and maintain the nitrogen use efficiency (NUE). Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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12 pages, 1695 KiB

Open AccessArticle

Enhancing Rice Yield and Nitrogen Utilization Efficiency through Optimal Planting Density and Reduced Nitrogen Rates

by Haijun Zhu, Tian Wen, Manwen Sun, Izhar Ali, Mohamed S. Sheteiwy, Abdul Wahab, Weijian Tan, Can Wen, Xiaoe He and Xuehua Wang

Agronomy 2023, 13(5), 1387; https://doi.org/10.3390/agronomy13051387 - 17 May 2023

Cited by 5 | Viewed by 2009

Abstract

Rice yields can only be achieved by selecting a high-quality population. Nitrogen rates and transplanting density play a significant role in determining population quality and yield. Field experiments were conducted in Heshan District, Hunan Province, China, to explore suitable nitrogen rates and appropriate [...] Read more.

Rice yields can only be achieved by selecting a high-quality population. Nitrogen rates and transplanting density play a significant role in determining population quality and yield. Field experiments were conducted in Heshan District, Hunan Province, China, to explore suitable nitrogen rates and appropriate transplanting densities for rice production in 2021 and 2022. In this study, three levels of nitrogen, e.g., N1, N2, and N3 (0, 150, and 210) kg ha⁻¹, and three transplanting densities, e.g., B1, B2, and B3 (1, 2, and 3) seedlings per hill were used to study their individual or combined effects on rice (Taiyou 390) population quality, yield, and yield components, nitrogen-related enzyme activities, and nitrogen absorption and utilization efficiency. The results showed that N2B3 had the highest yield, with an average yield of 9.30 t ha⁻¹ in two years, which was 3.7~49.6% higher than other treatments. This increase was attributed to higher dry matter accumulation (1538.22 g m⁻²) and effective panicle number (435.2 × 10⁴ ha⁻¹), influenced by increased nitrate reductase activity at the booting stage and glutamine synthase at the heading stage, along with maintenance of higher SPAD value and leaf area index. Nitrogen rates and transplanting densities significantly affected nitrogen use efficiency, with the contribution rate of nitrogen fertilizer to yield decreasing as nitrogen rates increased. However, N2B3 improved nitrogen use efficiency and stabilized rice yield by reducing nitrogen fertilizer application. This study suggested that N2B3 treatment could enhance rice yield by improving plant nitrogen use efficiency under low nitrogen supplementation. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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11 pages, 1637 KiB

Open AccessArticle

Biochar Can Partially Substitute Fertilizer for Rice Production in Acid Paddy Field in Southern China

by Shasha Qin, Feilong Rong, Manyun Zhang, Guirui Su, Wei Wang, Liqun Wu, Aiping Wu and Falin Chen

Agronomy 2023, 13(5), 1304; https://doi.org/10.3390/agronomy13051304 - 06 May 2023

Cited by 1 | Viewed by 1156

Abstract

Biochar application has been confirmed as an efficient way to increase the productivity of the agricultural system. However, the potential of biochar combined with reducing fertilization on the yield, and the fertilizer utilization efficiency of the rice (Oryza sativa) farming system [...] Read more.

Biochar application has been confirmed as an efficient way to increase the productivity of the agricultural system. However, the potential of biochar combined with reducing fertilization on the yield, and the fertilizer utilization efficiency of the rice (Oryza sativa) farming system on acidic soil remains to be further studied. Field micro-plot experiments with two factors were performed in 2018 and 2019 to evaluate the responses of the rice yield and nutrient utilization to the combined application of biochar (60, 80, and 100 t/ha) and fertilizer reduction (70%, 85%, and standard doses of N-P-K fertilizer). Taoyouxiangzhan and Taiyou 553 were used in the late growing season of 2018 and 2019, respectively. The results showed that compared with the control without adding biochar under standard fertilization, 70% doses of fertilizer application had no negative effects on the yield and the N, P, and K accumulation of rice after biochar application. K accumulation of rice increased with the increase of biochar application. The partial productivity of N, P, and K fertilizers increased as the fertilizer was decreased. The agronomic efficiency of N, P, and K fertilizers significantly increased after the combined applications of biochar and fertilizer. In both years, micro-plots with 70% doses of fertilizer had the highest N and P physiological efficiency, as well as K physiological efficiency in 2019. Compared with the control under standard fertilization, utilization efficiency of N, P, and K fertilizer under different biochar and fertilizer combinations significantly increased by 34.24~75.48%, 27.44~84.84%, and 78.52~166.70%, respectively. To sum up, biochar can partially substitute fertilizer for rice production in acid paddy fields in southern China. When the amount of biochar added is ≥60 t/ha, 70% doses of fertilizer application can still ensure the nutrient absorption of rice, improve the fertilizer utilization efficiency, and ensure the stable yield of rice. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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14 pages, 723 KiB

Open AccessArticle

Silicon Calcium Fertilizer Application and Foliar Spraying with Silicon Fertilizer Decreases Cadmium Uptake and Translocation in Rice Grown in Polluted Soil

by Shuai Yuan, Can Cui, Yu Han, Pingping Chen, Naimei Tu and Zhenxie Yi

Agronomy 2023, 13(4), 1170; https://doi.org/10.3390/agronomy13041170 - 20 Apr 2023

Viewed by 1200

Abstract

Rice cultivated in Cd-polluted acidic paddy soil poses important health risks in China. Decreasing Cd accumulation in rice is important for food safety and human health. Early rice cultivar ZY-819 and late rice cultivar XWX-13 with low Cd-accumulation potentials, and early rice cultivar [...] Read more.

Rice cultivated in Cd-polluted acidic paddy soil poses important health risks in China. Decreasing Cd accumulation in rice is important for food safety and human health. Early rice cultivar ZY-819 and late rice cultivar XWX-13 with low Cd-accumulation potentials, and early rice cultivar LY-996 and late rice cultivar YZX with high Cd-accumulation potentials, were grown in mildly polluted double-cropping paddy fields (Cd content 0.3–0.6 mg kg⁻¹). The effects of adding biochar (10 t ha⁻²), lime (1500 kg ha⁻²), and silicon–calcium fertilizer (SC; 2250 kg ha⁻²) and foliar spraying with silicon fertilizer solution (Si; 1500 g ha⁻²) on Cd uptake and transport in rice, were assessed in plot experiments. The soil amendments and foliar spraying decreased the Cd content of brown rice from the high Cd-accumulation potential cultivars. The soil amendments decreased the Cd content of LY-996 and YZX brown rice by 25.24–32.40% and 32.99–44.16%, respectively, and SC decreased the Cd content most. Foliar spraying with Si decreased the Cd content of LY-996 and YZC brown rice by 23.79% and 26.40%, respectively. When soil amendments and foliar spraying were combined, the Cd content of brown rice was decreased most by the SC–Si treatment. Compared with the control, the SC–Si treatment decreased the Cd content of LY-996, ZY-819, YZX, and XWX-13 brown rice by 45.63%, 35.67%, 52.79%, and 32.03%, respectively. Soil amendments can effectively decrease Cd uptake by rice roots and Cd migration from roots to shoots. Compared with the control, the soil amendments increased the soil pH and decreased Cd availability. The strongest effects were for the lime and SC treatments. Foliar spraying with Si can effectively decrease Cd translocation through stems and leaves to brown rice. Applying SC fertilizer and foliar spraying with Si is the best method for decreasing the Cd content of rice grown in mildly Cd-polluted paddy fields. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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13 pages, 2310 KiB

Open AccessArticle

Combined Utilization of Chinese Milk Vetch, Rice Straw, and Lime Reduces Soil Available Cd and Cd Accumulation in Rice Grains

by Changyu Fang, Yajie Gao, Jianglin Zhang, Yanhong Lu, Yulin Liao, Xue Xie, Jian Xiao, Zhenyu Yu, Fangxi Liu, Haoliang Yuan, Naimei Tu and Jun Nie

Agronomy 2023, 13(3), 910; https://doi.org/10.3390/agronomy13030910 - 18 Mar 2023

Cited by 2 | Viewed by 1411

Abstract

Cadmium (Cd) pollution poses a growing threat to rice production in acidic paddies. In south China, a common agricultural practice involves the combined utilization of Chinese milk vetch (M) and rice straw (R). However, it is unclear how the addition of lime to [...] Read more.

