Search Results (1,083)

The co-incorporation of green manure and rice straw is commonly used to increase rice yield and improve soil fertility in paddy fields. However, the effects on nutrient uptake and utilization of rice under the synergistic interaction mechanism in the Taihu Plain of the Yangtze River Delta remain unclear. Based on field experiments, this study investigated the effects of green manure with rice straw return (GMS) under different nitrogen (N) fertilization rates on rice yield, nutrient use efficiency, and soil fertility. The results revealed that green manuring significantly increased rice yield while improving the uptakes and use efficiencies of N, phosphorus (P) and potassium (K). Green manure (GM) with 40% N fertilizer reduction (GM_N60) maintained the grain and straw yields and nutrient uptakes compared to winter fallow with 100% conventional N application (WF_N100). The N recovery efficiency in GM_N60 reached 45.52%, increasing by 41.26% compared to WF_N100. Rice yield and K uptake in the GMS with 40% N fertilizer reduction treatment (GMS_N60) was 10,058 and 15.41 kg/hm², increasing by 14.43% and 9.43% compared to winter fallow with rice straw return and 100% conventional N (WFS_N100). The N, P and K agronomic efficiencies in GMS_N60 increased by 77.04%, 50.22%, and 50.22% compared to WFS_N100, respectively. These findings indicate that rice straw return enhances the fertilizer-saving and yield-increasing effects of GM, promotes rice K uptake and improves P and K use efficiencies. The GM treatment increased the soil organic matter (SOM), total potassium (TK), ammonium nitrogen (NH₄⁺-N) and nitrate nitrogen (NO₃⁻-N) contents. Among the soil fertility indicators, TK and SOM were the most important factors influencing rice yield and N uptake. In conclusion, GMS can maintain or increase rice yield with 40% N fertilizer reduction, improve nutrient use efficiencies, and increase the reuse of rice straw, thereby supporting green and efficient rice production in the southern Jiangsu paddy area. Full article

This study aimed to reveal the characteristics of returned water in paddy fields at different scales and the rules of its reuse in China’s Ganfu Plain Irrigation District through multiscale (field, lateral canal, main canal, small watershed) observations, thereby optimizing water resource management and improving water use efficiency. Subsequent investigations during the 2021–2022 double-cropping rice seasons revealed that the tillering stage emerged as a critical drainage period, with 49.5% and 52.2% of total drainage occurring during this phase in early and late rice, respectively. Multiscale drainage heterogeneity displayed distinct patterns, with early rice following a “decrease-increase” trend while late rice exhibited “decrease-peak-decline” dynamics. Smaller scales (field and lateral canal) produced 37.1% higher drainage than larger scales (main canal and small watershed) during the reviving stage. In contrast, post-jointing-booting stages showed 103.6% higher drainage at larger scales. Return flow utilization peaked at the field-lateral canal scales, while dynamic regulation of Fangxi Lake’s storage capacity achieved 60% reuse efficiency at the watershed scale. We propose an integrated optimization strategy combining tillering-stage irrigation/drainage control, multiscale hydraulic interception (control gates and pond weirs), and dynamic watershed storage scheduling. This framework provides theoretical and practical insights for enhancing water use efficiency and mitigating non-point source pollution in plain irrigation districts. Full article

