Rice Fish Research Articles

Effect of Rice–Carp Coculture on Phytoplankton and Microzooplankton Community Composition in Paddy Water during Different Rice Growth Stages

Integrated rice–fish farming, an agricultural practice that combines cultivating rice and breeding fish in the same field, has attracted widespread attention. However, there is limited research on how the rice–carp coculture impacts the community structure of phytoplankton and microzooplankton in paddy water. This study employed eDNA metabarcoding sequencing to analyze the composition of phytoplankton and microzooplankton in a rice monoculture system (RM) and a rice–carp coculture system (RF). Following annotation, we identified 9 phyla, 89 families, 275 genera, and 249 species of phytoplankton, along with 20 phyla (or subphyla and classes), 85 families, 222 genera, and 179 species of microzooplankton. The alpha diversity indices revealed significantly higher richness, diversity, and evenness in the RF group compared to the RM group during grain-filling stage. Principal coordinates analysis (PCoA) demonstrated notable differences in the phytoplankton and microzooplankton compositions between the two groups across various rice growth stages. Composition analysis showed that rice–carp coculture increased the relative abundance of dominant phytoplankton phyla such as Bacillariophyta, Chrysophyta, and Euglenophyta while decreasing that of Cryptophyta. In microzooplankton, the coculture resulted in an increased abundance of Intramacronucleata (subphylum) and a decrease in Conoidasida (class). In conclusion, the rice–carp coculture enhances the diversity of plankton, particularly during the grain-filling stage, and simultaneously alters the composition and abundance of dominant plankton species in the paddy water. These findings enhance understanding of the broader impacts of integrated rice–carp farming on agricultural ecosystems, emphasizing alterations in the diversity and composition of aquatic microorganisms

Evaluation of Tilapia (Oreochromis niloticus) Survival and Growth in Aquaculture Systems with Different Feed Types

Proper feeding is crucial for promoting fast and healthy growth in fish, contributing to increased overall production. However, access to high-nutritional feed is not always feasible. Utilizing locally available ingredients presents a potential solution to this challenge. Consequently, this research aims to assess the impact of locally available feed ingredients on the growth and production of tilapia (O. niloticus) in Liberia. Three types of fish feed were prepared, namely Africa Rice fish feed (diet 1), soybeans fish feed (diet 2), and Gbarnga fish feed (control), each with distinct compositions. These feeds were evaluated to determine their effects on the growth and production performance of tilapia fish for the duration of 31 weeks. Fifty fish with an initial body weight of 12 g each were stocked in each hapa net. Data on survival rate (%), feed conversion ratio (FCR), and growth (g) were collected and compared. The growth results revealed a statistically significant difference (P < 0.001) among the three selected fish feed types. Diet 1 exhibited a higher average mean weight of 1521.67 g per 92 fish followed by the control with an average mean weight of 1315.56 g per 88 fish, while diet 2 demonstrated comparatively lower growth, 1164.44 g per 96 fish. Survival rate and FCR, however, exhibited no significant differences. Notably, the cost of food supplies, particularly proteins, may constrain farmers' access to feed processing and formulation technology. Consequently, the findings of this study are expected to address challenges related to feed formulation and processing, providing valuable insights for the enhancement of fish farming practices.

Alterations in Soil Bacterial Community and Its Assembly Process within Paddy Field Induced by Integrated Rice–Giant River Prawn (Macrobrachium rosenbergii) Farming

Integrated rice–aquatic animal farming has become a vital strategy for enhancing food security. To assess the effects of integrated rice–giant river prawn (Macrobrachium rosenbergii) farming (IRPF) on agricultural ecosystems, we used 16S rRNA gene sequencing to analyze soil bacterial communities in comparison with traditional rice monoculture (RM). Our study revealed that the IRPF did not significantly affect the diversity of the soil bacterial community. However, during the initial culture stage, IRPF markedly increased the relative abundance of the phylum candidate division NC10 and the genus Candidatus Methylomirabilis, enhancing nitrogen-cycling-related functions within the bacterial community. Additionally, IRPF reduced the complexity and stability of these communities in the early to middle culture stages. While stochastic processes usually dominate the assembly of these communities, IRPF restricted bacterial migration and reduced the influence of these stochastic processes. Furthermore, IRPF had a significant impact on environmental factors within paddy soils, strongly correlating with shifts in bacterial communities, particularly through variations in soil nitrite concentration. In conclusion, the influence of IRPF on the bacterial community in paddy soils was primarily observed during the early and middle culture stages, and the impacts of IRPF on the soil bacterial community were primarily driven by environmental changes, especially soil nitrite concentration. These findings provide theoretical insights and a reference for understanding the microbiological impacts of different integrated rice–fish farming systems on agricultural ecosystems.