Cadmium (Cd) pollution poses a growing threat to rice production in acidic paddies. In south China, a common agricultural practice involves the combined utilization of Chinese milk vetch (M) and rice straw (R). However, it is unclear how the addition of lime to these amendments affects Cd bioavailability and accumulation in soil. Control (CK), chemical fertilizer (F), Chinese milk vetch + rice straw + chemical fertilizer (MRF), and Chinese milk vetch + rice straw + chemical fertilizer + lime (MRFL) treatments were applied to develop a kind of green, efficient, and practical amendment for acidic paddies. We conducted a microplot experiment to explore Cd immobilization in paddy soil and the Cd content in rice grains with these treatments. The results showed that compared with F, the rice Cd in the MRF and MRFL treatments were significantly decreased by 51.7% and 65.2% in early rice and 23.0% and 43.3% in late rice, respectively. Both the MRF and MRFL treatments significantly reduced soil available Cd and weak acid-extractable cadmium (Aci-Cd) concentrations and increased soil organic matter (SOM), exchangeable cation concentrations, and pH, which converted Cd into a stable form in soil. In addition, the MRF and MRFL treatments increased soil pH value by reducing soil exchangeable hydrogen ion concentration (E-H). Additionally, recombination of Cd forms was the primary factor in the reduction in available Cd concentration according to partial least squares path modeling (PLS-PM) analysis. The Cd concentration of rice grains was primarily associated with soil available Cd, soil pH value, and SOM. Overall, these results provide useful data and novel insights into reducing rice grain Cd in south China. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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20 pages, 5754 KiB

Open AccessArticle

Comparison of the Effect of NaOH Pretreatment and Microbial Agents on Rice Straw Decomposition

by Qiyu Chen, Yufei Li, Chengli Wang and Yue Wang

Agronomy 2023, 13(3), 816; https://doi.org/10.3390/agronomy13030816 - 10 Mar 2023

Viewed by 1305

Abstract

Rice straw contains a large amount of lignocellulose which is difficult to be decomposed. The objective of this study was to determine the effect of alkaline pretreatment (sodium hydroxide, NaOH) and microbial agents on the decomposition of rice straw. The experimental detail consisted [...] Read more.

Rice straw contains a large amount of lignocellulose which is difficult to be decomposed. The objective of this study was to determine the effect of alkaline pretreatment (sodium hydroxide, NaOH) and microbial agents on the decomposition of rice straw. The experimental detail consisted of NaOH (control and NaOH solution pretreatment) and microbial agent (Bacillus licheniformis agent, Bacillus subtilis agent, Trichoderma viride agent, and no microbial agent) treatments. Compared with no NaOH pretreatment, the pH of NaOH pretreatment increased by 6.30–18.28%, while the electrical conductivity decreased by 49.18%, but the change in total nutrient content was not obvious. Under no NaOH pretreatment, Bacillus subtilis agent improved the temperature of the rice straw decomposition. Compared with Bacillus licheniformis agent and Trichoderma viride agent, Bacillus subtilis agent increased the alkali-hydrolyzable nitrogen, available phosphorus, and available potassium in rice straw by 1.39–10.30%. The organic carbon content was reduced by 3.50% and 17.15%. The germination index was greater than 80%. Under NaOH pretreatment, the pile with Bacillus subtilis agent reached the maximum temperature (39.5 °C) on the 12th day. Compared with Bacillus licheniformis agent and Trichoderma viride agent, Bacillus subtilis agent increased the content of alkali-hydrolyzable nitrogen and available phosphorus in rice straw by 1.64–11.87%. The humus polymerization, organic carbon, and carbon/nitrogen ratio were reduced by 6.40–44.06%. In addition, gray analysis, principal component analysis, and comprehensive evaluation were used to comprehensively evaluate the effect of straw decomposition. The results showed that Bacillus subtilis agent under NaOH pretreatment and no NaOH pretreatment had the most obvious effect on rice straw composting. This study provides a scientific basis for efficient decomposition of rice straw. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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15 pages, 2367 KiB

Open AccessArticle

Special Microbial Communities Enhanced the Role of Aged Biochar in Reducing Cd Accumulation in Rice

by Xueyun Deng, Changzhi Long, Le Chen, Yanli Du, Zhengwei Zhang, Li Gan and Yongjun Zeng

Agronomy 2023, 13(1), 81; https://doi.org/10.3390/agronomy13010081 - 26 Dec 2022

Cited by 2 | Viewed by 1468

Abstract

Biochar exhibits a good adsorption ability for heavy metals in soil and has been widely used as a remediation material in Cd-contaminated soil. However, the status of Cd uptake by rice driven by soil physicochemical properties and rhizosphere microbial communities after years of [...] Read more.

Biochar exhibits a good adsorption ability for heavy metals in soil and has been widely used as a remediation material in Cd-contaminated soil. However, the status of Cd uptake by rice driven by soil physicochemical properties and rhizosphere microbial communities after years of biochar application is not well understood. In this study, the relationship between the rhizosphere microbial community and soil physicochemical properties and rice Cd accumulation were investigated during the main rice growth stages. The results showed that in comparison to the non-biochar treatment (control), a noticeable reduction in Cd content in rice stem sheaths, leaves, rice husks and milled rice with different growth stages were observed in the biochar treatment after four years, which decreased by 38.76–66.18%, 40.93–70.27%, 43.64–47.92% and 31.91–34.38%, respectively. Compared to non-biochar treatment (control), the properties of the soil in different growth stages by biochar treatment of the soil pH, soil organic matter (SOM), total nitrogen (TN) and available phosphorus (AP) were significantly increased, which increased by 10.5–16.13%, 8–25%, 75–130.13% and 132.95–191.43%, respectively. The content of available Cd (ACd) concentration in different stages by biochar treatment was significantly decreased, which decreased by 26.57–44.24%. Biochar application after four years changed the rhizosphere bacterial community structure composition (phyla level) in all stages. The relative abundance of Proteobacteria, Bacteroidetes and Nitrospirae was increased, while the relative abundance of Chloroflexi, Acidobacteria and Actinobacteria was decreased. Meanwhile, the biochar application enriched Rhodocyclaceae, Burkholderiaceae, Nitrosomonadaceae, Anaerolineaceae, Ignavibacteriales and Bacteroidales, which may contribute to the reduction of Cd uptake and accumulation in rice. These results suggest that biochar treatment after four years changed the rhizosphere microbial community structure and soil physicochemical properties and promoted the colonization of specific microbial populations in the rice rhizosphere to form a special protective system in the rice rhizosphere, which reduced Cd uptake by rice. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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17 pages, 3082 KiB

Open AccessArticle

Analysis of Photosynthetic Differences of Rice Germplasm in Southeast Asia Based on Leaf-Tissue Structure, Physiology, and iTRAQ

by Xiaoli Zhang, Maoyan Tang, Hui Wang, Wei Tao, Qiang Wang, Lei Chen, Guoqing Gao, Ronghua Lv and Tianfeng Liang

Agronomy 2022, 12(12), 3207; https://doi.org/10.3390/agronomy12123207 - 16 Dec 2022

Cited by 1 | Viewed by 1620

Abstract

Photosynthesis is responsible for 90–95% of organic matter in crop yield. The light energy utilization rate of high-yielding rice varieties is 1.0–1.5%, but the ideal value is about 3–5%. Yield can be further improved by improving photosynthetic function. Through the initial screening and [...] Read more.

Photosynthesis is responsible for 90–95% of organic matter in crop yield. The light energy utilization rate of high-yielding rice varieties is 1.0–1.5%, but the ideal value is about 3–5%. Yield can be further improved by improving photosynthetic function. Through the initial screening and re-screening of 220 Southeast Asian germplasm resources, we found that the net photosynthetic rate of Southeast Asian germplasm resource C1 was 36.96 μmol m⁻² S⁻¹, which is close to that of C₄ plant maize and 3.26 times higher than that of Southeast Asian germplasm resource G164 at 11.26 μmol m⁻² S⁻¹. Using C1 and G164 as materials, we compared the tissue structure, chloroplast ultrastructure, photosynthetic physiological indicators, and proteomics of sword leaves to determine the factors affecting photosynthetic function. Compared with G164, C1 exhibited increased number of vascular bundles, increased stomatal size and density, more abundant and neatly arranged chloroplasts and thylakoid grana, and higher chlorophyll fluorescence parameters. The activities and contents of the key photosynthetic enzyme Rubisco were higher in C1 than in G164. The two germplasm resources were subjected to iTRAQ analysis, and the results showed that compared with C1, nine proteins were down-regulated and one protein was up-regulated and associated with photosynthetic electron transport in G164; a total of 17 differential proteins were associated with CO₂ fixation, and nine were up-regulated and eight differential proteins were down-regulated in G164. The identified genes encode proteins in the photosynthesis and carbon fixation pathways, and the changes in gene expression were verified by real-time qPCR. The gene expression patterns were consistent with the protein expression patterns. The results suggest that most differential proteins are involved in electron transfer from PSII to PSI and in the CO₂ fixation pathway, and increasing the levels of such proteins can effectively enhance the photosynthetic efficiency. C1 can be used as a donor material for selection of high light efficiency varieties and in-depth photosynthesis studies. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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12 pages, 2485 KiB

Open AccessArticle

Potted-Seedling Machine Transplantation Simultaneously Promotes Rice Yield, Grain Quality, and Lodging Resistance in China: A Meta-Analysis

by Ping Liao, Yi Meng, Yuqiong Chen, Wenan Weng, Le Chen, Zhipeng Xing, Baowei Guo, Haiyan Wei, Hui Gao and Hongcheng Zhang

Agronomy 2022, 12(12), 3003; https://doi.org/10.3390/agronomy12123003 - 29 Nov 2022

Cited by 1 | Viewed by 1403

Abstract

Potted-seedling machine transplantation (PSMT) is an innovative method of mechanical rice transplanting to improve seedling quality and reduce mechanical injury relative to blanket-seedling machine transplantation (BSMT). However, the responses of yield, grain quality, and risk of lodging in rice to PSMT have not [...] Read more.

