Search Results (55)

Ratoon rice is a sustainable planting model, and its yield is closely linked to the light and temperature use efficiency. The photothermal quotient (PQ), a key parameter for evaluating the light and temperature use efficiency, significantly influences ratoon rice yield. However, research on how different stubble heights affect PQ and the utilization efficiency of light and temperature resources remains limited. Here, we conducted a two-year field experiment to investigate the radiation use efficiency (RUE), effective accumulated temperature use efficiency (TUE), PQ, interception percentage (IP), intercepted photosynthetically active radiation (IPAR), and total dry weight (TDW) of six ratoon rice varieties under two stubble height treatments (HS: high stubble, LS: low stubble) during the ratoon season. This study aimed to analyze how different stubble heights impact ratoon rice yield by evaluating light and temperature resource utilization efficiency and investigates the relationship between PQ and ratoon rice yield. The results showed that the HS treatment significantly increased ratoon season yield compared to LS treatment, with average yield increases of 21.2% and 28.1% in 2022 and 2023, respectively. This yield enhancement was attributed to improved TDW under HS treatment, driven by increased IP, IPAR, RUE, and TUE. Notably, PQ was significantly lower under HS than under LS treatment. This reduction was primarily attributed to the decreased duration available for light and heat accumulation, consequently lowering PQ. Correlation analysis revealed a significant positive association between main season yield and PQ, while ratoon season yield exhibited a negative correlation with PQ. In conclusion, the HS treatment increased IP and IPAR, enhanced TUE and RUE, and reduced PQ, collectively contributing to higher ratoon season yields. Importantly, our findings indicate that PQ can more effectively predict yield changes in the ratoon season under HS treatment, providing a theoretical basis for optimizing light and temperature resource utilization in ratoon rice. Full article

Rice cultivated in cadmium (Cd)-polluted acidic paddy soil poses important health risks in China. Mitigating Cd accumulation in rice is of crucial importance for food safety and human health. In this study, using Chuangliangyou 669 as the ratoon rice variety, a field experiment was conducted in paddy fields with severe Cd pollution (Cd concentration > 1.0 mg kg⁻¹). The aim was to explore the impacts of different nitrogen (N) fertilizer levels (N1-180 kg hm⁻², N2-153 kg hm⁻², N3-126 kg hm⁻²) and planting densities (D1-20 cm × 20 cm, D2-16.7 cm × 16.7 cm) in the main crop on the yield and Cd accumulation characteristics of ratoon rice. The results showed that reducing the amount of N fertilizer would lead to a decrease in the yield of ratoon rice, while increasing the planting density could increase the yield, mainly by increasing the effective panicle. Among the various combined treatments, the yields of N1M2 and N2M2 were relatively high. The planting density had no significant impact on the Cd concentration, translocation factor and bioaccumulation factor of ratoon rice. The Cd concentration in various tissues of ratoon rice decreased significantly with the reduction in N fertilizer application. Reducing N fertilizer application could increase the pH, reduce the concentration of available Cd in the soil and consequently reduce the Cd bioaccumulation factor of various tissues of ratoon rice and the Cd translocation factor from roots and stems to brown rice. Considering both the yield and the Cd concentration in brown rice, N2M2 was the optimal treatment of reducing N and increasing density, which could maintain a relatively high yield while significantly reducing the Cd concentration. Full article

