Double Rice Cropping Research Articles

Selenium Utilization, Distribution and Its Theoretical Biofortification Enhancement in Rice Granary of China

Selenium, as an essential trace element, is intricately linked to the onset and progression of numerous diseases due to deficiencies in selenium intake. Selenium compounds exhibit tumor specificity and can efficiently inhibit the growth of tumor cells, making them potential candidates for cancer treatment. Nevertheless, given its status as one of the most widely consumed crops globally, increasing the selenium content in rice could prove advantageous in alleviating the prevailing issue of selenium intake deficiency, particularly in China. This review explored the regulatory role of selenium in rice growth, the regional distribution characteristics of soil selenium content in various rice-growing regions in China, and the impact of cultivation practices on selenium fortification in rice, aiming to suggest improved rice cultivation management strategies to enhance the capacity for rice selenium biofortification. The findings revealed that: (1) In Northeast and North China, characterized by alkaline soils and severe selenium deficiency, it is advisable to moderately decrease the duration of flooding, elevate the soil redox potential, and apply organic and nitrogen fertilizers in a judicious manner. (2) In Southwest China, which is characterized by acidic soils, alternating wet and dry irrigation should be employed, and the biofortification of selenium can be facilitated by applying lime and foliar spraying of selenium fertilizer. (3) In the south-central region of China, distinguished by acidic soils and double-cropped rice, it is recommended that intermittent or alternating wet and dry irrigation be employed, and the reasonable application of organic, silica, and selenium fertilizers is advocated. (4) In the northwest region, characterized by slightly alkaline soil and mild selenium deficiency, it is recommended to implement various water management practices, including shallow water during the seedling stage, deep water during the booting stage, and wet grain filling. Additionally, a rational application of nitrogen, phosphorus, and potassium fertilizers, along with foliar application of selenium fertilizer, should be employed. (5) Cultivating selenium-enriched, high-yielding, and high-quality rice varieties proves to be an effective strategy in addressing selenium deficiency. In conclusion, the unique characteristics of diverse rice-growing regions in China indicate that suitable water management, fertilization techniques, and varietal selection practices can effectively enhance the selenium content in rice, thereby maximizing the nutritional requirements for selenium.

Plant Photosynthetic and Respiration Rates Are Key Populational Traits to Improve Yield and Quality for Good-Tasting Double-Cropped Rice

Improving the yield and quality for tasty rice varieties is a great challenge. In the present study, different nitrogen rates and plant density were utilized to form differential rice populational structures, which were determined to clarify key traits determining grain yield and quality for tasty rice varieties in a double-cropped rice system in subtropical China. The present results showed that the plant photosynthetic rate, leaf area index and plant respiration rate had important and significant impacts on the grain yields of both early and late rice, though the late rice yield was also significantly affected by the canopy temperature. In addition, among the studied populational traits, plant photosynthetic and/or respiration rates had significant effects on all quality traits. Consistently, grain yield and quality were significantly improved with the increasing plant photosynthetic and respiration rates through correlative analysis, which was also observed in principal components analysis. Overall, the present study suggests that both the grain yield and milling and appearance qualities could be improved through the optimal management of nitrogen and plant density through increasing plant photosynthetic and respiration rates.

Increased exposure of rice to compound drought and hot extreme events during its growing seasons in China

Against the backdrop of global warming, compound drought and hot extreme events (CDHEEs) have intensified markedly, attracting attention from both the scientific community and society. However, a comprehensive understanding of the characteristics of the CDHEEs and their impacts on rice production during growing seasons remains limited. Thus, in this study, we use daily maximum and minimum air temperatures to derive a meteorological drought composite index for CDHEE identification. Additionally, we employ the Crop Calendar and the CROPGRIDS data to define the rice-growing seasons and regions. Detailed analyses reveal that from 1961 to 2023, the CDHEE frequency in both single-cropping rice regions (Rice1) and double-cropping rice regions (Rice2) increased at rates of 0.79 days (decade)−1 and 1.26 days (decade)−1, respectively, with a notable acceleration in the post-1990 s. The duration of the CDHEEs has lengthened, and prolonged events have become more frequent. The intensity of the CDHEEs has also enhanced, primarily driven by hot extreme events in Rice1 and the synergistic effects of droughts and hot extreme events in Rice2. Furthermore, the time span of CDHEE occurrence has expanded, starting earlier (rates of − 3.21 days (decade)−1 in Rice1 and − 4.37 days (decade)−1 in Rice2) and ending later (rates of 4.81 days (decade)−1 in Rice1 and 8.20 days (decade)−1 Rice2) during rice-growing seasons, thereby extending the exposure duration of rice. Since the 1990 s, rice exposure to the CDHEEs has also intensified, especially for the persistent CDHEEs. These findings indicate the upward trends in the frequency, intensity and duration of the CDHEEs, as well as the exposure of rice to the CDHEEs, during the rice-growing seasons in China. This research provides crucial insights into CDHEE impacts and underscores the necessity of implementing targeted adaptation and mitigation strategies to safeguard rice production amidst escalating climate challenges.

