Potential of amino acids-modified biochar in mitigating the soil Cu and Ni stresses - Targeting the tomato growth, physiology and fruit quality.

Trace heavy metals (HMs) such as copper (Cu) and nickel (Ni) are toxic to plants, especially tomato at high levels. In this study, biochar (BC) was treated with amino acids (AA) to enhance amino functional groups, which effectively alleviated the adverse effects of heavy metals (HMs) on tomato growth. Hence, this study aimed to evaluate the effect of glycine and alanine modified BC (GBC/ABC) on various tomato growth parameters, its physiology, fruit yield and Cu/Ni uptake under Cu and Ni stresses. In a pot experiment, there was 21 treatments with three replications having two rates of simple BC and glycine/alanine enriched BC (0.5% and 1% (w/w). Cu and Ni stresses were added at 150 mg kg-1 respectively. Plants were harvested after 120 days of sowing and subjected to various analysis. Under Cu and Ni stresses, tomato roots accumulated more Cu and Ni than shoots and fruits, while GBC and ABC application significantly enhanced the root and shoot dry weight irrelevant to the stress conditions. Both rates of GBC decreased the malondialdehyde and hydrogen peroxide levels in plants. The addition of 0.5% GBC with Cu enhanced the tomato fruit dry weight by 1.3 folds in comparison to the control treatment; while tomato fruit juice content also increased (50%) in the presence of 0.5% GBC with Ni as compared to control. In summary, these results demonstrated that lower rate of GBC∼0.5% proved to be the best in mitigating the Cu and Ni stress on tomato plant growth by enhancing the fruit production.

Silicon-nanoparticles loaded biochar for soil arsenic immobilization and alleviation of phytotoxicity in barley: Implications for human health risk.

Arsenic (As)-induced environmental pollution and associated health risks are recognized on a global level. Here the impact of cotton shells derived biochar (BC) and silicon-nanoparticles loaded biochar (nano-Si-BC) was explored on soil As immobilization and its phytotoxicity in barley plants in a greenhouse study. The barley plants were grown in a sandy loam soil with varying concentrations of BC and nano-Si-BC (0, 1, and 2%), along with different levels of As (0, 5, 10, and 20 mg kg-1). The FTIR spectroscopy, SEM-EDX, and XRD were used to characterize BC and nano-Si-BC. Results revealed that As treatment had a negative impact on barley plant development, grain yield, physiology, and anti-oxidative response. However, the addition of nano-Si-BC led to a 71% reduction in shoot As concentration compared to the control with 20 mg kg-1 of As, while BC alone resulted in a 51% decline. Furthermore, the 2% nano-Si-BC increased grain yield by 94% compared to control and 28% compared to BC. The addition of 2% nano-Si-BC to As-contaminated soil reduced oxidative stress (34% H2O2 and 48% MDA content) and enhanced plant As tolerance (92% peroxidase and 46% Ascorbate peroxidase activity). The chlorophyll concentration in barley plants decreased due to oxidative stress. Additionally, the incorporation of 2% nano-Si-BC resulted in a 76% reduction in water soluble and NaHCO3 extractable As. It is concluded that the use of BC or nano-Si-BC in As contaminated soil for barley resulted in a low human health risk (HQ < 1), as it effectively immobilized As and promoted higher activity of antioxidants.

Adsorption of trace heavy metals through organic compounds enriched biochar using isotherm adsorption and kinetic models.

