Paddy Field Water Research Articles

Enhanced simultaneous removal of acetamiprid and cadmium from soil and water in paddy fields by Fe-Mn-BC ternary micro-electrolysis: Performance, mechanism and pathway

Acetamiprid (Ace) and cadmium (Cd) in paddy fields had caused serious impact on natural ecosystems and human health. In this study, Fe-Mn-BC ternary micro-electrolysis filler was successfully prepared and used to remove Ace and Cd in situ in paddy fields via constructing “Fe-Mn-BC micro-electrolysis-microorganism” system. The adsorption capacity of Fe-Mn-BC on Cd and Ace were 62.92 mg/g and 236.18 mg/kg, which were twice and six times than those of zeolites, respectively. In the laboratory simulated experiments, the removal efficiencies of Ace and Cd in CW with Fe-Mn-BC were around 85.0 %. The Ace was decomposed into macromolecular substances by electron transfer in the anodic oxidation process by Fe-Mn-BC and then degraded to water and carbon dioxide by microorganism, while Cd was mainly removed through adsorption of filler and microorganism and the coprecipitation with OH- form cathode and Fen+ from anode to form CdXFe(1-X)(OH)2. The introduce of Fe-Mn-BC promoted the production of microbial extracellular polymeric substances (mainly protein), favorable for Cd and Ace adsorption. Metagenomic sequencing results showed that the Fe-Mn-BC enriched the microorganism related to Ace degradation such as Streptomyces, Nonomuraea, Pseudonocardia, and Nocardia, and enhanced the relative abundances of Cd resistance genes (ABC.CD.P, ABC-2.A and ABC-2.P), and the Ace degradation genes (mcp, pht5, etbAa, TENA_E and ylmB), promoting the removal of Ace and Cd. This study proposed a multi-functional and easy-operated way for the removal of Ace and Cd from soil and water in paddy fields.

Different habitat use of two Cybister (Coleoptera: Dytiscidae) species larvae in a paddy field water system

AbstractIn recent years, it has been suggested that Cybister tripunctatus lateralis is increasing in abundance and expanding its distribution, and there is concern about the effects of interspecific competition with another congeneric species, Cybister brevis. Although the two species appear to have overlapping niches, they are often observed sympatrically. Larval habitat use by the two species was investigated in a paddy field water system. The results display that C. brevis was more abundant in ditches and C. tripunctatus lateralis was more abundant in paddy fields. It is thought that C. tripunctatus lateralis, which has an ecology suited to high temperatures, has selected paddy fields, where water temperatures tend to rise, as its reproductive habitat. In contrast, phenology was generally synchronized, and no differences in underwater position in the rice paddies were observed. Thus, niches overlap in paddy fields and interspecific competition may occur.

Modification and testing of SWAT for paddy field water consumption and yield

AbstractSWAT model is one of the primary tools for assessing irrigation district water management and water‐saving measures. However, its incapacity to consider the diverse growth and water requirements of paddy during various growth stages, as well as the insufficient availability of external water sources. This study introduces the Penman‐Monteith equation and Jensen model into the SWAT framework, setting crop coefficients, crop base coefficients, and growth stage sensitivity indices based on the different growth stage. Additionally, modifications are made to the external water source available for irrigation and paddy field leakage modules, establishing a distributed agricultural hydrological model suitable for accurately simulating water balance elements and paddy yield in multi‐source irrigation districts. The Yangshudang watershed in the Zhanghe irrigation district is chosen for the evaluation of the modified model's simulation performance, with a quantitative assessment of water‐saving and yield‐increasing effects. The results demonstrate that the modified model effectively meets the requirements for simulating paddy evapotranspiration of various growth stages, yield, agricultural irrigation water consumptions, and runoff, exhibiting a notable enhancement in performance. As two common water‐saving measures in irrigation areas, intermittent irrigation and irrigation district renovation were used as two water‐saving scenarios in the simulation of the modified SWAT model. Under intermittent irrigation, the watershed experiences a 6.58% reduction in net irrigation water use. In the scenario with irrigation district renovation, the water resources in the watershed are utilized more efficiently. The modified model from this study can be applied for assessing the synergistic effects of irrigation district water‐saving and yield‐increasing measures, providing crucial insights for the formulation of irrigation district water‐saving strategies and water resource optimization plans.