Non-point source (NPS) pollution from agriculture accounts for more than 20% of the total pollution load in the Republic of Korea, with the highest nutrient balance among OECD countries. Rice paddy fields are among the most important NPSs because of their large area, intensive fertilizer use, intensive use of irrigation water, and subsequent drainage. Therefore, the use of controlled drainage in paddy fields (Test) was evaluated for reduction in the discharged volumes and pollutant loads in drainage and stormwater runoff in comparison to plots using traditional drainages (Control). The results show that the loads were highly variable and that the reductions in the annual load of biochemical oxygen demand (BOD), suspended solid (SS), total nitrogen (T-N), total phosphorus (T-P), and total organic carbon (TOC) in the Test compared to that of the Control were 31.0 ± 28.9%, 83.5 ± 11.8%, 65.4 ± 12.2%, 69.1 ± 21.7%, and 64.9 ± 12.9%, respectively. It was shown that discharge in the post-harrowing and transplanting drainage (HD) was predominantly responsible for the total loads; therefore, the load reduction in HD was evaluated further at additional sites. The reduction at all studied sites was highly variable and as follows: 30.0 ± 33.6%, 70.9 ± 24.6%, 32.2 ± 45.5%, 45.7 ± 37.0%, and 27.0 ± 71.5%, for BOD, SS, T-N, T-P, and TOC, respectively. It was also demonstrated that controlled drainage contributed significantly to reducing the loads and volume of stormwater runoff from paddy fields. Correlations between paddy field conditions and multiple regression showed that the loads were significantly related to paddy water quality. The results of this study strongly suggest that controlled drainage is an excellent alternative for reducing the discharge of NPS pollutants from paddy fields. It is also suggested that the best discharge control would be achieved by combinations of various discharge mitigation alternatives, such as the management of irrigation, drainage, and fertilization, as well as drainage treatment, supported by more field tests, identification of the fates of pollutants, effects of rainfall, and climate changes. Full article

Cadmium (Cd) contamination in paddy soils severely threatens rice safety and human health. Currently, the high costs and technical barriers of existing Cd remediation methods limit their development, so it’s urgent to find an economical and feasible method. Herein, the synergistic effects of rhodochrosite slag and biochar on Cd immobilization in slightly acidic Cd-contaminated paddy soils have been investigated. A field experiment with four treatments—control (CK), rhodochrosite slag (R), biochar (B), and combined rhodochrosite slag + biochar (RB)—was conducted in Hunan Province, China. Results demonstrated that RB treatment significantly increased soil pH, transferred the mobile Cd to the residual fraction, and reduced Cd availability in the soil. Cd concentrations in rice roots, stems, leaves, and brown rice decreased by 26.37%, 47.20%, 31.03%, and 51.85%, respectively, under RB treatment, achieving the lowest TF and BCF values. Furthermore, RB treatment increased rice yield by 18.73%. The synergistic interaction between biochar’s adsorption capacity and rhodochrosite slag-derived competitive ions effectively transformed Cd into stable fractions, reducing bioavailability. This study proposes a novel remediation strategy that not only enhances the Cd immobilization ability of biochar but also achieves simultaneous waste valorization and soil remediation. Full article

During rice cultivation, extracting levees helps to delineate effective planting areas, thereby enhancing the precision of management zones. This approach is crucial for devising more efficient water field management strategies and has significant implications for water-saving irrigation and fertilizer optimization in rice production. The uneven distribution and lack of standardization of levees pose significant challenges for their accurate extraction. However, recent advancements in remote sensing and deep learning technologies have provided viable solutions. In this study, Youyi Farm in Shuangyashan City, Heilongjiang Province, was chosen as the experimental site. We developed the SCA-UNet model by optimizing the UNet algorithm and enhancing its network architecture through the integration of the Convolutional Block Attention Module (CBAM) and Squeeze-and-Excitation Networks (SE). The SCA-UNet model leverages the channel attention strengths of SE while incorporating CBAM to emphasize spatial information. Through a dual-attention collaborative mechanism, the model achieves a synergistic perception of the linear features and boundary information of levees, thereby significantly improving the accuracy of levee extraction. The experimental results demonstrate that the proposed SCA-UNet model and its additional modules offer substantial performance advantages. Our algorithm outperforms existing methods in both computational efficiency and precision. Significance analysis revealed that our method achieved overall accuracy (OA) and F1-score values of 88.4% and 90.6%, respectively. These results validate the efficacy of the multimodal dataset in addressing the issue of ambiguous levee boundaries. Additionally, ablation experiments using 10-fold cross-validation confirmed the effectiveness of the proposed SCA-UNet method. This approach provides a robust technical solution for levee extraction and has the potential to significantly advance precision agriculture. Full article