Trace heavy metals such as copper and nickel, when exceeds a certain level, cause detrimental effects on the ecosystem. The current study examined the potential of organic compounds enriched rice husk biochar (OCEB's) to remove the trace heavy metals from an aqueous solution in four steps. In 1st step, biochar' physical and chemical properties were analyzed through scanning electron microscope (SEM) and Fourier transforms infrared spectroscopy (FTIR). In the 2nd step, two biochar vis-a-vis glycine, alanine enriched biochar (GBC, ABC) was selected based on their adsorption capacity of four different metals Cr, Cu, Ni and Pb (chromium, copper, nickel, and lead). These two adsorbents (GBC, ABC) were further used to evaluate the best interaction of biochar for metal immobilization based on varying concentrations and times. Langmuir isotherm model suggested that the adsorption of Ni and Cu on the adsorbent surface supported the monolayer sorption. The qmax value of GBC for Cu removal increased by 90% compared to SBC (Simple rice husk biochar). The interaction of Cu and Ni with GBC and ABC was chemical, and 10 different time intervals were studied using pseud first and second-order kinetics models. The current study has supported the pseudo second-order kinetic model, which exhibited that the sorption of Ni and Cu occurred due to the chemical processes. The % removal efficiency with GBC was enhanced by 21% and 30% for Cu and Ni, respectively compared to the SBC. It was also noticed that GBC was 21% more efficient for % removal efficiency than the CBC. The study's findings supported that organic compound enriched rice husk biochar (GBC and ABC) is better than SBC for immobilizing the trace heavy metals from an aqueous solution.

Alleviation of chromium toxicity in mung bean (Vigna radiata L.) using salicylic acid and Azospirillum brasilense.

BACKGROUND: Chromium (Cr) contamination in soil poses a serious hazard because it hinders plant growth, which eventually reduces crop yield and raises the possibility of a food shortage. Cr's harmful effects interfere with crucial plant functions like photosynthesis and respiration, reducing energy output, causing oxidative stress, and interfering with nutrient intake. In this study, the negative effects of Cr on mung beans are examined, as well as investigate the effectiveness of Azospirillum brasilense and salicylic acid in reducing Cr-induced stress. RESULTS: We investigated how different Cr levels (200, 300, and 400 mg/kg soil) affected the growth of mung bean seedlings with the use of Azospirillum brasilense and salicylic acid. Experiment was conducted with randomized complete block design with 13 treatments having three replications. Significant growth retardation was caused by Cr, as were important factors like shoot and root length, plant height, dry weight, and chlorophyll content significantly reduced. 37.15% plant height, 71.85% root length, 57.09% chlorophyll contents, 82.34% crop growth rate was decreased when Cr toxicity was @ 50 µM but this decrease was remain 27.80%, 44.70%, 38.97% and 63.42%, respectively when applied A. brasilense and Salicylic acid in combine form. Use of Azospirillum brasilense and salicylic acid significantly increased mung bean seedling growth (49%) and contributed to reducing the toxic effect of Cr stress (34% and 14% in plant height, respectively) due to their beneficial properties in promoting plant growth. CONCLUSIONS: Mung bean seedlings are severely damaged by Cr contamination, which limits their growth and physiological characteristics. Using Azospirillum brasilense and salicylic acid together appears to be a viable way to combat stress brought on by Cr and promote general plant growth. Greater nutrient intake, increased antioxidant enzyme activity, and greater root growth are examples of synergistic effects. This strategy has the ability to reduce oxidative stress brought on by chromium, enhancing plant resistance to adverse circumstances. The study offers new perspectives on sustainable practices that hold potential for increasing agricultural output and guaranteeing food security.

Microplastics: a review of their impacts on different life forms and their removal methods.

The pollution of microplastics (MPs) is a worldwide major concern, as they have become a major part of our food chain. MPs enter our ecosystem via different pathways, including anthropogenic activities and improper disposal of plastics. The aim of this article is to review the current scientific literature related to MPs and how they affect different life forms on earth. Briefly, MPs induced negative effects on humans are primarily linked with the oxidative stress and disruption in immunity. MPs not only affect the soil chemical and physical properties such as reduction in soil health and productivity but also impose harmful effects on soil microorganisms. Moreover, MP-induced plant growth reduction results from three complementary mechanisms: (i) reduction in root and shoot growth, (ii) reduction in photosynthesis accompanied by higher reactive oxygen species (ROS) production, and (iii) reduction in nutrient uptake via altered root growth. Given the negative effects of MPs on different life forms, it is important to remove or remediate them. We have discussed different MP removal methods including coagulation, membrane filtration technology, biochar, and biological degradation of MPs in soil and wastewater effluents. The use of ozone as ultrafiltration technique has also been shown as the most promising technique for MP removal. Finally, some future research recommendations are also put forward at the end to further enhance our understanding of the MPs induced negative effects on different life forms. The flowchart shows the interaction of MPs from water contaminated with MPs with different parts of the ecosystem and final interaction with human health.