Evaluation of Mole Drainage and Nitrogen Fertilizer Management on Rapeseed Drain Water in Paddy Fields

Evaluation of Mole Drainage and Nitrogen Fertilizer Management on Rapeseed Drain Water in Paddy Fields

Comparison of ammonia volatilization in paddy and field soils fertilized with urea and ammonium sulfate during rice, potato, and Chinese cabbage cultivation

Ammonia in fertilizers used in agriculture is emitted into the atmosphere, which can be a precursor to the formation of fine dust that deteriorates air quality. This study investigated ammonia emissions from paddy and upland fields when urea (UR) and ammonium sulfate (AS) were used to grow rice, potato, and Chinese cabbage. Ammonia emissions from agricultural fields, water/soil properties, and meteorological data were monitored. In the paddy fields, the highest level of ammonia emissions was observed immediately after basal fertilization. However, this trend was not observed in the upland fields, where the application of a top dressing to moist soil led to an increase in ammonia emissions. In rice paddy fields and Chinese cabbage upland fields, higher ammonia emissions were observed under UR fertilization than under AS fertilization; whereas, no discrepancy was observed in the potato upland fields. A random forest model was used to determine the importance of environmental variables in ammonia emissions. The results indicated that UR application was the most significant factor affecting ammonia emissions, followed by the NH4+ concentration in ponding water in paddy fields. In upland fields, the soil water content was an important factor, and the temperature of ponding water influenced ammonia emissions. Most of the agronomic traits of rice and Chinese cabbage improved with increased amounts of fertilizer, whereas such a trend was not observed for potato. This study provides new insight into the environmental factors influencing ammonia emissions in agricultural settings. These findings serve as a foundation for the development of strategies and practices aimed at mitigating future ammonia emissions.

The water-exiting behavior and survival of predaceous diving beetles in responses to lambda-cyhalothrin, chlorantraniliprole, and thiamethoxam

Predaceous diving beetles (dytiscids) are important top insect predators in various natural, agricultural, and artificial water bodies. How they respond to human disturbances such as insecticide contamination to their habitats has been understudied. In this study, we investigated the lethal effects of lambda-cyhalothrin, chlorantraniliprole, and thiamethoxam at nominal field concentrations in 3 cm-deep water in a hypothetical paddy field (Ci,3) on adult Dytiscus sinensis Feng (Coleoptera: Dytiscidae). Lambda-cyhalothrin exhibited significant lethal effects on D. sinensis adults with its Ci,3 exceeding the 95 % confidence interval lower limits for 24, 48, 72, and 96 h- LC99. Chlorantraniliprole and thiamethoxam showed no significant lethal effects on D. sinensis adults at their respective Ci,3 at 24, 48, or 72 h. Additionally, we assessed the temporal propensity of D. sinensis adults to exit water contaminated with chlorantraniliprole and thiamethoxam, respectively. There were significantly more individuals that temporally exited the chlorantraniliprole-contaminated water than clean water 30 min after placing a tile island in the test arena. Meanwhile, thiamethoxam-contaminated water did not repel significantly more individuals than clean water when observed at 10, 30, or 60 min. The study highlights the availability and importance of selecting safer insecticides for dytiscid conservation in agricultural and adjacent habitats, considering the potential of these water bodies becoming ecological traps that keep attracting and killing aquatic beneficials. The water-exiting behavior found indicates the capability of some wildlife to effectively avoid further exposure to toxicants.