Potted-seedling machine transplantation (PSMT) is an innovative method of mechanical rice transplanting to improve seedling quality and reduce mechanical injury relative to blanket-seedling machine transplantation (BSMT). However, the responses of yield, grain quality, and risk of lodging in rice to PSMT have not yet been comprehensively defined. Here, we present a meta-analysis of 67 peer-reviewed studies with 382 field observations to investigate the impacts of PSMT on rice yield, grain quality, and lodging resistance in mainland China. The results indicated that compared to BSMT, PSMT increased grain yield, aboveground biomass, and nitrogen uptake by an average of 8.4%, 6.2%, and 7.2%, respectively. PSMT boosted grain yield with hybrid rice (+10.2%) more strongly than with inbred rice (+6.9%). PSMT improved the brown rice rate (+0.74%), milled rice rate (+1.1%), head rice rate (+2.3%), and gel consistency (+4.4%) while reducing the amylose content by 3.7% with no significant effects on the chalky grain rate, chalkiness, length/width ratio, or protein content. The increase in the milled rice rate under PSMT was greater with hybrid rice than with inbred rice. PSMT reduced the lodging index at the first (−5.1%), second (−9.4%), and third (−8.0%) internodes. In conclusion, PSMT is a promising practice for simultaneously improving rice yield, milling quality, cooking and eating quality, and lodging resistance in paddies. In addition, the grain yield and milling quality of hybrid rice under PSMT are higher than those of inbred rice. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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14 pages, 269 KiB

Open AccessArticle

Effects of Applying Different Organic Materials on Grain Yield and Soil Fertility in a Double-Season Rice Cropping System

by Jing Yang, Bin Liao, Changyu Fang, Mohamed S. Sheteiwy, Zhenxie Yi, Sichao Liu, Chao Li, Guozhu Ma and Naimei Tu

Agronomy 2022, 12(11), 2838; https://doi.org/10.3390/agronomy12112838 - 13 Nov 2022

Cited by 1 | Viewed by 1443

Abstract

Double-cropping rice cultivation reduces soil fertility, and the extensive use of chemical fertilizers has harmful effects on both the environment and grain yield. The application of organic materials could be used as a practical strategy to maintain soil fertility and improve grain yield [...] Read more.

Double-cropping rice cultivation reduces soil fertility, and the extensive use of chemical fertilizers has harmful effects on both the environment and grain yield. The application of organic materials could be used as a practical strategy to maintain soil fertility and improve grain yield in a double-season rice cropping system. For this purpose, field experiments with six growing seasons over three years, from 2016 to 2018, were conducted to assess the effects of five organic materials (biochar, Chinese milk vetch, rice straw, rapeseed cake fertilizer, and manure) on the grain yield and soil fertility, aiming to save about 25% of the chemical nitrogen (N) fertilizer required for all rice growing stages. The result showed that, compared with CK (the most common dose of fertilizer in this study region; 100% chemical fertilizer without organic fertilizer), the grain yield and soil fertility of double-cropped rice were increased after applying organic fertilizers for three consecutive years. Specifically, the CRC treatment (Chinese milk vetch (10.77 t ha⁻¹ in fresh)/rice straw (26.51 t ha⁻¹ in fresh) + 75% chemical fertilizer) showed significantly higher rates of effective panicles (4.65–10.92%) and annual grain yield (8.00–8.82%). The total N, total phosphorus (P), total potassium (K), alkaline N, and available P content in the CRC soil were significantly increased by 11.85%, 12.22%, 15.08%, 23.32%, and 41.04%, respectively, relative to CK. The decomposition of the applied Chinese milk vetch and rice straw combined with 75% chemical fertilizer resulted in more soil humus (9.50 g kg⁻¹), humic acid (3.19 g kg⁻¹), fulvic acid (3.26 g kg⁻¹), and active organic carbon (5.78 g kg⁻¹) and a significantly higher carbon pool management index (13.5%), as well as significantly higher soil urease activity (18.10%) and acid phosphatase activity (17.64%). Therefore, in this study, Chinese milk vetch (10.77 t ha⁻¹ in fresh) in the early rice season/rice straw (26.51 t ha⁻¹ fresh) in the late rice season + 75% chemical fertilizer treatment was the optimal dose for the double-season rice cropping system. It resulted in higher rice yields and has the potential to be used for more sustainable soil fertility. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

8 pages, 221 KiB

Open AccessCommunication

Quality Characteristics of Noodles Processed from Rice Grains of the Ratoon Crop

by Zhengwu Xiao, Chengjing Liao, Yuping Hu, Keqian Zhang, Jiana Chen, Fangbo Cao, Shengliang Fang and Min Huang

Agronomy 2022, 12(11), 2739; https://doi.org/10.3390/agronomy12112739 - 04 Nov 2022

Viewed by 1208

Abstract

Rice noodles are usually manufactured using rice grains of the main crop. There is limited information available on rice noodles processed from ratoon rice grains. In this study, two-year field experiments were conducted to compare the cooking and texture properties of noodles and [...] Read more.

Rice noodles are usually manufactured using rice grains of the main crop. There is limited information available on rice noodles processed from ratoon rice grains. In this study, two-year field experiments were conducted to compare the cooking and texture properties of noodles and the grain chemical properties of ratoon crops with those of main crops from two rice cultivars (Guichao 2 and Zhenguiai) that are widely used for processing noodles. Results showed that the cooked break rate and the cooking loss rate of rice noodles processed from grains of the ratoon crop were similar to those of the main crop in both cultivars; however, changes in texture of cooked rice noodles processed from grains of the ratoon crop compared with the main crop were cultivar-dependent, being significantly softer in Zhenguiai but not in Guichao 2. Hardness and chewiness of cooked rice noodles were significantly negatively correlated with amylopectin content in milled rice grains in Zhenguiai, indicating that amylopectin content is a key chemical property determining the texture differences between rice noodles processed from grains of ratoon and main crops. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

14 pages, 2589 KiB

Open AccessArticle

Varietal Variances of Grain Nitrogen Content and Its Relations to Nitrogen Accumulation and Yield of High-Quality Rice under Different Nitrogen Rates

by Jiale Wu, Renwei Que, Wenle Qi, Gangqiang Duan, Jingjing Wu, Yongjun Zeng, Xiaohua Pan and Xiaobing Xie

Agronomy 2022, 12(11), 2719; https://doi.org/10.3390/agronomy12112719 - 02 Nov 2022

Cited by 2 | Viewed by 1313

Abstract

Nitrogen (N) management is an important strategy for improving the yield, grain quality, and N use efficiency of rice (Oryza sativa). Exploring appropriate N application rates is essential for high-quality rice production in China, especially in the context of the large [...] Read more.

