Search Results (23)

Soil passivation conditioners effectively reduce cadmium (Cd) bioavailability and limit its accumulation in rice, though their efficacy and stability vary considerably among different types. A three-year paddy field study in southern China evaluated a calcium–silicon–magnesium composite (CSM) applied at 1500 and 3000 kg/ha (CSM1 and CSM2), with a no-CSM control (CK), on Cd behavior, soil properties, and functional groups. Results demonstrated a clear dose–response relationship, with CSM reducing brown rice Cd by 35−74% across sites (2021−2023). High-dose treatments achieved grain safety standards (0.183 mg/kg, p < 0.05). Soil pH increased annually by 0.2−0.37 units, while DTPA-extractable Cd decreased by 2.6−27% over three years. CSM application significantly transformed Cd speciation, reducing exchangeable Cd by 3% while increasing the iron–manganese oxide-bound fraction by 5%. Soil base saturation increased from 42.6% to 73.2% (HS) and 71% to 97.3% (XY). FTIR analysis revealed enhanced silicate polymerization, increased hydroxyl group abundance, and Si-O-Mg/Fe vibrations indicating a significant increase in Cd complexation in treated soil. The CSM passivator immobilizes Cd by elevating soil pH to promote its transformation into stable Fe-Mn-bound forms, enhancing hydroxyl and siloxane complexation with Cd, and synergizing with silicon–calcium ionic antagonism, collectively reducing Cd bioavailability while improving soil fertility through base saturation regulation. Full article

Cadmium (Cd) pollution severely constrains safe rice production and threatens food security. Leveraging Fe–Zn competitive antagonism to mitigate crop Cd accumulation is a green, sustainable remediation strategy. Based on our hypothesis, we proposed that combined Fe–Zn pretreatment in seedlings and foliar spraying during the reproductive period would reduce Cd accumulation in brown rice by inhibiting root uptake, impeding translocation, and enhancing vacuolar sequestration in flag leaves. A two-year, three-season field experiment was conducted in the Cd-contaminated double-cropping rice planting area in Hunan Province. Three treatments were applied: conventional (CK), Fe–Zn pretreatment at seedling stage (FZ), and Fe–Zn pretreatment + tillering and heading spraying (FZS). This study demonstrated that FZS reduced brown rice Cd by 25%, primarily by enhancing root retention (root Cd reduced by 17–19%) and flag leaf vacuolar sequestration (flag leaf Cd 31% higher than old leaves). FZS further decreased stem–leaf Cd by 47–54% and lowered the husk-to-grain transfer coefficient from 0.22 to 0.17. Multivariate analysis identified flag leaf interception (β = −0.25) as the dominant factor regulating grain Cd, followed by panicle accumulation (β = 0.122) and Fe–Zn dosage (β = −0.061). Integrated Fe–Zn treatment blocked soil-to-grain Cd transfer via physiological barriers and flag leaf sequestration. 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

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

Rice is a vital component of the Ecuadorian diet and plays a significant role in global food security. Agricultural practices aimed at boosting production can, however, compromise grain quality. This study explores the effects of various pest control methods on the nutritional and biochemical quality of both white and brown rice. Compounds such as total phenolics (TPC), dietary fiber (TDF), gamma oryzanol, phytic acid (PA), antioxidant activity (AA), and the presence of heavy metals were analyzed. The research was carried out in Taura, Guayas Province, Ecuador, using a bifactorial experimental design with three replications. Statistical analysis included ANOVA and Tukey HDS tests (α = 0.05), complemented by PCA biplot analysis for comprehensive data exploration. The results highlight significant differences in all variables depending on the rice type (R), with brown rice exhibiting higher values. In terms of pest control type (C), only phytic acid showed significant variance, an effect also evident in the interaction (R × C). Cadmium (<0.30 mg/kg) and arsenic (<0.55 mg/kg) levels remained below national standards, with no significant differences across treatments. The biplot analysis revealed PA independence, with higher values in grains managed with biological control, whereas those under chemical control displayed slightly higher and varied values for other studied variables. Full article

