Silicon Fertilization Research Articles

Determine the Balance of Nitrogen, Potassium, and Silicon Fertilization for the Control of Rice Tungro Disease Using Response Surface Methodology

This study evaluates the efficacy of combined N, K, and Si treatments to find the balance of these three elements for tungro disease control and rice grain production. The study was conducted in a pot under a glasshouse. These elements were chosen as several findings have indicated the positive benefits of nitrogen (N), potassium (K), and silicon (Si) fertilization on plant development, yield, and biotic stress relief. The methods used were central composite design and response surface methodology. Complete and balanced nutrition has always been the first line of defense for plants due to the direct involvement of mineral elements in plant protection. The results showed that rice tungro disease could be controlled with 138:42:62:200 (N:P2O5:K2O:Si). A high rate of nitrogen is needed to reduce disease development. The results on N may explain that not all conditions of rice plants are at risk with high N rates. Adding Si fertilizer contributes to plant defense mechanisms and plays a role in yield formation. In contrast, the balance of fertilizer for maximizing grain yield per plant was found to be not dependent on nitrogen but needed either low K (62 kg K2O/ha) or high K (80 kg K2O/ha) but with moderate Si (150 kg Si/ha). Prioritizing tungro disease control and adopting the rate of N:K2O:Si (138:62:200), it was found that there was a yield reduction of an average of 7.7%.

Silica Accumulation in Potato (Solanum tuberosum L.) Plants and Implications for Potato Yield Performance-Results from Field Experiments in Northeast Germany.

The potato is the most important non-cereal food crop, and thus improving potato growth and yield is the focus of agricultural researchers and practitioners worldwide. Several studies reported beneficial effects of silicon (Si) fertilization on potato performance, although plant species from the family Solanaceae are generally considered to be non-Si-accumulating. We used results from two field experiments in the temperate zone to gain insight into silica accumulation in potato plants, as well as corresponding long-term potato yield performance. We found relatively low Si contents in potato leaves and roots (up to 0.08% and 0.3% in the dry mass, respectively) and negligible Si contents in potato tuber skin and tuber flesh for plants grown in soils with different concentrations of plant-available Si (field experiment 1). Moreover, potato yield was not correlated to plant-available Si concentrations in soils in the long term (1965-2015, field experiment 2). Based on our results, we ascribe the beneficial effects of Si fertilization on potato growth and yield performance reported in previous studies mainly to antifungal/osmotic effects of foliar-applied Si fertilizers and to changes in physicochemical soil properties (e.g., enhanced phosphorus availability and water-holding capacity) caused by soil-applied Si fertilizers.

Impact of Silicon Fertilization in Crop Production: Enhancing Yield, Stress and Disease Resistance in Agriculture

Silicon (Si) is a vital macroelement widely present in the environment, playing a crucial role in helping plants recover from environmental stresses. Its primary function is to boost the plant's resistance against biotic and abiotic stress. Furthermore, silicon can enhance soil quality by mitigating the toxicity of heavy metals like iron (Fe), aluminum (Al), and manganese (Mn), while also increasing phosphorus (P) availability. Additionally, it improves plants' tolerance to drought and salinity by promoting the formation of silicified tissues. It is also effective in managing a range of pests and diseases in plants, including those caused by fungi and bacteria. Silicon positively interacts with other applied nutrients, enhancing their effectiveness and improving agronomic performance, particularly in terms of yield. Thus, incorporating silicate-containing fertilizers into agricultural practices is essential for enhancing plant performance and productivity.