Integrated Rice–Fish Culture Alters the Bacterioplankton Community and Its Assembly Processes

The rice–fish co-culture is an important model of carp farming in China; however, research on the dynamics and assembly of water bacterial communities in this system remains limited. Therefore, this study aimed to explore the dynamics and assembly of bacterial communities, as well as their correlation with environmental factors in paddy water. For these purposes, this study was divided into two groups: a rice–carp co-culture (WRC) group and a rice monoculture (WRM) group, with 20 rice fields in each group. After 60 days of farming, the concentrations of NH4+-N, NO2−-N, TN, and PO43− were significantly higher in the WRC group than those in the WRM group. Alpha diversity analysis showed that the Shannon index in the WRC group was significantly decreased compared with the WRM group. At the phylum level, the relative abundance of Actinobacteria significantly increased, while the relative abundance of Proteobacteria and Bacteroidetes significantly decreased in the paddy water of the WRC group. The neutral community model (NCM) indicated that a random process played a dominant role in the construction of bacterial communities in the two groups, and common carp cultivation increased migration rates, thereby affecting community assembly. The co-occurrence network displayed that common carp cultivation led to looser interactions between bacterial communities. In addition, the contents of nutrients significantly affected the abundance of bacteria in paddy water. In summary, carp cultivation decreased the diversity of bacteria and changed the relative abundance of dominant bacteria, thereby affecting the stability and assembly of bacterial communities.

Integrating of the domestic goat into the rice-fish coculture systems: Rice paddy yield, diet, growth parameters, and intestine microbiota of common carp Cyprinus carpio (Linnaeus, 1758)

Feeding the World while ensuring food security and biodiversity conservation is one of the sustainable development challenges. Integrating farming systems holds great promise for enhancing agricultural sustainability. To reach this goal, the domestic goat (Capra hircus) was integrated into the rice fish system. Four plots each 5 m × 10.65 m were made in two experimental systems, goat-rice-fish (GRF) and rice-fish (RF). We compared the impacts on rice productivity, fish growth performance, water quality, dietary patterns, and gut microbiota composition between both systems. On the one hand, the rice yield indicators, survival rate (SR), specific growth rate (SGR), pH temperature, dissolved oxygen (DO), total nitrogen (TN), and total phosphorus (TP) were compared. On the other hand, the frequency of occurrence (FOC) of food items of fish (Cyprinus carpio), and the microbiota communities in goat faeces (GoFe) and fish intestines were also examined and compared among both systems. The results showed that the rice yield, the number of filled spikelets per panicle, the number of panicles per land area, and the 1000-grain weight were significantly increased with the integration of goat in the rice-fish coculture system. The SR of fish under the goat-rice-fish system was 12.12% significantly higher than that of the fish under the rice-fish system, as well as the SGR of fish in the GRF system was 21.85% significantly higher than that of the rice-fish system. However, the water quality analyses indicated that the integration of goats significantly increased the concentration of TN and TP. The DO concentration in the GRF system was 25.93% lower than that in the RF system. Dietary analysis of the common carp in goat-rice fish systems revealed shifts in foraging behaviors and diet composition compared to the rice-fish system. Furthermore, the study showed higher diversity in the gut microbiota communities of fish in response to goat-rice-fish integration. In conclusion, this comprehensive investigation underscores the complex and interconnected dynamics within the goat-rice-fish integrated system. It highlights the importance of balanced management practices to harness the system's potential for improved rice yield, fish ecology, and water quality. The findings contribute to a deeper understanding of sustainable integrated farming practices and inform strategies for optimizing the productivity and ecological resilience of this integrated agroecosystem.

