Assessment of lithium bioaccumulation by quinoa (Chenopodium quinoa willd.) and its implication for human health.

Lithium (Li) is the lightest alkali metal and 27th most abundant element in the earth crust. In traces, the element has medicinal value for various disorders in humans, however, its higher concentrations may lead to treatment-resistant depression and altered thyroid functioning. Quinoa (Chenopodium quinoa) has gained popularity owing to its halophytic nature and its potential use as an alternative to the traditional staple foods. However, quinoa response to Li-salt in terms of growth, Li accumulation potential and health risks associated with consumption of the quinoa seeds grown on Li-contaminated soils has not been explored yet. During this study, quinoa was exposed to various concentrations of Li (0, 2, 4, 8 and 16 mM) at germination as well as seedling stages. The results showed that seed germination was the highest (64% higher than control) at Li concentration of 8 mM. Similarly, at 8 mM doses of Li shoot length, shoot dry weight, root length, root dry weight and grain yield were increased by 130%, 300%, 244%, 858% and 185% than control. It was also revealed that Li increased the accumulation of calcium and sodium in quinoa shoots. Carotenoids contents were increased, but chlorophyll contents remained un-changed under Li application. The activities of antioxidants viz. Peroxide dismutase, catalase and super oxide dismutase were also increased with an increase in the levels of Li in the soil. Estimated daily intake and hazard quotient of Li in quinoa were less than the threshold level. It was concluded that Li concentration of 8 mM is useful for quinoa growth and it can be successfully grown on Li contaminated soils without causing any human health risks.

Salinity mitigates cadmium-induced phytotoxicity in quinoa (Chenopodium quinoa Willd.) by limiting the Cd uptake and improved responses to oxidative stress: implications for phytoremediation.

Cadmium (Cd) contamination and soil salinity are the main environmental issues reducing crop productivity. This study aimed to examine the combined effects of salinity (NaCl) and Cd on the physiological and biochemical attributes of quinoa (Chenopodium quinoa Willd.). For this purpose, 30-day-old plants of quinoa genotype "Puno" were transplanted in Hoagland's nutrient solution containing diverse concentrations of Cd: 0, 50, 100, 200 µM Cd, and salinity: 0, 150, and 300 mM NaCl. Results demonstrated that plant growth, stomatal conductance, and pigment contents were significantly lower at all Cd concentrations than the control plants. Quinoa plants exhibited improved growth and tolerance against Cd when grown at a lower level of salinity (150 mM NaCl) combined with Cd. In contrast, the elevated concentration of salinity (300 mM NaCl) combined with Cd reduced shoot and root growth of experimental plants more than 50%. Combined application of salinity and Cd increased Na (25-fold), while lessened the Cd (twofold) and K (1.5-fold) uptake. A blend of high concentrations of Na and Cd caused overproduction of H2O2 (eightfold higher than control) contents and triggered lipid peroxidation. The activities of antioxidant enzymes: ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) were 13, 12, 7 and ninefold higher than control to mitigate the oxidative stress. Due to restricted root to shoot translocation, and greater tolerance potential against Cd, the quinoa genotype, Puno, is suitable for phytostabilization of Cd in saline soils.

Biowaste-based sorbents for arsenic removal from aqueous medium and risk assessment.