Trichoderma asperellum L. Coupled the Effects of Biochar to Enhance the Growth and Physiology of Contrasting Maize Cultivars under Copper and Nickel Stresses.

Crop cultivation in heavy metal (HM)-polluted soils is a routine practice in developing countries that causes multiple human health consequences. Hence, two independent studies have been performed to investigate the efficiency of rice husk biochar (BC) and three fungal species, Trichoderma harzianum (F1), Trichoderma asperellum (F2) and Trichoderma viride (F3), to improve the growth and physiology of Zea mays L. plants grown on soil contaminated with Cu and Ni. Initially, a biosorption trial was conducted to test the HM removal efficiency of species F1, F2 and F3. Among them, F2 sp. showed the maximum Cu and Ni removal efficiency. Then, a pot study was conducted with two cultivars (spring corn and footer corn) having eleven treatments with three replicates. The results demonstrated a significant genotypic variation among both cultivars under applied HM stress. The maximum decreases in leaf Chl a. (53%), Chl b. (84%) and protein (63%) were reported in footer corn with applied Cu stress. The combined application of biochar and F2 increased leaf CAT (96%) in spring corn relative to Cu stress. Altogether, it was found that BC + F2 treatment showed the maximum efficiency in combatting Cu and Ni stress in spring corn.

Investigating the role of bentonite clay with different soil amendments to minimize the bioaccumulation of heavy metals in Solanum melongena L. under the irrigation of tannery wastewater.

Wastewater from tanneries is a major source of heavy metals in soil and plants when used for crop irrigation. The unavoidable toxicological effects of this contamination, however, can be minimized through two independent steps discussed in the present study. In the first step, a batch sorption experiment was conducted in which Cr was adsorbed through bentonite clay. For this purpose, DTPA extraction method was used to analyze Cr concentration in the soil after regular time intervals (0.5, 1, 2, 6, 8, 9, 10.5, 11.5, and 20.3 h) which reduced Cr concentration from 38.542 mgL-1 for 30 min to 5.6597 mgL-1 for 20.3 h, respectively, by applying 1% bentonite. An increase in the contact time efficiently allowed soil adsorbent to adsorb maximum Cr from soil samples. In the second step, a pot experiment was conducted with 10 different treatments to improve the physiological and biochemical parameters of the Solanum melongena L. irrigated under tanneries' wastewater stress. There were four replicates, and the crop was harvested after 30 days of germination. It was seen that the application of wastewater significantly (P < 0.01) reduced growth of Solanum melongena L. by reducing root (77%) and shoot (63%) fresh weight when compared with CFOP (Ce-doped Fe2O3 nanoparticles); chlorophyll a and b (fourfolds) were improved under CFOP application relative to control (CN). However, the deleterious effects of Cr (86%) and Pb (90%) were significantly decreased in shoot through CFOP application relative to CN. Moreover, oxidative damage induced by the tannery's wastewater stress (P < 0.01) was tolerated by applying different soil amendments. However, results were well pronounced with the application of CFOP which competitively decreased the concentrations of MDA (95%), H2O2 (89%), and CMP (85%) by efficiently triggering the activities of antioxidant defense mechanisms such as APX (threefold), CAT (twofold), and phenolics (75%) in stem relative to CN. Consequently, all the applied amendments (BN, BT, FOP, and CFOP) have shown the ability to efficiently tolerate the tannery's wastewater stress; results were more pronounced with the addition of CFOP and FOP+BT by improving physiological and biochemical parameters of Solanum melongena L. in an eco-friendly way.

Microbial-assisted soil chromium immobilization through zinc and iron-enriched rice husk biochar.