Water and Nitrogen Balance under Various Water and Fertilizer Regulation Modes

A experiment was conducted at the Jiangxi Province Center Station of Irrigation Experiment from 2019 to 2021 to study the water and nitrogen balance under water and fertilizer regulation modes. The study aimed to propose a recommended mode for paddy fields that could save water, control pollution, reduce gas emission, and improve fertilizer use efficiency. This study examined the impact of different irrigation methods and nitrogen application levels on water saving and emission reduction in paddy fields. The experiment included six treatments, which involved two irrigation methods (intermittent irrigation and flooding irrigation, referred to as W1 and W0, respectively) and three application rates of nitrogen fertilizer (0 kg/ha, 135 kg/ha, 180 kg/ha, referred to as N0, N1 and N2, respectively). The study found that irrigation methods had a significant effect on the amount of irrigation, drainage, leakage, nitrogen load from drainage, soil nitrification potential, and ammonia volatilization. The results showed that compared to flooding irrigation, intermittent irrigation reduced the amount of irrigation, drainage, leakage and nitrogen load from drainage by an average of 25.98%, 16.03%, 8.43% and 10.86%, respectively. However, the study also found that the nitrification potential and ammonia volatilization increased by an average of 6.45% and 4.32%, respectively. Fertilization levels had a significant effect on drainage nitrogen load, early soil nitrification potential and ammonia volatilization. Compared with the treatment of N2 (180 kg N/ha), the drainage nitrogen load under the treatment of N1 (135 kg N/ha) decreased by 10.86% on average, while nitrification potential and ammonia volatilization increased by 38.74% and 3.33%, respectively. In terms of nitrogen output, the amount of nitrogen absorbed by crops was the largest, followed by the nitrogen load from field drainage, then ammonia volatilization, and then denitrification. Considering the goals of water saving, emission reduction, and the efficient utilization of water and fertilizer in paddy fields, the optimal water and fertilizer regulation mode was the W1N1 mode (intermittent irrigation combined with reduced nitrogen fertilizer application rate, 135 kg N/ha).

Effects of dietary chito-oligosaccharide and β-glucan on the water quality and gut microbiota, intestinal morphology, immune response, and meat quality of Chinese soft-shell turtle (Pelodiscus sinensis).

Chito-oligosaccharides (COS) and β-glucan are gradually being applied in aquaculture as antioxidants and immunomodulators. However, this study examined the effects of dietary supplementation of COS and β-glucan on the water quality, gut microbiota, intestinal morphology, non-specific immunity, and meat quality of Chinese soft-shell turtle. To investigate the possible mechanisms, 3-year-old turtles were fed basal diet (CK group) and 0.1%, 0.5%, and 1% COS or β-glucan supplemented diet for 4 weeks. Colon, liver, blood and muscle tissues, colon contents, water and sediment of paddy field samples were collected and analyzed after feeding 2 and 4 weeks. The results indicated that COS and β-glucan altered microbial community composition and diversity in Chinese soft-shell turtles. The relative abundance of Cellulosilyticum, Helicobacter and Solibacillus were increased after feeding COS, while Romboutsia, Akkermansia and Paraclostridium were increased after feeding β-glucan, whereas Cetobacterium, Vibrio and Edwardsiella were enriched in the control group. Furthermore, colon morphology analysis revealed that COS and β-glucan improved the length and number of intestinal villi, and the effect of 0.5% β-glucan was more obvious. Both β-glucan and COS significantly improved liver and serum lysozyme activity and antibacterial capacity. COS significantly increased the total antioxidant capacity in the liver. Further, 0.1% β-glucan significantly increased the activity of hepatic alkaline phosphatase, which closely related to the bacteria involved in lipid metabolism. Moreover, dietary supplementation with 1% COS and 1% β-glucan significantly enhanced the content of total amino acids, especially umami amino acids, in muscle tissue, with β-glucan exerting a stronger effect than COS. Additionally, these two prebiotics promoted the quality of culture water in paddy fields and reshaped the bacterial community composition of aquaculture environment. All these phenotypic changes were closely associated with the gut microbes regulated by these two prebiotics. In summary, the findings suggest that dietary supplementation with COS and β-glucan in Pelodiscus sinensis could modulate the gut microbiota, improve intestinal morphology, enhance non-specific immunity and antioxidant capacity of liver and serum, increase meat quality, and improve the culture water environment. This study provides new insights and a comprehensive understanding of the positive effects of COS and β-glucan on Pelodiscus sinensis.