Water contamination by arsenic (As) is widespread and is posing serious health threats globally. Hence, As removal techniques/adsorbents need to be explored to minimize potentials hazards of drinking As-contaminated waters. A column scale sorption experiment was performed to assess the potential of three biosorbents (tea waste, wheat straw and peanut shells) to remove As (50, 100, 200 and 400 µg L-1) from aqueous medium at a pH range of 5-8. The efficiency of agricultural biosorbents to remove As varies greatly regarding their type, initial As concentration in water and solution pH. It was observed that all of the biosorbents efficiently removed As from water samples. The maximum As removal (up to 92%) was observed for 400 µg L-1 initial As concentration. Noticeably, at high initial As concentrations (200 and 400 µg L-1), low pH (5 and 6) facilitates As removal. Among the three biosorbents, tea waste biosorbent showed substantial ability to minimize health risks by removing As (up to 92%) compared to peanut shells (89%) and wheat straw (88%). Likewise, the values of evaluated risk parameters (carcinogenic and non-carcinogenic risk) were significantly decreased (7-92%: average 66%) after biosorption experiment. The scanning electron microscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray and X-ray diffraction analyses confirmed the potential of biosorbents to remediate As via successful loading of As on their surfaces. Hence, it can be concluded that synthesized biosorbents exhibit efficient and ecofriendly potential for As removal from contaminated water to minimize human health risk.

Improving the fermentable sugar yields of wheat straw by high-temperature pre-hydrolysis with thermophilic enzymes of Malbranchea cinnamomea.

BACKGROUND: Enzymatic hydrolysis is a key step in the conversion of lignocellulosic polysaccharides to fermentable sugars for the production of biofuels and high-value chemicals. However, current enzyme preparations from mesophilic fungi are deficient in their thermostability and biomass-hydrolyzing efficiency at high temperatures. Thermophilic fungi represent promising sources of thermostable and highly active enzymes for improving the biomass-to-sugar conversion process. Here we present a comprehensive study on the lignocellulosic biomass-degrading ability and enzyme system of thermophilic fungus Malbranchea cinnamomea N12 and the application of its enzymes in the synergistic hydrolysis of lignocellulosic biomass. RESULTS: Malbranchea cinnamomea N12 was capable of utilizing untreated wheat straw to produce high levels of xylanases and efficiently degrading lignocellulose under thermophilic conditions. Temporal analysis of the wheat straw-induced secretome revealed that M. cinnamomea N12 successively degraded the lignocellulosic polysaccharides through sequential secretion of enzymes targeting xylan and cellulose. Xylanase-enriched cocktail from M. cinnamomea N12 was more active on native and alkali­pretreated wheat straw than the commercial xylanases from Trichoderma reesei over temperatures ranging from 40 to 75 °C. Integration of M. cinnamomea N12 enzymes with the commercial cellulase preparation increased the glucose and xylose yields of alkali­pretreated wheat straw by 32 and 166%, respectively, with pronounced effects at elevated temperature. CONCLUSIONS: This study demonstrated the remarkable xylanase-producing ability and strategy of sequential lignocellulose breakdown of M. cinnamomea N12. A new process for the hydrolysis of lignocellulosic biomass was proposed, comprising thermophilic enzymolysis by enzymes of M. cinnamomea N12 followed with mesophilic enzymolysis by commercial cellulases. Developing M. cinnamomea N12 as platforms for thermophilic enzyme mixture production will provide new perspectives for improved conversion yields for current biomass saccharification schemes.

Unraveling the toxic effects of iron oxide nanoparticles on nitrogen cycling through manure-soil-plant continuum.

Soil contamination with metallic nanoparticles is increasing due to their increased use in industrial and domestic settings. These nanoparticles are potentially toxic to soil microbes and may affect their associated functions and thereby the nutrient cycling in agro-ecosystems. This study examined the effects of iron oxides nanoparticles (IONPs) on carbon (C) and nitrogen (N) dynamics of poultry (PM) and farmyard manure (FYM) in the soil. The application of IONPs increased iron content in soil microbial biomass, which reflected its consumption by the microbes. As a result, colony-forming units of bacteria and fungi reduced considerably. Such observations lead to a decrease in CO2 emission from PM and FYM by 27 and 28%, respectively. The respective decrease fractions in the case of N mineralization were 24 and 35%. Consequently, soil mineral N content was reduced by 16% from PM and 12% from FYM as compared to their sole application without IONPs. Spinach dry matter yield and apparent N recovery were increased by the use of organic waste (FYM, PM). The use of IONPs significantly reduced the plant N recovery fraction by 26 and 24% (P < 0.05) from PM and FYM, respectively. All the results mentioned above lead us to conclude that IONPs are toxic to soil microbes and affect their function i.e., carbon and N mineralization of applied manure, and thereby the on-farm N cycling from the manure-soil-plant continuum.