Combined Application of Biochar and Silicon Fertilizer for Improved Soil Properties and Maize Growth

Biochar can be a good soil amendment to reduce the soil pH, increase crop growth rate, and improve the efficient use of fertilizer. Other than that, silicon fertilizer also would promote photosynthetic ability on plant development that would help to produce high yield. In this work, a series of experiments was conducted to observe the effect of rice husk biochar and silicon fertilizer on the maize growth rate and soil pH. A 45-day pot experiment in the greenhouse with three replicates of 9 experimental treatment combinations of RHB at two rates (5 and 2.5 t.ha-1) with silicon fertilizer at three rates (125%, 100%, 75%), sole biochar (10 t.ha-1), sole silicon fertilizer (100%) and control (NPK) to observe the best rate and combination to improve growth rate and change in soil chemical in acid soil. The result showed that the co-application of sole biochar and biochar with Silicon significantly improved growth development, increased photosynthesis rate, altered soil pH, and reduced Fe concentration compared to control. The plant height increased 88.35% from T4 (5 t.ha-1 RHB + 100% Si) compared to the control and the conductance was higher in T4 (0.53) followed by T8 (0.438) while T1 (0.071) recorded the lowest conductance. The shoot fresh weight was higher in T4 (127.83 g) followed by T8 (57.14 g). However, the weight increased by 343.7% at T4 followed by T8 (2.5 t.ha-1 RHB + 75% Si) at 98.33%. The highest pH increment of 1.24 units (T1 = 5.53, T4 = 6.77) of soil pH was noted from T4 (5 t.ha-1 RHB + 100% Si) compared to control (NPK), and the highest total Fe in soil was observed from T1 (442.30 mg.kg-1). The current study results showed that T4 (50% RHB + 100% Silicon) was the best treatment over the other rates of RHB and silicon increased plant height, photosynthetic rate, and biomass.

Performance of coal slime-based silicon fertilizer in simulating lead-contaminated soil: Heavy metal solidification and multi-nutrient release characteristics

High-ash coal slime-based silica fertilizer (CSF) has the potential to provide mineral nutrients and passivate lead (Pb) in the soil to ensure the sustainable development of the coal industry and agriculture. This study investigated the performance and passivation mechanism of CSF, which contains potassium tobermorite and potassium silicate as the main components for soil improvement. Leaching experiments showed that low-crystalline muscovite was the only crystalline phase for CSF etching and that the silicon (Si), calcium (Ca), and potassium (K) in CSF had significant citric solubility. Soil cultivation and planting trials confirmed the ability of CSF to neutralize soil acidity, increase available soil Si and K, improve exchangeable Ca content, reduce the bioefficacy of Pb (exchangeable Pb by 19–75 % and carbonate-bound Pb by 6–18 %), and increase residual state Pb content. Compared to untreated Pb-contaminated soil, the 0.4 % CSF treatment reduced Pb in Chinese cabbage (Brassica rapa) by 25 % and increased plant biomass, Ca, and K by 37 %, 36 %, and 4 %, respectively. At the same time, soil pH increased by 0.58, and residual state Pb increased by 5 %. In CSF-treated soils, lead silicate is the dominant form of Pb present in the residual state. First-principle calculations showed that Pb3Si2O7 (cohesion energy −1.98 eV) formed by the passivation of Pb by CSF had greater stability in the soil compared to lead carbonate (PbCO3) (cohesion energy −1.38 eV) and lead sulfate (PbSO4) (cohesion energy −1.41 eV). This work shows the promising application of coal slime mineral fertilizers prepared using hydrothermal methods for soil improvement.

Silicon: A Powerful Aid for Medicinal and Aromatic Plants against Abiotic and Biotic Stresses for Sustainable Agriculture