The denitrification process is the main process of the soil nitrogen (N) cycle in paddy fields, which leads to the production of large amounts of nitrous oxide (N₂O) and increases N loss in paddy soil. Plant-derived bio denitrification inhibitor procyanidins are thought to inhibit soil denitrification, thereby reducing N₂O emissions and soil N loss. However, the denitrification inhibition effect of procyanidins in paddy soils with high organic matter content remains unclear, and their high price is not conducive to practical application. Therefore, this study conducted a 21-day incubation experiment using low-cost proanthocyanidins (containing procyanidins) and paddy soil with high organic matter content in Northeast China to explore the effects of proanthocyanidins on N₂O emissions and related microorganisms in paddy soil. The results of the incubation experiment showed that the application of proanthocyanidins in paddy soil in Northeast China could promote the production of N₂O in the first three days but inhibited the production of N₂O thereafter. Throughout the incubation period, proanthocyanidins inhibited the enzyme nitrate reductase (NaR) activity and the abundance of nirS and nirk denitrifying bacteria, with a significant dose-response relationship. Although the application of proanthocyanidins also reduced the soil nitrate nitrogen (NO₃⁻-N) content, the soil NO₃⁻-N content increased significantly with increasing incubation time. In addition, the application of proanthocyanidins increased soil microbial respiration, ammonia-oxidizing archaea (AOA) amoA gene abundance, and soil ammonium nitrogen (NH₄⁺-N) content. Therefore, the application of proanthocyanidins to paddy soil in Northeast China can effectively regulate denitrification. However, in future studies, it is necessary to explore the impact of proanthocyanidins on the nitrification process and use them in combination with urease inhibitors and/or nitrification inhibitors to better regulate soil N transformation and reduce N₂O emissions in paddy soil. Full article

This study investigated the impact of the response mechanism of tillage construction on paddy yield in black soil fields by adopting four mechanical tillage techniques, namely, rotary tillage (RT), shallow plowing (SP), deep plowing (DP), and culvert pipe drainage (CD), to solve the problems associated with the reduction in the effective tillage layer in black soil paddy fields, as well as the poor quality and low yield of paddy rice. The results showed that SP, DP, and CD techniques were able to increase the rice yield and improve the effective tillage layer of the soil and the soil structure. Among them, DP had the most obvious effect, compared with traditional RT; the fast-acting N was 37.27 mg/kg higher in the 20–30 cm soil layer, and the soil solid phase decreased by 1.86–3.90% in the soil tripartite ratio. The soil bulk density of DP in the 10–20 cm soil layer decreased by 0.08 g/cm³, and, in the 20–30 cm soil layer, it decreased by 0.03 g/cm³. These physicochemical properties promoted the development and growth of roots and increased the growth of the root system by 6.53–16.33%, with the yield also increased by up to 9.81%. The CD technique could improve paddy field drainage and increase crop yields. This study combines four mechanical tillage techniques and proposes a mechanism of tillage construction from soil structure improvement to soil physicochemical property enhancement, and then to root system and yield enhancement. This mechanism may help to guide the implementation of mechanical tillage methods in paddy fields, which will provide important insights for future agricultural practices. Full article

Biogas slurry (BS), a nutrient-rich byproduct of anaerobic digestion, is increasingly utilized in agriculture to enhance soil fertility and crop productivity. However, the long-term effects of BS on soil microbial communities in paddy fields have not been thoroughly investigated. This study investigated the impacts of continuous BS irrigation over 0–3 years on soil microbial diversity, community composition, and their relationships with environmental factors in southeastern China. The results showed that bacterial diversity (Shannon index) significantly decreased from 6.96 (0 year) to 6.58 (3 years) (p < 0.05), while fungal diversity displayed a U-shaped trend, initially declining to 4.13 (1 year) and subsequently recovering to 4.86 (3 years) (p < 0.05). Dominant bacterial phyla such as Chloroflexi and Bacteroidetes increased in abundance under BS treatment, whereas Gemmatimonadetes decreased. Fungal communities shifted, with Mortierellomycota replacing Basidiomycota as the dominant phylum. Redundancy analysis (RDA) accounted for 91% and 74.9% of the variance in bacterial and fungal communities, respectively. Correlation analysis further indicated that soil available nitrogen and Cr were the primary drivers of bacterial community composition (p < 0.001), whereas soil available potassium and Cd were the key factors influencing the fungal community structure (p < 0.001). This study highlights that BS application alters microbial dynamics, favoring anaerobic bacteria and suppressing pathogenic fungi like Fusarium, thereby supporting sustainable soil management in rice cultivation systems. Full article