Ratoon rice can improve rice yield by increasing the multiple cropping index in China. However, the greenhouse gas (CH₄ and N₂O) emission characteristics from ratoon rice fields and the cultivation methods to reduce CH₄ and N₂O emissions are rarely reported. This study first conducted the analysis of genotype differences in greenhouse gas emission fluxes using five strong ratoon ability rice varieties in 2020. Second, water management methods, including alternating the wet–dry irrigation (AWD) pattern and conventional flooding irrigation (CF) during the main season, were carried out in 2021. CH₄ and N₂O emission flux, agronomic traits, and rice yield during both main and ratoon seasons were investigated. The results showed that the CH₄ emission flux during the main and ratoon seasons was 157.05–470.73 kg·ha^–1 and 31.03–84.38 kg·ha^–1, respectively, and the total N₂O emission flux was 0.13–0.94 kg·ha^–1 in the ratoon rice system over the two seasons (RRSTS). Compared with the main season, the CH₄ emission flux during the ratoon season was significantly reduced, thus decreasing the greenhouse gas global warming potential (GWP) and greenhouse gas emission intensity (GHGI) in the ratoon rice system. Cliangyouhuazhan (CLYHZ) showed a high yield, and the lowest GWP and GHGI values among the five rice varieties in RRSTS. Compared with CF, the AWD pattern reduced the CH₄ emission flux during the main and ratoon seasons by 67.4–95.3 kg·ha^–1 and 1.7–5.1 kg·ha^–1, respectively, but increased the N₂O emission flux by 0.1–0.6 kg·ha^–1 during the RRSTS. Further, compared with CF, the AWD pattern had a declined GWP by 14.3–19.4% and GHGI by 30.3–34.3% during the RRSTS, which was attributed to the significant reduction in GWP and GHGI during the main season. The AWD pattern significantly increased rice yield by 21.9–22.9% during the RRSTS, especially for YX203. Correlation analysis showed that CH₄, GWP, and GHGI exhibited significant negative correlations with spikelet number per m² and the harvest index during the main and ratoon seasons. Collectively, selecting the high-yield, low-emission variety CLYHZ could significantly reduce greenhouse gas emissions from ratoon rice while maintaining a high yield. The AWD pattern could reduce total CH₄ emission during the main season, reducing the GWP and GHGI while increasing the ratoon rice system yield. It could be concluded that a variety of CLYHZ and AWD patterns are worthy of promotion and application to decrease greenhouse gas emissions in the ratoon rice area in the upper reaches of Yangtze River, China. Full article

Ratooning rice plants have a high moisture content and strong adhesion during harvesting. Traditional cleaning devices are prone to clogging when processing ratooning rice, resulting in a series of problems such as high grain loss rate and high grain impurity rate. In response to the above issues, this article adopts the CFD-DEM coupling method to design a spiral step cleaning device. A detailed analysis was conducted on the influence of the cone angle and thickness of the spiral-stepped skeletons on the flow state, and flow velocity and pressure distribution cloud maps were obtained under different structural parameters. The vortex morphology under different thicknesses of the spiral-stepped skeletons was compared, and the structural parameters of the device were determined. The motion trajectory and distribution of impurity particles under different inlet flow velocities were analyzed using data superposition, and the appropriate inlet flow velocity range was determined. A test bench was built, and a three-factor quadratic regression orthogonal rotation combination experiment was conducted with fan speed, feeding rate, and device inclination angle as experimental factors. The results of the bench test show that the performance index reaches its optimum when the device inclination angle, fan speed, and feeding rate are 2.47°, 2906 r/min, and 4.0 kg/s, respectively. At this time, the grain impurity rate, grain loss rate, and sieve clogging rate are 2.21%, 2.15%, and 3.5%, respectively. Compared to those of traditional cleaning equipment, these value are reduced by 44.5%, 39.6%, and 83.9%, respectively. This study can provide ideas for the design of ratooning rice cleaning devices. Full article

This study aimed to develop and genetically characterize thermosensitive genic male-sterility (TGMS) lines for use in hybrid rice (Oryza sativa L.) breeding. Male-sterile F₂ to F₄ generation lines were screened during the high-temperature summer season, and ratoon crops of selected male-sterile rows were harvested for pure seed. Sixty-six F₅ TGMS lines were genotyped using DNA markers controlling 16 traits from the LSU80 QA/QC Rice PlexSeq SNP Panel. Ten TGMS lines with desirable traits that included semidwarf, glabrous, non-aromatic, long-grain, narrow brown leaf spot resistance, and blast resistance genes were selected for further genotypic characterization using markers for low chalkiness (chalk5), wide compatibility (S5-n), cold tolerance (qSCT-11 and qCST-12), and anaerobic germination (AG1 and AG2). TGMS lines TIL21051S and TIL21052S possess favorable alleles for each of the genes evaluated in this study and are desirable parents for two-line hybrid breeding in the southeast United States. TIL21044S, TIL21095S, TIL21060S, and TIL21066S each contain three blast resistance genes and have potential as parental lines. TIL21014S-2, TIL21015S, and TIL21016S-1 include the fgr allele for aroma and can also be used as parental lines for aromatic two-line hybrids. Full article