Existence of Lathyrus Beyond Lathyrism

Lathyrus (Lathyrus sativus) pulse is better known as the causative agent of a crippling neurological disorder called Lathyrism. Patients suffer from gradual progressive increasing spasticity and bony changes, which ultimately result in crippling stages throughout life. The present literature aimed to discover the L. sativus existence beyond Lathyrism. We searched the electronic databases of PubMed and Google Scholar using the keywords. We have taken reference to previously published literature on the Lathyrus and Lathyrism. In the current literature, we have found that Lathyrus is nutritionally rich and tolerant to different kinds of environmental stress, and it could be included in human meals or used to feed animals. In India, Lathyrus is banned due to its proposed neurotoxicity. However, the literature suggests that alone, Lathyrus cannot cause Lathyrism. Other factors like environmental factors such as availability of water in paddy fields, associated genetic disorders, and metal content of soil decide the amount of beta-N-oxalyl-amino-L-alanine and Oxalyl-diamino-propionic acid (ODAP) in Lathyrus seeds and its effects. There are new technologies and physical methods that can minimize the toxic nature of Lathyrus. A low ODAP containing Lathyrus is an economic cereal for poor people and grazing animals.

Models of Pb distribution and uptake in inundated paddy and maize cropping systems

<p>High-traffic highway crossing agricultural fields impacts the quality of food crops grown on Vertisol agricultural fields in Pasuruan. Lead (Pb) released from the exhaust of motor vehicles into the air can eventually enter the soil and be absorbed by plants. This study aimed to examine the effect of Pb from exhaust motor vehicles emission on the Pb status and its behavior in soil, water, and plants. The study was initiated by conducting a survey to determine the sampling locations in selected inundated paddy and maize cropping systems. A stratified random sampling method was used to collect soil, water, and plant samples. The soil of the study area is dominated by Vertisol, with clay content ranging from 54% to 76%. The soil attributes a high cation exchange capacity ranging from 80.53 meq 100 g<sup>-1</sup> to 93.57 meq 100 g<sup>-1</sup>. Pb emitted from 2,913,000 vehicles within four months period that entered the agricultural field was not absorbed by paddy and maize crops. Pb entered the soil in the adsorbed form, and no Pb was observed in the soluble form, so it was not absorbed by the roots. In the paddy field, the total Pb of 84.33% was influenced by pollutant distance. Likewise, in the maize field, 83.18% of total Pb was influenced by pollutant distance. The far the pollutant distance from the agricultural field, the lower its total Pb. Paddy field water is adsorbed onto the colloidal clay, which is dispersed due to inundation and sloughing of the paddy, moving with the clay and then dissolved in the water flow.</p>

Biochar-activated persulfate oxidation of arsenic(III): Nonnegligible roles of environmentally persistent free radicals

The water ecosystem and public health are often threatened by Arsenic (As). The primary type of As in paddy field and ground water is As(III), which is more toxic and mobile than As(V). In this research, biochar prepared from sewage sludge (SBC) through hydrothermal technique was used to activate persulfate (PS) to oxidate As(III), making it less toxic As(V). The developed SBC/PS system could oxidate As(III) effectively in the wide pH values (2−10). Excluding the influence of specific surface area and functional groups, the concentration of environmental persistent free radicals (EPFRs) had a good linear relationship with the oxidation of As(III), reaching above 0.96. According to a mechanism analysis, EPFRs on SBC could transfer electrons to directly activate PS to produce SO4−·, ·OH, O2−·, and 1O2 to improve the oxidation of As(III). These results not only indicated that the biochar/PS system’s application scope can be successfully increased by adjusting the preparation conditions, but also revealed the invaluable role of EPFRs in As(III) oxidation process.

Multi-objective decision-making for efficient utilization of water and fertilizer in paddy fields: A case study in Southern China