Soil chromium toxicity usually caused by the tannery effluent compromises the environment and causes serious health hazards. The microbial role in strengthening biochar for its soil chromium immobilization remains largely unknown. Hence, this study evaluated the effectiveness of zinc and iron-enriched rice husk biochar (ZnBC and FeBC) with microbial combinations to facilitate the chromium immobilization in sandy loam soil. We performed morphological and molecular characterization of fungal [Trichoderma harzianum (F1), Trichoderma viride (F2)] and bacterial [Pseudomonas fluorescence (B1), Bacillus subtilis (B2)] species before their application as soil ameliorants. There were twenty-five treatments having ZnBC and FeBC @ 1.5 and 3% inoculated with bacterial and fungal isolates parallel to wastewater in triplicates. The soil analyses were conducted in three intervals each after 20, 30, and 40 days. The combination of FeBC 3%+F2 reduced the soil DTPA-extractable chromium by 96.8% after 40 days of incubation (DAI) relative to wastewater. Similarly, 92.81% reduction in chromium concentration was achieved through ZnBC 3%+B1 after 40 DAI compared to wastewater. Under the respective treatments, soil Cr(VI) retention trend increased with time such as 40 > 30 > 20 DAI. Langmuir adsorption isotherm verified the highest chromium adsorption capacity (41.6 mg g-1) with FeBC 3% at 40 DAI. Likewise, principal component analysis (PCA) and heat map disclosed electrical conductivity-chromium positive, while cation exchange capacity-chromium and pH-organic matter negative correlations. PCA suggested the ZnBC-bacterial while FeBC-fungal combinations as effective Cr(VI) immobilizers with >70% data variance at 40 DAI. Overall, the study showed that microbes + ZnBC/FeBC resulted in low pH, high OM, and CEC, which ultimately played a role in maximum Cr(VI) adsorption from wastewater applied to the soil. The study also revealed the interrelation and alternations in soil dynamics with pollution control treatments. Based on primitive soil characteristics such as soil metal concentration, its acidity, and alkalinity, the selection criteria can be set for treatments application to regulate the soil properties. Additionally, FeBC with Trichoderma viride should be tested on the field scale to remediate the Cr(VI) toxicity.

Comparative efficiency of silica gel, biochar, and plant growth promoting bacteria on Cr and Pb availability to Solanum melongena L. in contaminated soil irrigated with wastewater.

Crop irrigation with untreated wastewater is a routine practice in developing countries that causes multiple human health consequences. A comparative study was performed to regulate total Cr and Pb stress in soil and Solanum melongena L. plant. For this purpose, 0.2% chitosan polymerized silica gel (CP-silica gel), 1.5% zinc-enriched biochar (ZnBc), and three bacterial species such as Trichococcus sp. (B1), Pseudomonas alcaligenes (B2), and Bacillus subtilis (B3) were selected. Initially, a biosorption trial was conducted to test the heavy metal removal efficiency of three bacterial species B1, B2, and B3 for 24 h. Hence, B3 showed maximum Cr and Pb removal efficiency among the studied bacterial isolates. Then, a pot study was conducted with 12 different treatments having three replicates. After harvesting, different growth and biochemical parameters such as chlorophyll concentration, proteins, phenolics, reactive oxygen species, and antioxidant enzymes were analyzed. The results demonstrated that wastewater application significantly (p ≤ 0.01) reduced the fresh and dry weights of the root, stem, and leaves due to high total Cr and Pb toxicity. However, CP-silica gel and ZnBc treatments performed best when applied in combination with B3. The concentration of leaf total Cr was significantly decreased (91 and 85%) with the application of ZnBc + B3 and CP-Silica gel + B3, respectively, as compared to control. There was a reduction in stem hydrogen peroxide (87%) and malondialdehyde (81%) recorded with CP-silica gel + B3 treatment due to enhanced activities of antioxidant enzymes viz. ascorbate peroxidase (6-folds) and catalase (7-folds) relative to control. Similarly, leaf total phenolics (3-folds) and protein (6-folds) contents were enhanced with CP silica gel+B3 application relative to control. Overall, CP-silica gel and ZnBc with B3 application proved to be the most appropriate treatments and can be used in developing countries to limit the deleterious effects of total Cr and Pb pollution.

Foxtail millet [Setaria italica (L.) Beauv.] over-accumulates ammonium under low nitrogen supply.

