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.

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.

Impacts of COVID-19 pandemic on environment, society, and food security.

Coronavirus disease (COVID)-19 is a viral and transferable disease caused by severe respiratory syndrome-coronavirus-2. It can spread through breathing droplets in human beings. It caused 5.32 million deaths around the world at the end of 2021. COVID-19 has caused several positive impacts as well, such as a reduction in air, water, and noise pollution. However, its negative impacts are by far critical such as increased death rate, increased release of microcontaminants (pesticides, biocides, pharmaceuticals, surfactants, polycyclic aromatic hydrocarbons (PAHs), flame retardants, and heavy metals), increased biomedical waste generation due to excessive use of safety equipment and its disposal, and municipal solid waste generation. Environmental pollution was significantly reduced due to lockdown during the COVID-19 period. Therefore, the quality of air and water improved. COVID-19 affected all sections of the population, particularly the most vulnerable members of society, and thus pushed more people into poverty. At the world level, it increased risks to food safety by increasing prices and lowering revenues, forcing households to reduce their food consumption in terms of quantity and quality. COVID-19 also upset various exercises e.g., horticulture, fisheries, domesticated animals, and agribusiness hence prohibiting the development of merchandise for poor-country ranchers. Most of the patients can self-recover from COVID-19 if they do not have any other diseases like high blood pressure, diabetes, and heart problems. Predictably, the appropriate execution of the proposed approaches (vaccination, wearing face masks, social distancing, sustainable industrialization) is helpful for worldwide environmental sustainability.

Evaluating the Impact of Nitrogen Application on Growth and Productivity of Maize Under Control Conditions.

Climatic conditions significantly affect the maize productivity. Among abiotic factors, nitrogen (N) fertilizer and temperature are the two important factors which dominantly affect the maize (Zea mays L.) production during the early crop growth stages. Two experiments were conducted to determine the impact of N fertilizer and temperature on the maize growth and yield. In the first experiment, the maize hybrids were screened for their sensitivity to temperature variations. The screening was based on the growth performance of the hybrids under three temperatures (T 1 = ambient open-air temperature, T 2 = 1°C higher than the ambient temperature, and T 3 = 1°C lower than the ambient temperature) range. The results showed that an increase in temperature was resulted less 50% emergence and mean emergence (4.1 and 6.3 days, respectively), while emergence energy and full emergence were higher (25.4 and 75.2%, respectively) under the higher temperature exposure. The results showed that Syngenta 7720 and Muqabla S 25W87 were temperature tolerant and sensitive maize hybrids, respectively. The second experiment was carried out to study the response of the two selected maize hybrids (Syngenta 7720 and Muqabla S 25W87) to four N fertilizer applications. The results revealed that the maximum N use efficiency (19.5 kg kg-1) was achieved in maize hybrids with low N application (75 kg N ha-1 equivalent to 1.13 g N plant-1). However, the maximum maize grain yield (86.4 g plant-1), dry weight (203 g plant-1), and grain protein content (15.0%) were observed in maize hybrids that were grown with the application of 300 kg N ha-1 (equivalent to 4.52 g N plant-1). Therefore, it is recommended that the application of 300 kg N ha-1 to temperature tolerant maize hybrid may be considered best agricultural management practices for obtaining optimum maize grain yield under present changing climate.

Zinc in soil-plant-human system: A data-analysis review.

Zinc (Zn) plays an important role in the physiology and biochemistry of plants due to its established essentiality and toxicity for living beings at certain Zn concentration i.e., deficient or toxic over the optimum range. Being a vital cofactor of important enzymes, Zn participates in plant metabolic processes therefore, alters the biophysicochemical processes mediated by Zn-related enzymes/proteins. Excess Zn can provoke oxidative damage by enhancing the levels of reactive radicals. Hence, it is imperative to monitor Zn levels and associated biophysicochemical roles, essential or toxic, in the soil-plant interactions. This data-analysis review has critically summarized the recent literature of (i) Zn mobility/phytoavailability in soil (ii) molecular understanding of Zn phytouptake, (iii) uptake and distribution in the plants, (iv) essential roles in plants, (v) phyto-deficiency and phytotoxicity, (vi) detoxification processes to scavenge Zn phytotoxicity inside plants, and (vii) associated health hazards. The review especially compares the essential, deficient and toxic roles of Zn in biophysicochemical and detoxification processes inside the plants. To conclude, this review recommends some Zn-related research perspectives. Overall, this review reveals a thorough representation of Zn bio-geo-physicochemical interactions in soil-plant system using recent data.

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.

Silicon-mediated growth promotion in maize (Zea mays L.) occurs via a mechanism that does not involve activation of the plasma membrane H+-ATPase.

Silicon (Si)-mediated growth promotion of various grasses is well documented. In the present study, Si-induced changes in maize shoot growth and its underlying mechanisms were studied. Maize plants were grown with various concentrations of Si (0-3 mM) in the nutrient solution. Silicon nutrition improved plant expansion growth. Silicon-supplied maize plants (0.8 and 1.2 mM) showed higher plant height and leaf area compared to no-Si amended plants. It was assumed that Si-induced expansion growth was due to positive Si effects on plasma membrane (PM) H+-ATPase. In this context, western blot analysis revealed an increase in PM H+-ATPase abundance by 77% under Si nutrition. However, in vitro measurements of enzyme activities showed no significant effect on apoplast pH, proton pumping, passive H+ efflux and enzyme kinetics such as Km, Vmax, and activation energy. Further, these results were confirmed by in vivo ratiometric analysis of apoplastic pH, which showed non-significant changes upon Si supply. In contrast, 1 mM Si altered the relative transcripts of specific PM H+-ATPase isoforms. Silicon application resulted in a significant decrease of MHA3, and this decrease in transcription seems to be compensated by an increased concentration of H+-ATPase protein. From these results, it can be concluded that changes in cell wall composition and PM H+-ATPase may be responsible for Si-mediated growth improvement in maize.

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.