Investigating drivers of N2 loss and N2O reducers in paddy soils across China

Denitrification plays a pivotal role in nitrogen (N) cycling in rice paddies, significantly impacting N loss and greenhouse gas emissions. Accurate quantification of net N2 emissions from paddy fields is therefore essential for improving fertilizer N use efficiency. However, challenges in directly measuring gaseous N2 hinder our understanding of microbially-mediated N loss in paddy soils at large scales. In this study, we investigated net N2 loss and its influencing factors in 45 paddy soils across China using membrane inlet mass spectrometry and N2/Ar technique, complemented by microbial community analysis via metagenomics. Potential N2 loss rates varied from 0.41 to 3.58 nmol N g−1 h−1, with no significant regional differences. However, soils from rice-upland rotation (1.72 ± 0.64 nmol N g−1 h−1) and mono-rice cropping systems (1.41 ± 0.53 nmol N g−1 h−1) exhibited higher N2 loss rates compared to double-rice cropping soils (1.13 ± 0.62 nmol N g−1 h−1). Our results revealed a unimodal relationship between soil N2 loss rates and soil pH, with N2O reducers and soil properties primarily regulating regional variations in N2 loss. Significant ecological differentiation was observed within both nosZ Clade I and Clade II, with soil pH emerging as the key factor shaping their community composition. Specifically, in rice-upland rotations, soil moisture and pH significantly influenced nosZ Clade I, while in double-rice cropping systems, soil texture and pH were the main factors affecting nosZ Clade II, thereby driving N2 loss. These findings enhance our understanding of N2 loss dynamics in paddy soil ecosystems, underscoring the critical role of N2O reducers on microbial-derived N2 loss and highlighting the importance of developing strategies to mitigate N2O emissions by balancing N2 loss through the manipulation of N2O-reducing and N2O-producing microbes.

Effects of tillage management on soil organic carbon mineralization under double cropping rice system of southern China

Soil organic carbon (SOC) plays a vital role in maintaining or enhancing soil fertility and quality of paddy field, but there is still limited information about how SOC mineralization responds to different tillage managements under the double-cropping rice (Oryza sativa L.) system in southern of China. Therefore, this study was designed to explore the changes in SOC content, soil enzyme activities (invertase, cellulose and urease), SOC mineralization at 0–10 cm and 10–20 cm layers and its relationship with 7-years tillage management under the double-cropping rice system of southern China. The experiment included four tillage managements: rotary tillage with all residues removed as a control (RTO), conventional tillage with residue incorporation (CT), rotary tillage with residue incorporation (RT), and no-tillage with residue retention (NT). The results indicated that SOC and soil labile organic carbon contents at 0–10 cm and 10–20 cm layers in paddy field with CT and RT treatments were significantly higher than the RTO treatment. Compared to the RTO treatment, SOC mineralization and accumulation at 0–10 cm and 10–20 cm layers in paddy field with CT, RT and NT treatments were increased. SOC accumulation and potential mineralization at 0–10 cm layer with NT treatment were significantly higher than the CT, RT and RTO treatments. Soil mineralization constant at 10–20 cm layer with CT treatment was significantly higher than those of RT, NT and RTO treatments. This result indicated SOC mineralization rate and accumulation at 10–20 cm layer of CT, RT, NT and RTO treatments were lower than those of treatments at 0–10 cm layer. Compared to RTO treatment, soil invertase, cellulose and urease activities with CT and RT treatments were significantly increased. Compared to RTO treatment, soil invertase, cellulose and urease activities at 0–20 cm layer of CT treatment increased by 22.6%, 46.2% and 89.0%, respectively. There was significantly positive correlation between SOC accumulation and SOC content, soil invertase, cellulose, urease activities, but SOC accumulation was significantly negative correlated with soil pH, bulk density. Therefore, CT and RT treatments were beneficial managements to improve SOC content and SOC mineralization in the double-cropping rice field of southern China.