Silicon plays a crucial role in enhancing plant tolerance to various abiotic and biotic stresses, including drought, salinity, heavy metals, and pathogen/pest attacks. Its application has shown promising results in improving stress tolerance and productivity in medicinal plants. This review synthesizes findings from numerous studies investigating the mechanisms by which silicon confers stress tolerance, including the regulation of antioxidant systems, water relations, nutrient homeostasis, phytohormone signaling, and stress-responsive gene expression. Additionally, it examines the effects of silicon supplementation on the production of valuable secondary metabolites and essential oils in medicinal plants. Silicon application can significantly mitigate stress-induced damage in plants, including medicinally important species such as borage, honeysuckle, licorice, Damask rose, savory, basil, and eucalyptus. The deposition of silicon in cell walls provides physical reinforcement and acts as a barrier against pathogen invasion and insect herbivory. Furthermore, silicon fertilization can enhance the production of valuable secondary metabolites in medicinal crops under stress conditions. The findings underscore the potential of silicon fertilization as a sustainable strategy for improving the productivity and quality of medicinal crops under changing environmental conditions, highlighting the need for further research to elucidate the molecular mechanisms underlying silicon-mediated stress tolerance and practical applications in medicinal plant cultivation.

Mitigating citrus fruit cracking: the efficacy of chelated calcium or silicon foliar fertilizers in 'Okitsu no. 58' citrus fruit.

The 'Okitsu No. 58' citrus variety is highly prone to fruit cracking, which jeopardizes yield and results in economic losses. In this study, we investigated the impacts of spraying 5 distinct concentrations (0.1, 0.2, 0.3, 0.4, and 0.5 g/L) of chelated calcium (Ca) or silicon (Si) fertilizers at the young fruit stage (60-90 days after flowering, DAF) on fruit cracking and quality in the citrus variety 'Okitsu No. 58'. The results showed either Ca or Si fertilizer treatments reduced fruit cracking. We found that all Ca and partial Si treatments (0.4 and 0.5 g/L) significantly promoted the accumulation of Ca content in the peel. Notably, Ca or Si treatments significantly reduced polygalacturonase (PG) activity and inhibited the production of water-soluble pectin (WSP) in the peel. Additionally, Ca or Si treatments elevated the superoxide dismutase (SOD) activity and decreased the malondialdehyde (MDA) content of the peels. Changes in these parameters likely contributed to strengthening the durability of peel cell wall constituents, thus enhancing the fruit's resistance to fruit cracking. Overall, except for the C3 (0.3 g/L of Ca), Ca or Si fertilizers contributed to fruit conventional quality, mainly in terms of higher soluble sugars (SS) and SS/TA (titratable acid). Therefore, our findings will provide a reference for the prevention and control of citrus fruit cracking and the development of new fertilizers.

Optimized silicon fertilization regime weakens cadmium translocation and increases its biotransformation in rice tissues

In acidic paddy fields of South China, rice (Oryza sativa L.) faces the dual challenges of cadmium (Cd) toxicity and silicon (Si) deficiency. Although previous studies have highlighted the functions of Si application timing and strategies in mitigating Cd-stressed rice, the precise mechanisms underlying the health restoration of Cd-toxic rice and the assurance of grain safety remain elusive. This study explored Cd translocation and detoxification in the shoots of rice regulated by various Si fertilization regimes: Si(T) (all Si added before transplanting), Si(J) (all Si added at jointing), and Si(TJ) (half Si added both before transplanting and at jointing). The findings revealed that the regime of Si(TJ) was more beneficial to rice health and grain safety than Si(T) and Si(J). The osmotic regulators such as proline, soluble sugars, and soluble proteins were significantly boosted by Si(TJ) compared to other Si treatments, and which enhanced membrane integrity, balanced intracellular pH, and increased Cd tolerance of rice. Furthermore, Si(TJ) was more effective than Si(T) and Si(J) on the Cd sequestration in the cell wall, Cd bio-passivation, and the down-regulated expression of the Cd transport genes. The concentrations of Cd in the xylem and phloem treated with Si(TJ) were reduced significantly. Additionally, Si(TJ) facilitated much more Cd bound with the outer layer proteins of grains, and promoted Cd chelation and complexation by phytic acid, phenolics, and flavonoids. Overall, Si (TJ) outperformed Si(T) and Si(J) in harmonizing the phycological processes, inhibiting Cd translocation, and enhancing Cd detoxification in rice plant. Thereby the split Si application strategy offers potential for reducing Cd toxicity in rice grain.

