Response of soil enzyme activity and bacterial community to copper hydroxide nanofertilizer and its ionic analogue under single versus repeated applications

Responses of soil microbiome to copper-based materials (nano and bulk) for agricultural applications: An indoor-mesocosm experiment

The foreseen increasing application of copper-based nanomaterials (Cu-NMs), replacing or complementing existing Cu-agrochemicals, may negatively impact the soil microbiome. Thus, we studied the effects on soil microbiome function and composition of nano copper oxide (nCuO) or copper hydroxide NMs in a commercial (Kocide®3000) or a lab-synthetized formulation (nCu(OH)2) or bulk copper hydroxide (Cu(OH)2-B), at the commonly recommended Cu dose of 50 mg(Cu)kg-1 soil. Microbial responses were studied over 28 days in a designed indoor mesocosm. On day-28, in comparison to non-treated soil (CT), all Cu-treatments led to a reduction in dehydrogenase (95% to 68%), arylsulfatase (41% to 27%), and urease (40% to 20%) activity. There was a 32% increase in the utilization of carbon substrates in the nCuO-treatment and an increased abundance of viable bacteria in the nCu(OH)2-treatment (75% of heterotrophic and 69% of P-solubilizing bacteria). The relative abundance of Acidobacteria [Kocide®3000, nCuO, and Cu(OH)2-B treatments] and Flavobacteriia [nCu(OH)2-treatment] was negatively affected by Cu exposure. The abundance of Cu-tolerant bacteria increased in soils treated with Kocide®3000 (Clostridia) and nCu(OH)2 (Gemmatimonadetes). All Cu-treated soils exhibited a reduced abundance of denitrification-related genes (0.05% of nosZ gene). The DTPA-extractable pool of ionic Cu(II) varied among treatments: Cu(OH)2-B > Kocide®3000 ∼ nCuO>nCu(OH)2, which may explain changes on the soil microbiome composition, at the genera and OTU levels. Thus, our study revealed that Cu-materials (nano and bulk) influence the soil microbiome with implications on its ecological role. It highlights the importance of assessing the impact of Cu-materials under dynamic and complex exposure scenarios and emphasizes the need for specific regulatory frameworks for NMs.

Soil protists are more resilient to the combined effect of microplastics and heavy metals than bacterial communities

Heavy metals and micro-/nanoplastic pollution seriously threaten the environment and ecosystems. While many studies investigated their effects on diverse microbes, few studies have focused on soil protists, and it is unclear how soil protists respond to the combined effect of micro-/nanoplastics and heavy metals. This study investigated how soil protistan and bacterial communities respond to single or combined copper and micro-/nanoplastics. The bacterial community exhibited an instantaneous response to single copper pollution, whereas the combined pollution resulted in a hysteresis effect on the protistan community. Single and combined pollution inhibited the predation of protists and changed the construction of ecological networks. Though single and combined pollution did not significantly affect the overall community structure, the exposure experiment indicated that combined pollution harmed soil amoeba's fitness. These findings offer valuable new insights into the toxic effects of single and combined pollution of copper and plastics on soil protistan and bacterial communities. Additionally, this study shows that sequencing-based analyses cannot fully reflect pollutants' adverse effects, and both culture-independent and dependent methods are needed to reveal the impact of pollutants on soil microbes.

Environmental hazards of WELGRO® Cu+Zn: A nano-enabled fertilizer

Nanoagrochemicals have the potential to revolutionize agriculture towards a precision farming system, able to reduce application rates and consequently their environmental footprint, while keeping efficacy. Several nanoagrochemicals (including nanopesticides (Npes) and nanofertilizers (Nfer)) are already commercialized but the environmental risk assessment of these advanced materials is often lacking. In the present study, we studied the commercial fertilizer WELGRO® Cu + Zn and assessed its ecotoxicity to the soil invertebrate species Enchytraeus crypticus (Oligochaeta), further comparing it to its individual active substances CuO and ZnO. To get a comprehensive picture of possible effects, we used four types of highly relevant tests in LUFA 2.2 soil: 1) avoidance behaviour (2 days), 2) reproduction (OECD standard, 28 d), 3) its extension (56 d), and 4) the full life cycle (FLC) (46 d) - this high level of hazard screening allows for increased interpretation. The results confirmed the nano-features of WELGRO® and a higher toxicity than the mixture of the individual components CuO + ZnO. E. crypticus avoided the soil spiked with WELGRO® and CuO + ZnO, this being the most sensitive endpoint - avoidance behaviour. Both WELGRO® and the active substances were little to non-toxic based on the OECD standard test. However, the toxicity dramatically increased in the tests focussing on longer-term sustainability measures, i.e., 56 days, ca. 170 for WELGRO®. This seems related to the nano-features of WELGRO®, e.g., slow release of ions from the nanoparticles throughout time. The FLCt results showed WELGRO® affected hatching and juveniles' survival, being these the most sensitive life stages. Hence, under actual real world field usage scenarios, i.e., based on the recommended application rates, nanoenabled WELGRO® can affect oligochaete populations like enchytraeids, both via the immediate avoidance behaviour and also via prolonged exposure periods.