Effective water and fertilizer management modes (WFMMs) are crucial for mitigating non-point source pollution, enhancing grain quality, and improving resource utilization in paddy fields. Nevertheless, screening WFMMs that can effectively synergize these benefits is challenging, particularly in the wake of climate change. A two-year lysimeter experiment was conducted to investigate the effects of WFMMs on water balance components, nitrogen and phosphorus loss loads, grain yield and quality, and nitrogen utilization efficiency. Four treatments were established, including flooding irrigation (FI) and alternate wetting and drying irrigation (AWD), paired with conventional fertilizers (CF) and sulfur-coated fertilizer (SCF). A multi-criteria evaluation framework was developed to assess the potential values of WFMMs under diverse hydrological conditions using the vertical and horizontal scattering degree method. The results indicated that the AWD regime increased irrigation and drainage by approximately 8% compared to CF during the wet season, while reducing irrigation, percolation, and augmenting capillary rise during the dry season. Irrigation had not a significant effect on rice yield and quality. Compared to CF, AWD significantly increased nitrogen accumulation at maturity and nitrogen recovery efficiency by 20% and 31% on average. The SCF had a significant effect on the nitrogen accumulation at maturity, nitrogen recovery efficiency, N partial factor productivity, yield (increased 8–9% across two years), and protein content (increased ∼8% across two years), but at the cost of higher leachate concentration when compared to CF. Integration of AWD and SCF treatments demonstrates the potential for improved water productivity, yield, and nitrogen utilization efficiency, along with an enhanced ability to purify pollutants. The vertical and horizontal scattering degree method assessment showed that the AWD+SCF treatment exhibits superior performance in water saving, pollution reduction, yield and quality, and nitrogen efficient utilization, which was amplified during the dry season. These findings offer novel perspectives for optimizing WFMMs under varying hydrological conditions in hilly areas of Southern China.

Electric field-enabled aptasensing interfacial engineering to simultaneously enhance specific preconcentration and electrochemical detection of mercury and lead ions

Aptamers with strong affinity to heavy metal ions (HMIs) allow fabrication of electrochemical sensors with high selectivity and sensitivity, while controllable regulation of aptamer-HMI recognition at the sensing interface, which is vital for better analytical performance, remains challenging. Here, an electric field-based strategy for engineering an aptasensing interface was proposed to realize the specific preconcentration and accurate detection of mercury (Hg2+) and lead (Pb2+) ions with a ratiometric electrochemical sensor. The working principle is to apply an electric field to drive HMIs to approach the aptamer and retain the orientation of the DNA structure. Anthraquinone-2-carboxylic acid (AQ)-labeled complementary DNA was designed to simultaneously bind a ferrocene (Fc)-labeled aptamer for Hg2+ and a methylene blue (MB)-labeled aptamer for Pb2+, and the sensing interface was fabricated with this presynthesized DNA structure. For preconcentration, an electric field of 3.0 V pushed HMIs to approach the aptamer and retained the orientation of DNA to favor the following recognition; for detection, the oriented DNA in 2.5 V electric field offered a stable current of AQ as a reference. In this way, currents of AQ, Fc and MB were used to produce ratiometric signals of IAQ/IFc and IAQ/IMB for Hg2+ and Pb2+, respectively. Such a strategy allowed the simultaneous detection of Hg2+ and Pb2+ within 30 min with detection limits of 0.69 pM and 0.093 pM, respectively. The aptasensor was applied for soil, water, and crayfish analysis in paddy fields. The electric field-enabled strategy offers a new way to fabricate high-performance electrochemical aptasensor for HMIs detection.

Comparing the eddy covariance and gradient methods for measuring water and heat fluxes in paddy fields

Rice is distributed worldwide; thus, quantitative analyses of water and heat fluxes between the land and air in paddy fields are vital for understanding basin-scale water cycles. In this study, eddy covariance and meteorological gradient systems on a 20-meter flux tower in the Jianghan Plain, Yangtze River Basin, China, were used to measure turbulent and meteorological parameters in paddy fields in 2021. Three micrometeorological methods, namely the eddy covariance (EC), Bowen Ratio-Energy Balance (BREB), and aerodynamic (AERO) methods, were used to calculate the latent heat flux (LE) and sensible heat flux (H); BREB and AERO are collectively referred to as gradient methods. The effects of measurement heights, growth stage, and weather conditions on the consistency among them were analyzed. The difference in meteorological measurement heights affected the results of gradient methods. Among the five height combinations, the error in the 2 and 4 m combination was the smallest, and the coefficients of determination of LEEC–LEBREB/AERO and HEC–HBREB/AERO reached 0.96 and 0.84, respectively. The stratification of the near-surface layer was formed due to the heterogeneous underlying surface of the experimental area, and the instrument needed to be installed within the range between roughness layer and new equilibrium layer. The height difference of gradient methods can be amplified within this range to avoid the influence of instrument resolution. The difference among methods was affected by growth stage, and weather conditions (sunny, cloudy, rainy days and different wind speed class). Both factors influenced atmospheric stability, and the error was the maximum in neutral stratification. This study provides a reference for the selection of flux calculation methods and error analyses for paddy fields in humid areas.