Silicon Fertilization Improves Sunflower Rhizosphere Microbial Community Structure and Reduces Parasitism by Orobanche cumana Wallr.

Sunflower broomrape (Orobanche cumana Wallr.) has severely restricted the development of the sunflower industry in China, and more efficient and convenient control methods are urgently needed. In this experiment, we investigated the effects of N, P and silica fertilizers on the parasitism rate of O. cumana, as well as on the yield of sunflower and native microbial communities in the field. Firstly, pot experiments were conducted to select the most effective fertilization method and to determine the physiological and biochemical indexes of sunflowers. Subsequently, field application studies were carried out to determine the physiological indexes, yield, O. cumana parasitism on sunflower, and the effect on the indigenous microbial community. The results demonstrate that compared with the CNP treatment (Control), the number of parasites under the N1P5 treatment significantly decreased by 66.15%. The exogenous application of silica can significantly reduce the number of O. cumana parasites. The treatments with N1P5 (N/P = 1:5) and available SiO2 content higher than 40 mg/kg (NS2, NS3, SF2 and SF3) significantly increased superoxide dismutase (SOD) activity and decreased malondialdehyde (MDA) content in sunflower leaves. In the field, fertilization significantly decreased the number of O. cumana parasites. The S treatment improved the native microbial community structure and enriched beneficial microorganisms, including Vicinamibacteria and Pyrinomonadaceae. Additionally, applying the S treatment significantly increased sunflower yield by 23.82% and crude protein content by 20.20%. In summary, the application of silicon fertilizer can effectively improve the host microbial community, reduce O. cumana parasitism and improve the yield and quality of sunflower.

Silicon drip fertigation improved sugar beet root and canopy growth and alleviated water deficit stress in arid areas

Crop growth is highly susceptible to drought stress due to water scarcity in arid areas. Silicon (Si) fertilizer could improve the tolerance of crops to drought stress, but the effect of drip fertigation of Si fertilizer on the growth and yield of sugar beets under drought stress is still unclear. In this field experiment conducted in 2022 and 2023 in the arid northwest China, the effects of different Si fertilizer application rates (0 kg ha−1 (Si0), 15 kg ha−1 (Si1), 38 kg ha−1 (Si2), 75 kg ha−1 (Si3)) on the growth, yield, and resource use efficiency of sugar beets (cultivars Beta356 (BT) and Strube13092 (ST)) under deficit irrigation (60 % of crop evapotranspiration (ETc), W2) were explored. The results showed that deficit irrigation (W2Si0) reduced the taproot and fibrous root growth, leaf net photosynthetic rate (Pn), leaf relative water content (LRWC), and leaf area index (LAI) of cultivar BT compared with full irrigation (100 % of ETc, W1). Under deficit irrigation, Si application (W2Si1, W2Si2, and W2Si3) alleviated the drought stress by increasing the number of fibrous roots in 17.5–70.0 cm soil layer and promoted the growth of taproots. Besides, it also increased the leaf moisture and photoassimilate production by increasing plant Si uptake, LRWC, LAI, and Pn. This finally increased the taproot yield (TY), irrigation water use efficiency (IWUE), and partial factor productivity of nitrogen (PFPN) by 11.2 % - 22.9 %, 6.5 % - 19.3 %, and 6.3 % - 19.3 %, respectively in cultivar BT and by 8.8 % - 27.1 %, 13.4 % - 30.8 %, and 13.4 % - 30.8 %, respectively in cultivar ST, compared with W2Si0. Regression analysis showed that the Si fertilizer application rate 64 kg ha−1 could maximize the TY of cultivar BT, but the net revenue (NR) was significantly lower than that of the W1 treatment. The Si fertilizer application rate 71 kg ha−1 could increase the TY of cultivar ST and achieve a NR similar to that of the W1 treatment. Therefore, in arid regions, Si application could alleviate the adverse effects of drought stress on drip-irrigated sugar beet root and shoot growth and improve yield, but the Si application rate varied with sugar beet cultivars.