Carbon sequestration potential and soil characteristics of various land use systems in arid region.

Soils contain one of the largest carbon (C) pools in the biosphere with the greatest potential of C sequestration to mitigate climate change impacts. The present study aimed at comparing C sequestration potential of various land use systems including forestlands, croplands, agroforests, and orchards in the arid region of Pakistan. Soil samples from the layers of 0-20, 20-40, 40-60, and 60-80 cm depths were collected and analysed for soil physico-chemical properties namely texture, pH, EC, NPK-soil, organic matter (SOM), and soil organic C (SOC). Additionally, the above and below ground plant biomass and C contents were estimated. Results revealed that the highest C sequestration potential (64.54 Mg ha-1) was in the above ground biomass of forest land and the lowest (33.50 Mg ha-1) in cropland. The below ground plant biomass at 0-20 cm soil depth was 14.09, 12.38, 11.78, 11.76, and 10.92 Mg ha-1 for forest land, mango orchards, agroforests, citrus orchards and cropland, respectively. The respective values in case of total C content were, 6.84, 6.79, 6.10, 5.69 Mg ha-1. Irrespective to the soil depth, below ground biomass and total C followed the order: forest land > mango orchard > citrus orchard > agroforests > crop lands. It is concluded that the forest land have greater potential for C sequestration than the other land use systems studied in the arid region of Pakistan. Therefore, in order to cope up with climate change disasters in Pakistan the massive reforestation project - named the Billion Tree Tsunami of the Government of Pakistan will prove beneficial.

Assessment of arsenic exposure by drinking well water and associated carcinogenic risk in peri-urban areas of Vehari, Pakistan.

Arsenic (As) is a highly toxic and carcinogenic element. It has received considerable consideration worldwide in recent years due to its highest toxicity to human, and currently, high concentrations observed in the groundwater. Some recent media and research reports also highlighted possible As contamination of groundwater systems in Pakistan. However, there is a scarcity of data about As contents in groundwater in different areas/regions of the country. Consequently, the current study estimated the As concentration in the groundwater used for drinking purpose in 15 peri-urban sites of district Vehari, Pakistan. In total, 127 groundwater samples were collected and examined for As contents in addition to physicochemical characteristics such as temperature, electrical conductivity, pH, total soluble salts, chloride, carbonates, bicarbonates, sodium, potassium, lithium, calcium and barium. Results indicated that the groundwater samples were not fully fit for drinking purposes with several parameters, especially the alarming levels of As (mean As: 46.9 µg/L). It was found that 83% groundwater samples of peri-urban sites in district Vehari have As concentration greater than WHO lower permissible limit (10 µg/L). The risk assessment parameters (mean hazard quotient: 3.9 and mean cancer risk: 0.0018) also showed possible carcinogenic and non-carcinogenic risks associated with ingestion of As-contaminated groundwater at peri-urban sites. Based on the findings, it is anticipated that special monitoring and management of groundwater is necessary in the studied area in order to curtail the health risks associated with the use of As-contaminated drinking water. Moreover, appropriate remediation and removal of As from groundwater is also imperative for the study area before being used for drinking purpose to avoid As exposure and related risks to the local community.

Use of plant growth promoting Rhizobacteria (PGPR) and mycorrhizae to improve the growth and nutrient utilization of common bean in a soil infected with white rot fungi.

