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Paddy fields contaminated by arsenic-containing acid mine drainage (AMD) may also have rich iron in soil. Whether this iron can be loaded onto biochar to passivate the dissolved arsenic is worth further exploration. Soil was mixed with biochar prepared at 400, 550, and 700 °C and incubated under alternating anaerobic and aerobic conditions. Soil, soil solution and biochar samples were analysed using ICP-MS, FTIR, SEM, XPS, etc. The results showed that biochar prepared at lower pyrolysis temperatures contained a higher number of functional groups. Under the combined action of microorganisms, primarily from the Firmicutes phylum, biochar promoted the dissolution of arsenic-containing iron oxides in soil, with the residual arsenic also undergoing transformation. The biochar rapidly loaded dissolved iron onto its surface, likely in the form of Fe3O4 and FeOOH, and adsorbed arsenic primarily as As(III). Although the iron oxides detached over time, they were more stable on the biochar prepared at 400 °C compared to those prepared at higher pyrolysis temperatures. Meanwhile, the arsenic content on the biochar increased, raising the As/Fe molar ratio to above that of the soil. This study lays the foundation for further exploring the long-term use of biochar in AMD-contaminated paddy fields. [ABSTRACT FROM AUTHOR]

Soil aggregate stability is an important factor that impacts ecological restoration and soil erosion. Soil organic carbon (SOC) is also an important factor affecting soil characteristics and quality. The triple-cropping system has the potential to enhance soil aggregate stability by promoting a more diverse and continuous plant cover, which could lead to improved soil structure and resistance to erosion. Over two consecutive years, this study was conducted to explore the impacts of the triple-cropping system on soil aggregate stability, soil carbon pool, and carbon sequestration characteristics in the middle reaches of the Yangtze River. This study set up five planting modes, namely milkvetch–early rice–late rice (CRR, CK), milkvetch–early rice–sweet potato||soybean (CRI), rape–early rice–late rice (RRR), rape–early rice–sweet potato||soybean (RRI) and potato–early rice–late rice (PRR). The contribution of soil aggregates > 2 mm under CRI increased by 20.77%, 6.71%, and 2.19% to the control in winter cropping and early and late rice harvesting periods, respectively. During the winter harvest period, the geometric mean diameter (GMD) and mean weight diameter (MWD) of the CRI treatment were significantly higher than other treatments (p < 0.05), with increases of 7.53–16.28% and 4.67–10.28% respectively. After the late rice harvest, the GMD values of the CRI and PRR treatments were significantly higher than the control treatment by 13.56%, and the MWD values were higher than those of other treatments by 4.24–13.17%, 3.74–12.63% (p < 0.05). Furthermore, CRI also improved the GMD and MWD of soil aggregates, and the stability of soil aggregates was improved by winter milkvetch (treatment of CRI) and paddy-upland multi-crop models (treatment of PRR). RRR treatment was beneficial to the accumulation of soil organic carbon and slowed the loss of soil organic carbon. Irrigation and drought multiple cropping can effectively increase the content of soil active organic carbon, among which the treatment of CRI had the best performance and the most significant effect in increasing the content of soil active organic carbon. After the late rice harvest, the soil's active organic carbon content in the CRI treatment was the highest, which was significantly different from the control treatment and increased by 35.62% compared with the control (p < 0.05). Compared with before planting, the soil microbial biomass carbon content in each treatment increased by 12.07–27.59% after the late rice harvest. The soil-dissolved organic carbon content in CRI treatment was the highest, which was significantly higher than CK treatment, RRR, and PRR, with an increase of 46.88%, 42.42%, and 30.56%, respectively (p < 0.05). In addition, the accumulation of soil microbial biomass carbon, soil dissolved organic carbon content, and soil easily oxidized organic carbon content was promoted by multi-cropping in rice fields, and the increase from CRI and RRI treatment was more significant. In conclusion, in the triple-cropping area of paddy fields in the middle reaches of the Yangtze River, the milkvetch–early rice–sweet potato||late soybean and rape–early rice–sweet potato||late soybean models are conducive to the optimal management of the soil carbon pool and carbon sequestration. These models can improve the multiple cropping index, reduce costs, and increase revenue. [ABSTRACT FROM AUTHOR]

The current investigation amid the alleviating of the macronutrient [Nitrogen (N), Phosphorus (P), and Potassium (K)] deficiency effects on rice yield, yield components, and grain biofortification by foliar spraying of Zn and Fe chelated by glycine amino acid (ZFCG) on the flooded rice conditions. Three-factor factorial experiment was conducted based on a randomized complete block design with three replications. The experimental factors were: macronutrients [Nitrogen (N), Phosphorous (P), and Potassium (K)] soil application at two levels (100 and 50% of the recommended dose) and foliar application of ZFCG during the booting and ripening stages at three levels (0, 1, and 1.5 kg ha−1). The results clearly showed that the foliar spraying of 1.5 kg ha−1 ZFCG significantly increased the growth characters, yield attributes, yields, and white rice nutritional quality of Hashemi cultivar both at the application of 100% (normal condition) and 50% (nutrient stresses condition) of the recommended rate of NPK. The foliar application of 1.5 kg ha−1 ZFCG increased the rice grain, straw, biological yield, head rice yield, and harvest index of the plots that received 50% of the recommended rate by about 14.6, 10.12, 50, 7.5, and 6.7% compared to the values of the control plots (no adding the NPK), respectively and 49.25, 31.21, 31.60, and 16.67% at the plots that received 100% of recommended NPK, respectively. Moreover, the foliar application of glycine amino acid-Fe and Zn chelate at two vital rice growth stages increased the value of the Zn, Fe and protein content of white rice at the plots that received 1/2 of the recommended dose of NPK by about 52.37%, 2 times, and 8.64% compared to control plots, respectively, and also 20.77%, 2 times, and 12% at the plots that received 100% of recommended NPK, respectively. The observed values are close to their values in those plots that have received 100% of recommended rate of NPK without foliar application. Therefore, it can be concluded that the foliar co-application of 1.5 kg ha−1 ZFCG during the two important rice growth stages (booting and ripening) might both alleviate the improper and imbalanced macronutrient deficiency stresses and enhance the rice grain yield and biofortification at flooded rice cultivation. [ABSTRACT FROM AUTHOR]