Nitrogen (N) management is an important strategy for improving the yield, grain quality, and N use efficiency of rice (Oryza sativa). Exploring appropriate N application rates is essential for high-quality rice production in China, especially in the context of the large extension of these varieties in recent years. Field experiments were conducted to study changes of grain N content and their correlations to yield and yield components using twenty high-quality rice varieties grown at three N application rates (105, 165 and 225 kg ha⁻¹) in 2019 and 2020. Additionally, a micro-plot experiment based on ¹⁵N isotope tracing technique was also conducted with two contrasting high-quality rice varieties of Y-liangyou 911 and Yeiangyoulisi under two N application rates (165 and 225 kg ha⁻¹) in 2021, with grain N accumulation, its subdivision, and N utilization investigated. We found that the grain N content of high-quality rice increased with the increase of N application rates, while there was no consistent response in grain yield. There was a significant quadratic relationship between grain yield and grain N content, while panicles m⁻² and grain-setting rate had a positive and a negative correlation with grain N content, respectively, in both 2019 and 2020. Across three N application rates and two years, the coefficient of variation (CV) of grain N content ranged from 10.36% to 21.26% among twenty varieties, of which Y-liangyou 911 had the smallest CV, and six varieties, including Yexiangyoulisi, had the largest CV. The micro-plot experiment showed that, in comparison with N₁₆₅, the grain N content, grain N accumulation, and N recovery rate increased under N₂₂₅ in both varieties, but a significant increase in grain yield was only observed for Y-liangyou 911. Grain N accumulation derived from panicle N fertilizer and its ratios to total grain N accumulation and the N recovery rate was significantly higher than those derived from basal and tillering N fertilizers. Nevertheless, increasing N application rates had much greater effects on the grain N accumulation derived from basal and tillering fertilizers and on ratios to total grain N accumulation in Yexiangyoulisi than those in Y-liangyou 911. Our results suggested that adopting a moderate N application rate (165 kg ha⁻¹) is conducive to maintaining an appropriate grain N content and achieving higher grain yield and N use efficiency as well as better quality of high-quality rice. Besides, moderately reducing basal and/or tillering N fertilizers is necessary for those varieties with a larger CV of grain N content. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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8 pages, 447 KiB

Open AccessCommunication

Changes in Grain Yield and Yield Attributes Due to Cultivar Development in Indica Inbred Rice in China

by Zui Tao, Ruichun Zhang, Jiana Chen, Fangbo Cao, Longsheng Liu, Ming Zhang and Min Huang

Agronomy 2022, 12(10), 2541; https://doi.org/10.3390/agronomy12102541 - 18 Oct 2022

Cited by 5 | Viewed by 1180

Abstract

Inbred rice has been grown more and more widely, while the planting area of hybrid rice has decreased by approximately 25% in China since 1995. This study aimed to assess the changes in grain yield and yield attributes due to cultivar development in [...] Read more.

Inbred rice has been grown more and more widely, while the planting area of hybrid rice has decreased by approximately 25% in China since 1995. This study aimed to assess the changes in grain yield and yield attributes due to cultivar development in indica (Oryza sativa ssp. indica) inbred rice in China. Field experiments were conducted in 2019 and 2020 to determine the performance of grain yield and yield attributes of an indica super inbred rice cultivar Jinnongsimiao (JNSM) released in 2010 by comparing it with an indica high-yielding inbred rice cultivar Guichao 2 (GC2) released in 1978 and an indica super hybrid rice cultivar Y-liangyou 900 (YLY900) released in 2016. Results showed that JNSM produced 18% higher grain yield than GC2 but 6% lower grain yield than YLY900. Compared with GC2, JNSM had higher spikelets per panicle, spikelet-filling percentage, and harvest index by 67%, 4%, and 11%, respectively. Compared with YLY900, JNSM had 14% lower grain weight and 19% lower biomass production during the pre-heading period. The difference in biomass production during the pre-heading period between JNSM and YLY900 was explained more by crop growth rate than growth duration. This study suggests that (1) the recently released indica super inbred rice cultivar JNSM outyields the old indica high-yielding inbred rice cultivar GC2 as a result of increasing panicle size, spikelet-filling percentage, and harvest index, and (2) further improvement in grain yield in indica inbred rice can be achieved by improving biomass production through promoting pre-heading crop growth. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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11 pages, 2188 KiB

Open AccessArticle

Expansion of Field Margin Size Mitigate the Hazard of Rotary Tillage to Earthworm in Rice-Rape Rotation System

by Chao Li, Yang Zhao, Kaikai Cheng, Junyu Zhou, Xiaoping Xiao, Anas Iqbal, Haiming Tang and Min Huang

Agronomy 2022, 12(9), 2209; https://doi.org/10.3390/agronomy12092209 - 16 Sep 2022

Viewed by 1382

Abstract

Field margin (FM) provides refuges for earthworm survival in rape-rice system after flooding, while the effects of FM with different size on earthworm in arable field (AF) is unclear. In this study, we investigated the effects of different FM sizes, a conventional size [...] Read more.

Field margin (FM) provides refuges for earthworm survival in rape-rice system after flooding, while the effects of FM with different size on earthworm in arable field (AF) is unclear. In this study, we investigated the effects of different FM sizes, a conventional size (FM I) and three expanding sizes (FM II, FM III, FM IV), on earthworm population characteristics in FM and AF. The results showed that the mean abundance of earthworm under the expanding sizes at 1 day and 60 day of flooding after rape harvest was 16.5 and 20.2 times higher than that of FM I, respectively. After stopping flooding, juveniles first migrated from FM to AF, whereas more than half of them were killed by subsequent rotary tillage, and the mortality decreased with expanding FM size. Subsequently, expanding FM sizes promoted earthworm to distribute evenly through the AF at faster speeds. At rape maturity, the mean abundance and total biomass of earthworm of AF under expanding FM sizes were significantly greater than that of FM I, and this positive effect increased with expanding FM size. The results indicated that expanding FM size can mitigate the hazard of rotary tillage to earthworm and promote rapid recovery of earthworm population in AF. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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13 pages, 890 KiB

Open AccessArticle

Effects of Different Concentrations of Micro-Nano Bubbles on Grain Yield and Nitrogen Absorption and Utilization of Double Cropping Rice in South China

by Yinfei Qian, Xianjiao Guan, Caihong Shao, Caifei Qiu, Xianmao Chen, Jin Chen and Chunrui Peng

Agronomy 2022, 12(9), 2196; https://doi.org/10.3390/agronomy12092196 - 15 Sep 2022

Cited by 1 | Viewed by 1676

Abstract

Micro-nano bubble (MNB) irrigation can effectively improve the hypoxia stress caused by conventional irrigation and shows great potential in plant development, yield improvement, and saving of water and fertilizer, and has been recognized as a new and high-efficiency technology in crop planting. However, [...] Read more.

Micro-nano bubble (MNB) irrigation can effectively improve the hypoxia stress caused by conventional irrigation and shows great potential in plant development, yield improvement, and saving of water and fertilizer, and has been recognized as a new and high-efficiency technology in crop planting. However, former research on MNB concentration had no clear segmentation, and other MNB concentrations can achieve better or worse effects. This remains to be further explored in order to explore the optimal concentration of MNBs for the yield and nitrogen absorption and utilization of the double cropping rice. With early rice Ganxin203 and late rice WufengyouT025 as the experimental cultivars, the effects of MNBs on growth, yield, and nitrogen absorption and utilization of the potted double cropping rice were analyzed by setting three concentrations of MNBs (LM, low concentration; MM, middle concentration; HM, high concentration), compared with the ordinary running water (CK). Compared with CK, grain yield of the early rice under the MNB treatment increased by 4.84~10.95% and the late rice increased by 6.10~14.31%. It was found that the higher the concentration of the MNBs, the higher the yield of the rice. This is due to that the MNBs improved the tiller-bearing rate, increased the SPAD and Pn values of the flag leaves in the whole growth period, slowed down the drop of the leaf SPAD and Pn from heading stage to maturity, increased the number of the adventitious roots, improved the α-NA oxidation of the root, and simultaneously promoted the nitrogen accumulation, absorption, and utilization. The HM treatment obtained the best benefits, and the effect of the MNBs on the late rice was better than the early rice. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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12 pages, 554 KiB

Open AccessArticle

Delaying Application and Reducing the N Rate Enhances Grain Yield and N Use Efficiency in No-Tillage, Direct-Seeded Hybrid Rice

by Peng Jiang, Xingbing Zhou, Lin Zhang, Mao Liu, Hong Xiong, Xiaoyi Guo, Yongchuan Zhu, Lin Chen, Jie Liu and Fuxian Xu

Agronomy 2022, 12(9), 2092; https://doi.org/10.3390/agronomy12092092 - 01 Sep 2022

Viewed by 1153

Abstract

The no-tillage, direct-seeded (NTDS) rice cropping system has attracted considerable attention because of its social, economic, and environmental benefits. However, very limited research has been conducted on optimizing nitrogen (N) management practices to enhance grain yield and N use efficiency (NUE) of rice [...] Read more.