Effects of Different Stocking Densities on the Growth, Antioxidant Status, and Intestinal Bacterial Communities of Carp in the Rice–Fish Co-Culture System

Common carp (Cyprinus carpio) is a freshwater fish commonly farmed in rice fields, yet there were few studies on the intestinal functions and microbial community structure of common carp in the rice–carp co-culture system. Therefore, this study aimed to explore the effects of different stocking densities on the growth, antioxidant status, and intestinal bacterial composition of common carp in this system. This study was divided into three different stocking densities, including low density (LD, 10 fish, 52.9 g/m2), medium density (MD, 20 fish, 105.8 g/m2), and high density (HD, 30 fish, 158.7 g/m2), with a culturing period of 60 days. The results indicated that HD treatment inhibited the growth of common carp, as evidenced by the reduced final weight, WG, and SGR. In serum, the TG content in the HD group and the Cor content in the MD group were significantly increased. Meanwhile, HD treatment induced oxidative stress, manifesting specifically as increased SOD and CAT activities in the intestine or serum while reducing Gpx, GSH, and T-AOC in the serum. The 16S rDNA analysis indicated that the Simpson and Shannon indices of intestinal microbiota in the HD group were significantly higher than those in the LD group. At the phylum level, Proteobacteria, Cyanobacteria, and Firmicutes were dominant microbial communities in two groups. In addition, there was a significant difference between the two groups in the abundances of Actinobacterota and Bifidobacterium. Based on growth performances, biochemical indicators, and microbial diversity in rice–carp co-culture, low density (52.9 g/m2) may be more suitable in the rice–carp co-culture systems. In summary, this study contributes to a better understanding of common carp response to different stocking densities in the rice–carp co-culture system.

Enhancing biomass and ecological sustainability in rice–fish cocropping systems through the induction of functional microbiota with compound biogenic bait

Enhancing biomass and ecological sustainability in rice–fish cocropping systems through the induction of functional microbiota with compound biogenic bait

Carbon footprint research and mitigation strategies for rice-cropping systems in China: a review

Reducing greenhouse gas (GHG) emissions and quantifying the carbon footprint (CF) of rice-cropping systems in the context of food security is an important step toward the sustainability of rice production. Exploring the key factors affecting emission reduction in rice production is important to properly evaluate the impact of China’s rice-cropping systems on global climate change. This review provides an overview of the direct and indirect CF in rice-cropping systems; analyzes the influencing factors in terms of rice-based cropping systems, varieties and agronomic practices; and proposes mitigation strategies. Different studies have shown that direct and indirect GHG emissions in rice-based cropping systems accounted for 38.3 to 95.5% and 4.5 to 61.7% of total emissions, respectively. And the CFs of ratoon rice, rice–wheat, rice–maize, rice–rapeseed, and rice–fish systems ranged from 316,9 kg CO2-eq kg−1 to 258,47 kg CO2-eq kg−1, which are lower than that in a double-rice planting system. High-yielding rice, drought-resistant rice, and other hybrids can mitigate GHG emissions from paddy fields by 3.7 ~ 21.5%. Furthermore, organic matter, water, tillage, straw incorporation, conservation tillage, reduced nitrogen fertilizer use, and added biochar and methane inhibitors could reduce emissions. Therefore, through reasonable agronomic measures, variety selection and optimal layout of rice-based rotation systems, the carbon neutral rate of rice production can be improved to help the national carbon sequestration and emission reduction target.

Sustainable Rice Fish Farming: A Case Study in the Kuttanad Region

Integrated rice farming is a sustainable agricultural practice that aims to optimise resource use, increase productivity, and reduce environmental impacts. This study focuses on the need for a sustainable farming method in Kuttanad region in Alappuzha , a low-lying, waterlogged region in Kerala. This region is situated below sea level and is highly prone to many natural calamities like floods and will result in huge crop failure. Hence, to increase the income and the biological habit of the area, the study investigates the sustainability of integrated rice fish farming in the study area. Thus, a sustainable farming methodology as Integrated rice-fishing culture is considered. A case study analysis of two farmland is used to reach the research objective. As well, in one farmland, paddy is cultivated twice a year and the other farmland practices rice cultivation in one half and fish farming in the other half of the year. Although, the profit of fish cultivation along with paddy and also through variables like crop yielding, labour inputs, output value, input cost, environmental impacts and social impacts are also analysed. As a result, the integrated rice farming system helps to maintain the water quality of the region, which is essential for the survival of the aquatic ecosystem. The system not only provides economic benefits to the farmers but also enhances the biodiversity and ecosystem services of the region.The findings suggest that the integrated rice farming system in Kuttanad is a successful example of sustainable agriculture, which can be adopted in other regions with similar ecological conditions.