A novel red-edge vegetable index for paddy rice mapping based on Sentinel-1/2 and GF-6 images

ABSTRACT Accurate paddy rice mapping is crucial for ensuring food security and guiding agricultural production. Vegetation indices are extensively employed to map paddy rice. However, most traditional normalized indices tend to be oversaturated during periods of lush vegetation due to normalization errors, resulting in uncertainties in paddy rice mapping. To address this issue, we introduce a novel red-edge rice index (RERI) in this study; this index comprises information from red, near-infrared, and red-edge bands without normalization. To extract single- and double-cropping rice features from potential rice areas, we employ GF-6 and Sentinel-2 images based on the proposed RERI and the random forest algorithm. The proposed method is validated in the Dingcheng District of Changde city, China, and the results are compared with those based on three normalized vegetation indices. The results show that the RERI yielded the highest levels of the accuracy for all the metrics, achieving an overall accuracy (OA) of 92.50% and a kappa coefficient of 0.8875. The RERI exhibited F1 scores of 92.26% for single-cropping rice, 93.00% for double-cropping rice, and 92.28% for non-rice areas. Our results highlight the potential of using the RERI for rice identification, and the effectiveness of our method for rice extraction is demonstrated.

Response of seed vigor to experimental warming in a double rice cropping system

Climate warming affects rice seed vigor during ripening, which plays a crucial role in seed quality. However, the actual response of rice seed vigor to warming is still unclear. In this study, seeds after warming treatment in a double rice cropping system were used to determine seed vigor and related physiological traits during germination. Warming treatment significantly improved the germination index (GI), seed vigor index (VI), and seedling dry weight (SDW) for the late-season rice seeds but had no effect on hull thickness, grain weight, and starch and protein contents for both early- and late-season rice seeds, and these parameters were highly associated with germination rate, GI, VI, and SDW. Warming treatment increased gibberellin (GA) content and α-amylase and β-amylase activities in endosperm and coleoptile in both seasons during the later stage of germination, reaching a significant level on the 7th d. Moreover, indole-3-acetic acid (IAA) content was consistently increased in the coleoptile but decreased in the endosperm in response to warming, and warming did not affect zeatin content. These results suggest that future global warming will improve rice seed vigor by regulating the synthesis of endogenous hormones and amylases, especially in the late-season rice.

Rural labor migration and farmers’ arrangements of rice production systems in Central China: Insight from the intergenerational division of labor

Rice production is crucial for food security in China, and its relationship with rural labor migration has been studied extensively. Labor migration in rural China has taken new forms in recent years. There has been a discernible trend wherein adult children have started migrating to cities while their elderly parents return to villages to re-engage in on-farm work. The phenomenon has notably shaped the intergenerational division of labor (IDL) within households. However, it remains to be seen how farmers adjust their rice production systems in response to the IDL. The age of 60 years for employment injury insurance is the eligibility threshold for off-farm employment and is used to obtain a source of exogenous variation in the IDL. Based on a representative household survey of 1,752 rice farmers in the Hubei Province of Central China, our fuzzy regression discontinuity analysis reveals that farmers in IDL households are more likely to adopt ratoon rice (RR) than single cropping rice (SR) or double cropping rice (DR). The effect of the IDL varies under different levels of operational scales and specialized agricultural service availability. Further analysis suggests that farmers’ arrangements are associated with two potential mechanisms of downward intergenerational transfer. Monetary transfer for urban housing purchases increases RR in IDL households, and time transfer for intergenerational childcare significantly promotes SR in IDL households. This study enhances the understanding of the relationship between rural labor migration and rice production in China, providing a reference for adjusting rice production systems to ensure food security.

Joint utilization of Chinese milk vetch and lime materials mitigates soil cadmium risk and improves soil health in a double-cropping rice system