The no-tillage, direct-seeded (NTDS) rice cropping system has attracted considerable attention because of its social, economic, and environmental benefits. However, very limited research has been conducted on optimizing nitrogen (N) management practices to enhance grain yield and N use efficiency (NUE) of rice grown in NTDS. An N fertilization field experiment with two rice hybrids was conducted in 2020 and 2021; the experiment consisted of three N rates (180, 153, and 0 kg N ha⁻¹; N₁₈₀, N₁₅₃, and N₀, respectively) and two N-application ratios split among the basal, seedling (three-leaf stage), mid-tillering, and panicle initiation stages (50%, 0%, 30%, and 20% and 0%, 30%, 40%, and 30%; R₁ and R₂, respectively). Although the N rate was 15% lower in the N₁₅₃ treatment than in the N₁₈₀ treatment, grain yield for N₁₅₃ was equal to or slightly higher than that for N₁₈₀. N₁₅₃ had a higher agronomic efficiency of applied N (AE_N), partial factor productivity of applied N (PFP_N), and recovery efficiency of applied N (RE_N) compared to N₁₈₀ by 10.1–24.7%, 15.0–20.1%, and 1.8–12.6%, respectively. Grain yield, AE_N, PFP_N, and RE_N in R₂ were higher than those in R₁ by 0.8–4.6%, 2.4–19.7%, 0.7–4.6%, and 3.5–30.0%, respectively. The increase in grain yield was due to improvement in the sink size that resulted from larger panicles, higher biomass production at maturity, which was partially attributable to increased biomass accumulation after heading, and a higher harvest index. Our results suggest that it is feasible to simultaneously improve grain yield and NUE in hybrid rice under NTDS through delayed and reduced N application rate, and current breeding programs need to target large panicle size as a primary objective for NTDS rice. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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12 pages, 2684 KiB

Open AccessArticle

Assessing the Genetic Improvement in Inbred Late Rice against Chilling Stress: Consequences for Spikelet Fertility, Pollen Viability and Anther Characteristics

by Maofei Ren, Weiqin Wang, Siwei Pu, Wanju Shi, Teng Hu, Qiyuan Tang and Huaqin Xu

Agronomy 2022, 12(8), 1894; https://doi.org/10.3390/agronomy12081894 - 12 Aug 2022

Cited by 2 | Viewed by 1434

Abstract

The development of varieties with strong tolerance is one of the important strategies to diminish the negative impact of chilling stress during heading on the spikelet fertility and yield formation of late-season rice. However, whether such genetic improvement has been made in inbred [...] Read more.

The development of varieties with strong tolerance is one of the important strategies to diminish the negative impact of chilling stress during heading on the spikelet fertility and yield formation of late-season rice. However, whether such genetic improvement has been made in inbred late rice lines in China is not clear. In the present study, three late-season inbred rice varieties, Xiangwanxian2 (XWX2, released in 1988), Xiangwanxian8 (XWX8, released in 1998) and Xiangwanxian17 (XWX17, released in 2008) were subjected to moderate (20 °C) and extreme (17 °C) chilling stress during heading, and the grain yield components and flowering-related traits of the three varieties in response to different temperature were investigated. The results showed that the newly released inbred late rice variety XWX17, demonstrated better chilling tolerance during heading than the early released varieties with respect to higher grain filling percentage. The improved grain filling percentage in XWX17 might be the results of increased spikelet fertility, which was attributed to the increase in pollen viability, anther dehiscence length and anther volume. In addition, the SPAD value and the chlorophyll a content of the flag leaf can be used as indicators to predict the rice spikelet fertility when suffering from chilling stress during heading. The present study provides evidence that the genetic approach has been made to improve the chilling tolerance of inbred late rice lines during heading; however, further research is needed to explore the physiological and molecular mechanism underlying the relationship between leaf characteristics and function with rice spikelet fertility. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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6 pages, 1875 KiB

Open AccessCommunication

Slimming the Grain through Breeding Is a Practical Way to Reduce the Chalky Grain Rate of Middle-Season Hybrid Rice

by Min Huang, Jialin Cao, Jiana Chen, Fangbo Cao and Chuanming Zhou

Agronomy 2022, 12(8), 1886; https://doi.org/10.3390/agronomy12081886 - 11 Aug 2022

Cited by 4 | Viewed by 1081

Abstract

The production of middle-season rice is an important part of agriculture in the Yangtze River basin of China. In recent years, the chalky grain rate of middle-season rice has decreased with the release of new cultivars. However, limited information is available on the [...] Read more.

The production of middle-season rice is an important part of agriculture in the Yangtze River basin of China. In recent years, the chalky grain rate of middle-season rice has decreased with the release of new cultivars. However, limited information is available on the factors responsible for this change in the chalky grain rate. This study evaluated the trends in the chalky grain rate and grain size traits of the new cultivars and the relationships between the chalky grain rate and grain size traits for middle-season hybrid rice in a province located in the middle reaches of the Yangtze River basin during 2006–2021. The results indicate that the recently reduced chalky grain rate of middle-season hybrid rice in the new cultivars is closely associated with a decrease in rice width, suggesting that it is feasible to reduce the chalky grain rate of middle-season hybrid rice by slimming the grain through breeding. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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10 pages, 3124 KiB

Open AccessArticle

Long-Term Straw Return with Reducing Chemical Fertilizers Application Improves Soil Nitrogen Mineralization in a Double Rice-Cropping System

by Liming Chen, Shiqi Yang, Junfeng Gao, Ling Chen, Huaying Ning, Zheng Hu, Jiahui Lu, Xueming Tan, Yongjun Zeng, Xiaohua Pan and Yanhua Zeng

Agronomy 2022, 12(8), 1767; https://doi.org/10.3390/agronomy12081767 - 28 Jul 2022

Cited by 5 | Viewed by 1808

Abstract

The partial replacement of chemical fertilizer with straw return is considered an effective method for improving the accumulation of organic matter and soil fertility, but the characteristics of soil nitrogen fixation and mineralization in a double-cropped rice paddy system are unclear. Based on [...] Read more.

The partial replacement of chemical fertilizer with straw return is considered an effective method for improving the accumulation of organic matter and soil fertility, but the characteristics of soil nitrogen fixation and mineralization in a double-cropped rice paddy system are unclear. Based on a 12-year field experiment, we conducted a waterlogged incubation experiment for 49 days to determine the effect of long-term straw return combined with reducing chemical fertilizer application on the dynamic changes of mineralized soil nitrogen (N) content and mineralized N rate under the treatments, including NPK (chemical fertilizers application with straw removal), SBR (straw burned return), and SR (straw return). Results showed that, compared with SBR and NPK, SR significantly increased available nitrogen by 7.4% and 16.5%, respectively, due to the higher ammonium nitrogen and nitrate nitrogen, as well as the total carbon, available phosphorus, and slowly available potassium, suggesting that it could stock a sufficient nitrogen source. During the incubation period, the amount of N mineralization was relatively higher under SR than under SBR and NPK treatments, especially during the later mineralization time, whereas there was no difference in the N mineralization rate. In addition, SR significantly increased soil cumulative N mineralization and N mineralization potential. However, SBR significantly decreased the soil mineralizable N ratio compared with SR and NPK, which may result in a worsening of the N mineralization potential. The results indicated that long-term straw return combined with reducing chemical fertilizer application could significantly improve the N supply capacity of paddy rice field soil to better coordinate the soil N supply and immobilization. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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8 pages, 957 KiB

Open AccessArticle

Comparison of Short-Duration and Long-Duration Rice Cultivars Cultivated in Various Planting Densities

by Jiana Chen, Fangbo Cao, Yu Liu, Zui Tao, Tao Lei, Salah Fatouh Abou-Elwafa and Min Huang

Agronomy 2022, 12(8), 1739; https://doi.org/10.3390/agronomy12081739 - 23 Jul 2022

Cited by 1 | Viewed by 1857

Abstract

The selection of high-yielding, short-duration rice cultivars is essential for the double-rice cropping system. High hill density could be achieved with less labor under machine transplanted conditions. Therefore, dense planting is more practical for machine-transplanted rice. While few studies have been conducted to [...] Read more.

The selection of high-yielding, short-duration rice cultivars is essential for the double-rice cropping system. High hill density could be achieved with less labor under machine transplanted conditions. Therefore, dense planting is more practical for machine-transplanted rice. While few studies have been conducted to certify the feasibility of short-duration cultivar combined with dense planting in machine transplanted conditions. The current study was executed to determine the effects of dense planting on yield attributes and grain yield of short-duration cultivars under mechanically transplanted conditions. A field experiment comprises two treatments—i.e., the short-duration cultivar Lingliangyou104 cultivated at a high planting density (SDH) and the long-duration Taiyou390 cultivar cultivated at a low planting density (LDL)—were conducted in the 2018 and 2019 late seasons. The results showed that the SDH exhibited 17% and 19% higher panicle number in a unit, 26% and 24% higher spikelet filling, 8% and 8% higher grain weight, 21% and 11% higher harvest index, and consequently 12% and 4% higher grain yield and 13 and 15 days shortened growth duration compared to the LDL in the 2018 and 2019, respectively. The data revealed that the difference in grain yield between the SDH and LDL was mainly due to the higher harvest index and reasonable dry matter distribution of the SDH, which was conducive to improving yield components and increasing rice grain yield. As a result, short-duration rice cultivars combined with dense planting is a feasible strategy for improving the grain yield of mechanically transplanted late rice. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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16 pages, 19619 KiB

Open AccessArticle

Density-Dependent Fertilization of Nitrogen for Optimal Yield of Perennial Rice

by Guangfu Huang, Yujiao Zhang, Shilai Zhang, Jing Zhang, Fengyi Hu and Fengmin Li

Agronomy 2022, 12(7), 1698; https://doi.org/10.3390/agronomy12071698 - 18 Jul 2022

Cited by 2 | Viewed by 1526

Abstract

In the absence of tillage, perennial rice is an innovation and supplement to rice production. Proper N fertilizer application connected to planting density has been proposed as an effective way to improve rice yields. The tradeoff between crop N uptake and N supply [...] Read more.