Soil Microbial Biomass and Bacterial Diversity Enhanced through Fallow Cover Cropping in Rice–Fish Coculture

Traditional rice production is often reliant on the unsustainable practice of utilizing intensive inputs in monoculture cropping systems. Alternatives fallow cover cropping and rice–fish coculture (RFC) offer promising solutions. However, the potential of fallow cover cropping in RFC remains underexplored, and its impact on soil microbes is poorly understood. In this study, assessments of soil–plant–microbe interactions were conducted across three cover cropping systems: Chinese milk vetch (Astragalus sinicus L.) single cropping (CM), Rapeseed (Brassica napus L.) single cropping (RP), and a combination of Chinese milk vetch and rapeseed intercropping (CM_RP). These systems were evaluated with and without nitrogen (N) addition, encompassing both the RFC and rice monoculture (RMC) systems. The findings indicate a notable increase in soil microbial biomass nitrogen (MBN) with CM. Soil microbial biomass carbon (MBC), influenced more by N-fertilizer than crop species, decreased with N addition. In the RFC system, the soil bacterial co-occurrence network exhibited more connections, yet negative links increased. CM_RP displayed similarities to CM without N but shifted closer to RP with N addition. N addition in intercropping significantly increased the root–shoot ratio (R/S) of A. sinicus, associated with decreased aboveground biomass and total root length. Compared to RMC, RFC with N addition reduced the relative abundance of Anaerolineaceae in CM while increasing Bacillus and Pontibacter across cover cropping systems. Overall, with N addition, both RFC and RMC showed decreased soil bacterial diversity indices. Changes in soil bacterial diversity correlated significantly with soil MBC, MBN, and plant R/S. Continuous fallow cover cropping altered soil microbial biomass and affected cover crop biomass distribution, impacting bacterial composition in paddy soil. These results shed light on how bacterial communities respond to N addition and fallow cover cropping in RFC and RMC systems, offering insights for sustainable nutrient management in paddy systems.

Saltwater Intrusion and Agricultural Land Use Change in Nga Nam, Soc Trang, Vietnam

Under the effects of saltwater intrusion from rising sea water levels, climate change, and socioeconomic issues, the Nga Nam district in Vietnam has suffered damage to its agriculture and changes in agricultural land use. This study aimed to investigate the factors that influenced land use changes and to propose approaches to limit the changes in agricultural land use. The damage caused by saltwater intrusion on agricultural production was evaluated via the use of secondary data collected from the Department of Infrastructure Economics of the Nga Nam district in the period of 2010–2021. The results show that during the 2010–2015 period, agricultural production areas were affected in 2010, 2012, and 2015. In the period of 2015–2021, the trend of saltwater intrusion along the damaged area remarkably decreased due to the work of saltwater-preventing structures. In this period, the area of annual plants increased, while that of fruit trees decreased. In the area comprising annual plants, the area using the triple rice land use type converted into an area using the double rice and double rice–fish ones. Lands for fruit trees transitioned from mixed farming to specialized farming to raise the economic efficiency for farmers. These changes were affected by four main factors: the physical factor, the economy, society, and the environment. The environmental and economic factors were seen to play the most important role as drivers of changes in land use. The factors of saltwater intrusion and acid-sulfate-contaminated soil, consumer markets, floods, drought, profit, and investments were noted to be significant drivers in agricultural land use change. Thus, both structural and non-structural approaches are suggested to inhibit the safeguard changes in the future.