The soybean cultivar, ‘Jangpung’, is adaptable for mechanized harvest with fewer branches and a higher first pod height. ‘Jangpung’ was developed through a pedigree method involving a cross between ‘Shingi’ and ‘SS03102-B-B-3S-21-4’ cultivars from 2010-2021. The promising line, ‘YS2243-B-B-35-1-1-1’, was selected and designated as ‘Milyang361’, whereafter it was tested in regional yield trials (RYT) for three years from 2019-2021. Its performance and stability were approved after the RYT and thereafter released as ‘Jangpung’. It has a determinate growth habit, purple flowers, grey pubescence, yellow seed coat, yellow hilum, spherical seed shape, and large seeds (28.2 g/100 seeds). ‘Jangpung’ is a late-maturing cultivar; its flowering and maturing dates were 9 August and 22 October, respectively. ‘Jangpung’ exhibited resistance to bacterial pustule and soybean mosaic virus, as well as tolerance to lodging and shattering resistance, as confirmed through genetic validation using the marker, qPDH-KS. Considering its higher first pod height, lodging and shattering tolerance, and disease resistance, the soybean cultivar, ‘Jangpung’, might assist soybean producers in achieving high adaptability for mechanization and paddy field cultivation (Registration number: 9972). [ABSTRACT FROM AUTHOR]

Drainage equipment is an important part of paddy field drainage and irrigation system, and its performance research and application are conducive to the promotion and implementation of high‐standard farmland construction. Aiming at the different water demand of rice in different growing stages, low water level control precision, large manual operation and extensive management of existing drainage machinery, a tilting‐plate drainage equipment using upper overflow mode was proposed in this paper. Based on the Geneva mechanism principle, a unique linkage mechanism is designed, which can realize water retaining operation and silt discharge operation through a single motor drive, and the relationship between the motor angle and the water retaining height is established. Through mechanical analysis and dynamic simulation of the mechanism, the motion characteristics of the water baffle, silt plate and the change of the motor torque are studied. A remote control system based on a 4G module is designed to control the drainage equipment easily through the user layer. The performance test of the prototype shows that the precision error of the optimized water retaining height control is less than 3.75%. The maximum height of water retaining operation is 180 mm, and the maximum load of silt discharge operation is 10 kg, which can meet the actual operation requirements. The design is beneficial to improve the precision and intelligence level of paddy field drainage management, and the research process can provide some help for the development and application of this kind of equipment. [ABSTRACT FROM AUTHOR]

Abstract Background Phytoremediation is affected by physical and chemical properties of the soil such as soil pH, moisture, and nutrient content. Soil pH is a key element influencing Cd bioavailability and can be easily adjusted in agricultural practices. The soil pH level may relate to the effectiveness of phytoremediation; however, this has not been extensively investigated. In the current study, we evaluated the effect of Cd contamination level (0.56 and 0.92 mg/kg) and soil pH (5, 6, and 7) on Cd accumulation and allocation in Artemisia argyi, a fast-growing perennial crop. Results Our results indicated that higher soil Cd concentrations reduce A. argyi biomass, and the loss of the root mass was particularly significant. Higher soil pH decreased Cd content in stems and roots of A. argyi cultivated in moderately Cd-polluted soil, and increased Cd content in stems and roots of the plant grown in low Cd-polluted soil. Higher soil pH decreased the percentage of Cd distributed in the soluble fraction and cell walls and increased the percentage of Cd in the organelles of leaf cells for moderate soil Cd levels. The bioconcentration and translocation factor exceeded 4.0 and 1.0, respectively, across all tested treatments, indicating that A. argyi is a promising candidate for phytoremediation. Notably, the effects of soil pH on Cd accumulation and subcellular distribution in A. argyi differed between low and moderately Cd-contaminated soils. Conclusion Adjustments to soil pH based on the degree of Cd contamination can enhance Cd extraction by A. argyi, thereby reducing the overall remediation cycle of cadmium-polluted paddy fields of South China. Graphical Abstract

Abstract 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.