In the absence of tillage, perennial rice is an innovation and supplement to rice production. Proper N fertilizer application connected to planting density has been proposed as an effective way to improve rice yields. The tradeoff between crop N uptake and N supply is essential for optimal N management and soil environment benefit in the perennial rice cropping system. To assess the response of perennial rice to N fertilizer and planting density, field experiments with four consecutive growing seasons within two years, from 2016 to 2017, were conducted in southern China. Four nitrogen rates (N0, N1, N2, and N3 refer to 0, 120, 180, and 240 kg N ha⁻¹, respectively) combined with three planting densities (D1, D2, and D3 refer to 100 × 10³, 167 × 10³ and 226 × 10³ plants ha⁻¹, respectively) were designed. The results showed that both N rate and planting density significantly affected crop production (p < 0.05), N uptake and soil N balance. Specifically, the N2D3 mode could achieve sustainable and higher dry matter accumulation (15.15 t ha⁻¹) and grain yield (7.67 t ha⁻¹) among all the treatments over the four seasons. A positive relationship between N uptake and dry matter/grain yield was observed. The N2D3 mode showed significantly higher N uptake (201 kg ha⁻¹ each season) and less soil N loss (27.1%), relative to C.K. Additionally, the N2D3 mode could reach the optimal N balance (−0.2 kg ha⁻¹) with a low N requirement (23.9 kg N Mg⁻¹ grain), resulting in higher N use efficiency (NAE: 26.5 kg N kg⁻¹, NRE: 64.9%). In the perennial rice cropping system, therefore, 180 kg N ha⁻¹ integrated with 226 × 10³ plants ha⁻¹ could deliver higher grain yields with less N requirement, higher N use efficiency and less soil N loss. This optimal combination between planting density and nitrogen rate can result in soil N balance for sustainable perennial rice production. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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16 pages, 1777 KiB

Open AccessArticle

High Sink Capacity Improves Rice Grain Yield by Promoting Nitrogen and Dry Matter Accumulation

by Fangwei Cheng, Shiyou Bin, Anas Iqbal, Lijian He, Shanqing Wei, Hao Zheng, Pengli Yuan, He Liang, Izhar Ali, Dongjie Xie, Xinxin Yang, Anjie Xu, Saif Ullah and Ligeng Jiang

Agronomy 2022, 12(7), 1688; https://doi.org/10.3390/agronomy12071688 - 16 Jul 2022

Cited by 5 | Viewed by 1748

Abstract

Sink capacity, nitrogen (N), and dry matter accumulation (DMA) all play essential roles in promoting high rice grain yield, but their relationship is unclear. Here, a field experiment was conducted from 2020 to 2021 with Zhuangxiangyou Baijin 5 as the test cultivar. Two [...] Read more.

Sink capacity, nitrogen (N), and dry matter accumulation (DMA) all play essential roles in promoting high rice grain yield, but their relationship is unclear. Here, a field experiment was conducted from 2020 to 2021 with Zhuangxiangyou Baijin 5 as the test cultivar. Two rates of N (T1 = 90 kg ha⁻¹ N and T2 = 180 kg ha⁻¹ N) and three transplanting densities (272,000 hills ha⁻¹ (M1), 238,000 hills ha⁻¹ (M2), and 206,000 hills ha⁻¹ (M3)) were used to investigate rice grain yield and corresponding yield attributes. The results showed significant differences in rice yield, sink capacity, N and DMA, and the leaf area index (LAI) at the heading stage among the different treatments. The results showed that the output of T2M1 was the highest in 2020, increasing by 16.6% compared with the lowest output, while the output of T2M2 was the highest in 2021, increasing by 11.9% compared with the lowest output. During 2020, the highest sink capacity, LAI at the heading stage, and maximum dry matter accumulation at the maturity stage of rice were recorded in T2M1, while the highest N accumulation was recorded in T2M2. Furthermore, the sink capacity, as well as levels of N and DMA, of rice in 2020 was higher in T2M2, and the LAI was higher in T2M1 at the heading stage. Correlation analyses showed that yield was significantly positively correlated with N and DMA. In addition, a significant positive correlation between sink capacity and DMA was observed during both years, while a significant positive correlation between sink capacity and N accumulation was observed in 2021. Thus, we conclude that a high sink capacity can increase rice yield by increasing N and DMA because a high sink capacity is the internal driving force of high rice grain yield. In conclusion, the T2M1 regimen is a promising approach for improving the grain yield of paddy rice. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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14 pages, 2100 KiB

Open AccessArticle

Optimizing Irrigation and Nitrogen Management to Increase Yield and Nitrogen Recovery Efficiency in Double-Cropping Rice

by Haijun Zhu, Ting Zhang, Chunlan Zhang, Xiaoe He, Ailong Shi, Weijian Tan, Zhenxie Yi and Xuehua Wang

Agronomy 2022, 12(5), 1190; https://doi.org/10.3390/agronomy12051190 - 16 May 2022

Cited by 6 | Viewed by 1730

Abstract

Water and nitrogen are the key factors affecting the yield and nitrogen recovery efficiency of double-cropping rice, but information about optimizing nitrogen fertilizer and irrigation management to achieve high yield is still limited. The purpose was to study the effects of different nitrogen [...] Read more.

Water and nitrogen are the key factors affecting the yield and nitrogen recovery efficiency of double-cropping rice, but information about optimizing nitrogen fertilizer and irrigation management to achieve high yield is still limited. The purpose was to study the effects of different nitrogen application rates (D1, D2, D3, D4 (0, 112.5, 150.0, and 187.5 kg ha⁻¹ for early-season rice and 0, 135, 180, and 225 kg ha⁻¹ for late-season rice)) and irrigation conditions (G1, Alternate wetting and drying irrigation, G2, flooding irrigation) on rice yield and nitrogen recovery efficiency. Field experiments were carried out in the early and late seasons of the subtropical environment in Heshan County, Hunan Province, China in 2018 and 2019. The results showed that the yield was increased by the comprehensive action of reasonable irrigation mode and nitrogen management. Under G1D4 and G1D3 treatments, the maximum grain yield of early-season rice was 7.42 t ha⁻¹, which was 0.8~35.9% higher than other treatments, and that of late-season rice was 8.20 t ha⁻¹, which was 13.3~67.0% higher than other treatments. The increase of yield in G1D4 and G1D3 treatments was due to the increase in dry matter accumulation, effective Panicles number, and Spikelets per panicle, whose increase was due to an increase in photosynthesis and nitrate reductase activity. Compared with other treatments, late-season rice G1D3 treatment achieved a higher yield with less nitrogen fertilizer, while early-season rice G1D4 treatment achieved the highest yield, but the nitrogen recovery efficiency decreased. We should focus on more effective nitrogen fertilizer and irrigation management to further improve the yield potential of double-cropping rice. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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15 pages, 666 KiB

Open AccessArticle

Genetic Association between Blast Resistance and Yield Traits in Rice Detected Using a High-Density Bin Map

by Lydia Kanyange, Ye-Yang Fan, Zhen-Hua Zhang, De-Run Huang, Ting-Xu Huang, Jie-Yun Zhuang and Yu-Jun Zhu

Agronomy 2022, 12(5), 1173; https://doi.org/10.3390/agronomy12051173 - 12 May 2022

Cited by 1 | Viewed by 1593

Abstract

Avoiding linkage drag of the resistance genes will facilitate the use of gene resources for rice breeding. This study was conducted to confirm the avoidance of linkage drag due to Pi26 and Pi25 blast resistance genes, and to analyze the association of Pi26 [...] Read more.