Implementation of Rice Fish Farming as an Environmentally Friendly Alternative for Pest and Weed Control to Support Food Security in Talotenreng Village

Implementation of Rice Fish Farming as an Environmentally Friendly Alternative for Pest and Weed Control to Support Food Security in Talotenreng Village

Implementation of Rice Fish Farming as an Environmentally Friendly Alternative for Pest and Weed Control to Support Food Security in Talotenreng Village

Implementation of Rice Fish Farming as an Environmentally Friendly Alternative for Pest and Weed Control to Support Food Security in Talotenreng Village

Variations in Soil Organic Carbon Fractions and Microbial Community in Rice Fields under an Integrated Cropping System

Combining rice cultivation and aquaculture into an integrated cropping system is a management approach that enhances the sustainability of rice fields. However, how soil characteristics influence soil microbial community characteristics following implementation of such an integrated system, particularly in the waterlogged paddies of the Pearl River Delta, is poorly understood. An integrated cropping system (rice–fish–duck integrated cropping system, RFD) and a rice–pepper rotation system (RPS) were compared using a conventional rice cropping system (CRS) as a reference. We used phospholipid-derived fatty acid (PLFA) analysis to assess soil microbial community structure and function and measured soil nutrient content and organic carbon fractions. Our results indicated that the soil nutrient content, organic carbon fractions, and C-hydrolyzing activities differed among the cropping systems. The RFD resulted in higher microbial PLFA concentrations and a lower ratio of Gram-positive to Gram-negative bacteria than CRS. Additionally, the integrated system reduced microbial nutrient stress by increasing soil pH. Further analysis revealed that active soil organic carbon significantly affected the soil microbial community. Thus, the RFD integrated cropping systems that alter the combined actions of pH and active organic carbon fractions can be used to improve soil microbial communities.

Optimizing rice-fish co-culture: Investigating the impact of rice spacing density on biochemical profiles and production of genetically modified tilapia (Oreochromis spp.) and Cyprinus carpio.

Rice fish co-culture synergistically boosts food production, resulting in numerous advantages across the environmental, social, and financial domains. A study was conducted to investigate the effects of three different rice spacing densities, rice high density (RHD) 9inch×12inch, rice medium density (RMD) 12inch × 12inch, rice low density (RLD) 15inch×12inchon both rice and fish. Various parameters were assessed to evaluate the performance of the co-culture system, including water quality, growth parameters, muscle quality, soil characteristics, rice stem characteristics, and rice yield parameters. When comparing the species, it was observed that GMT (Genetically Male Tilapia) demonstrated superior weight gain (303.13g vs 296.41g) and specific growth rate (1.16 vs 1.15). Regarding the proximate composition, results showed that RMD had the highest crude protein and fat content compared to RLD and RHD. GMT also exhibited greater crude protein and fat content than Cyprinus carpio, with RMD showing the highest values. Treatment groups significantly influenced the amino acid profile of experimental species, with RMD exhibiting the highest values. GMT showed significantly higher levels of essential, non-essential, half-essential, and umami amino acids compared to Cyprinus carpio. The interaction between RMD and GMT further demonstrated significant differences in various amino acid categories with RMD. A non-significant difference was observed among the treatments regarding soil biochemical characteristics. Regarding the rice stem characters, the height of the plant, panicle length, and stem length of rice were found to be comparable in the RMD and RLD groups however, significantly higher in RHD. Regarding rice yield parameters, no significant differences were observed among the other treatment groups, except for yield per hectare (yield/ha), which was significantly higher in the RHD group compared to RMD and RLD. Additionally, 1000-grain weight and panicle number (ears per hill) were significantly higher in the RLD treatment than in the other treatments. In conclusion, our findings indicate that the RMD treatment consistently yielded superior results compared to RLD and RHD. Furthermore, within the rice-fish co-culture system, GMT proved to be a more competent species compared to Cyprinus carpio. The study provides data to understand the interactions between rice spacing density, fish growth and overall productivity can guide the development of sustainable and profitable rice-fish co-culture systems.