Partisipasi Petani Terhadap Ketersediaan Sumberdaya Air Irigasi Aceh Besar

The participation of farmers who own irrigated paddy fields has an effect on the availability of water resources because the participation of farmers in managing irrigation water resources can help the availability of water in paddy fields even though the availability of water is limited. One of the factors causing the non-optimal distribution of water and the long distance between the water source and the irrigated paddy fields causes an uneven distribution of water in the paddy fields so that some farmers use water pumps to irrigate the paddy fields. The purpose of this study was to determine the level of participation of paddy farmers. irrigation on the availability of water resources in Blang Bintang District, Aceh Besar District. The data analysis model used is Likert scale analysis. The results showed that the average level of participation of irrigated rice farmers on the availability of water resources was in the medium category or 63.82%. This shows that involvement in each activity is only when entering the rice planting season. Based on the partial test (t test) shows that the variables of land area (X1), income (X2), motivation (X3) and experience (X4) partially have no significant effect on the participation of irrigated rice farmers in the availability of water resources in Blang Bintang District, Aceh BesarRegency

Analisis Sifat Fisika dan Kimia terhadap Kualitas Air Irigasi Pada Lahan Sawah di Desa Cisarua RT 01 RW 03 Bogor

Indonesia is very interested in the existence of water to support the agricultural sector by utilizing water for irrigation. The purpose of this study was to determine the physical and chemical properties of irrigation water quality in rice fields in Cisarua Village RT 01 RW 03 Bogor. The research method is a qualitative descriptive research where this method focuses on in-depth observations and focuses on facts in the field. Samples were taken at 6 irrigation water points on paddy fields. In each predetermined paddy field, water sampling is carried out for quality testing in physical properties (water temperature, color, TDS and odor) and chemically, namely the degree of acidity (pH). The results of the study from point 1 to point 6 of irrigation water in paddy fields successively from temperature tests were 28 °C, 27 °C, 27 °C, 28 °C and 27 °C. Test the color of the six points that are colorless. Test from all six odorless points. pH tests from point 1 to point 6 are 7.4, 7.2, 7.3, 7.3, 7.3, 7.2, 7.1, respectively. Furthermore, the total dissolve solid (TDS) test at points 1 to 6 respectively is 40 ppm, 42 ppm, 42 ppm, 32 ppm, 39 ppm, 23 ppm. So it can be concluded that the quality of irrigation water on paddy fields in Cisarua Village RT 01 RW 03 Bogor is in accordance with the standards of 492 / MENKES / PER / IV / 2010 and PP No. 82/2001.

Effects of Aeration on Surface Water Nutrient Dynamics and Greenhouse Gas Emission in Different Straw Returning Paddy Fields

Straw returning is of great significance for improving soil structure, soil fertility, crop yield, and quality. However, straw returning causes environmental problems such as increased methane emission and non-point source pollutant emission risk. How to reduce the negative effects of straw returning is an urgent problem to be solved.In this study, the effects of aerobic treatment on carbon and nitrogen concentration in surface water and greenhouse gas emissions in paddy fields with different treatments of straw returning were systematically compared.The results showed that different treatments of straw returning significantly increased chemical oxygen demand (COD) in the surface water of the paddy field and significantly promoted the methane emission of the rice field and the global warming potential (GWP), although it slightly reduced N2O emission. The increasing trends showed that wheat straw returning>rape straw>broad bean straw returning.Straw returning increased rice yield when compared with the control without straw returning, but the difference was not significant. Aerobic treatment reduced the COD in surface water by 15%-32%, the methane emission of the paddy field by 10.4%-24.8%, and the GWP of paddy field by 9.7%-24.4% under different straw returning treatments, without affecting the rice yield. The mitigation effect of aerobic treatment with wheat straw returning was the best. The results indicated the potential of oxygenation measures in greenhouse gas emission mitigation and COD emission risk reduction in straw returning paddy fields, especially in wheat straw returning paddy fields.