CONTENT AND EXPORT OF N, P, K AND SI WITH MAIZE BIOMASS DEPENDING ON THE FERTILIZATION ON ALLUVIAL-MEADOW SOIL

The aim of the study in a pot experiment on Alluvial-meadow soil (Fluvisol, FAO) was to evaluate the effect of different rates and combinations of nitrogen, phosphorus, potassium and silicon fertilizers on the growth of maize (Zea mays L.) an early hybrid Р-8834 from group 310 FAO “Syngenta”. The experiment included 16 variants of fertilization in 3 replications. Data were obtained on the yield of fresh and absolutely dry biomass of maize plants and the content of N, P, K and Si in the dry biomass was assessed. It was found that the concentrations and the export of the studied macroelements with the biomass were significantly influenced by the fertilization applied. Nitrogen export was the highest in the N200, N300 and N400 rate treatments, and in comparison with the export of the other investigated elements. The export of N, P, K, and Si with maize dry biomass corresponded to a significant extent the contents of the macroelements in it. With increasing fertilization rates, not only the content, but also the export of nitrogen, phosphorus, and silicon increased. Regarding the potassium, this tendency was expressed to a less extent.

Study of the effects of silicon and sulphur foliar fertilization on yield components and yield in different winter oat cultivars

The aim of this work was to study the effect of sulphur and silicon foliar fertilisation treatment in different Hungarian-bred winter oat cultivars on the yield and the yield components, e.g. panicle ear-1 numbers per square meters, number of panicle nodes, number of spikelets per panicle, and thousand kernel weight (TKW) in the 2022–2023 growing season. The obtained results show that the applied fertilisers influenced the measured parameters, and we get the highest yield at the combined treatment – where silicon and sulphur was both applied –, and unexpectedly the lowest when only silicon was applied during the growing period. We measured the highest number of panicles m-2 at the sulphur treated experimental plots, and the lowest at the silicon treatment. We measured the average number of nodes of the panicle, and we can say that the sulphur fertilisation caused significantly higher values than any other treatment. Talking about the spikelet numbers, we get the highest value at the sulphur fertilisation, and the lowest at the control plots. However, our result wasn’t that prominent in the case of TKW, we get the highest weight at the silicon treatment, and the lowest at the sulphur fertilisation.

Improving the Yield and Quality of Tomato by Using Organic Fertilizer and Silicon Compared to Reducing Chemical Nitrogen Fertilization

Essential macronutrient nitrogen (N) is crucial for plant growth and yield, but excessive chemical N fertilizer not only increases unnecessary production costs but also causes environmental pollution. Therefore, reducing N fertilizer use by increasing organic fertilizer use is crucial for sustainable agriculture. In this study, we investigated the effects of three nitrogen levels—the recommended rate (N), a 20.0% reduced rate (0.8N), and a 40.0% reduced rate (0.6N)—and two levels of organic fertilizer—a normal dose (M) and a four-times the normal dose (4M)—combined with root application of the beneficial element silicon (Si) on the photosynthetic characteristics, yield, and fruit quality of the tomato cultivar ‘Tianxi No. 5’. Compared with M + N treatment, the longitudinal diameter, transverse diameter, fruit weight, and fruit yield of tomato fruit in 4M + 0.6N treatment significantly increased by 12.4%, 14.6%, 14.5%, and 12.8%, respectively, while the yield was further improved with Si application. In addition, a reduction in N fertilizer and an increase in organic fertilizer, combined with Si application, improved fruit quality parameters such as concentrations of vitamin C, lycopene, phenols, flavonoids, sucrose, fructose, etc., and promoted sugar metabolism-related enzyme activity (sucrose synthase, invertase, and sucrose phosphate synthase) and the accumulation of N in the fruit. The principal component analysis and three-factor analysis of variance (ANOVA) of the fruit quality and yield indices showed that nitrogen fertilizer, organic fertilizer, silicon fertilizer, and the interaction of the three had significant effects on the quality and yield of tomato fruits, and that the 4M + 0.6N + Si treatment had the best combined effect on the yield and quality of the tomatoes. Thus, a moderate reduction in chemical N fertilizer, combined with increased organic fertilizer and Si, could be an effective agronomic practice for improving the yield and quality of tomatoes.