Phenanthrene release-migration characteristics and potential influencing mechanisms from paddy soil to overlying water under bioturbation in a rice-fish coculture agroecosystem

Currently, polycyclic aromatic hydrocarbons (PAHs) such as phenanthrene (Phe) in rice-fish (RF) coculture paddy fields in Northeast China pose widespread environmental pollution risks. This study constructed experimental microcosm systems to explore the release-migration rules and reveal the potential influencing mechanisms of Phe from paddy soil to overlying water under bioturbation in an RF coculture agroecosystem in this area. (1). The release of particulate Phe (P-Phe) and dissolved Phe (D-Phe) was significantly promoted by bioturbation (p<0.05). The results of Pearson correlation analysis revealed strong correlations between P-Phe and total suspended solids (TSS), D-Phe and dissolved organic carbon (DOC) (p<0.05). (2). The adsorption process of Phe at the paddy soil-overlying water interface conformed to the competitive adsorption-solubilization (CAS) model of large-molecule biological dissolved organic matter (Bio-DOM) at low concentrations (7 mg/L) (L-CBio-DOM-LM-CAS) and the coadsorption and accumulation model of small-molecule Bio-DOM at high concentrations (45 mg/L) (H-CBio-DOM-SM-CAA). (3). Ultraviolet fluorescence (UV-FS) tracing technology and reaction diffusion modeling were used to qualitatively and quantitatively simulate the migration pathway of Phe-containing paddy soil particles. The maximum fluorescent particle (f-ps) concentration of Phe migration in paddy soil was 8.23%, and the maximum bioturbation diffusion coefficient (Db) was 23.6 × 10−3 cm2/d. Bioturbation significantly altered the physicochemical properties of paddy soil (p<0.05). The results of principal component analysis (PCA) showed that particle size (<0.05 mm) is the key factor causing the Phe maximum migration concentration to be 68.39 ng/g in paddy soil. This study will provide an important research basis for the prevention and control of secondary release and migration of pollutants under bioturbation in RF coculture agroecosystems.

Frontiers of NIR Imaging

After a brief introduction to the technique, this review will discuss the state-of-the-art NIR imaging instrumentation and its applications, including applications of an ordinary NIR imaging system to solvent diffusion into a polymer. Other imaging applications discussed include the use of a portable NIR imaging system in the pharmaceutical industry, high-speed and wide-area monitoring of polymers, and imaging for fish embryos development research. Also discussed is an imaging-type two-dimensional Fourier spectroscopy (ITFS) system and its application to medaka (Japanese rice fish, Oryzias latipes) egg development. Finally, general perspectives on NIR imaging will be provided.

Risiko Paparan Formaldehida dari Beberapa Jenis Ikan pada Masyarakat di Kecamatan Dramaga, Bogor, Jawa Barat

Residual formaldehyde compounds may be found in fish either naturally or intentionally added. Exposure of formaldehyde from food can cause damage to the gastrointestinal tract, liver, kidney, and is carcinogenic in humans. This study aims to estimate the risk value of formaldehyde exposure level due to fish consumption in the community population in Dramaga Subdistrict with deterministic approach. Fish consumption data was obtained from a consumption survey using a semi food frequency questionnaire (FFQ). The fish consumption survey was conducted on 505 respondents with an age range of 5-60 years and over. Formaldehyde analysis was conducted on four types of fish that are popular and often consumed by the community, namely salted peda fish, salted anchovy rice fish, salted japuh fish, and fresh anchovy fish. The results showed that formaldehyde levels in four types of fish range from 8.30 – 105.09 mg/kg. The average daily consumption of salted peda, salted anchovy rice, salted japuh, and fresh anchovy was 11.58±8.32; 8.85±4.93; 7.72±4.51; and 9.85±6.45 (g/day). The average daily exposure values of formaldehyde in salted peda, salted anchovy rice, salted japuh, and fresh anchovy were 0.0025; 0.0088; 0.0146; and 0.0014 (mg/kg bw/day). The overall of daily exposure value is still below the maximum oral exposure limit of 0.2 (mg/kg bb/day). The value of exposure risk with hazard quotient (HQ) in four types of fish is 0.007–0.073. The HQ was found to be below 1, indicating risk level of exposure to formaldehyde in the community in Dramaga Subdistrict is still within safe limits.