Rice cultivated in cadmium (Cd)-polluted acidic paddy soil poses important health risks in China. Mitigating Cd accumulation in rice is of crucial importance for food safety and human health. In this study, using Chuangliangyou 669 as the ratoon rice variety, a field experiment was conducted in paddy fields with severe Cd pollution (Cd concentration > 1.0 mg kg⁻¹). The aim was to explore the impacts of different nitrogen (N) fertilizer levels (N1-180 kg hm⁻², N2-153 kg hm⁻², N3-126 kg hm⁻²) and planting densities (D1-20 cm × 20 cm, D2-16.7 cm × 16.7 cm) in the main crop on the yield and Cd accumulation characteristics of ratoon rice. The results showed that reducing the amount of N fertilizer would lead to a decrease in the yield of ratoon rice, while increasing the planting density could increase the yield, mainly by increasing the effective panicle. Among the various combined treatments, the yields of N1M2 and N2M2 were relatively high. The planting density had no significant impact on the Cd concentration, translocation factor and bioaccumulation factor of ratoon rice. The Cd concentration in various tissues of ratoon rice decreased significantly with the reduction in N fertilizer application. Reducing N fertilizer application could increase the pH, reduce the concentration of available Cd in the soil and consequently reduce the Cd bioaccumulation factor of various tissues of ratoon rice and the Cd translocation factor from roots and stems to brown rice. Considering both the yield and the Cd concentration in brown rice, N2M2 was the optimal treatment of reducing N and increasing density, which could maintain a relatively high yield while significantly reducing the Cd concentration. Full article

Cadmium (Cd) is a highly toxic metal that is difficult to completely eliminate from soil, despite advancements in modern agricultural and environmental technologies that have successfully reduced Cd levels. However, rice remains a key source of Cd exposure for humans. Even small amounts of Cd absorbed by rice can pose a potential health risk to the human body. Laser-induced breakdown spectroscopy (LIBS) has the advantages of simple sample preparation and fast analysis, which, combined with the transfer learning method, is expected to realize the real-time and rapid detection of low-level heavy metals in rice. In this work, 21 groups of naturally matured rice samples from potentially Cd-contaminated environments were collected. These samples were processed into rice husk, brown rice, and polished rice groups, and the reference Cd content was measured by ICP-MS. The XGBoost algorithm, known for its excellent performance in handling high-dimensional data and nonlinear relationships, was applied to construct both the XGBoost base model and the XGBoost-based transfer learning model to predict Cd content in brown rice and polished rice. By pre-training on rice husk source data, the XGBoost-based transfer learning model can learn from the abundant information available in rice husk to improve Cd quantification in rice grain. For brown rice, the XGBoost base model achieved R_C² of 0.9852 and R_P² of 0.8778, which were improved to 0.9885 and 0.9743, respectively, with the XGBoost-based transfer learning model. In the case of polished rice, the base model achieved R_C² of 0.9838 and R_P² of 0.8683, while the transfer learning model enhanced these to 0.9883 and 0.9699, respectively. The results indicate that the transfer learning method not only improves the detection capability for low Cd content in rice but also provides new insights for food safety detection. Full article

The technology for reducing cadmium (Cd) contamination in rice is being explored globally. In this study, the ratios of nitrogen fertilizers used were 5:5:0:0 (T1), 4:4:2:0 (T2), 6:0:2:2 (T3), and 3:2:2:3 (T4). The objective of the pot experiment was to understand how nitrogen management can reduce Cd accumulation in rice by influencing soil pH, the bioavailability of Cd concentrations in soil, Cd adsorption by iron membranes on rice roots, and the transport of mineral elements. The results indicated that nitrogen fertilizer application acidifies the soil and increases the bioavailable Cd concentration. A correlation analysis revealed a significant positive correlation between Cd concentration in the Fe plaque on rice roots and Cd concentration in the roots. Overall, the application of nitrogen fertilizers increased the concentrations of Cd and mineral elements in rice tissues, particularly in Cu, Mn, and Zn, but reduced the transfer of Cd between tissues. After nitrogen application, the concentrations of mineral elements in brown rice significantly increased, with negative correlations being observed between the Cu, Mn, and Zn concentrations and Cd concentration in brown rice. The brown rice with a nitrogen fertilizer proportion of 6:0:2:2 exhibited the lowest Cd concentration, showing significant reductions of 48.04% (X13H) and 43.46% (YZX) compared to the control treatment. These findings suggest that nitrogen management can enhance the coefficients of mineral element uptake in rice, compete against the transport of Cd to the grains, and that late-growth-stage nitrogen application can be more effective in reducing Cd concentration in brown rice. Full article

The ratoon rice planting area is gradually expanding, and decreasing Cadmium (Cd) accumulation in ratoon rice is important for food safety and human health. In this study, conventional indica rice (HHZ, Huanghuazhan), three-line indica–japonica hybrid rice (YY-4149, Yongyou 4149), and two-line indica hybrid rice (LY-121, Liangyou 121) were compared regarding ratoon rice yield and Cd uptake, transport, and accumulation. The distribution of Cd at different nodes in the ratoon crop was also examined. The rank-order of the Cd contents in each part (root, stem, leaf, stubble, and spike) of the main and ratoon crops of the tested cultivars was HHZ > LY-121 > YY-4149. The rank-order of the Cd content in each plant part at different nodes in the ratoon crop was HHZ > LY-121 > YY-4149. The Cd content in each plant part increased as the node position (i.e., according to the germination position of regenerated seedlings, the nodes are divided into the second, third, and fourth or fifth node from the top in stubble) was lowered. The redundancy analysis indicated that the low-node brown rice Cd content had the largest effect on the total brown rice Cd content in the ratoon crop. Accordingly, indica–japonica hybrid cultivars should be selected for the production of ratoon rice in mildly Cd-polluted areas, and the height of the main crop stubble should be maximized during harvest. Full article