The Beneficial Effects of Soluble Silicon Fertilizer in Dendrobium Orchids: Silicon-Augmented Resistance against Damage by Insect Pests and Fungal Pathogens.

The effects of soluble silicon fertilization on monocots and dicots have been widely studied. However, little is known regarding its effects on protecting epiphytes against insect and fungal pests. The efficacy of silicon fertilizer to reduce damage by thrips pest complexes, namely: Thrips palmi Karny, Frankliniella occidentalis Pergande, Chaetanaphothrips orchidii Moulton, and Chaetanaphothrips signipennis Bagnall (Thysanoptera: Thripidae), and the fungal pathogens: Botrytis cinerea Persoon (Helotiales: Sclerotiniaceae) and Fusarium spp. Link (Hypocreales: Nectriaceae) was examined during a nine-month greenhouse trial in Hawaii. The trial assessed yield, quality, and pest damage across three common varieties of dendrobiums. All replicates received additional soluble silicon fertilizer applications alternating weekly between soil drench and foliar (50 mg Si/plant) applications. Yield, quality, and spray length, pest damage, plant vigor, SPAD, and leaf temperature were measured. Data were analyzed using a generalized linear model (glm) with repeated measures followed by post-hoc pair-wise comparisons in R, version 4.3.1. Treatment effects were significant at p < 0.001 for the majority of the explanatory variables including: marketable yield, spray length, thrips damage, and fungal damage. Overall, the lavender variety ('Uniwai Supreme') benefited the most from silicon applications with a 73.0% increase in marketable yield, compared to the white variety ('Uniwai Mist'), which had an increase of 50.6% marketable sprays in contrast to its untreated control. Si benefits conferred to the purple variety ('Uniwai Royale') were intermediate to the lavender and white varieties. Although the magnitude of Si benefits varied among the varieties, all dendrobium varieties significantly benefited from silicon fertilization.

Silicon Improves Soil Environment and Promotes Crop Growth under Compound Irrigation via Brackish Water and Reclaimed Water

Not only is solving freshwater resource shortages effective but also an important measure for realizing the sustainable development of agriculture through the development and use of unconventional water resources. This pot experiment investigated the role of exogenous silicon in the risk of secondary soil salinization and the growth physiology of Lvxiu pakchoi cabbage under irrigation by using brackish water alone (BW), reclaimed water alone (RW), and compound irrigation with brackish water and reclaimed water at a ratio of 1:1, as well as the distribution of silicon in a soil–crop system. The results showed that with the extension of the spraying period of silicon fertilizer, the electrical conductivity (EC) decreased under 1:1 compound irrigation. The pH values in all treatments ranged from 7.95 to 8.10 without a potential risk of alkalization. Spraying silicon fertilizer had a positive effect on increasing the ratio of exchangeable potassium to sodium in soil. Spraying silicon fertilizer significantly reduced the percentage of exchangeable sodium (ESP) and the sodium adsorption ratio (SAR) in soils irrigated using BW, and increased the soil ESP and SAR under compound irrigation and RW irrigation, but these factors did not exceed the threshold of soil salinization. The proper application of silicon fertilizer had no significant effect on the total silicon content in the soil but increased the total silicon content in the plants to some extent. In addition, the yield was improved through proper silicon fertilizer application. In summary, exogenous silicon has positive effects on soil physical and chemical properties and crop growth, and relieves secondary salinization risk under compound irrigation via brackish water and reclaimed water.