Earthworms are highly active in Southeast Asian paddy fields, yet their activity is challenging to measure in flooded soils. Therefore, this study investigates the influence of the subaquatic earthworm Glyphidrilus papillatus (Michaelsen, 1896) on soil properties and rice (Oryza sativa L.) physiology in Northern Vietnam, specifically focusing on rice cultivation at three distinct water levels: 5 cm above the soil surface (HIGH), at the soil level (ZERO), and 5 cm below the soil surface (LOW). Our findings indicate that water levels significantly affect earthworm activity, with the lowest activity observed at the shallowest water depth, as evidenced by reduced pore production in the soil and fewer casts on the surface. While earthworms are typically associated with enhanced soil fertility, this study did not confirm this relationship. Consequently, despite the substantial reorganization of soil structure, no significant interactions were found between earthworm presence and rice biomass, physiological parameters (such as leaf stomatal conductance to water vapor, chlorophyll content, and maximum quantum yield of PSII), or overall yield. In conclusion, this research highlights the critical role of the water level in influencing both earthworm activity and rice development. It underscores the necessity of considering additional ecological factors, such as carbon dynamics, greenhouse gas emissions, and plant resilience to environmental stressors. Full article

Biochar application and controlled irrigation (CI) enhance water conservation, lower emissions, and increase crop yields. However, the synergistic effects on the relationship between paddy soil microstructure and microbiome remain poorly understood. This study investigates the impact of different irrigation regimes and biochar applications on soil physicochemical properties, soil microstructure, and the composition and functions of soil microorganisms in paddy soil. The CA treatment (CI with 60 t/hm² biochar) showed higher abundances of Mycobacteriaceae, Streptomycetaceae, Comamonadaceae, and Nocardioidaceae than the CK treatment (CI without biochar), which was attributed to two main factors. First, CA increased the pore throat equivalent radius (EqR), throat surface area (SAR), total throat number (TTN), volume fraction (VF), and connected porosity (CP) by 1.47–9.61%, 7.50–25.21%, 41.55–45.99%, 61.12–73.04%, and 46.36–93.75%, respectively, thereby expanding microbial habitats and providing refuges for microorganisms. Second, CA increased the cation exchange capacity (CEC), mean weight diameter (MWD), soil organic carbon (SOC), and total nitrogen (TN) by 22.14–25.06%, 42.24–56.61%, 22.98–56.5%, and 9.41–87.83%, respectively, reinforcing soil structural stability and carbon storage, which promoted microbial community diversity. FK (flood irrigation without biochar) showed no significant correlations with these environmental factors. Compared to CK soil metabolites at Level 2 and Level 3, FK exhibited higher levels of the citrate cycle, indicating that changes in water and oxygen environments due to CI reduced soil organic matter decomposition and carbon cycle. CA and CK strongly correlated with the soil microstructure (VF, CP, TTN, SAR, EqR), and CA notably enhanced soil metabolites related to the synthesis and degradation of ketone bodies, suggesting that biochar can mitigate the adverse metabolomic effects of CI. These results indicate that biochar application in CI paddy fields highlights the critical role of soil microstructure in microbial composition and function and better supports soil sustainability. Full article

Alkaline fertilizers demonstrate significant potential in mitigating rice cadmium (Cd) accumulation, yet the combined effects of calcium–magnesium phosphate (CMP) with potassium (K) fertilizer types and split application strategies remain unclear. Through multi-site field trials in Cd-contaminated paddy soils, we evaluated split applications of K₂CO₃, K₂SO₄, and K₂SiO₃ at tillering and booting stages following basal CMP amendment. Optimized K regimes reduced brown rice Cd concentrations (up to 89% reduction) compared to conventional fertilization. Notably, at the CF site, split K₂SiO₃ application (TB-K₂SiO₃) and single tillering-stage K₂SO₄ (T-K₂SO₄) achieved brown rice Cd levels of 0.13 mg/kg, complying with China’s food safety standard (≤0.20 mg/kg), thereby eliminating non-carcinogenic risks. Mechanistically, TB-K₂SiO₃ enhanced soil pH by 0.21 units and increased available K (AK) by 50.26% and available Si (ASi) by 21.35% while reducing Cd bioavailability by 43.55% compared to non-split K₂SiO₃. In contrast, T-K₂SO₄ elevated sulfate-driven Cd immobilization. Structural equation modeling prioritized soil available Cd, root Cd, and antagonistic effects of AK and ASi as dominant factors governing Cd accumulation. The integration of CMP with split K₂SiO₃ application at the tillering and booting stages or single K₂SO₄ application at the tillering stage ensures safe rice production in Cd-contaminated soils, offering scalable remediation strategies for paddy ecosystems. Full article