Extensive use of fertilizers and pesticides led to dangerous ecological effects and therefore the biological approaches have been widely recommended to prevent further deterioration for the environment. The current study was conducted to explore the potentiality of using single or combined inoculations by mycorrhizae, Bacillus subtilis and Pseudomonas fluorescence for controlling the infection of common bean plants with Sclerotium rolfsii on one hand and as bio-fertilizers for improving plants nutritional status on the other hand. The soil of study was mildly infected with S. rolfsii and contained high total-P content. Thus, minimal P inputs were added to the inoculated soil in the form of rock phosphate. Activities of plant defense enzymes i.e. chitinase, peroxidase and polyphenol oxidase were determined under the greenhouse conditions and the results obtained herein indicated that activities of such enzymes increased significantly owing to bio-agent inoculations. In this concern, combined treatments resulted in further significant increases over the single ones. A field study was then conducted for two successive years and the results reveal that single inoculations increased straw and green pod yields as well as the uptake of P and Fe by plants as compared with the non-inoculated treatment. Combined inoculants recorded further significant increases in these parameters even when compared with the fungicide treated plants. Generally, straw and pod yields obtained from the second growing season were significantly higher than those attained in the first growing one. Our study confirms the success of the used bio-treatments in minimizing soil pollution through fertilizer and/or pesticide inputs.

Regulation of antioxidant production, ion uptake and productivity in potato (Solanum tuberosum L.) plant inoculated with growth promoting salt tolerant Bacillus strains.

The exchangeable sodium (Na+) in salt affected soils is a major constraint in potassium (K+) availability to plants that disturb ion transport and inhibit plant growth, adversely. Salt tolerant plant growth promoting rhizobacteria (PGPR) may regulate the Na+/K+ efflux and increase K+ uptake by the plant from the soil. Therefore, a pot study was performed to examine the effect of salt tolerant PGPR Bacillus sp. alone and in consortium, on antioxidant enzyme activity, ion uptake and potato (Solanum tuberosum L.) tuber yield in normal and salt affected soils. We observed that Bacillus sp. (strains SR-2-1 and SR-2-1/1) solubilized insoluble phosphorous and produced indole-3-acetic acid while only SR-2-1/1 produced ACC deaminase in culture medium supplemented with various concentrations of NaCl (0-6%). In the pot experiment, the consortium treatment of strains was found to increase relative leaf water contents whereas decreased the electrolyte leakage and antioxidant enzyme activity both in normal and salt affected soils. Similarly, consortium treatment decreased Na+ whereas increased K+, Ca+2, K+/Na+ and Ca+2/Na+ in plant dry matter in both soils. It has been investigated that inoculation of PGPR significantly (p < 0.05) increased plant biomass, number of tubers per plant and tuber weight as compared to un-inoculated plants in both soils. In addition, PGPR inoculation enhanced auxin production in root exudates of young potato plants and bacterial population dynamics in both soils. Na+ ion regulation (R2 = 0.95) and tuber weight (R2 = 0.90) in salt affected soil were significantly correlated with auxin production in the rhizosphere. Results of this study conferred that consortium of Bacillus strains (SR-2-1, SR-2-1/1) enhanced auxin production in the rhizosphere of potato plants and that ultimately regulated antioxidant enzyme production and uptake of Na+, K+ and Ca+2 in potato plants resulted into a higher tuber yield in both normal and salt affected soils.

Biosorption of Pb(II) from contaminated water onto Moringa oleifera biomass: kinetics and equilibrium studies.