Role of silicon and silicon fertilizers in the world: a review of papers from the Scopus database published in English for the period of 2012–2022

Role of silicon and silicon fertilizers in the world: a review of papers from the Scopus database published in English for the period of 2012–2022

Zinc and silicon fertilizers in conventional and nano‐forms: Mitigating salinity effects in maize (Zea mays L.)

AbstractBackgroundSalinity stress, an escalating concern in the realm of agriculture, significantly hampers crop productivity worldwide. In recent years, nano‐fertilizers have been identified as an innovative and promising avenue for improving nutrient use efficiency and mitigating salt stress in plants.AimsThis study delves into the comparative efficacy of nano‐fertilizers (Zn and Si) and their conventional sources in bolstering maize's resilience against salt stress.MethodsThe hydroponic experiment was conducted to test maize plants under salt stress along with Zn and Si nanoparticles (NPs) application. The analysis extends to their impacts on ionic homeostasis, specifically focusing on potassium and sodium concentrations, K/Na ratio, stomatal conductance, chlorophyll content, and the osmotic potential (OP) within the shoots and roots of maize.ResultsNanoparticles relatively helped plants better under stress, compared to their respective bulk mode of applications. Nano‐Zn treatment considerably boosts the K+ concentration and enhanced K/Na ratio, as a key physiological trait in salt‐resistant species, while nano‐Si demonstrates a prominent role in modulating OP and limiting Na+ accumulation along with higher Zn and Si accumulation in plants. The salt tolerance index confirmed the contribution of these ionic and osmotic adjustments in helping maize plant against salt stress.ConclusionsOur findings confirm that the application of nutrients as nano‐fertilizers, particularly nano‐Zn, enhanced K/Na ratio and improved nutrient availability and uptake of the plant. Si nanoparticles are also attributed to better osmotic adjustment and facilitating water movement, thus highlighting the potential of nano‐fertilizers in improving overall agricultural productivity and related environmental issues.

Silicon Fertilizer Addition Can Improve Rice Yield and Lodging Traits under Reduced Nitrogen and Increased Density Conditions

Reducing nitrogen fertilizer application, selecting a reasonable planting density, and adding silicon fertilizer can be used together to decrease excessive nitrogen fertilizer inputs in rice fields, reduce production costs, and ensure stable rice yield. However, the dynamics of the stem and internodes, as well as the changes in the physical and physiological characteristics of rice under a combination of these three strategies, are still unclear. In this study, we aimed to clarify these effects to improve the efficiency of rice production in northeastern China. A 2-year field experiment was conducted using five treatments: a conventional densification treatment (DM), a densification combined with reduced N input (−20%) treatment (DLM), and three densifications combined with reduced N input (−20%) and basal silicon fertilizer treatments (low fertilizer: DLMS1; medium fertilizer: DLMS2; and high fertilizer: DLMS3). This study revealed that the addition of silicon fertilizer improved rice yield compared to that under reduced nitrogen or increased density treatments alone, prevented excessive ineffective tillering after a density increase, and increased the number of productive panicles. Among the treatments, the DLMS3 treatment had the highest yields of 10.53 t/ha and 10.73 t/ha over the 2 years. Reducing nitrogen and increasing density reduced the weight and length of single panicles, while the addition of silicon fertilizer was beneficial for improving stem toughness, improving the physical and physiological characteristics of the plants and panicles, and enhancing plant bending resistance. Among the treatments, DLMS3 had the highest bending resistance, which increased by 440.1 g and 503.8 g compared to the lowest values in the DM treatment in 2020 and 2021, respectively. Nitrogen reduction resulted in the lowest lodging index values, with DLMS3 having the lowest values in both years, which decreased by 19.6% and 22.5% compared to the highest values in DM (2020) and DLM (2021), respectively. This study indicates that the application of 150.0 kg/ha silicon fertilizer in combination with reduced nitrogen and increased density (DLMS3) reduces the lodging index while ensuring rice yield, preventing a tradeoff between yield reduction and lodging due to a density increase or due to nitrogen reduction combined with a density increase and allowing for a reduction in nitrogen fertilizer input, which could ensure a uniform yield and an increase in lodging resistance. These results provide a scientific basis for rice cultivation measures that lead to high yield and lodging resistance while protecting the environment.