Cadmium (Cd) in paddy soil poses significant risks to humans due to its strong biological migration and toxicity. Chinese milk vetch (MV) is commonly used as green manure in the paddy fields of southern China and its potential to decrease the availability of Cd has been identified. Nevertheless, the effects of MV combined with lime materials (lime, L; limestone, LS) on Cd availability, soil properties, enzyme activity and comprehensive benefits are still not fully understood in double-cropping rice system. A field study was conducted to investigate these changes. The results indicated that all treatments notably decreased soil available Cd (Avail-Cd) by 19.3–44.3% and 14.9–43.1% during early and late rice, compared with CK. Moreover, the Cd fractions transformed to more stable forms. Compared to CK, all treatments reduced brown rice Cd content by 34.6–64.2% and 12.7–52.5% during the two periods. Furthermore, the translocation factors root to shoot, as well as shoot to brown rice, decreased. The combination led to improvements in soil properties, soil enzyme activity. Meantime, Cd in iron-manganese plaque (IMP) decreased by 31.9–51.1% and 29.0–42.7% respectively during two periods in amendments treatments. Soil pH and DOC were more important factors for Cd bioavailability than other properties. Additionally, rice Cd uptake was positively correlated with Cd in IMP. Enzyme activity exhibited a negative correlation with soil active Cd. Partial Least Squares Path Model (PLS-PM) indicated that the mitigation of Cd pollution helped to improve soil enzyme activity. Grey correlation analysis (GRA) indicated that MVLS showed the best comprehensive benefits in soil-plant system. Overall, the combination of MV and lime materials could reduce Cd availability, enhance soil properties and enzyme activity. And this could be strengthened by the combination. These findings will provide valuable insights for Cd-contaminated soil remediation.

Effects of Organic Farming on Soil Probiotics of Double Rice Cropping System in South China

Organic management practices of double rice cropping can contribute to soil health and crop productivity. However, the impact of organic versus conventional farming practices (CK) on the diversity and functionality of soil probiotics remains poorly understood, despite growing interest in sustainable agricultural methods. To this end, this study evaluated the effects of these farming systems in double rice production on soil microbial communities using metagenomic sequencing and the PROBIO database. Our study accessed the Shannon and Simpson diversity indices of soil probiotics between the two farming systems. Specifically, the Shannon index values were 93.82 for CK and 93.51 for organic farming, showing no statistically significant difference. Similarly, the Simpson index values were 6.18 for CK and 6.46 for organic farming, also demonstrating no significant variance. However, distinct variations in microbial community compositions were observed. Organic farming significantly increased (P < 0.05) the abundance of probiotics that benefit plant growth and nitrogen supply, but reduced those associated with plant nutrient supply and yield. The results show that while organic farming can positively influence certain microbial functions beneficial for sustainable agriculture, it also presents challenges that may affect crop productivity and ecosystem services. These findings suggest that organic farming practices need to be carefully managed to harness the benefits of enhanced microbial functions without compromising crop yields.

Lime Application Reduces Methane Emissions Induced by Pig Manure Substitution from a Double-Cropped Rice Field

Abstract: The substitution of chemical fertilizers with organic manure plays a critical role in sustainable crop production. Nevertheless, organic amendments promote the global warming potential (GWP) in rice paddies due to increased methane (CH4) emissions. Increasing evidence shows that lime application can reduce CH4 emissions from acidic paddy soils; however, it is still not clear whether liming can reduce the GWP in rice fields under organic manure substitution. A two-year field experiment was conducted to investigate the impacts of pig manure substitution and lime application on grain yield, CH4 and nitrous oxide (N2O) emissions in a subtropical double-cropped rice field in China. The experiment consisted of three treatments: CF (100% chemical nitrogen fertilizer), 1/2N + M (50% of the applied nitrogen substituted by pig manure, M represents manure), and 1/2N + M + L (lime amendment with 50% of the applied nitrogen substituted with pig manure, L represents lime). On average, 1/2N + M reduced rice yield by 5.65% compared to CF, while the lime application had no effect on rice yield. Mean cumulative CH4 emissions were 218.8% higher in 1/2N + M than in CF, whereas 1/2N + M + L reduced CH4 emissions by 36.6% compared to 1/2N + M. Neither pig manure substitution nor lime application affected N2O emissions. Consequently, 1/2N + M increased the GWP and greenhouse gas intensity (GHGI) by 214.6% and 228.3%, respectively, compared to CF. In contrast, 1/2N + M + L reduced the GWP and GHGI by 36.4% and 36.5% compared to 1/2N + M. Lime application can mitigate CH4 emissions and GWP induced by pig manure amendment in double-cropped rice fields.