The present study aims at evaluating a batch scale biosorption potential of Moringa oleifera leaves (MOL) for the removal of Pb(II) from aqueous solutions. The MOL biomass was characterized by FTIR, SEM, EDX, and BET. The impact of initial concentrations of Pb (II), adsorbent dosage, pH, contact time, coexisting inorganic ions (Ca2+, Na+, K+, Mg2+, CO32-, HCO3-, Cl-), electrical conductivity (EC) and total dissolved salts (TDS) in water was investigated. The results revealed that maximum biosorption (45.83 mg/g) was achieved with adsorbent dosage 0.15 g/100 mL while highest removal (98.6%) was obtained at adsorbent biomass 1.0 g/100 mL and pH 6. The presence of coexisting inorganic ions in water showed a decline in Pb(II) removal (8.5% and 5%) depending on the concentrations of ions. The removal of Pb(II) by MOL decreased from 97% to 89% after five biosorption/desorption cycles with 0.3 M HCl solution. Freundlich model yielded a better fit for equilibrium data and the pseudo-second-order well described the kinetics of Pb(II) biosorption. FTIR spectra showed that -OH, C-H, -C-O, -C = O, and -O-C functional groups were involved in the biosorption of Pb(II). The change in Gibbs free energy (ΔG = -28.10 kJ/mol) revealed that the biosorption process was favorable and thermodynamically driven. The results suggest MOL as a low cost, environment-friendly alternative biosorbent for the remediation of Pb(II) contaminated water.

Manure storage operations mitigate nutrient losses and their products can sustain soil fertility and enhance wheat productivity.

Livestock manure is a valuable source of nutrients for plants. However, poor handling practices during storage resulted in nutrient losses from the manure and decrement in its nitrogen (N) fertilizer value. We explored the influence of divergent storage methods on manure chemical composition, carbon (C) and N losses to the environment as well as fertilizer value of storage products after their application to the wheat. Fresh buffalo manure (FM) was subjected to different storage operations for a period of ∼6 months, (i) fermentation by covering with a plastic sheet (CM) (ii) placed under the roof (RM) (iii) heap was unturned (SM) to remain stacked at an open space and (iv) manure heap turned monthly (TM) to make compost. During storage, 8, 24, 45 and 46% of the initial Ntotal was lost from CM, RM, SM, and TM, respectively. The respective C losses from these treatments were 16, 34, 47 and 44% of the initial C content. After stored manures application to the wheat crop, mineral N in the soil remained 27% higher in CM (14.1 vs. 11.1 kg ha-1) and 3% (10.8 vs. 11.1 kg ha-1) lower in SM compared to FM treatment. In contrast, microbial biomass C and N was 35 (509 vs.782 mg C kg-1 soil) and 25% (278 vs.370 mg N kg-1 soil) lower in CM than FM treatment, respectively indicating lower N immobilization of CM in the soil. These findings could result in the highest grain yield (5166 kg ha-1) and N uptake (117 kg ha-1) in CM and the lowest in SM treatments (3105 and 61 kg ha-1, respectively). Similarly, wheat crop recovered 44, 15 and 13% N from CM, TM and SM, respectively. Hence, management operations play a critical role in conserving N during storage phase and after stored manure application to the field. Among the studied operations, storing animal manure under an impermeable plastic sheet is a much better and cheaper option for decreasing N losses during storage and improving wheat yield when incorporated into the soil. Therefore, by adopting this manure storage technique, farmers can improve the agro-environmental value of animal manure in Pakistan.

Cadmium tolerance and phytoremediation potential of acacia (Acacia nilotica L.) under salinity stress.

In this study, we explored the effect of salinity on cadmium (Cd) tolerance and phytoremediation potential of Acacia nilotica. Two-month-old uniform plants of A. nilotica were grown in pots contaminated with various levels of Cd (0, 5, 10, and 15 mg kg-1), NaCl (0%, 0.5%, 1.0% (hereafter referred as salinity), and all possible combinations of Cd + salinity for a period of six months. Results showed that shoot and root growth, biomass, tissue water content and chlorophyll (chl a, chl b, and total chl a+b) contents decreased more in response to salinity and combination of Cd + salinity compared to Cd alone. Shoot and root K concentrations significantly decreased with increasing soil Cd levels, whereas Na and Cl concentrations were not affected significantly. Shoot and root Cd concentrations, bioconcentration factor (BCF) and translocation factor (TF) increased with increasing soil Cd and Cd + salinity levels. At low level of salinity (0.5%), shoot and root Cd uptake enhanced, while it decreased at high level of salinity (1.0%). Due to Cd tolerance, high shoot biomass and shoot Cd uptake, this tree species has some potential for phytoremediation of Cd from the metal contaminated saline and nonsaline soils.