To solve the problem of the high loss rate of threshing devices during the mechanical harvesting of ratoon rice, we propose a method using the principle of rigid–flexible coupling in this paper to reduce losses. Through analysis of the forces and collisions on ratoon rice grains during the threshing process, it has been confirmed that changing the structure and materials of the threshing contact components can effectively reduce grain loss. A rigid–flexible coupling rod tooth was designed, and the overall structural parameters of the device were determined based on force analysis results and dimensional boundary conditions. The MBD-DEM coupling method was used to simulate the threshing process, and the force conditions of the threshing rod teeth and threshing drum were obtained. The influence of the feeding amount and of the flexible body thickness on the crushing of ratoon rice grains was analyzed. In order to obtain the device’s optimal parameter combination, a three-factor quadratic regression orthogonal rotation combination experiment was conducted with drum speed, flexible body thickness, and rod tooth length as experimental factors. The optimization results showed that when the drum speed, flexible body thickness, and rod tooth length were 684 r/min, 3.86 mm, and 72.7 mm, respectively, the crushing rate, entrainment loss rate, and uncleaned rate were 1.260%, 2.132%, and 1.241%, respectively. The bench test showed that it is feasible to use the MBD–DEM coupling method to measure the motion and force of ratoon rice. The rigid–flexible coupling threshing device can reduce the grain crushing rate while ensuring grain cleanliness. Compared with traditional threshing devices, the crushing rate and entrainment loss rate of the rigid–flexible coupling threshing device were reduced by 55.7% and 27.5%, respectively. The research results can provide a reference for the design of threshing devices for ratoon rice harvesters. Full article

Selenium (Se) is an essential trace element that has various beneficial effects for human healthy. However, the effects of different Se forms and concentrations on growth and development, photosynthetic characteristics and antioxidant capacity are still unclear with regard to the dual grain-and-feed dual-use of ratoon rice (RR). In this study, three concentrations of three different Se forms were applied to RR using the foliar spraying method, and the results showed that Se treatment can increase the Se content of rice grain and straw. All the Se treatments improved the photosynthetic indexes and activities of antioxidant enzymes. The Se and trace elements contents, and the percentages of organic Se and protein Se of brown rice were found to be similar in all three Se forms. A higher organic Se content was found in the grain by spraying sodium selenite and Se-Met, in which the resistant starch (RS) content was increased with the increase in amylose content in grains. The main Se species in the grain was SeMet and the SeMeCys was found only with SeMet treatments. The grain quality showed that all three Se forms increased the consistency of gelatinization. Our study indicated that exogenous Se could improve the nutritional quality of both grain and straw by improving photosynthetic traits and antioxidant enzyme activities, especially sodium selenite and Se-Met. These results underscore the potential of foliar biofortification to enhance the functional component contents of RR grains and provide an insight into the Se enrichment of ratoon rice. Full article

The sustainability of rice-cropping systems hinges on balancing resources, output, and environmental impacts. China is revitalizing the ancient ratoon rice (RR) system for input savings and environmental benefits. Prior research has explored the RR system’s performance using various individual indicators, but few studies have focused on its overall balance of these factors. Environmental efficiency (EE) analysis addresses this gap. Using field survey data from Hunan Province in China and the slacks-based data envelopment analysis method, we quantified the EE of the RR, double-season rice (DR), and single-season rice (SR) systems. Key findings include: (1) the RR system outperforms in carbon emissions and non-point source pollution; (2) the RR system’s EE is 0.67, significantly higher than the DR (0.58) and SR (0.57) systems, indicating superior performance; and (3) despite its relatively high EE, the RR system can still improve, mainly due to input redundancy and production value shortfall. These findings provide strategies for optimizing RR systems to enhance agricultural sustainability. Full article

Perennial rice has recently garnered global attention due to its potential to save on seeds and labor costs and its high production efficiency. The “mid-season rice–ratoon forage” mode is a new planting system that has emerged in recent years. However, detailed information is still lacking on the regenerative characteristics, grain and ratoon forage yields, and forage nutrient content of perennial rice under different planting densities, nitrogen (N) rates, stubble heights, and water management practices. Four experiments with perennial rice were conducted in Sichuan Province, Southwest China, from 2017 to 2022. The results show that the rice grain and ratoon forage yields were significantly affected by year, planting density, and N. The grain yield was 28.18% and 60.81% lower in 2018F and 2019F, respectively, than in 2017F; similarly, the ratoon forage yield was 29.01% and 52.74% lower in 2018S and 2019S, respectively, than in 2017S. The low grain yield was mainly associated with lower numbers of spikelets per panicle and panicles per m², which resulted from a lower regrowth rate, and the low ratoon forage yield was mainly attributed to the lower regrowth rate. The rice grain and ratoon forage yields increased with an increase in the N rate and planting density. The ratoon forage was found to be rich in crude protein, crude fat, crude fiber, calcium, nitrogen, phosphorus, potassium, and other nutrients. Moreover, the content of these nutrients increased significantly with an increase in the N rate. The regrowth rate and maximum tillers showed trends of first increasing and then decreasing with an increase in the stubble height under dry and wet alternation irrigation during the winter season. When the relative soil moisture decreased to below 80% during the winter season, the regrowth rate and seedling development index could reach more than 99% and 84%, respectively. Our results suggest that integrating N, water, and other management practices (including the combination of a 150 kg ha⁻¹ N rate, 18.0 hills per m², 10–20 cm rice stubble height, and alternating dry and wet irrigation during the winter season) is a feasible approach for achieving high grain and ratoon forage yields in perennial rice systems. Full article