Magnetite-loaded biochar has recently received attention owing to its ability to remove arsenic from contaminated soil. In this study, mulberry stem biochar (MBC) and Fe3O4-loaded mulberry stem biochar (Fe3O4@MBC) were produced and used in a 100-day incubation experiment to investigate their performance in the stabilization of arsenic in paddy soil severely polluted by the As (237.68 mg·kg−1) mechanism. Incubation experiments showed that Fe3O4@MBC was more effective in immobilizing As after incubation for 100 days. Moreover, adding Fe3O4@MBC facilitated the transformation of exchangeable heavy metals into organic-bound and residual forms, thereby reducing As available concentrations, mobility, and bioavailability in the soil, and elevating slightly the soil pH and dissolved organic carbon (DOC). The concentration of TCLP-extractable As (AsTCLP) in contaminated soil was reduced from 93.85 to 7.64 μg·L−1 within 10 d, below the safety limit for drinking water set by the World Health Organization (WHO). The characterization results of Fe3O4@MBC after incubation indicated that the mechanisms for As passivation are linked to redox reactions, complexation, electrostatic attraction, surface adsorption, and coprecipitation. Conclusively, Fe3O4@MBC is a promising amendment in highly As-contaminated soil and provides a theoretical reference in such polluted paddy soil remediation. [ABSTRACT FROM AUTHOR]

Paddy fields are classified as wetland environments, and they comprise freshwater ecosystems. They are ecologically important habitats and breeding grounds for many aquatic insects, amphibians, and reptiles. However, paddy field ecosystems are constantly threatened by climate change and the indiscriminate use of pesticides. The metabarcode analysis of eDNA (environmental DNA) method is highly effective at accumulating information on many organisms that inhabit paddy field ecosystems. It can indirectly identify the existence of taxa that are no longer found in the target ecosystem due to behavioral characteristics, such as those exhibited by amphibians. In the metabarcoding results of this study, genes of five species of frogs were found, but it was impossible to confirm all of the frogs' taxa, morphological pictures, and croak sounds. On the other hand, some frog taxa were only found in the metabarcoding analysis. The eDNA of the frogs found only in the metabarcoding analysis is estimated to have been introduced from nearby areas inhabited by frogs rather than the target region. Due to the powerful analytical resolution of eDNA metabarcoding, this eDNA-based paddy field search is expected to help investigate the biodiversity in agricultural ecosystems. [ABSTRACT FROM AUTHOR]

Background: Phytoremediation is affected by physical and chemical properties of the soil such as soil pH, moisture, and nutrient content. Soil pH is a key element influencing Cd bioavailability and can be easily adjusted in agricultural practices. The soil pH level may relate to the effectiveness of phytoremediation; however, this has not been extensively investigated. In the current study, we evaluated the effect of Cd contamination level (0.56 and 0.92 mg/kg) and soil pH (5, 6, and 7) on Cd accumulation and allocation in Artemisia argyi, a fast-growing perennial crop. Results: Our results indicated that higher soil Cd concentrations reduce A. argyi biomass, and the loss of the root mass was particularly significant. Higher soil pH decreased Cd content in stems and roots of A. argyi cultivated in moderately Cd-polluted soil, and increased Cd content in stems and roots of the plant grown in low Cd-polluted soil. Higher soil pH decreased the percentage of Cd distributed in the soluble fraction and cell walls and increased the percentage of Cd in the organelles of leaf cells for moderate soil Cd levels. The bioconcentration and translocation factor exceeded 4.0 and 1.0, respectively, across all tested treatments, indicating that A. argyi is a promising candidate for phytoremediation. Notably, the effects of soil pH on Cd accumulation and subcellular distribution in A. argyi differed between low and moderately Cd-contaminated soils. Conclusion: Adjustments to soil pH based on the degree of Cd contamination can enhance Cd extraction by A. argyi, thereby reducing the overall remediation cycle of cadmium-polluted paddy fields of South China. [ABSTRACT FROM AUTHOR]

Two novel Gram-stain-negative strains designated P7T and P8T, were isolated from the soil of a paddy field in Goyang, Republic of Korea, and identified as new species within the genus Roseateles through a polyphasic taxonomic approach. These aerobic, rod-shaped, non-sporulating strains demonstrated optimal growth at 30 °C, pH 7, and in the absence of NaCl (0% w/v). Phylogenetic analysis based on 16S rRNA gene sequences indicated close relationships with Roseateles saccharophilus DSM654T (98.7%) and Roseateles puraquae CCUG 52769T (98.96%), respectively. The average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values between the isolates with the most closely related strains with publicly available whole genomes were 82.0–85.5% and 25.0–30.2%, respectively. The predominant fatty acids identified were C16:0 and summed feature 3 (composed of C16:1 ω6c and/or C16:1ω7c), with minor amounts of C12:0, C10:0 3–OH and summed feature 8 (composed of C18:1ω7c and/or C18:1ω6c; 26.4%). Ubiquinone 8 was the main quinone, and the polar lipid profile included phosphatidylethanolamine, phosphatidylglycerol, two unidentified phosphoaminolipids, one unidentified phosphoglycolipid, three unidentified phospholipids, and one unidentified aminolipid. The draft genome sequences revealed genomic DNA G + C contents of 70.1% for P7T and 68.2% for P8T. Comprehensive physiological, biochemical, and 16S rRNA sequence analyses confirm these isolates as novel species of the genus Roseateles, proposed to be named Roseateles caseinilyticus sp. nov for strain P7T (= KACC 22504T = TBRC 15694T) and Roseateles cellulosilyticus sp. nov. for strain P8T (= KACC 22505T = TBRC 15695T). [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Biogas slurry, as a substitute for chemical fertilizers, is usually applied according to the needs of biogas slurry to be consumed at onetime. This poses a great risk of short-term nutrient overload in soils, resulting in high losses of nitrogen (N) and phosphorus (P) from farmland. Therefore, a field experiment was conducted to identify the optimal irrigation pattern for biogas slurry in paddy field by monitoring N and P losses via surface runoff, leaching, NH3 volatilization, and denitrification as well as rice yield and soil residue with five fertilizer application patterns: no fertilizer application, conventional chemical fertilizer, and three biogas slurry irrigation patterns including the current irrigation pattern of three times (BS1), irrigation pattern of five times (BS2), and 20% reduction of N input with five irrigations (BS3). BS2 treatment significantly increased the yield of rice by 13.91 and 23.37% compared to the CF and BS1 treatments, respectively. But the BS2 treatment promoted NH3 volatilization loss by 70% compared with the BS1 treatment. The BS3 treatment decreased the total N loss and P loss by 14.33 and 21.95%, respectively, compared to the BS1 treatment, along with a 10.26% increase in yield. Therefore, increasing the irrigation frequency of the biogas slurry to five times and reducing the fertilizer application rate by 20% was the optimal irrigation pattern in paddy field with the best agricultural and environmental benefits. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