At present, the mechanism of varietal differences in cadmium (Cd) accumulation in rice is not well understood. Two rice cultivars, ZZY (high translocation-high grain Cd) and SJ18 (low translocation-low grain Cd), were used to analyze transcriptome differences in the spike-neck tissue in field trials. The results showed that, compared with ZZY, 22,367 differentially expressed genes (DEGs) were identified in SJ18, including 2941 upregulated and 19,426 downregulated genes. GO analysis enriched 59 downregulated terms, concerning 24 terms enriched for more than 1000 DEGs, including cellular and metabolic processes, biological regulation, localization, catalytic activity, transporter activity, signaling, etc. KEGG enrichment identified 21 significant downregulated pathways, regarding the ribosome, metabolic pathways, biosynthesis of secondary metabolism, signaling transduction, cell membrane and cytoskeleton synthesis, genetic information transfer, amino acid synthesis, etc. Weighted gene co-expression network analysis (WGCNA) revealed that these DEGs could be clustered into five modules. Among them, the yellow module was significantly related to SJ18 with hub genes related to OsHMA and OsActin, whereas the brown module was significantly related to ZZY with hub genes related to mitogen-activated protein kinase (MAPK), CBS, and glutaredoxin. This suggests that different mechanisms are involved in the process of spike-neck–grain Cd translocation among varieties. This study provides new insights into the mechanisms underlying differences in Cd transport among rice varieties. Full article

Soil contamination by cadmium (Cd) has presented a major challenge in China. The objective of the field experiments in this study was to examine the influence of nitrogen fertilizer application at the full heading and milky stages on minimizing the absorption of Cd in rice. This was achieved by affecting the distribution of Cd in root plaques and subcellular compartments of the root and flag leaf. The hydroponic culture experiments aimed to examine the effect of nitrogen and Cd interaction or deficiency on Cd accumulation in rice during the late growth stage. The findings revealed that adequate nitrogen supply during the early growth stage, coupled with nitrogen application during the full heading and milky stages, led to a notable increase in Fe concentration in the root plaques during the milk and mature stages. Furthermore, it elevated the Cd proportion in the soluble fraction of the flag leaves at the milky stage. Conversely, nitrogen deficiency during the early growth stage resulted in a significant increase in Fe concentration in the root plaques, along with a decrease in Cd concentration. Additionally, the proportion of Cd in the flag leaf cell walls increased significantly, while the proportion in the soluble fraction decreased notably. Irrespective of nitrogen supply during the early growth stage, applying nitrogen at the full heading stage significantly reduced Cd transport from shoots to brown rice, leading to a considerable reduction in the Cd concentration in brown rice. Under hydroponic culture conditions, combined Cd exposure with nitrogen supply significantly increased the Cd concentration in brown rice. Nitrogen supply had no impact on the Cd concentration in brown rice in the absence of Cd. The study showed that applying nitrogen fertilizer at the full heading stage effectively decreased the brown rice Cd concentration. This was achieved by elevating the concentration of Fe in the root plaque, thereby influencing the adsorption of Cd by the roots. Additionally, nitrogen application at the full heading stage can influence the distribution of Cd in flag leaf cells during the filling stage. Ensuring ample nitrogen supply in the early stage of rice growth is crucial, and nitrogen application at the full heading stage can effectively reduce the Cd concentration in brown rice. Full article

Water management and soil conditions affect the bioavailability of cadmium (Cd) and inorganic arsenic (As) in the soil, and hence, their accumulation in rice grains. A field experiment was conducted to investigate the effects of two water management regimes (flooding and dry–wet alternation) on Cd and inorganic As uptake and transport in rice under different soil conditions (paddy soil developed from gray-brown alluvium, K1; paddy soil developed from weathered shale and slate, K2) in the Sichuan Basin, Western China. The results indicated that compared to the wet–dry rotation, long-term flooding led to a substantial decrease of 49.3~55.8% in soil-available Cd content (p < 0.05), accompanied by a significant increase of 16.0~74.2% in As(Ⅲ) content (p < 0.05), causing no significant difference in As(V) content at the K1 site (p > 0.05). However, differences in soil-available Cd and inorganic As content under different water management treatments were both insignificant at the K2 site (p > 0.05). Long-term flooding treatment at the K1 site resulted in a remarkable reduction of 90.2% in Cd content in rice husks and 92.2% in brown rice (p < 0.05), along with a significant increase of 263.6% and 153.3%, respectively, in As(Ⅲ) content; no significant differences in As(V) content were observed at the K2 site (p > 0.05). In conclusion, the effect of water management on rice Cd and inorganic As varied under different soil conditions, with the change in rice Cd and inorganic As in paddy soil developed from gray-brown alluvium being significantly greater than that in paddy soil developed from weathered shale and slate. Full article