Ratoon rice occupies an important position in rice production owing to its time-saving, labor-saving and low-pollution planting, and increased benefits. However, the impact of tillage management on the yield in rice ratooning system has not yet been reported. Thus, field experiments were carried out to investigate the impact of seven tillage methods on the yield of ratoon rice crop in Jingzhou City in 2021–2022. The managements included winter plowing + rotary 2 times (PTw + RT2) or 3 times (PTw + RT3), spring plowing + rotary 2 times (PTs + RT2) or 3 times (PTs + RT3), no plowing + rotary 2 times (P0 + RT2) or 3 times (P0 + RT3) and no tillage (NT). PTw + RT3 had the highest total rice yield. The experimental data were collected in 2021 and 2022. In terms of main season rice yield, the order of ranking was PTw > PTs ≈ NT ≈ P0, while for ratoon rice yield, the ranking was NT > PTw ≈ PTs > P0. Generally, the root function ranked as PTw > PTs > P0 > NT. The photosynthetic capacity of the main season rice always maximized in PTw, those of the ratoon rice all maximized in NT, and those of both the main season rice and ratoon rice always minimized in P0. In the three tillage modes (PTw, PTs, P0), an additional rotary tillage did not affect the growth or yield of rice. PTw + 3RT was the highest yielding tillage management, but it is still necessary to explore other PTw + 3RT methods and more economical tillage management to increase the yield of ratoon rice. Full article

Ratoon rice is characterized by higher production combined with enhanced rice quality. However, the relationship between the differences in the structure and properties of the starch and variations in the ratoon season and rice quality is still unclear. In this study, we conducted a field experiment in 2023 to assess the relationship between rice quality differences and starch characteristics of four different hybrid rice varieties (Longjingyou1212: LJY1212; Taoyouxiangzhan: TYXZ; Liangyou6326: LY6326; Fengliangyouxiang1: FLYX1) in the ratoon season. In terms of appearance, the chalkiness degrees and chalky grain percentage of LJY1212 (0.6%, 2.3%) and TYXZ (1.2%, 6.0%) were 53.5% and 53.9% lower than those of LY6326 (2.4%, 10.0%) and FLYX1 (1.6%, 7.8%), indicating that the appearances of LJY1212 and TYXZ were better than those of LY6326 and FLYX1. The average amylose contents of LJY1212 (18.5%) and TYXZ (19.0%) were 10.8% higher than those of LY6326 (17.7%) and FLYX1 (15.7%), and there was no significant difference in protein content between the varieties in the ratoon season. Regarding the starch microstructure, the starch granules of LJY1212 and TYXZ in the ratoon season were arranged more closely. The average ratios of 1045/1022 cm⁻¹ of LJY1212 (0.77) and TYXZ (0.76) were 7.0% higher than those of LY6326 (0.71) and FLYX1 (0.72), indicating that the internal orders of LJY1212 and TYXZ’s starch were better than those of LY6326 and FLYX1. The average relative crystallinities of LJY1212 (24.8%) and TYXZ (24.5%) were 5.2% lower than those of LY6326 (25.7%) and FLYX1 (26.6%). The relative crystallinity of starch decreased with the increase in amylose content, while the short-range order degree, gelatinization temperature, and gelatinization enthalpy increased with the increase in amylose content. Therefore, the LJY1212 and TYXZ varieties, with better rice qualities, are recommended for planting in southern China. Full article