To study the relationship between soil phosphorus content and soil phosphatase activity, the paddy soils in the karst area (KA) and non - karst area (NKA) of the Mao Village experimental field in Guilin City were selected as research subjects. Total phosphorus, available phosphorus, inorganic phosphorus components, and alkaline phosphatase activity in the soil were investigated. The results revealed low total phosphorus content in the KA soil, with abundantly available phosphorus content characterized by Fe-P, Ca8-P, and Ca10-P as the main inorganic phosphorus components. Alkaline phosphatase activity ranged from 0.76~1.27 mg ∙ kg-1 in the KA soil. In contrast, the NKA soil exhibited extremely low total phosphorus content, and moderate available phosphorus content. The main inorganic phosphorus components were Fe-P, Ca10-P, and Al-P, with alkaline phosphatase activity ranging from 0.06~0.35 mg∙kg-1 . The contents of total phosphorus and available phosphorus and alkaline phosphatase activity were significantly higher in the KA soil than in the NKA soil. Alkaline phosphatase activity in both the KA and NKA soils had a negative correlation with available phosphorus. In the KA soil, Fe-P content showed a significantly positive correlation with alkaline phosphatase activity, while in the NKA soil, total phosphorus, Ca8-P, and Al-P were all significantly negatively correlated with alkaline phosphatase activity. These findings suggest that available phosphorus and inorganic phosphorus fractions may be crucial factors influencing the differences in soil alkaline phosphatase activity between the KA and NKA soils. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The denitrification process is known to contribute to soil nitrogen (N) loss, which is strongly affected by fertilization strategies; however, the effects of distinct straw retention modes on soil denitrification activity have rarely been discriminated and the underlying mechanisms remain unclear. This study coupled field and incubation experiments to explore the characteristics of soil denitrification activity, soil and standing water physicochemical properties, and the abundance, community diversity, and co-occurrence network of nosZ denitrifiers, based on a paddy field implementing 10-year straw retention under a rice–wheat rotation system. Four straw retention treatments with equivalent chemical fertilizers were applied, namely no straw (NS), wheat straw only (WS), rice straw only (RS), and wheat and rice straw (WRS). Results indicated a significant increase (by 41.93–45.80% when compared to that with NS) in the soil denitrification activity with RS and WRS. Correspondingly, treatments with rice straw retention resulted in the development of a similar community composition (P < 0.05), structure (P = 0.001), and more positively interconnected network, as well as similar specific keystone taxa of nosZ denitrifiers, relative to those in non-rice straw mode. Under long-term rice straw retention conditions, the core nosZ-denitrifying phylogroups shifted (r = 0.83, P < 0.001), with the recruitment of keystone taxa from the phyla Bacteroidetes and Euryarchaeota playing a key role in enhancing denitrification activity and stimulating N loss. Accordingly, in a rice–wheat rotation field, the practice of wheat straw retention in a single season is recommended because it will not markedly sacrifice soil N availability impaired by the denitrification process.

Abstract Drainage equipment is an important part of paddy field drainage and irrigation system, and its performance research and application are conducive to the promotion and implementation of high‐standard farmland construction. Aiming at the different water demand of rice in different growing stages, low water level control precision, large manual operation and extensive management of existing drainage machinery, a tilting‐plate drainage equipment using upper overflow mode was proposed in this paper. Based on the Geneva mechanism principle, a unique linkage mechanism is designed, which can realize water retaining operation and silt discharge operation through a single motor drive, and the relationship between the motor angle and the water retaining height is established. Through mechanical analysis and dynamic simulation of the mechanism, the motion characteristics of the water baffle, silt plate and the change of the motor torque are studied. A remote control system based on a 4G module is designed to control the drainage equipment easily through the user layer. The performance test of the prototype shows that the precision error of the optimized water retaining height control is less than 3.75%. The maximum height of water retaining operation is 180 mm, and the maximum load of silt discharge operation is 10 kg, which can meet the actual operation requirements. The design is beneficial to improve the precision and intelligence level of paddy field drainage management, and the research process can provide some help for the development and application of this kind of equipment.