Avoiding linkage drag of the resistance genes will facilitate the use of gene resources for rice breeding. This study was conducted to confirm the avoidance of linkage drag due to Pi26 and Pi25 blast resistance genes, and to analyze the association of Pi26, Pi25, Pib and Pita with quantitative trait loci (QTL) for yield traits. A recombinant inbred line population was derived from an indica rice cross Dan 71/Zhonghui 161. A linkage map consisting of 1219 bin markers, 22 simple sequence repeats and five gene markers was constructed. A total of 75 QTL were identified, including 2 for leaf blast resistance and 73 for eight yield traits. The two QTL for blast resistance were closely linked and located in the Pi26 and Pi25 regions, explaining 69.06 and 12.73% of the phenotypic variance, respectively. In a region covering Pi26 and Pi25, QTL were detected for grain yield and its key components. The alleles for enhancing blast resistance and grain yield were all from Dan 71. Not only was the linkage drag due to Pi26 and Pi25 avoided, but the results also indicate that these resistance genes may be used for simultaneously enhancing blast resistance and grain yield in rice. In the Pib and Pita regions, QTL was not detected for blast resistance, but was for yield traits. In each region, the allele for improving trait performance was derived from the parent carrying the resistance allele. In addition, four QTL clusters for grain weight and size, qGL4/qGW4.1, qGL11.2/qRLW11, qTGW11/qGW11 and qGL12/qGW12/qRLW12, were shown to be promising candidates for map-based cloning. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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18 pages, 3079 KiB

Open AccessArticle

Matter Production Characteristics and Nitrogen Use Efficiency under Different Nitrogen Application Patterns in Chinese Double-Cropping Rice Systems

by Wentao Zhou, Wenfei Long, Hongrui Wang, Pan Long, Ying Xu and Zhiqiang Fu

Agronomy 2022, 12(5), 1165; https://doi.org/10.3390/agronomy12051165 - 11 May 2022

Cited by 6 | Viewed by 1587

Abstract

Panicle-stage nitrogen fertilizer is popular in parts of China due to its higher nitrogen recovery efficiency compared to basal and tiller nitrogen. However, the effect of conversion from basal to panicle-stage nitrogen on matter production, grain yield, and nitrogen use efficiencies (NUE) in [...] Read more.

Panicle-stage nitrogen fertilizer is popular in parts of China due to its higher nitrogen recovery efficiency compared to basal and tiller nitrogen. However, the effect of conversion from basal to panicle-stage nitrogen on matter production, grain yield, and nitrogen use efficiencies (NUE) in Chinese double-cropping rice systems remains largely unknown. Here, we elucidate the effect by using two types of one-time basal nitrogen patterns (A and B), three panicle-N allocation patterns (C, D, and E), and the local conventional patterns (CK). The two-year experiment demonstrates that E (basal/tiller/spikelet-promoting /spikelet-developing nitrogen = 0:4:3:3) produced the greatest annual grain yield, nitrogen agronomic efficiency, and nitrogen partial productivity. The annual dry matter weight and nitrogen increment of panicle, nitrogen transportation of stems contributes the most to annual yield and NUE. Furthermore, the yield increase could be attributed to the higher effective panicles, plant dry matter weight at tillering, and net photosynthesis rate at heading. Moreover, years and varieties affect the yield in different N treatments. The improvement in the net photosynthesis rate at the milk stage also significantly increases nitrogen recovery efficiency. These findings suggest that it is worth paying attention to the rational ratio of tillering to panicle fertilizer without applying a base fertilizer, to synchronously increase the grain yield, NUE in Chinese double-cropping rice systems. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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17 pages, 2768 KiB

Open AccessArticle

Effect of Integrated Organic–Inorganic Amendments on Leaf Physiological and Grain Starch Viscosity (Rapid Visco-Analyzer Profile) Characteristics of Rice and Ultisols Soil Quality

by Anas Iqbal, Izhar Ali, Quan Zhao, Pengli Yuan, Min Huang, He Liang, Muhammad Zeeshan, Ihsan Muhammad, Shanqing Wei and Ligeng Jiang

Agronomy 2022, 12(4), 863; https://doi.org/10.3390/agronomy12040863 - 31 Mar 2022

Cited by 2 | Viewed by 1798

Abstract

Current farming systems are highly reliant on chemical fertilizers (CF), which negatively affect soil health, the environment, and crop productivity. Substituting organic fertilizer for chemical fertilizer (CF) is an important agricultural practice that improves soil health and crop productivity and is eco-friendly. To [...] Read more.

Current farming systems are highly reliant on chemical fertilizers (CF), which negatively affect soil health, the environment, and crop productivity. Substituting organic fertilizer for chemical fertilizer (CF) is an important agricultural practice that improves soil health and crop productivity and is eco-friendly. To explore the effects of organic fertilizer in the form of cattle manure (CM) or poultry manure (PM) combined with CF on soil properties, leaf physiological traits, and grain physiochemical characteristics of rice, a 2-year field experiment was conducted in a dual cropping system with six treatments: Neg-CF (no N fertilizer control), Pos-CF (100% CF), High-CM (60% CM + 40% CF), Low-CM (30% CM + 70% CF), High-PM (60% PM + 40% CF), and Low-PM (30% PM + 70% CF). The results exhibited that the adding of organic manure significantly improved soil chemical traits such as soil organic C (SOC), total N (TN), and available N (AN). Similarly, applying the combined fertilizer led to significant increases in the leaf net photosynthetic rate (Pn), SPAD values, and rice grain nutritional and cooking characteristics according to Rapid Visco-Analyzer (RVA) profile. Average increases in SOC, TN, Pn, starch content (SC), and amylose content (AC) were 16%, 12%, 9%, 7%, 9%, and 12%, respectively, across the year in the Low-PM compared to the Pos-CF treatment. Moreover, the manure amendments significantly altered the RVA profile attributes, including peak viscosity, tough viscosity, final viscosity, and the setback and pasting temperatures compared to Pos-CF. Linear regression analysis revealed that SOC and TN were positively associated with leaf Pn and SPAD values. Further, leaf Pn and SPAD were positively correlated with rice grain SC and AC. The correlation heat map analyses revealed a positive correlation in the RVA profile between the soil properties and leaf physiological traits. These correlation analyses showed that the increase in soil chemical traits and leaf physiological activities played a significant role in higher rice grain nutritional and cooking quality. Overall, the findings of this study show that the integrated use of organic fertilizers and CF in rice fields enhances soil functionality and the quality of rice on a sustainable basis. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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9 pages, 4747 KiB

Open AccessArticle

Multidimensional Relationships of Starch Digestibility with Physicochemical, Pasting and Textural Properties of 30 Rice Varieties

by Liqin Hu, Jialin Cao, Yu Liu, Zhengwu Xiao, Mingyu Zhang, Jiana Chen, Fangbo Cao, Anas Iqbal, Salah Fatouh Abou-Elwafa and Min Huang

Agronomy 2022, 12(3), 720; https://doi.org/10.3390/agronomy12030720 - 16 Mar 2022

Cited by 3 | Viewed by 1738

Abstract

Consuming rice with low starch digestibility is beneficial for reducing the risk of diabetes. Several factors have been shown to influence starch digestibility, but the combined effects of these factors on starch digestibility have not been studied. We assessed multidimensional relationships between the [...] Read more.

Consuming rice with low starch digestibility is beneficial for reducing the risk of diabetes. Several factors have been shown to influence starch digestibility, but the combined effects of these factors on starch digestibility have not been studied. We assessed multidimensional relationships between the glucose production rate (GPR) of cooked rice with 16 indexes, including physicochemical, pasting and textural properties in 30 rice varieties. The stepwise multiple regression analysis showed that amylose content (AC), gel consistency (GC) and pasting temperature (PT) were closely related to GPR. This relationship could be described by the equation: GPR = −0.080 AC + 0.008 GC + 0.034 PT + 0.720, with a determination coefficient of 0.84. The variation partitioning analysis further indicated that AC, GC and PT independently explained 36%, 5% and 4% of the GPR variation, respectively. The interaction of AC and GC explained 46% of the variation in GPR. This study identifies the key indexes (AC, GC and PT) affecting starch digestibility and quantifies contributions of these indexes to the variation in GPR. The finding of our study provides useful information for breeding and selecting rice varieties with low GPR. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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13 pages, 1928 KiB

Open AccessArticle

Effects of Short-Term Tillage Managements on CH₄ and N₂O Emissions from a Double-Cropping Rice Field in Southern of China

by Haiming Tang, Chao Li, Lihong Shi, Kaikai Cheng, Li Wen, Weiyan Li and Xiaoping Xiao

Agronomy 2022, 12(2), 517; https://doi.org/10.3390/agronomy12020517 - 18 Feb 2022

Cited by 6 | Viewed by 1741

Abstract

Soil carbon (C) content plays an important role in maintaining or increasing soil quality and soil fertility. However, the impacts of different tillage and crop residue incorporation managements on greenhouse gas (GHG) emissions from paddy fields under the double-cropping rice (Oryza sativa [...] Read more.