Ratoon rice represents a viable means to enhance rice production efficiency in terms of both area and time. Nonetheless, the development of specific varieties tailored for ratoon rice has been hindered by the complexity of trait considerations required during breeding/screening processes. A pivotal step towards advancing ratoon rice breeding programs involves reducing the dimensionality of selection traits. In this study, we performed a comprehensive analysis exploring whether the yield of the main crop could serve as a predictor for ratoon crop yield, thereby simplifying the selection process. Our findings revealed significant variability in the rice yields of both main and ratoon crops, with the ratoon crop yield averaging 51% of the main crop. Importantly, the correlation between grain yields of the main and ratoon crops did not deviate from the identity line, substantiating the feasibility of predicting ratoon crop yield based on the main crop yield. The number of panicles in the ratoon crops was found to be closely linked to that of the main crop; however, the size values of the panicles in the ratoon crops exhibited less of a dependency on the main crop’s panicle size. Additionally, a general decrease in grain weight was observed in the ratoon crops compared to the main crop. In summary, this study elucidates a pathway for the simplification of selection traits, thereby enhancing the efficiency of breeding high-yielding ratoon rice varieties, with the ultimate aim of fostering the sustainable development of ratoon rice. Full article

Biochar is beneficial as a clean, stable, and efficient soil amendment to improve rice quality and yield. However, there are few reports on the effects of no-tillage in combination with biochar application on rice growth, yield, and quality in regenerative rice systems. This study evaluated rice yield, grain quality, multiple antioxidant enzyme activities, and malondialdehyde content under four treatments: rotary tillage alone, rotary tillage + biochar application, no-tillage alone, and no-tillage + biochar. The results showed that the rice yield under no-tillage alone was 15% lower than that under rotary tillage alone, but that biochar application significantly increased rice yield by 10% and 20% under rotary tillage and no-tillage conditions, respectively, which might be attributed to the fact that biochar application increased panicle number, spikelet number per panicle, grain filling rate, and antioxidant enzyme activities. Additionally, biochar application also increased fine rice rate and protein content, meanwhile reducing chalkiness degree and chalky grain rate in both the main-season rice and ratoon-season rice. These results suggest that biochar application could enhance the yield and grain quality of ratoon rice, thus compensating for the no-tillage-induced yield loss. This study reveals the role of biochar in main-season rice and ratoon rice cultivation, providing a valuable reference for improved fertilizer utilization and cleaner agricultural production. Full article

Ratoon rice (RR) has emerged as an active adaptation to climate uncertainty, stabilizing total paddy rice yield and effectively reducing agriculture-related ecological environmental issues. However, identifying key remote sensing parameters for RR under cloudy and foggy conditions is challenging, and existing RR monitoring methods in these regions face significant uncertainties. Here, given the sensitivity of synthetic aperture radar (SAR) backscattering signals to the crop phenological period, this paper introduces a threshold model utilizing Sentinel-1A SAR data and phenological information for mapping RR. The Yongchuan District of Chongqing, which is often cloudy and foggy, was selected as a specific study region where VH-polarized backscatter coefficients of Sentinel-1 images were obtained at 10 m spatial resolution in 2020. Based on the proposed threshold model, the RR extraction overall accuracy was up to 90.24%, F1 score was 0.92, and Kappa coefficient was 0.80. Further analysis showed that the extracted RR boundaries exhibited high consistency with true Sentinel-2 remote sensing images and the RR extracted area was in good agreement with the actual planted area situation. This threshold model demonstrated good applicability in the studied cloudy and foggy region, and successfully distinguished RR from other paddy rice types. The methodological framework established in this study provides a basis for extensive application in China and other significant RR-producing regions globally. Full article

The ratoon rice planting area is gradually expanding, and decreasing Cadmium (Cd) accumulation in ratoon rice is important for food safety and human health. In this study, conventional indica rice (HHZ, Huanghuazhan), three-line indica–japonica hybrid rice (YY-4149, Yongyou 4149), and two-line indica hybrid rice (LY-121, Liangyou 121) were compared regarding ratoon rice yield and Cd uptake, transport, and accumulation. The distribution of Cd at different nodes in the ratoon crop was also examined. The rank-order of the Cd contents in each part (root, stem, leaf, stubble, and spike) of the main and ratoon crops of the tested cultivars was HHZ > LY-121 > YY-4149. The rank-order of the Cd content in each plant part at different nodes in the ratoon crop was HHZ > LY-121 > YY-4149. The Cd content in each plant part increased as the node position (i.e., according to the germination position of regenerated seedlings, the nodes are divided into the second, third, and fourth or fifth node from the top in stubble) was lowered. The redundancy analysis indicated that the low-node brown rice Cd content had the largest effect on the total brown rice Cd content in the ratoon crop. Accordingly, indica–japonica hybrid cultivars should be selected for the production of ratoon rice in mildly Cd-polluted areas, and the height of the main crop stubble should be maximized during harvest. Full article