Long-term effects of compound passivator coupled with silicon fertilizer on the reduction of cadmium and arsenic accumulation in rice and health risk evaluation

Cadmium (Cd) and arsenic (As) are precedence-controlled contaminants in paddy soils, that can easily accumulate in rice grains. Limestone and sepiolite (LS) compound passivator can obviously reduce Cd uptake in rice, whereas Si fertilizer can effectively decrease rice As uptake. Here, the synergistic effects of the LS compound passivator coupled with Si fertilizer (LSCS) on the soil pH and availability of Si, Cd, and As, as well as rice grain Cd and As accumulation and its health risk were studied based on a 3-year consecutive field experiment. The results showed that the LSCS performed the best in terms of synchronously decreasing soil Cd and As availability and rice Cd and As uptake. In the LSCS treatments, soil pH gradually decreased with the rice-planting season, while soil available Cd and As contents gradually increased, suggesting that the influence of LSCS on Cd and As availability gradually weakened with rice cultivation. Nonetheless, the contents of Cd and inorganic As (i-As) in rice grains treated with LSCS were slightly affected by cultivation but were significantly lower than the single treatments of LS compound passivator or Si fertilizer. According to the Cd and As limit standards in food (GB2762-2022), the Cd and i-As content in rice grains can be lowered below the standard by using the 4500 kg/hm2 LS compound passivator coupled with 90 kg/hm2 Si fertilizer in soil and spraying 0.4 g/L Si fertilizer on rice leaves for at least three years. Furthermore, health risk evaluation revealed that LSCS treatments significantly reduced the estimated daily intake, annual excess lifetime cancer risk, and hazard quotient of Cd and i-As in rice grains. These findings suggest that LSCS could be a viable approach for reducing Cd and As accumulation in rice grains and lowering the potential health risks associated with rice.

Alleviating the adverse effects of Cd–Pb contamination through the application of silicon fertilizer: Enhancing soil microbial diversity and mitigating heavy metal contamination

The use of silicon fertilizer (SF) as a means of remediating cadmium (Cd) and lead (Pb) pollution has proven to be beneficial. However, the mechanism via which SF enhances soil quality and crop productivity under Cd- and Pb-contaminated soil (S) remains unclear. This study investigated the impacts of chemical fertilizer, mineral SF (MSF), and organic SF (OSF) on microbial community structure, activity of nutrient acquisition enzymes, and growth of tobacco in the presence of S condition. SF significantly reduced the contents of Cd and Pb in soil under S condition by 6.92–42.43% and increased plant height and leaf area by 15.27–81.77%. Moreover, the use of SF was observed to increase the efficiency of soil carbon and phosphorus cycling under S condition by 6.88–23.08%. Concurrently, SF was found to play a crucial role in facilitating the establishment of a complex, efficient, and interdependent molecular ecological network among soil microorganisms. In this context, Actinobacteriota, Bacteroidota, Ascomycota, and Basidiomycota were observed to be integral components of this network. SF was found to have a substantial positive impact on the metabolic functions and organismal systems of soil microorganisms. Moreover, the combined utilization of the Mantel test and partial least squares path model provided empirical evidence supporting the assertion that the administration of SF had a positive impact on both soil nutrient acquisition enzyme activity and tobacco growth, which was attributed to the enhancement of soil microbial diversity resulting from the application of SF. Furthermore, compared with MSF, OSF has advantages in reducing soil Pb and Cd content, promoting tobacco agronomic traits, increasing the number of key microbial communities, and maintaining the structural stability of microbial networks. The aforementioned findings, therefore, suggest that the OSF played a pivotal role in alleviating the adverse impacts of S, thereby demonstrating its efficacy in this particular process.