Evaluating Rice Varieties for Suitability in a Rice–Fish Co-Culture System Based on Lodging Resistance and Grain Yield

Rice–fish co-cultures have been practiced for over 2000 years, and they have tremendous potential in terms of increasing food security and economic benefits. However, little research has been conducted into achieving stable yields and high lodging resistance with regard to rice while simultaneously promoting the harmonious and healthy growth of fish in rice–fish co-culture paddy fields. We conducted a field study aimed at selecting suitable rice varieties for rice–fish co-culture systems (encompassing both ratoon and main crop). This selection process was grounded in an evaluation of lodging resistance and grain yield among 33 rice varieties used throughout the studied region. The results revealed a range of lodging indices of the main crop for the second internode, spanning from 62.43 to 138.75, and the annual grain yield (main crop and ratoon crop) ranged from 7.17 to 13.10 t ha−1 within rice–fish co-culture systems. We found that the use of rice–fish co-culture farming could improve the milling quality, nutrient quality, and appearance quality of rice, though the improvement gained through co-culturing varied across rice varieties. Moreover, the lodging index of the three basal internodes of rice plants was significantly and positively correlated with the plant height and the culm fresh weight, but it was negatively correlated with the bending strength of the rice basal internodes. Additionally, the 33 tested rice varieties were clustered in accordance with their lodging resistance (i.e., high resistance with lodging indices 62.43–75.42; medium resistance with lodging indices 80.57–104.62; and low resistance with lodging indices 113.02–138.75) according to the hierarchical cluster analysis. The 33 rice varieties were also clustered in accordance with the annual (main crop and ratoon crop) grain yield (i.e., high yield with 11.17–13.10 t ha−1; medium yield with 10.15–10.83 t ha−1; and low yield with 7.16–9.88 t ha−1). In all, 11 rice varieties were identified by a comprehensive evaluation as suitable varieties for grain production in the rice–fish co-culture system. These varieties displayed favorable traits, including a high annual rice yield, strong lodging resistance, and good grain quality. This is the first study to systematically evaluate rice varieties based on grain yield, lodging resistance, and grain quality in rice–fish co-culture systems.

Integrated rice-aquatic animals culture systems promote the sustainable development of agriculture by improving soil fertility and reducing greenhouse gas emissions

Integrated rice–aquatic animals culture systems (RACSs) are of interest in sustainability research because they have been found to host diverse species and there is potential for positive synergistic effects between the plant (rice) and aquatic animal culture. However, their effect on soil fertility, rice productivity, and greenhouse gas (GHG) emissions, as well as the associations among them, remain unclear. A meta-analysis was conducted to systematically evaluate the sustainability of RACSs from the perspective of “rice productivity–GHG emissions–soil fertility” and their associations and to clarify how environmental factors and fertilizer-management practices affect responses of rice yield and GHG emissions to RACSs. We conducted a meta-analysis of 1807 paired observations collected from 78 published papers covering four countries that compared soil fertility, rice yield, and GHG emissions in a conventional rice monoculture system (CRMS) and in a RACS. Overall, the RACSs improved soil structure (soil bulk density declined by 5.8 % and total and capillary porosity increased by 6.4 % and 5.7 %, respectively), increased soil organic carbon (C, 7.9 %) and nitrogen (N, 6.6 %) storage, and reduced CH4 (9.2 %) and N2O (4.5 %) emissions; rice yield were little higher (by 2.0 %) than that of the CRMS. However, the effects varied under different RACS modes, environmental factors, and fertilizer-management practices. For instance, compared to CRMS, yields were 4.1 % higher in the rice–duck mode, 3.9 % lower in the rice–crayfish mode, and the no significantly change in the rice–fish system. The effects on GHG emissions and soil fertility were more pronounced in the rice–duck and rice–crayfish modes than in the rice–fish mode. Furthermore, paddy soils with low fertility (lower soil organic C and N) and less nutrient (nitrogen and phosphorus) input provide a higher rice yield and lower GHG emissions under RACSs. Overall, the RACSs stabilized rice productivity and reduced GHG emissions by improving the soil structure and increasing soil C and N sequestration; however, the effects varied by different RACS modes, initial soil properties, fertilizer input rate, and climate conditions. As such, environmental factors and nutrient management should be considered when designing and deciding what type of RACSs to employ. Our results also highlight the great potential of RACSs in the development of sustainable agriculture practices in the context of climate change. Future research and applications should consider the response of RACSs to climate and environmental factors and fertilizer-management practices, to achieve greater production and environmental benefits.