Increased levels of the non-essential hazardous metalloid arsenic (As) in rice grains pose a threat to human health and the sustainability of the rice industry. In several counties, the average As contamination in polished rice has been detected to range from 0.002 to 0.39 mg/kg, which is above the safe limit of 1 mg/kg as recommended by the World Health Organisation. Beyond this limit, the digestive tract, circulatory system, skin, liver, kidney, nervous system and heart can be affected. Humans can develop cancer from consuming or inhaling As. In addition, long-term exposure to drinking water contaminated with arsenic has also been linked to a dose-response relationship with an increased risk of hypertension and diabetes mellitus. Rice has been shown to be an indirect source of arsenic accumulation in human bodies. Under flooded paddy soil, trivalent arsenate (AsIII) occupies 87-94% of the total As, while under non-flooded soil, pentavalent arsenate (AsV) predominates (73-96% of the total As). This review aims to provide a thorough and interdisciplinary understanding of the behaviour of As in the paddy soil and transportation to rice grain and further investigate efficient ways to limit arsenic contamination. Supplementation of soil with specific mineral nutrients such as iron (Fe), sulphur (S) and silicon (Si) can significantly decrease the arsenic accumulation in rice grain by minimising its uptake and translocation. The hydrogen bonding potentials of uronic acids, proteins and amino sugars on the extracellular surface of soil microorganisms facilitate the detoxification of arsenic species. Further, rice is absorbed less when exposed to aerobic water management practices than anaerobic ones since it reduces the build-up of As in rice, and the solution is immobilised as in the soil.

With growing concerns about global warming, it is crucial to adopt agronomic practices that enhance rice yields from paddy fields while reducing greenhouse gas (GHG) emissions for sustainable agriculture. An optimal nitrogen (N) fertilization rate and planting density are vital to ensure high rice yields, minimize GHG emissions, and understand emission behavior for better field management. We hypothesized that optimizing N application rates and planting density to improve nitrogen use efficiency (NUE) in rice cultivation would reduce resource losses and GHG emissions. To test this hypothesis, we implemented five treatments with a rice straw return cultural system: two planting densities (16 hills m−2 (traditional density, D1) and 20 hills m−2 (25% higher density, D2)) and three N application rates (no N fertilizer (N0), 180 kg N ha−1 (N1), and 144 kg N ha−1 (N2)). The control treatment (CK) was traditional planting density with no N fertilizer. The four new cropping modes were N1D1, N1D2, N2D1, and N2D2. We investigated the effects of N application rates and planting density on rice grain yield, NUE, and GHG emissions in multiple rice-growing seasons. The N1D2 treatment exhibited the highest grain yield over the three years, with a value of 10,452 kg ha−1, representing an increase of 12.2% compared to CK. Moreover, N uptake in N1D2 was the highest, averaging 39.2% (p < 0.05) higher than CK, and 8.5%, 3.5%, and 2.8% (p < 0.05) higher than N1D1, N2D1 and N2D2, respectively. N2D2 exhibited the highest NUE, with a value of 58.99 kg kg−1, surpassing all other treatments over the three years. GHG emissions, global warming potential (GWP), and greenhouse gas intensity (GHGI) in N2D2 were lower than in N1D1, N1D2, and N2D1. Additionally, reducing N application (comparing N1D1 to N2D1) and increasing plant density (comparing N1D1 to N1D2) improved N agronomic efficiency (NAE) and N partial productivity (PFPN). The negative correlation between the NAE and PFPN with GWP and GHG emissions further supports the potential for optimized N management and denser planting density to reduce environmental impact. These findings have important implications for sustainable rice cultivation practices in Southwest China and similar agroecosystems, emphasizing the need for integrated nutrient management strategies to achieve food security and climate change mitigation goals. [ABSTRACT FROM AUTHOR]

Frogs play crucial roles in ecosystems as both predator and prey within food webs. The decline in their populations is attributed, in part, to modern, intensive rice farming practices. In the Tajima region of Hyogo Prefecture, Japan, a subset of farmers has embraced a "white stork friendly farming" (WSFF) method since 2003, which promotes environment-friendly rice production to preserve and restore biodiversity while aiding the reintroduction of the Oriental White Stork (Ciconia boyciana) into the ecosystem. Here, we hypothesize that the WSFF method has a positive impact on the conservation of black-spotted pond frog (Pelophylax nigromaculatus) populations inhabiting paddy fields. To test this hypothesis, we evaluated the influence of the WSFF method on the population density of P. nigromaculatus. Using a line transect method, we identified and quantified individual frogs observed on the paddy field levees in June 2016. Subsequently, we analyzed the effects of rice production using the WSFF method and land-use factors on the frogs' population density. Our findings indicate that P. nigromaculatus population density increased with the expansion of paddy-field areas managed under the WSFF method within a 100 m radius of the paddy-field center. These results suggest that rice production following the WSFF method has a positive impact on the conservation of this frog species. [ABSTRACT FROM AUTHOR]

Bioorganic fertilizer (BOF) represents favorable potential for agricultural production, but the safe and residual effects of BOF application in heavy-metal-contaminated soils still remain unclear. A two-year field experiment of four rice-growing cycles were conducted to study the effects of the one-time addition of BOF (low and high dosages, 0.45 and 0.9 kg/m2, namely, BOF1 and BOF2, respectively) on the lead (Pb) and arsenic (As) accumulations in brown rice, rice yield, and soil properties in an acidic and Pb-As-contaminated paddy field. The results show that BOF application enhanced the rice yields by 7.9–25.5% and increased the soil pH, organic carbon contents, and fluorescein diacetate hydrolase activity in the former two rice-growing cycles, while these attributes declined gradually and were not significant in the last two cycles. The soil bulk density decreased marginally due to the BOF. Furthermore, the BOF1 treatment barely affected the rice Pb and As concentrations during all cycles, whereas the BOF2 treatment clearly increased the Pb concentrations in brown rice, exceeding the food quality standard limit of 0.2 mg/kg in the last three cycles, and slightly increased the rice As in the former three cycles. The BOF effects on Pb and As in brown rice were due to the changes in the available soil Pb and As, respectively. Our results indicate that a one-time application of BOF could ameliorate the soil conditions of rice growth in two rice-growing cycles, while the high-dose BOF seemed undesirable in toxic-metal-contaminated soils. BOF application at the rate of 0.45 kg/m2 per annum may be a potential strategy for safe rice production in Pb-As-contaminated fields. [ABSTRACT FROM AUTHOR]