Nitrogen (N) deficiency is a primary limiting factor for crop production worldwide. Previously, we reported root system architectural modifications of hydroponically cultured foxtail millet [Setaria italica (L.) Beauv.] to facilitate N translocation under N limitation. Here, we investigated foxtail millet for its shoot adaptation to low N in terms of internal N regulation under hydroponic culture. The results of this study revealed that the shoot N and nitrate (NO3-) concentrations significantly declined as compared to control (CK); however, the shoot over-accumulated ammonium (NH4+) under low N (LN). N shortage resulted in down-regulation of expressions of SiPetA, SiccsA, SipsbA, SirpoB, SipsaA, SiatpA, Sirps16, and SiPEPC which, undermined chloroplast functioning and CO2 assimilation for the provision of carbon skeleton. Carbon deficiency and lower activities of GS decelerated ammonia assimilation and led to over-accumulation of NH4+ in the LN-shoot, as indicated by lower concentrations of total amino acids. Thus, enhanced GOGAT activity was to assimilate NH4+ while, those of catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD) were to scavenge reactive oxygen species (ROS) of NH4+ toxicity framework. The weakened chloroplast factory eventually minimized photosynthesis and reduced dry mass of the LN shoot. Such regulation of N by the shoot, perhaps, resurrected physiological functions which maintained internal mineral status under nitrogen limitation in foxtail millet.

Iron oxide nanoparticles doped biochar ameliorates trace elements induced phytotoxicity in tomato by modulation of physiological and biochemical responses: Implications for human health risk.

Use of untreated municipal wastewater (WW) contains toxic trace elements that pose a serious threat to the soil-plant-human continuum. The use of biochar (BC) is a promising approach to minimize trace element induced toxicity in the ecosystem. Therefore, the present study aims to evaluate the efficacy of BC derived from wheat straw and iron oxide nanoparticles doped biochar (IO-BC) to reduce trace element buildup in soil and plants that consequently affect tomato plant growth and physiological activity under WW irrigation. The BC and IO-BC were applied at four levels (0, 0.5, 1, and 1.5%) in WW irrigated soils. The results indicated that the addition of WW + BC and WW + IO-BC resulted in significant reduction in trace element mobility in soil. Interestingly, the application of WW + IO-BC (1.5%) was more effective in reducing trace element mobility and bioavailability in soil by 78% (As), 58% (Cr), 46% (Pb) and 50% (Cd) compared to WW irrigation, and thus reduced trace element accumulation and toxicity in plants. Results revealed that WW irrigation negatively affected tomato growth, fruit yield, physiology and antioxidative response. Addition of WW + BC and WW + IO-BC ameliorated the oxidative stress (up to 65% and 58% in H2O2 and MDA) and increased plant tolerance (up to 49% in POD and APX activity). The risk indices also showed minimum human health risk (H1 < 1) from tomato after the addition of BC or IO-BC in WW irrigated soils. It is concluded that IO-BC addition in WW irrigated soil could assist in reducing trace elements accumulation and toxicity in tomato and associated human health risks.

Vulnerability, well-being, and livelihood adaptation under changing environmental conditions: a case from mountainous region of Pakistan.

Climatic changes pose serious risks to the rural community's livelihoods of many developing countries whereas people in mountainous regions are exposed to multiple hazards with limited livelihood resources and heavy dependence on natural resources. The objective of the current study is to assess the livelihood practices and adaptive capacity of a mountainous region of Pakistan, the Balakot, where people are highly vulnerable to climatic changes. The study uses a triangulation method to explore various issues and options of climate change risks sand adaptation and impact of well-being on resilience capacity and livelihood strategies. For this purpose, ten focus group discussions (FGDs) with carefully selected key informants and structured interviews with randomly selected 200 local households are conducted to evaluate different hazards and their associated livelihood effects. It is observed that the changing climate has significantly influenced livelihoods of the local community in the recent past through resource degradation, gradual unavailability of sufficient basic services (quantity and quality of drinking water, crop food diversity, fuel wood, and non-timber forest products), low agricultural productivity, and social inequity viz. income distribution, health, education, and food storage. Such a brunt is felt disproportionately more by poor households due to their low adaptive capacity to climate change with constrained livelihood resources. The study emphasizes the need for targeted efforts to move from coping strategies to adaptations among people considering their social inequalities. Timely information sharing, livelihood diversification and preservation of livelihood resources such as crop and forest production, livestock grazing, creating awareness on the pace, and pattern of climate change in the region and subsequent role of adaptation options are major interventions that should be emphasized by the public bodies.