Bedding additives reduce ammonia emission and improve crop N uptake after soil application of solid cattle manure.

This study examined the influences of three potential additives, i.e., lava meal, sandy soil top-layer and zeolite (used in animal bedding) amended solid cattle manures on (i) ammonia (NH3), dinitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) emissions and (ii) maize crop or grassland apparent N recovery (ANR). Diffusion samplers were installed at 20 cm height on grassland surface to measure the concentrations of NH3 from the manures. A photoacoustic gas monitor was used to quantitate the fluxes of N2O, CH4 and CO2 after manures' incorporation into the maize-field. Herbage ANR was calculated from dry matter yield and N uptake of three successive harvests, while maize crop ANR was determined at cusp of juvenile stage, outset of grain filling as well as physiological maturity stages. Use of additives decreased the NH3 emission rates by about two-third from the manures applied on grassland surface than control untreated-manure. Total herbage ANR was more than doubled in treated manures and was 25% from manure amended with farm soil, 26% and 28% from zeolite and lava meal, respectively compared to 11% from control manure. In maize experiment, mean N2O and CO2 emission rates were the highest from the latter treatment but these rates were not differed from zero control in case of manures amended with farm soil or zeolite. However, mean CH4 emissions was not differed among all treatments during the whole measuring period. The highest maize crop ANR was obtained at the beginning of grain filling stage (11-40%), however ample lower crop recoveries (8-14%) were achieved at the final physiological maturity stage. This phenomenon was occurred due to leaf senescence N losses from maize crop during the period of grains filling. The lowest losses were observed from control manure at this stage. Hence, all additives decreased the N losses from animal manure and enhanced crop N uptake thus improved the agro-environmental worth of animal manure.

Effect of water management and silicon on germination, growth, phosphorus and arsenic uptake in rice.

Silicon (Si) is the 2nd most abundant element in soil which is known to enhance stress tolerance in wide variety of crops. Arsenic (As), a toxic metalloid enters into the human food chain through contaminated water and food or feed. To alleviate the deleterious effect of As on human health, it is a need of time to find out an effective strategy to reduce the As accumulation in the food chain. The experiments were conducted during September-December 2014, and 2016 to optimize Si concentration for rice (Oryza sativa L.) exposed to As stress. Further experiment were carried out to evaluate the effect of optimum Si on rice seed germination, seedling growth, phosphorus and As uptake in rice plant. During laboratory experiment, rice seeds were exposed to 150 and 300µM As with and without 3mM Si supplementation. Results revealed that As application, decreased the germination up to 40-50% as compared to control treatment. Arsenic stress also significantly (P < 0.05) reduced the seedling length but Si supplementation enhanced the seedlings length. Maximum seedling length (4.94cm) was recorded for 3mM Si treatment while, minimum seedling length (0.60cm) was observed at day7 by the application of 300µM As. Silicon application resulted in 10% higher seedling length than the control treatment. In soil culture experiment, plants were exposed to same concentrations of As and Si under aerobic and anaerobic conditions. Irrigation water management, significantly (P˂0.05) affected the plant growth, Si and As concentrations in the plant. Arsenic uptake was relatively less under aerobic conditions. The maximum As concentration (9.34 and 27.70mgkg DW-1 in shoot and root, respectively) was found in plant treated with 300µM As in absence of Si under anaerobic condition. Similarly, anaerobic condition resulted in higher As uptake in the plants. The study demonstrated that aerobic cultivation is suitable to decrease the As uptake and in rice exogenous Si supply is beneficial to decrease As uptake under both anaerobic and aerobic conditions.

Using space-time scan statistic for studying the effects of COVID-19 in Punjab, Pakistan: a guideline for policy measures in regional agriculture.