Increased levels of the non-essential hazardous metalloid arsenic (As) in rice grains pose a threat to human health and the sustainability of the rice industry. In several counties, the average As contamination in polished rice has been detected to range from 0.002 to 0.39 mg/kg, which is above the safe limit of 1 mg/kg as recommended by the World Health Organisation. Beyond this limit, the digestive tract, circulatory system, skin, liver, kidney, nervous system and heart can be affected. Humans can develop cancer from consuming or inhaling As. In addition, long-term exposure to drinking water contaminated with arsenic has also been linked to a dose-response relationship with an increased risk of hypertension and diabetes mellitus. Rice has been shown to be an indirect source of arsenic accumulation in human bodies. Under flooded paddy soil, trivalent arsenate (AsIII) occupies 87-94% of the total As, while under non-flooded soil, pentavalent arsenate (AsV) predominates (73-96% of the total As). This review aims to provide a thorough and interdisciplinary understanding of the behaviour of As in the paddy soil and transportation to rice grain and further investigate efficient ways to limit arsenic contamination. Supplementation of soil with specific mineral nutrients such as iron (Fe), sulphur (S) and silicon (Si) can significantly decrease the arsenic accumulation in rice grain by minimising its uptake and translocation. The hydrogen bonding potentials of uronic acids, proteins and amino sugars on the extracellular surface of soil microorganisms facilitate the detoxification of arsenic species. Further, rice is absorbed less when exposed to aerobic water management practices than anaerobic ones since it reduces the build-up of As in rice, and the solution is immobilised as in the soil. [ABSTRACT FROM AUTHOR]

The interconnection between the objectives of territorial development and those of the agro-ecological transition highlights the value of past knowledge in the sustainable management of resources and agro-ecological systems. However, the lack of data creates difficulties for retrospection in rural areas. This paper contributes to the search for such knowledge from the past by developing an interactive methodology capable of combining heterogeneous information sources with the activation of local collective memory. Its effectiveness is based on ensuring the interoperability of information and communication in an environment simultaneously shaped by geoinformatics and 3D geovisualisations. This virtual environment fostered participation and interactivity, supported by representations of the paleo-landscape (Ottoman period). Furthermore, synergies were achieved between information sources, which were integrated into local spatial systems. The application example involved identifying a rice field that existed between the 15th and 19th centuries in Thessaly, Greece. It is an interesting case because the research results indicated that the location and organisation of the crop, combined with the spatio-temporal coordination required, ensured the sustainable use of natural resources. The interplay between information and communication facilitated community participation and the activation of its collective memory as an information source that enriched the search itself and local intelligence. [ABSTRACT FROM AUTHOR]

In order to study the content of heavy metals in paddy soil-rice system in typical areas of southern China. Soil, rice and irrigation water samples were collected from six typical paddy fields in Jinxian County, Jinxi County, Yushui District, Gao'an City, Anfu County and Xingguo County of Jiangxi Province. The contents of lead, cadmium, arsenic and mercury in soil and rice and soil nutrients were analyzed. The content of heavy metals in soil-rice system was evaluated by single factor pollution index and Nemero comprehensive index. Results show that the mean values of soil pH, organic matter, total nitrogen, total phosphorus, total potassium, available nitrogen, available phosphorus and available potassium are 5. 48, 32. 99 g / kg, 2. 06 g / kg, 0. 54 g / kg, 16. 04 g / kg, 156. 71 mg / kg, 14. 00 mg / kg and 94. 98 mg / kg, respectively. The total average contents of lead, cadmium, arsenic and mercury are 35. 46, 0. 18, 7. 21, 0. 17 mg / kg in the soil of the study area. The single factor pollution index is less than 1, the Nemero comprehensive pollution index is 0. 56, and the soil environmental quality grade is clean. While the soil cadmium content is 0. 37 mg / kg in Yushui, exceeding the limit standard (0. 30 mg / kg), and the soil environmental quality is alert. The total average contents of lead, cadmium, arsenic and mercury are 0. 06, 0. 17, 0. 24, 0. 008 6 mg / kg in brown rice of the study area. The single factor pollution index is less than 1, and the average Nemero comprehensive pollution index is 0. 77. The environmental quality grade of brown rice is alert. The cadmium contents in brown rice of Xingguo and Yushui are 0. 22, 0. 35 mg / kg, which exceeds the limit standard (0. 20 mg / kg). The environmental quality grades are warning limit and mild pollution, respectively. Correlation analysis show that cadmium in brown rice is significantly positively correlated with cadmium and lead in soil, while negatively correlates with arsenic in soil. The arsenic in brown rice is significantly positively correlated with arsenic and available phosphorus in soil. In short, heavy metal cadmium is the most important potential pollution element for rice safety in the survey area, and it is necessary to focus on rice food safety in Xingguo and Yushui. [ABSTRACT FROM AUTHOR]