Potential of miscanthus biochar to improve sandy soil health, in situ nickel immobilization in soil and nutritional quality of spinach.

The complex interaction of biochar (BC) with soil health reflecting properties, the feedstock used to prepare BC and application rate of BC in sandy soil is still a question for the researchers. An incubation study was conducted where nine different sorts of BC, each prepared from the different feedstock, were applied at 2% rate to evaluate their relative suitability to improve sandy soil health. Results revealed that BC prepared from miscanthus (MIB) significantly increased soil medium and fine pores, available water content (AWC), electrical conductivity (EC), and cation exchange capacity (CEC) while decreased soil wide pores, pH, bulk density (BD) and particle density (PD) compared to the rest sorts of BC. Later, spinach was grown in pots containing same soil but spiked with 50 ppm nickel (Ni) and amended with 1, 2, 3, 4 and 5% rates of MIB. The results showed a significant increment in spinach biomass, reduction in the concentrations of Ni in spinach tissues and DTPA-extractable Ni with the increasing rate of MIB till 3% and later, no significant changes with 4 and 5% rates thereafter. However, significant improvement in the activities of antioxidant enzymes, chemical and biochemical attributes of spinach were observed at 5% MIB when compared to lower rates. Similarly, post-harvest soil physicochemical and enzymatic parameters were also significantly (P < 0.05) improved with increasing rates of MIB. This study implies that application of MIB at 5% rate can improve the nutritional quality of spinach, sandy soil health and can reduce Ni concentrations in spinach tissues.

In situ immobilization of Cd by organic amendments and their effect on antioxidant enzyme defense mechanism in mung bean (Vigna radiata L.) seedlings.

In situ immobilization of Cd is desirable due to the damaging effects of ex situ remediation techniques on soil. In this greenhouse study, the role of biochar (BC), chitosan (CH), and green waste (GW) was studied for in-situ Cd immobilization and alleviating Cd toxicity in mung bean seedlings. Amendments were applied at rates of 0.5% and 1% (w/w). The minimum mean value of Cd, in root, shoot, and soil (DTPA-Cd) (12.2, 4.7, and 0.7 mg kg-1, respectively), occurred in the Cd + 1% CH treatment compared to all Cd amended treatments. Shoot dry weight (21%) increased significantly in Cd + 1% BC amended soil compared to the control. Reactive oxygen species were affected significantly, with the lowest increased value of hydrogen peroxide (4%) in the Cd + 1% CH treatment while the minimum increase in the value of superoxide (O2•-) occurred in the Cd + 1% BC soil compared to the control. Malondialdehyde (20%) increased lowest with Cd + 1% CH treatment. Protein, ascorbate (AsA) contents, and catalase (CAT) activity increased the most (3, 2, and 15%, respectively) in the Cd + 1% BC treatment while dehydroascorbate reductase (DHAR) and superoxide dismutase (SOD) activity increased the most (9 and 234%, respectively) in the Cd + 1% CH soil compared to the control. Glutathione reductase (GR), ascorbate peroxidase (APX), and glutathione peroxidase (GPX), activity were reduced the most in the Cd + 1.0% BC treatment while dehydroascorbate (DHA) and glutathione S-transferase (GST) activity decreased the most in the Cd + 1% CH soil. Overall, in situ immobilization by amendments improved growth and antioxidant defense mechanisms of mung bean seedlings and was reflected by tolerance to Cd-toxicity.

Improved quinoa growth, physiological response, and seed nutritional quality in three soils having different stresses by the application of acidified biochar and compost.