Soil carbon (C) content plays an important role in maintaining or increasing soil quality and soil fertility. However, the impacts of different tillage and crop residue incorporation managements on greenhouse gas (GHG) emissions from paddy fields under the double-cropping rice (Oryza sativa L.) system in southern China still need further study. Therefore, a field experiment was conducted to determine the impacts of different short-term (5-years) tillage and crop residue incorporation managements on soil organic carbon (SOC) content, SOC stock, and GHG emissions from paddy fields under the double-cropping rice system in southern China. The field experiment included four tillage treatments: rotary tillage with all crop residues removed as a control (RTO), conventional tillage with crop residue incorporation (CT), rotary tillage with crop residue incorporation (RT), and no-tillage with crop residue retention (NT). These results indicated that SOC stock in paddy fields with CT, RT, and NT treatments increased by 4.64, 3.60, 3.50 Mg ha⁻¹ and 4.68, 4.21, and 4.04 Mg ha⁻¹ in 2019 and 2020, respectively, compared with RTO treatment. The results showed that early rice and late rice yield with CT treatment increased by 7.22% and 19.99% in 2019 and 6.19% and 6.40% in 2020, respectively, compared with RTO treatment. A two-year (2019–2020) investigation of GHG results indicated that methane emissions from paddy fields with NT treatment were decreased, but nitrous oxide emissions from paddy fields were increased. The lowest mean global warming potential (GWP) and per yield GWP carbon dioxide were found with NT treatment, compared to RT and CT treatments. Therefore, it was a beneficial practice for maintaining SOC stock and decreasing GHG mitigation under the double-cropping rice system in southern China by applying no-tillage with crop residue retention management. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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5 pages, 523 KiB

Open AccessTechnical Note

Do You Get What You Pay for? Evaluating the Reliability of an Inexpensive Portable Photosynthesis System in Measuring Gas Exchange in Rice (Oryza sativa L.) Leaves

by Xiaohong Yin, Xing Li, Jiaxin Xie, Zhengwu Xiao, Chunrong Zhao, Yuling Kang, Chuanming Zhou, Fangbo Cao, Jiana Chen and Min Huang

Agronomy 2022, 12(11), 2775; https://doi.org/10.3390/agronomy12112775 - 07 Nov 2022

Cited by 1 | Viewed by 1065

Abstract

The availability of commercially available portable photosynthesis systems has facilitated widespread photosynthetic research. Our study aimed to evaluate the reliability of a recently developed inexpensive portable photosynthesis system, Yaxin-1105, in measuring gas exchange in rice (Oryza sativa L.) leaves. Gas exchange parameters, [...] Read more.

The availability of commercially available portable photosynthesis systems has facilitated widespread photosynthetic research. Our study aimed to evaluate the reliability of a recently developed inexpensive portable photosynthesis system, Yaxin-1105, in measuring gas exchange in rice (Oryza sativa L.) leaves. Gas exchange parameters, including net photosynthetic rate (A_net), stomatal conductance (g_s), intercellular CO₂ concentration (C_i), and transpiration rate (E), were measured on 88 rice leaves across seven rice cultivars and three growth stages (panicle initiation, heading, and early ripening), using both Yaxin-1105 and LI-6400XT. There were significant difference between each gas exchange parameter at each growth stage measured by Yaxin-1105 and LI-6400XT, except C_i at the heading stage. Mean A_net, g_s, and E measured by Yaxin-1105 were 26–66% lower than those measured by LI-6400XT at panicle initiation, heading, and early ripening stages. Mean C_i measured by Yaxin-1105 was 13–22% higher than that measured by LI-6400XT at panicle initiation and early ripening stages. The coefficients of determination between each gas exchange parameter measured by Yaxin-1105 and by LI-6400XT at panicle initiation, heading, and early ripening stages ranged from only 0.0007 to 0.1889. These results indicate that the Yaxin-1105 is not a reliable tool for measuring gas exchange in rice leaves. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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10 pages, 1477 KiB

Open AccessCase Report

Yield Attributes Response to Nitrogen Fertilization in Low-Nitrogen Tolerant Hybrid Rice

by Zui Tao, Yu Liu, Jiana Chen, Fangbo Cao and Min Huang

Agronomy 2022, 12(10), 2320; https://doi.org/10.3390/agronomy12102320 - 27 Sep 2022

Viewed by 1097

Abstract

The development of low-nitrogen (N) tolerant varieties is an effective way to improve the use efficiency of N in rice and is crucial to the sustainable rice production in China. Recently, we observed that higher grain yields were obtained in the hybrid rice [...] Read more.

The development of low-nitrogen (N) tolerant varieties is an effective way to improve the use efficiency of N in rice and is crucial to the sustainable rice production in China. Recently, we observed that higher grain yields were obtained in the hybrid rice variety Deyou 4727 (DY4727) than in the hybrid rice variety Y-liangyou 900 (YLY900) under zero-N fertilization conditions, suggesting that DY4727 has higher low-N tolerance compared to YLY900. In this study, field experiments were performed in 2020 and 2021 to compare the responses of yield attributes to N fertilization (180 kg N ha^–1) relativized to zero-N fertilization between DY4727 and YLY900. Results showed that the response of grain yield to N fertilization was 13–55% for two varieties in two years. DY4727 had lower response of grain yield to N fertilization than YLY900 by 47% in 2020 and by 70% in 2021. There were no significant or consistent differences in responses of spikelets per m², spikelet filling percentage, aboveground biomass, intercepted radiation, radiation use efficiency, and aboveground N uptake to N fertilization between DY4727 and YLY900. DY4727 had 32% and 26% lower positive response of grain weight to N fertilization compared to YLY900 in 2020 and 2021, respectively. The response of harvest index to N fertilization was negative (−3% in 2020 and −9% in 2021) for DY4727 but positive (1% in 2020 and 12% in 2021) for YLY900. DY4727 had higher negative response of internal N-use efficiency to N fertilization (−41% in 2020 and −24% in 2021) than YLY900 (−11% in 2020 and −10% in 2021). This study suggests that grain weight, harvest index, and internal N-use efficiency are key traits determining the difference in response of grain yield to N fertilization between DY4727 and YLY900. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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4 pages, 557 KiB

Open AccessBrief Report

The Fraction of Intercepted Radiation to Nitrogen Absorption as an Indicator for Assessing Physiological Nitrogen Use Efficiency in Rice

by Min Huang, Jiana Chen and Fangbo Cao

Agronomy 2022, 12(7), 1603; https://doi.org/10.3390/agronomy12071603 - 02 Jul 2022

Cited by 3 | Viewed by 1195

Abstract

Improving nitrogen (N) use efficiency is important for achieving sustainable rice production in China. Physiological N use efficiency (PNUE) is a measure of a plant’s ability to convert absorbed N into biomass, and can be calculated as the product of the fraction of [...] Read more.

Improving nitrogen (N) use efficiency is important for achieving sustainable rice production in China. Physiological N use efficiency (PNUE) is a measure of a plant’s ability to convert absorbed N into biomass, and can be calculated as the product of the fraction of intercepted radiation to N absorption (FIRNA) and radiation use efficiency (RUE). This study evaluated the relationships between PNUE with FIRNA and RUE in three widely grown, high-yielding rice varieties using data obtained from two N fertilization experiments conducted in 2020 and 2021. The results show that PNUE was significantly positively related to FIRNA, but not significantly related to RUE in all three rice varieties. PNUE increased by 7.4–10.3 g g⁻¹ for each 10 MJ g⁻¹ increase in FIRNA. These results suggest that FIRNA can serve as an indicator for assessing PNUE in rice, which has implications for the phenotypic identification of rice varieties with high PNUE. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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7 pages, 833 KiB

Open AccessObituary

In Memory of the Father of Hybrid Rice

by Zhiyuan Huang, Yeyun Xin, Qiming Lv and Lihuang Zhu

Agronomy 2022, 12(6), 1249; https://doi.org/10.3390/agronomy12061249 - 24 May 2022

Viewed by 2373

Abstract

Prof. Yuan devoted his whole life to the research of hybrid rice. On the first anniversary of Prof. Yuan Yuan’s death, our research team wrote a paper to commemorate him. In this paper, we recalled his life, his research progress and achievements of [...] Read more.

Prof. Yuan devoted his whole life to the research of hybrid rice. On the first anniversary of Prof. Yuan Yuan’s death, our research team wrote a paper to commemorate him. In this paper, we recalled his life, his research progress and achievements of hybrid rice. He led and guided his research team to overcome difficulties in hybrid rice research. Hybrid rice has made important contributions to China and world’s food security. He is a great researcher worthy of our memory forever in the world. Full article

(This article belongs to the Special Issue In Memory of Professor Longping Yuan, the Father of Hybrid Rice)

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