Controlled irrigation and drainage technology for rice is crucial water management that has been widely promoted in northeastern China. It is of great significance to clarify the response mechanism of the drainage volume and nitrogen loss load in the paddy field for realizing water saving, emission reduction, pollution control and high yield in rice-planting areas. In this study, we conducted field experiments and simulations on drainage volume and nitrogen loss load regulations of paddy fields in a cold black soil region under different hydrological years and irrigation and drainage modes. The key parameters for simulating drainage volume and nitrogen loss load in paddy fields using DRAINMOD-NII were determined by combining field experiments, data analysis, and numerical simulation. The results showed that the simulated drainage volume and nitrogen loss load showed a high coefficient of determination with the observed results, which were all above 0.83. The Nash–Sutcliffe efficiency coefficient ranged from 0.72 to 0.97 in model calibration and verification, indicating that the model effectively simulated drainage volume and nitrogen loss load in paddy fields under controlled irrigation and drainage in the cold black soil region. The paddy field drainage volume was not only influenced by rainfall frequency but also by the distribution of rainfall. Compared with traditional irrigation and drainage, the controlled irrigation and drainage significantly reduced the irrigation amount by 39.07% and increased rainwater utilization efficiency by 13.07%. It also reduced the drainage volume by 44.71% and NO3−-N and NH4+-N loss load by 59.38% and 44.96%. The controlled irrigation and drainage mode optimized natural rainfall resources and increased irrigation water productivity and rice yield by 97.85% and 16.88%, respectively. Controlled irrigation and drainage outperformed the traditional mode in different hydrological years, with more pronounced effects in dry years, which highlights its significant value in practical agricultural production. [ABSTRACT FROM AUTHOR]

Rice is one of the main food crops in China. It is of great importance for the timely, rapid, and accurate acquisition of rice field area and its spatial distribution in agricultural production, particularly for national food security. However, the traditional classification variables of remote sensing and pixel-based machine learning have posed great challenges in identifying the paddy fields with high fragmentation. The phenological parameters have been used to represent the growth dynamics of vegetation. Object-oriented random forests can also effectively avoid the 'salt and pepper' noise for the high accuracy of paddy fields. In this study, the object-oriented algorithm was selected to identify the paddy field, according to the rice phenological parameters. The research area was taken as the paddy field in Zhangzhou City, Fujian Province, a typical mountainous and hilly area in southern China. Firstly, the recursive feature elimination (RFE) and variance inflation factor (VIF) were applied to optimize the remote sensing variables. As a result, the normalized difference vegetation index (NDVI), modified normalized difference water index (MNDWI), soil-adjusted vegetation index (SAVI), vertical transmit/vertical receive (VV), vertical transmit/horizontal receive (VH), and six phenological parameters were taken to construct the classification model. Secondly, the object-oriented and pixel-based random forest was used to identify the paddy fields. Three combinations of the variables were used as the input parameters of the classification model. The effectiveness of phenological parameters and the object-oriented random forest were verified to improve the accuracy of paddy field identification in the complex terrain areas in southern China. The results are as follows: 1) The highest identification accuracy of paddy fields was 94.47%, where the Kappa coefficient was 0.92. A better performance was achieved to identify the paddy fields using the remote sensing variables, phenological parameters, and object-oriented random forest; 2) The phenological parameters shared the significant advantages to characterizing the vegetation growth among various types. Thus, the phenological parameters and remote sensing variables were combined to improve the accuracy of paddy field identification by 8.78-9.36 percentage points, compared with the experimental group with remote sensing variables only; 3) The object-oriented random forest was outstanding defined the shape and boundary of paddy fields with a high degree of fragmentation in the complex terrain areas. The artifact of 'salt and pepper' was effectively avoided. The object-oriented classification improved the accuracy of paddy fields by 0.58-1.53 percentage points, compared with the traditional pixel-based one. Therefore, the improved model was more suitable for the extraction of fragmented farmland in the complex topographic areas using remote sensing images. The finding can provide a strong reference to further improve the accuracy of paddy field mapping products in complex terrain areas. [ABSTRACT FROM AUTHOR]

Biochar application is widely recognized as an effective approach for increasing soil organic carbon (SOC) and mitigating climate change in agroecosystems. However, the effects of biochar application on net accumulations and relative contributions of different SOC sources remain unclear. Here, we explored the effects of biochar application on plant‐derived (PDC) and microbial necromass C (MNC) in a 10‐year experimental rice–wheat rotation field receiving four different intensities of biochar application (0, 2.25, 11.5, and 22.5 t ha−1 for each crop season), using phospholipid fatty acids (PLFAs), lignin phenols and amino sugars as biomarkers of microbial biomass, PDC and MNC, respectively. Our results showed that biochar application increased SOC content and stock by 32.6%–203% and 26.4%–145%, respectively. Higher biochar application (11.5 and 22.5 t ha−1) increased soil pH, total nitrogen (TN), total phosphorus (TP), SOC/TN, and root biomass. In addition, higher biochar application enhanced bacterial, fungal, and total microbial biomass. Plant lignin phenols and MNC contents significantly increased, whereas their contributions to SOC significantly decreased with the increase in biochar application rates due to the disproportionate increase in PDC and MNC, and SOC. Fungal necromass had a greater contribution to SOC than bacterial necromass. The fungal/bacterial necromass decreased from 2.56 to 2.26 with increasing biochar application rates, because of the higher abundances of bacteria than that of fungi as indicated by PLFAs under higher biochar application rates. Random forest analyses revealed that pH, TP, and SOC/TN were the main factors controlling plant lignin and MNC accumulation. Structural equation modeling revealed that biochar application increased lignin phenols by stimulating root biomass, whereas enhanced MNC accumulation was primarily from increased microbial biomass and lignin phenols. Overall, our findings suggest that biochar application increases the accumulation of the two SOC sources but decreases their contributions to SOC in paddy soils. [ABSTRACT FROM AUTHOR]