<span>Assessing the impact of land-use/land-cover change on provisioning ecosystem services in the Long Xuyen Quadrangle from 2000 to 2021</span>

Changes in land use/land cover (LULC) have a significant impact on the changes in ecosystem service values. This study aims to assess the impacts of LULC changes on provisioning ecosystem services (pES) in the Long Xuyen Quadrangle region (LXQ) from 2000 to 2021. Using Landsat 5 TM and Landsat 8 OLI imagery, this study analyzes the normalized difference vegetation index (NDVI) time series using MODIS imagery to monitor and evaluate the impacts of LULC changes in the LXQ region. Additionally, interviews with farmers were conducted to estimate the ecosystem service values of different rice cultivation models. The research results in the creation of LULC maps for the LXQ in 2000 and 2021, with relatively high reliability, including overall accuracy (OA) of 83.18% (K = 0.772) and 94.26% (K = 0.9284), respectively. The main LULC change observed in the LXQ region from 2000 to 2021 is the conversion from wetlands to double-cropped rice and triple-cropped rice systems. The study identified an area of 54,667.722 ha (26.24%) where wetlands were converted to double-cropped rice, and an area of 36,779.633 ha (17.65%) where wetlands were converted to triple-cropped rice. Furthermore, the estimated ecosystem service values after the conversion from wetlands to triple-cropped rice were approximately 122,504,931 VND/ha/year, and for double-cropped rice, it was approximately 87,772,604.88 VND/ha/year. The research findings indicate that wetland agriculturalization, including double-cropped rice and triple-cropped rice, has affected the ecosystem service provision in the LXQ region. These research results provide significant considerations for future comprehensive valuation of ecosystem service values in the LXQ, Vietnamese MD.

How does single- or double-cropped rice policy influence spatially irrigated land value in China?

How does single- or double-cropped rice policy influence spatially irrigated land value in China?

Effects of Short-Term Tillage on Rhizosphere Soil Nitrogen Mineralization and Microbial Community Composition in Double-Cropping Rice Field.

Soil extracellular enzyme plays a vital role in changing soil nitrogen (N) mineralization of rice field. However, the effects of soil extracellular enzyme activities (EEA) and microbial community composition response to N mineralization of rice field under short-term tillage treatment needed to be further explored. In this study, we investigated the impact of short-term (8-year) tillage practices on rhizosphere soil N transformation rate, soil enzyme activities, soil microbial community structure, and the N mineralization function gene abundances in double-cropping rice field in southern China. The experiment consisted of four tillage treatments: rotary tillage with crop straw input (RT), conventional tillage with crop straw input (CT), no-tillage with crop straw retention (NT), and rotary tillage with all crop straw removed as a control (RTO). The results indicated that the rhizosphere soil N transformation rate in paddy field under the NT and RTO treatments was significantly decreased compared to RT and CT treatments. In comparison to the NT and RTO treatments, soil protease, urease, β-glucosaminidase, and arginase activities were significantly improved by the CT treatment, as were abundances of soil sub, npr, and chiA with CT and RT treatments. Moreover, the overall diversity of soil bacterial communities in NT and RTO treatments was significantly lower than that in RT and CT treatments. Soil chitinolytic and bacterial ureolytic communities were also obviously changed under a combination of tillage and crop straw input practices.

Effects of Long-Term Fertilizer Managements on Soil Organic Carbon Mineralization Under the Double-Cropping Rice System in Southern China

ABSTRACT Soil organic carbon (SOC) plays an important role in maintaining or increasing soil fertility and quality in paddy field, but there is limited information about how SOC mineralization responds to different fertilizer managements under the double-cropping rice system in southern China. Therefore, this study was designed to explore changes in SOC content, soil enzyme activities, SOC mineralization at 0–10 cm and 10–20 cm layers, and its relationship with long-term fertilizer managements in a double-cropping rice system of southern China. The experiment included four fertilizer treatments: chemical fertilizer alone (CF), rice straw and chemical fertilizer (RS+F), 30% organic manure and 70% chemical fertilizer (OM+F), and without fertilizer input as a control (Con). These results showed that SOC and labile organic carbon contents at 0–10 cm and 10–20 cm layers in paddy field with RS+F and OM+F treatments were increased, compared to CF and Con treatments. Compared with Con treatment, SOC mineralization rate and accumulation with CF, RS+F, and OM+F treatments were increased. SOC accumulation and potential mineralization at 0–10 cm and 10–20 cm layers with RS+F and OM+F treatments were increased, compared with CF and Con treatments. SOC mineralization rate and accumulation at 0–10 cm layer with CF, RS+F, OM+F, and Con treatments were higher than that of 10–20 cm layer. These results indicated that soil invertase, cellulose and urease activities in paddy field with RS+F and OM+F treatments were significantly higher than that of CF and Con treatments. There was a significant positive relationship between SOC accumulation and SOC content, soil invertase, cellulose, urease activities but were significant negative correlated with soil pH, bulk density. As a result, these were beneficial practices for improving SOC content and SOC mineralization in a double-cropping rice field of southern China by combined application of rice residue or organic matter with chemical fertilizer managements.