SDS-degrading Bacterium Isolated from a Paddy Field

A bacterium capable of degrading sodium dodecyl sulphate (SDS) isolated from a paddy field water is characterized. In this report, we showed that almost complete degradation of SDS was observed in 6 to 10 days when the bacterium was grown on medium supplemented with SDS ranging from 0.75 to 1.75 g/L while higher concentrations showed partial degradation with no degradation was observed at concentrations higher than 2.0 g/L. The SDS-degrading bacterium was partially identified and provisionally named Pseudomonas sp. strain Maninjau1. We also showed that the presence of metal ions such as silver, copper, cadmium, chromium, lead and mercury inhibit the ability of the bacterium to degrade SDS by 50%. Growth kinetic studies show a correlation coefficient value of 0.99 for the Haldane model indicates it fits the curve while a low correlation coefficient value of 0.67 for the Monod model indicates poor fitting. The specific growth rate μ was discovered to rise as the substrate concentration was increased but it reached a peak value followed by a slow decrease indicating substrate inhibition. The calculated qmax or maximum degradation rate was 0.917 h-1 (95% confidence interval or C.I. from 0.664 to 1.171) while the saturation constant Ks or half velocity constant was 0.178 g/L SDS (95% C.I. from 0.089 to 0.266). The inhibition constant Ki was 0.605 g/L SDS (95% C.I. from 0.358 to 0.941). The very high maximum degradation rate obtained in this study indicates that this bacterium can be an efficient agent for bioremediation of SDS especially in soils.

Temp-Spatial Heterogeneity of Water Recharge and Its Stable Mechanisms of the Mountainous Rice Terraces in East Asia Monsoon Region

The paddy field water recharge system and the mechanism of its stability are key scientific issues related to reducing the threat to global food security and enhancing the well-being of humans. In this study, we sampled the field water, precipitation, and groundwater in the Hani terrace areas and measured the values of hydrogen and oxygen stable isotopes. The results indicated that precipitation and groundwater were the main sources of terrace water recharge in the Hani terrace area. Spatially, the terrace areas were divided into rain-fed terraces, which were mainly recharged by precipitation, and spring-fed terraces, where groundwater was the primary source of recharge. Temporally, there were two different recharge periods: the rain-fed season (>70% recharge from precipitation) and the spring-fed season (>30% recharge from groundwater). The temporally alternating recharge periods of the spring-fed and rain-fed seasons and the interconnected spatial distribution of rain-fed and spring-fed types were essential to maintain stable water sources in the Hani terraces. Meanwhile, the spatial heterogeneity of groundwater recharge and the timing of agricultural cultivation adjusted the system to some extent. Rice cultivation will be sustainable if the changes in monsoonal precipitation due to global climate change align with the anthropogenic agricultural cultivation cycle, including land preparation, planting, growing, and harvesting. This is the key reason that the mountainous rice cultivation systems of the Hani terraces have lasted for thousands of years under the influence of the East Asian monsoon.

Modelling of paddy soil using the CFD-DEM coupling method

Soil dynamics has been the core of studying the mechanism of soil-tool interaction. However, it is very challenging to study the dynamics of paddy soil that contains a significant amount of water. In this study, a paddy soil model, namely coupling model was developed using the CFD-DEM coupling method. In the coupling model, spherical particles with Johnson-Kendall-Roberts (JKR) surface energy were used to represent paddy soil. The Volume of Fluid (VOF) gas-liquid two-phase flow model was used to represent the characteristics of the water in paddy field. A test and a simulation of soil rotation were performed to calibrate the critical model parameter of soil particle, JKR surface energy. The calibrated value was 2.5 J·m−2, and the relative average error between the simulation and the test was 1.27 %. To verify the accuracy of the coupling model, an experiment of a fertilizer banding opener was conducted in a paddy soil in laboratory conditions. Also, the interaction of the opener with paddy soil was simulated using the coupling model. Then, soil disturbance characteristics and the soil resistance force of the opener were compared between the experiment and model prediction. When using the coupling model to predict, the relative errors were less than 10 % for soil disturbance characteristics and less than 15 % for soil resistance force. This suggests that the model developed using the CFD-DEM coupling method is able to predict the dynamics of soil-tool interaction in paddy fields with reasonably good accuracies.