Heavy-metal contamination in agricultural soil, particularly of cadmium (Cd), poses serious threats to soil biodiversity, rice production, and food safety. Soil microbes improve soil fertility by regulating soil organic matter production, plant nutrient accumulation, and pollutant transformation. Addressing the impact of Cd toxicity on soil fungal community composition, soil health, and rice yield is urgently required for sustainable rice production. Vermicompost (VC) is an organic fertilizer that alleviates the toxic effects of Cd on soil microbial biodiversity and functionality and improves crop productivity sustainably. In the present study, we examined the effects of different doses of VC (i.e., 0, 3, and 6 tons ha−1) and levels of Cd stress (i.e., 0 and 25 mg Cd kg−1) on soil biochemical attributes, soil fungal community composition, and fragrant-rice grain yield. The results showed that the Cd toxicity significantly reduced soil fertility, eukaryotic microbial community composition and rice grain yield. However, the VC addition alleviated the Cd toxicity and significantly improved the soil fungal community; additionally, it enhanced the relative abundance of Ascomycota, Chlorophyta, Ciliophora, Basidiomycota, and Glomeromycta in Cd-contaminated soils. Moreover, the VC addition enhanced the soil's chemical attributes, including soil pH, soil organic carbon (SOC), available nitrogen (AN), total nitrogen (TN), and microbial biomass C and N, compared to non-VC treated soil under Cd toxicity conditions. Similarly, the VC application significantly increased rice grain yield and decreased the Cd uptake in rice. One possible explanation for the reduced Cd uptake in plants is that VC amendments influence the soil's biological properties, which ultimately reduces soil Cd bioavailability and subsequently influences the Cd uptake and accumulation in rice plants. RDA analysis determined that the leading fungal species were highly related to soil environmental attributes and microbial biomass C and N production. However, the relative abundance levels of Ascomycota, Basidiomycota, and Glomeromycta were strongly associated with soil environmental variables. Thus, the outcomes of this study reveal that the use of VC in Cd-contaminated soils could be useful for sustainable rice production and safe utilization of Cd-polluted soil. [ABSTRACT FROM AUTHOR]

Concerns about methane (CH4) emissions from rice, a staple sustaining over 3.5 billion people globally, are heightened due to its status as the second-largest contributor to greenhouse gases, driving climate change. Accurate quantification of CH4 emissions from rice fields is crucial for understanding gas concentrations. Leveraging technological advancements, we present a groundbreaking solution that integrates machine learning and remote sensing data, challenging traditional closed chamber methods. To achieve this, our methodology involves extensive data collection using drones equipped with a Micasense Altum camera and ground sensors, effectively reducing reliance on labor-intensive and costly field sampling. In this experimental project, our research delves into the intricate relationship between environmental variables, such as soil conditions and weather patterns, and CH4 emissions. We achieved remarkable results by utilizing unmanned aerial vehicles (UAV) and evaluating over 20 regression models, emphasizing an R2 value of 0.98 and 0.95 for the training and testing data, respectively. This outcome designates the random forest regressor as the most suitable model with superior predictive capabilities. Notably, phosphorus, GRVI median, and cumulative soil and water temperature emerged as the model's fittest variables for predicting these values. Our findings underscore an innovative, cost-effective, and efficient alternative for quantifying CH4 emissions, marking a significant advancement in the technology-driven approach to evaluating rice growth parameters and vegetation indices, providing valuable insights for advancing gas emissions studies in rice paddies. [ABSTRACT FROM AUTHOR]

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Biological invasions cause huge environmental and socio-economic losses worldwide. Among successful invaders, there are also several decapod crustacean species. In this study, we report the presence of an potentially invasive crab species that damages rice crops in Sumatra, Indonesia. This paddy-field crab Parathelphusa convexa De Man, 1879 is a freshwater species native to Java, which was introduced in Sumatra around 2000 via an uncertain pathway. The sampling was conducted from July to September 2021 in paddy fields in West Sumatra, where its well-established population was discovered. The crab negatively impacts rice plants and paddy fields in the region through grazing and burrowing behaviour. Since the species is too small to be attractive for human consumption and also, it is not popular for ornamental keeping due to indistinct colouration, it has no benefits for local communities and is considered unwanted. The continuous monitoring of the species with possible regulation or eradication activity in Sumatra is recommended. [ABSTRACT FROM AUTHOR]

Off-target pesticide drift in paddy fields following unmanned aerial vehicle (UAV) spraying was evaluated using cellulose deposition samplers (CDSs). An analytical method for quantifying ferimzone Z and E isomers deposited on CDSs was developed using LC-MS/MS. The suitability of the CDS method was confirmed by comparing deposition patterns on CDSs with residue levels in rice plant samples. To assess pesticide deposition in paddy fields, CDSs were strategically placed at varying distances from target areas, followed by UAV spraying. The fungicide agrochemicals were applied with and without adjuvants, and wind direction affected the drift trajectory for all treatment groups. Adjuvants, particularly soy lecithin as the major component, significantly enhanced pesticide deposition within the spray pathway while reducing drift rates relatively by 47.9–68.0 %. Higher wind speeds were found to exacerbate drift, but adjuvant-treated sprays showed less variability in deposition patterns under these conditions. Pesticide residues in harvested brown rice were found to be below the maximum residue limits (MRLs), ensuring safety for consumption. These findings highlight the importance of selecting appropriate adjuvants in UAV-based pesticide applications to optimize deposition efficiency and minimize environmental contamination.