Soil acidification is a significant threat to agricultural sustainability, particularly in paddy fields, where acidic conditions can limit crop productivity and soil health. This study aimed to explore the combined effects of alkaline amendments—lime, magnesia, and silicon fertilizer—on the acid-neutralizing capacity (ANC) of paddy soils and the rice yield, with the objective of identifying effective strategies to mitigate soil acidification and enhance agricultural productivity. From 2018 to 2021, a four-year field trial in Hunan tested lime, magnesia, and silicon fertilizers. Soil samples (0–20 cm depth) were collected once post-harvest in 2021 to evaluate the cumulative treatment effects. After four years, the control soil pH was 6.12. Lime and light magnesia treatment increased it to 6.70 and 6.99, respectively. Silicon fertilizer showed no significant difference (pH 6.05). ANC analysis revealed the following anti-acidification capacity ranking: light magnesia > lime > control > silicon fertilizer. Light magnesia boosted the rice yield by 13.02% over the control. Statistical analyses indicated a significant positive correlation between the soil acid-neutralizing capacity and pH (ANC4.0 = 7.53 × pH − 30.00, R²adj = 0.70; ANC5.0 = 6.96 × pH − 37.49, R²adj = 0.58). The rice yield was correlated with exchangeable magnesium (yield = 0.42 × Ex-Mg + 24.54, R²adj = 0.44). The continuous application of lime and light magnesia enhanced the nutrient availability and soil anti-acidification, with light magnesia also improving the rice yield. These findings provide insights to aid in enhancing soil quality and agricultural productivity in acid-affected regions. Full article

Flusulfinam is a 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide applied post-emergence (POST) to control Echinochloa crus-galli (L.) P.Beauv., Leptochloa chinensis (L.) Nees, Digitaria sanguinalis (Linn.) Scop. and other annual weeds in directly seeded and transplanted paddy fields in China, registered in September 2024. Notably, compared with other HPPD inhibitors in rice, flusulfinam exhibits consistently high safety in both japonica and indica rice varieties. Meanwhile, flusulfinam has no target-site cross-resistance with traditional acetolactate synthase (ALS)-inhibiting, acetyl-CoA carboxylase (ACCase)-inhibiting, and auxin herbicides. Moreover, as the only heterocyclic-amide-structured herbicide in the HPPD inhibitors, it poses a low risk of metabolic cross-resistance with the other HPPD inhibitors, making it a promising candidate for managing herbicide-resistant weeds in rice fields. In this study, the baseline sensitivity to flusulfinam of E. crus-galli and L. chinensis in paddy fields in China was established using dose–response assays between June and October 2023. Thirty-nine populations of E. crus-galli and forty-three populations of L. chinensis, collected from rice fields across various major rice-producing regions in China, exhibited susceptibility to flusulfinam. The GR₅₀ values ranged from 0.15 to 19.39 g active ingredient (a.i.) ha⁻¹ for E. crus-galli and from 7.82 to 49.92 g a.i. ha⁻¹ for L. chinensis, respectively, far below the field recommended rate of flusulfinam. Meanwhile, the GR₅₀ values of E. crus-galli and L. chinensis to flusulfinam were both distributed as a unimodal curve, with baseline sensitivity (GR₅₀b) of 6.48 g a.i. ha⁻¹ and 22.38 g a.i. ha⁻¹, respectively. The SI₅₀ value showed 129.27-fold and 6.38-fold variability in flusulfinam sensitivity among the 39 E. crus-galli field populations and 43 L. chinensis filed populations, while the variability declined to 2.99-fold and 2.23-fold when the SI₅₀b value was used. This study substantiated the efficacy of flusulfinam against E. crus-galli and L. chinensis in Chinese paddy fields and furnished a benchmark for monitoring temporal variations in the susceptibility of field populations of E. crus-galli and L. chinensis to flusulfinam. Full article