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

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

Silicon–calcium fertilizer increased rice yield and quality by improving soil health

It is important to ensure the nutritional quality and safe production of rice. Here, plot experiments were used to analyze the effects of three soil amendments—10 t ha−1 of biochar (BC), 1.5 t ha−1 of lime (LM), and 2.25 t ha−1 of silicon–calcium fertilizer (SC)—on the soil characteristics, rice yield and quality of double-cropping rice grown in mildly cadmium-polluted paddy fields. Compared with the control treatment (CK), the BC and SC treatments significantly improved rice processing, appearance and nutritional quality, but reduced cooking quality. All three soil amendments significantly reduced cadmium (Cd) content in brown rice. Soil amendments could significantly increase soil pH and reduce soil available Cd content. The application of the BC and SC treatments increased the content of each nutrient index in the soil (SOM, NN, AP, AK). Correlation analysis showed that the improvement in rice processing, appearance, and nutritional quality was mainly affected by the comprehensive effects of soil SOM, NN, AP and AK; the hygiene quality was mainly affected by soil pH and available Cd. In terms of benefit analysis combined with cost, the SC treatment had the highest benefit effect. Taken together, in mildly cadmium-polluted paddy fields, the application of silicon–calcium fertilizer improved the soil quality, thereby increased the yield and quality of rice, and had the best effect on increasing income.

Effects of 3-year organic farming management on soil antibiotic resistant genes and virulence factors in a double rice cropping system

Investigating the antibiotic resistance genes (ARGs) and virulence factors (VFs) within soil microbial communities is crucial for understanding microbial ecology and the evolution of antibiotic resistance. However, the study of ARGs, VFs, and their predominant microbial hosts in soils under varying rice production management practices remains largely underexplored. To this end, a three-year field experiment was conducted under organic management within a double rice cropping system in South China. The study revealed that, in contrast to conventional management (CK), organic farming practices did not significantly alter the total reads of ARGs and VFs. However, there was a notable alteration in the ARGs abundance at the antibiotic class level, such as an increase (P < 0.05) in the abundance of Multidrug ARGs (by 1.7 %) and a decrease (P < 0.05) in Rifamycin (by 17.5 %) and Fosfomycin ARGs (by 15.3 %). Furthermore, a significant shift in VFs was observed under organic farming compared to CK, characterized by an increase (P < 0.05) in offensive VFs and a decrease (P < 0.05) in nonspecific VFs and the regulation of virulence-associated genes. Key microbial taxa identified as influencing ARGs and VFs in the tested soil samples, e.g., Proteobacteria. The findings highlight the need for more detailed attention to soil ecology within organic rice production systems in South China, particularly concerning the significant alterations observed in ARGs and VFs.

Remote sensing monitoring and application research on the "Non Grain" cultivated land of arable lands in the Nandu River Basin

Remote sensing monitoring and application research on the "Non Grain" cultivated land of arable lands in the Nandu River Basin

Roles of Microbial Community and Keystone Taxa in Rice Productivity under Green Manuring in South China

Green manure (GM)–rice–rice rotation is an important management practice for improving soil fertility and rice productivity. The microbiological mechanisms for the increase in grain yield in GM–rice–rice rotation remain unclear. The responses of soil biodiversity, bacterial and fungal communities, and their interactions in the GM–rice–rice rotation were investigated based on two long-term field experiments in Gaoqiao (GQ) and Nanxian (NX) in Hunan Province, south China. Results showed that rice yields were raised by 11.79% and 15.03% under GM in GQ and NX, respectively. GM promoted Shannon diversity and Pielou’s evenness and changed the community structures of bacteria and fungi. The co-occurrence network analysis found that the percentages of negative edges were higher in GM (40.79% and 44.32% in GQ and NX, respectively) than those in the corresponding winter fallow (34.86% and 29.13% in GQ and NX, respectively) in the combined bacterial–fungal networks, suggesting more stable microbial community under GM. Moreover, GM had higher percentages of bacterial–fungal and fungal–fungal edges than winter fallow, indicating that GM increased the interaction between bacteria and fungi and fungi play more essential roles in affecting soil processes under GM. The keystone taxa in GM were positively linked with C metabolism-related enzymes and soil multifunctionality, and were important in improving soil fertility and rice productivity. We concluded that the fungal community was more sensitive to GM application than the bacterial community and that keystone taxa had important influences on soil properties and rice productivity in the GM–double-rice cropping system, which can effectively support the sustainable development of the paddy field ecosystem in southern China.