Pakistan is included in top 50 countries which are estimated to face serious agriculture and food deficiency related challenges due to the worldwide pandemic coronavirus 2019 (COVID-19). The aim of this study was to evaluate the effects of COVID-19 on food supply chain and agriculture in Punjab, Pakistan, by using space-time scan statistic (STSS). A survey was conducted at 720 points in different districts of the province. The STSS detected "active" and emerging clusters that are current at the end of our study area-particularly, 17 clusters were formed while adding the updated case data. Software ArcGIS 10.3 was used to find relative risk (RR) values; the maximum RR value was found to be 42.19 and maximum observed cases 53,265 during June 15-July 1, 2020. It was not always necessary that if the number of active cases in Punjab increased, there should be higher relative risk for more number of districts and vice versa. Due to the highest number of cases of COVID-19 and RR values during July, mostly farmers faced many difficulties during the cultivation of cotton and rice. Mostly farmers (72%) observed increase in prices of inputs (fertilizers and pesticides) during lockdown. If the supply chain of agriculture related inputs is disturbed, farmers may find it quite difficult to access markets, which could result in a decline in production and sales of crops and livestock in study area. It is suggested that to protect the food security and to decrease the effect of the lockdown, Punjab government needs to review food policy and analyse how market forces will respond to the imbalanced storage facilities and capacity, supply and demand and price control of products. The findings of this study can also help policy-makers to formulate an effective food security and agriculture adaptation strategy.

Impact of Cadmium Contamination on Fertilizer Value and Associated Health Risks in Different Soil Types Following Anaerobic Digestate Application.

Cadmium (Cd) contamination in the soil potentially hampers microbial biomass and adversely affects their services such as decomposition and mineralization of organic matter. It can reduce nitrogen (N) metabolism and consequently affect plant growth and physiology. Further, Cd accumulation in plants can pose health risks through vegetable consumption. Here, we investigated consequences of Cd contamination on fertilizer value and associated health risks following the application of biogas residues (BGR) to various soil types. Our results indicate that the application of BGR to all soil types significantly increased dry matter (DM) yield and N uptake. However, the Cd contamination negatively affected DM yield and N recovery from BGR in a dose-dependent manner. Organic N mineralization from BGR also decreased in Cd-contaminated soils. The highest DM yield and N recovery were recorded in sandy soil, whereas the lowest values were observed in clay soil. Cadmium was accumulated in spinach, and health risk index (HRI) associated with its dietary intake revealed that consuming spinach grown in Cd-contaminated soil, with or without BGR, is unsafe. Among the soil types, values of daily intake of metals (DIM) and HRI were lowest in clay soil and highest in sandy soil. However, the application of BGR curtailed HRI across all soil types. Notably, the application of BGR alone resulted in HRI values < 1, which are under the safe limit. We conclude that soil contamination with Cd reduces fertilizer value and entails implications for human health. However, the application of BGR to the soil can decrease Cd effects.

Hyperthermophilic pretreatment composting can reduce ammonia emissions by controlling proteolytic bacterial community and the physicochemical properties.

Proteolysis is the rate-limiting step in the mineralization of organic nitrogen into ammonium (NH4+) and thereby the ammonia (NH3) released during the composting. However, the dynamics of bacterial proteolytic communities related to NH3 emissions during the composting systems are mostly unknown. This study aimed to examine and compare the effects of hyperthermophilic pretreatment composting (HPC) and traditional composting (TC) methods on (i) the difference of NH3 loss and nitrogenous compounds; (ii) the dynamics of the proteolytic bacterial community involved in the proteolysis and (iii) the correlation between the proteolytic bacterial community, biophysiochemical characteristics and NH3 loss. Results revealed that the HPC decreased NH3 loss by 42% as compared to TC during 60-day composting period. This was accompanied with an inhibitory effect on protease activity in the HPC where the relative abundances of the proteolytic bacteria (Bacillus megaterium and Staphylococcus cohnii) were reduced significantly as compared to TC. Partial least-squares path modeling suggested that various physicochemical properties such as higher temperature as well as lower C/N ratio during composting played a dominant role in affecting the abundance of proteolytic bacteria, which may have been an important factor contributing to the lower NH3 loss in HPC. All these findings lead us to conclude that the HPC can significantly reduce NH3 loss by inhibiting the proteolytic bacteria and protease activity responsible for NH3 release.