Accurate evapotranspiration (ET) monitoring is important for making scientific irrigation decisions. Unmanned aerial vehicle (UAV) remote sensing platforms allow for the flexible and efficient acquisition of field data, providing a valuable approach for large-scale ET monitoring. This study aims to enhance the accuracy and reliability of ET estimation in rice paddies through two synergistic approaches: (1) integrating the energy flux diurnal variations into the Two-Source Energy Balance (TSEB) model, which considers the canopy and soil temperature components separately, for physical estimation and (2) optimizing the flight altitudes and observation times for thermal infrared (TIR) data acquisition to enhance the data quality. The results indicated that the energy flux in rice paddies followed a single-peak diurnal pattern dominated by net radiation (Rn). The diurnal variation in the ratio of soil heat flux (G) to Rn could be well fitted by the cosine function with a max value and peak time (R² > 0.90). The optimal flight altitude and time (50 m and 11:00 am) for improved identification of temperature differentiation between treatments were further obtained through cross-comparison. These adaptations enabled the TSEB model to achieve a satisfactory accuracy in estimating energy flux compared to the single-source SEBAL model, with R² values of 0.8501 for Rn − G and 0.7503 for latent heat (LE), as well as reduced rRMSE values. In conclusion, this study presents a reliable method for paddy field scale ET estimation based on a calibrated TSEB model. Moreover, the integration of ground and UAV multimodal data highlights its potential for precise irrigation practices and sustainable water resource management. Full article

Rice direct seeding for bunch planting is a sustainable agricultural production method that reduces production costs, improves rice lodging resistance, and conserves irrigation water in the field. However, there are notable differences in seed treatment between direct seeding on dry land and in paddy fields, which can impact the seeding process’s accuracy. This study employs the numerical simulation methods of computational fluid dynamics (CFDs) and discrete element method (DEM) to examine the motion characteristics of dry and wet rice seeds in a fluid–solid coupled domain and their impact on seeding accuracy. The aim is to guide the optimization of the rice air-suction seed metering device. Rice seeds were divided into dry and wet groups, and their physical properties were measured. Discrete element models of rice seeds were constructed and calibrated using a polyhedral method. The results show that the static friction coefficient between the seed meter and the seed ranged from 0.902 to 0.950, and the thousand-grain weights ranged from 25.89 to 32.42 g, which were higher than those of the dry rice seed, which ranged from 0.774 to 0.839, and from 25.89 to 32.42 g. After calibration, the errors between the simulated dynamic stacking angles of HHZD, HYD, YLYD, HHZW, HYW, and YLYW and the physical–dynamic stacking angles were 0.12%, 0.13%, 0.75%, 0.62%, 0.08%, 0.75%, 0.59%, and 1.24%, respectively, which indicated that the discrete element model for rice was reliable. Additionally, a seeding accuracy test revealed that wet seeds of the same variety had higher missing and single indices, while dry seeds had higher triple and multiple indices. Furthermore, CFD-DEM simulations demonstrated that wet seeds’ normal and tangential forces were more significant than those on dry seeds during the seed-filling process. At 40 rpm, the normal and tangential forces during the seed-filling process of HYW are 37.69 × 10⁻³ N and 12.47 × 10⁻³ N, respectively, which are higher than those of HYD (25.18 × 10⁻³ N and 9.19 × 10⁻³ N). The action force of suctioned rice seeds was directly proportional to the missing and single indices. The primary factors contributing to the discrepancy in seeding accuracy between dry and wet rice are the thousand-grain weight, the static friction coefficient between the seed meter and the seed, and the action force exerted between the rice seeds. In addition, using a shaped hole structure and optimizing the seed chamber structure can reduce normal and tangential forces and improve seeding accuracy. This study provides a reference for the simulation of rice seed flow-solid coupling and optimization of air-suction seed metering devices. Full article