Quinoa (Chenopodium quinoa Willd.) is a traditional Andean agronomical resilient seed crop having immense significance in terms of high nutritional qualities and its tolerance against various abiotic stresses. However, finite work has been executed to evaluate the growth, physiological, chemical, biochemical, antioxidant properties, and mineral nutrients bioavailability of quinoa under abiotic stresses. Depending on the consistency in the stability of pH, intended rate of S was selected from four rates (0.1, 0.2, 0.3, 0.4 and 0.5% S) for the acidification of biochar and compost in the presence of Thiobacillus thiooxidans by pH value of 4. All three soils were amended with 1% (w/w) acidified biochar (BCA) and compost (COA). Results revealed that selective plant growth, yield, physiological, chemical and biochemical improved significantly by the application of BCA in all stressed soils. Antioxidants in quinoa fresh leaves increased in the order of control > COA > BCA, while reactive oxygen species decreased in the order of control < COA < BCA. A significant reduction in anti-nutrients (phytate and polyphenols) was observed in all stressed soils with the application of BCA. Moreover, incorporation of COA and BCA reduced the pH of rhizosphere soil by 0.4-1.6 units in all stressed soils, while only BCA in bulk soil decreased pH significantly by 0.3 units. These results demonstrate that BCA was more effective than COA to enhance the bioavailability, translocation of essential nutrients from the soil to plant and their enhanced bioavailability in the seed.

Cost-effective enhanced iron bioavailability in rice grain grown on calcareous soil by sulfur mediation and its effect on heavy metals mineralization.

Calcareous soil, high pH, and low organic matter are the major factors that limit iron (Fe) availability to rice crop. The present study was planned with the aim to biofortified rice grain with Fe, by integrated use of chemical and organic amendments in pH-manipulated calcareous soil. The soil pH was reduced (pHL2) by using elemental sulfur (S) at the rate of 0.25 % (w/w). The organic amendments, biochar (BC) and poultry manure (PM) [1 % (w/w)], along with ferrous sulfate at the rate of 7.5 mg kg-1 soil were used. The incorporation of Fe with BC in soil at pHL2 significantly improved plant biomass, photosynthetic rate, and paddy yield up to 99, 97, and 36 %, respectively, compared to control. A significant increase in grain Fe (190 %), protein (58 %), and ferritin (400 %) contents was observed while anti-nutrients, i.e., polyphenols (37 %) and phytate (21 %) were significantly decreased by the addition of Fe and BC in soil at pHL2 relative to control. Among the organic amendments, PM significantly increased Cd, Pb, Ni, and Cr concentrations in rice grain relative to control but their concentration values were below as compared to the toxic limits of hazard quotients and hazard index (HQ and HI). Hence, this study implies that Fe applied with BC in the soil at pHL2 can be considered as an effective strategy to augment Fe bioavailability and to reduce non-essential heavy metal accumulation in rice grain.

Effect of different amendments on rice (Oryza sativa L.) growth, yield, nutrient uptake and grain quality in Ni-contaminated soil.

Rice ( Oryza sativa L.) is one of the main staple food crops which is inherently low in micronutrients, especially iron (Fe), and can lead to severe Fe deficiency in populations having higher consumption of rice. Soils polluted with nickel (Ni) can cause toxicity to rice and decreased Fe uptake by rice plants. We investigated the potential role of biochar (BC) and gravel sludge (GS), alone and in combination, for in situ immobilization of Ni in an industrially Ni-contaminated soil at original and sulfur-amended altered soil pH. Our further aim was to increase Fe bioavailability to rice plants by the exogenous application of ferrous sulfate to the Ni-immobilized soil. Application of the mixture of both amendments reduced grain Ni concentration, phytate, Phytate/Fe, Phyt/Zn molar ratios, and soil DTPA-extractable Ni. In addition, the amendment mixture increased 70 % Fe and 229 % ferritin concentrations in rice grains grown in the soil at original pH. The Fe and ferritin concentrations in S-treated soil was increased up to 113 and 383 % relative to control respectively. This enhanced Fe concentration and corresponding ferritin in rice grains can be attributed to Ni/Fe antagonism where Ni has been immobilized by GS and BC mixture. This proposed technique can be used to enhance growth, yield, and Fe biofortification in rice by reducing soil pH while in parallel in situ immobilizing Ni in polluted soil.