Nano agrochemical zinc oxide influences microbial activity, carbon, and nitrogen cycling of applied manures in the soil-plant system.

The widespread use of nano-enabled agrochemicals in agriculture for remediating soil and improving nutrient use efficiency of organic and chemical fertilizers is increasing continuously with limited understanding on their potential risks. Recent studies suggested that nanoparticles (NPs) are harmful to soil organisms and their stimulated nutrient cycling in agriculture. However, their toxic effects under natural input farming systems are just at its infancy. Here, we aimed to examine the harmful effects of nano-agrochemical zinc oxide (ZnONPs) to poultry (PM) and farmyard manure (FYM) C and N cycling in soil-plant systems. These manures enhanced microbial counts, CO2 emission, N mineralization, spinach yield and N recovery than control (unfertilized). Soil applied ZnONPs increased labile Zn in microbial biomass, conferring its consumption and thereby reduced the colony-forming bacterial and fungal units. Such effects resulted in decreasing CO2 emitted from PM and FYM by 39 and 43%, respectively. Further, mineralization of organic N was reduced from FYM by 32%, and PM by 26%. This process has considerably decreased the soil mineral N content from both manure types and thereby spinach yield and plant N recoveries. In the ZnONPs amended soil, only about 23% of the applied total N from FYM and 31% from PM was ended up in plants, whereas the respective fractions in the absence of ZnONPs were 33 and 53%. Hence, toxicity of ZnONPs should be taken into account when recommending its use in agriculture for enhancing nutrient utilization efficiency of fertilizers or soil remediation purposes.

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.

Risk assessment of heavy metal(loid)s via Spinacia oleracea ingestion after sewage water irrigation practices in Vehari District.

The use of sewage water as an irrigation source can be beneficial in agricultural practices, however, it may result in human health risks due to the consumption of heavy metal(loid)-contaminated food. This study evaluated the suitability of using sewage water (SW), freshwater (FW), and groundwater (GW) for vegetable irrigation in District Vehari. Spinach (Spinacia oleracea) plants were grown in pots irrigated with FW, GW, and SW in different proportions and combinations. The results indicated the substantial lesser buildup of heavy metal(loid)s (As (- 0.8%), Cd (- 38%), Cr (- 6.2%), Cu (- 20%), Fe (- 9.2%), Mn (- 13%), Ni (- 16%), Pb (- 19%), and Zn (-15%)) in soil after S. oleracea cultivation compared to unirrigated soil possibly due to high metal(loid) uptake by S. oleracea. Irrigation with all types of waters resulted in metal(loid) accumulation in S. oleracea predominantly in roots. The combinations of FW, GW, and SW resulted in high metal(loid) accumulation (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in the edible S. oleracea leaves than their alone application. Owing to high metal(loid) buildup, plants showed a linear trend in physiological imbalance in terms of reduced pigment content, induction of peroxidation, and oxidation of lipids. The severe oxidative stress was observed in S. oleracea plants under FW and GW irrigation due to high metal(loid) accumulation. The risk indices showed possible carcinogenic risk (CR > 0.0001) and non-carcinogenic risk (HI > 1) from the consumption of metal(loid)-contaminated S. oleracea leaves. Results revealed unsuitability of all waters and their combinations for S. oleracea irrigation. Moreover, this study does not encourage the use of mixed water for vegetable irrigation in Vehari District. Therefore, it is of utmost importance to monitor the quality of irrigation waters to ensure food safety and prevent chronic health risks to the exposed population.