Cadmium (Cd), a highly toxic heavy metal for crops in China, poses a significant threat to rice cultivation. It is crucial to identify the genotypes with robust resistance to heavy metals, including Cd, in rice. The experiment was conducted to examine the mitigation effect of silicon (Si) on Cd toxicity levels in Se-enriched Z3055B and non-Se-enriched G46B rice genotypes. A basal dose of Si improved the growth and the quality of rice significantly by reducing the Cd content in rice roots, stems, leaves and grains and increased the yield, biomass and selenium (Se) content of brown rice in both genotypes. Additionally, Se content in brown rice and polished rice was notably higher in Se-enriched rice than in non-Se-enriched rice, with the highest amount at 0.129 mg/kg and 0.085 mg/kg, respectively. The results demonstrated that a basal fertilizer concentration of 30 mg/kg of Si was more effective in reducing Cd transport from roots to shoots in Se-enriched rice than in non-Se-enriched rice genotypes. Therefore, it can be concluded that Se-enriched rice genotypes are a viable option for food crop production in Cd-contaminated areas. Full article

To study the synergistic effects of water management and silicon (Si) foliar spraying on the uptake and transport of cadmium (Cd) in rice, we designed four treatments: conventional intermittent flooding + no Si foliar spraying (CK), continuous flooding throughout the growth stage + no Si foliar spraying (W), conventional intermittent flooding + Si foliar spraying (Si) and continuous flooding throughout the growth stage + Si foliar spraying (WSi). The results show that WSi treatment reduced the uptake and translocation of Cd by rice and significantly reduced the brown rice Cd content, with no effect on rice yield. Compared with CK, the Si treatment increased the net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) of rice by 6.5–9.4%, 10.0–16.6% and 2.1–16.8%, respectively. The W treatment decreased these parameters by 20.5–27.9%, 8.6–26.8% and 13.3–23.3%, respectively, and the WSi treatment decreased them by 13.1–21.2%, 3.7–22.3% and 2.2–13.7%, respectively. The superoxide dismutase (SOD) and peroxidase (POD) activity decreased by 6.7–20.6% and 6.5–9.5%, respectively, following the W treatment. Following the Si treatment, SOD and POD activity increased by 10.2–41.1% and 9.3–25.1%, respectively, and following the WSi treatment, they increased by 6.5–18.1% and 2.6–22.4%, respectively. Si foliar spraying ameliorated the detrimental effects of continuous flooding throughout the growth stage on photosynthesis and antioxidant enzyme activity. We conclude that synergistic continuous flooding throughout the growth stage, combined with Si foliar spraying, can significantly block Cd uptake and translocation and is therefore an effective means of reducing the accumulation of Cd in brown rice. Full article

Humic acid amendments in the remediation of soils contaminated with heavy metals have received widespread attention. However, the impacts and related mechanisms of mineral-based humate substances on the remediation of alkaline paddy soils with different levels of cadmium (Cd) contamination are still unclear. Pot trials with four mineral-based potassium humate (MBPH) doses (0, 0.25%, 0.5%, 1%, w/w) and three Cd rates (slightly, moderately, and highly, 1, 2, and 4 mg Cd kg⁻¹) were conducted to evaluate the effects of MBPH on rice. Results showed that the application of MBPH effectively reduced brown rice Cd concentrations of all Cd rates by 46.82–65.04%, 44.02–59.21%, and 15.84–43.99%, such that Cd in brown rice fell within the safe edible standards in the highly contaminated soils with the 0.5% and 1% MBPH applications. The application of MBPH significantly alleviated Cd toxicity by increasing soil solution pH, dissolved organic carbon (DOC), and potassium (K) and decreasing free Cd and the bioavailability of rhizosphere soil Cd, as reflected by promoting rice plant growth, photosynthesis, F_v/F_m, and antioxidant enzymes activities. Additionally, high dose applications (0.5% and 1%) of MBPH significantly reduced the translocation factor of Cd from flag leaf to brown rice. Furthermore, the application of MBPH enhanced the accumulation of mineral elements (iron, manganese, copper, zinc, potassium) in brown rice. Stepwise regression analysis revealed that soil solution K at maturity stage and soil solution DOC at tillering and filling stages were the most important factors affecting Cd accumulation in brown rice under slightly, moderately, and highly Cd-contaminated soils, respectively. Therefore, MBPH application on slightly and moderately Cd-contaminated alkaline soils contributed to achieving rice grains rich with mineral elements but Cd free and Cd safe in highly Cd-contaminated soil. Full article