Nanofertilizers: Types, Delivery and Advantages in Agricultural Sustainability

In an alarming tale of agricultural excess, the relentless overuse of chemical fertilizers in modern farming methods have wreaked havoc on the once-fertile soil, mercilessly depleting its vital nutrients while inflicting irreparable harm on the delicate balance of the surrounding ecosystem. The excessive use of such fertilizers leaves residue on agricultural products, pollutes the environment, upsets agrarian ecosystems, and lowers soil quality. Furthermore, a significant proportion of the nutrient content, including nitrogen, phosphorus, and potassium, is lost from the soil (50–70%) before being utilized. Nanofertilizers, on the other hand, use nanoparticles to control the release of nutrients, making them more efficient and cost-effective than traditional fertilizers. Nanofertilizers comprise one or more plant nutrients within nanoparticles where at least 50% of the particles are smaller than 100 nanometers. Carbon nanotubes, graphene, and quantum dots are some examples of the types of nanomaterials used in the production of nanofertilizers. Nanofertilizers are a new generation of fertilizers that utilize advanced nanotechnology to provide an efficient and sustainable method of fertilizing crops. They are designed to deliver plant nutrients in a controlled manner, ensuring that the nutrients are gradually released over an extended period, thus providing a steady supply of essential elements to the plants. The controlled-release system is more efficient than traditional fertilizers, as it reduces the need for frequent application and the amount of fertilizer. These nanomaterials have a high surface area-to-volume ratio, making them ideal for holding and releasing nutrients. Naturally occurring nanoparticles are found in various sources, including volcanic ash, ocean, and biological matter such as viruses and dust. However, regarding large-scale production, relying solely on naturally occurring nanoparticles may not be sufficient or practical. In agriculture, nanotechnology has been primarily used to increase crop production while minimizing losses and activating plant defense mechanisms against pests, insects, and other environmental challenges. Furthermore, nanofertilizers can reduce runoff and nutrient leaching into the environment, improving environmental sustainability. They can also improve fertilizer use efficiency, leading to higher crop yields and reducing the overall cost of fertilizer application. Nanofertilizers are especially beneficial in areas where traditional fertilizers are inefficient or ineffective. Nanofertilizers can provide a more efficient and cost-effective way to fertilize crops while reducing the environmental impact of fertilizer application. They are the product of promising new technology that can help to meet the increasing demand for food and improve agricultural sustainability. Currently, nanofertilizers face limitations, including higher costs of production and potential environmental and safety concerns due to the use of nanomaterials, while further research is needed to fully understand their long-term effects on soil health, crop growth, and the environment.

Improved photocatalytic dye degradation and seed germination through enzyme-coupled titanium oxide nanopowder - A cost-effective approach

Enzyme-coupled titanium oxide nanopowder samples were prepared usingdifferent volumes of vermiwash using a cost-effective soft chemical method and their photocatalytic efficiency was studied against Methylene Blue (MB) dye decomposition. The volume of vermiwash used in the starting solution was varied from 50 to 200 mL in steps of 50 mL and the effect of enzymes prevalent in the vermiwash on the photocatalytic activity of titanium oxide (TiO₂) was studied. The resultant water obtained after the photocatalytic dye degradation was found to inherit the enzymes from the nanoproduct. This enzyme-activated treated water showed effective seed germination of black gram (Vigna mungo L.). The results suggested that the enzyme-coupled TiO₂ can be used as an effective and eco-friendly material for the treatment of contaminated water and consequently the treated water can also be utilized for enhanced seed germination.

Nanofertilizers for agricultural and environmental sustainability

Indiscriminate use of chemical fertilizers in the agricultural production systems to keep pace with the food and nutritional demand of the galloping population had an adverse impact on ecosystem services and environmental quality. Hence, an alternative mechanism is to be developed to enhance farm production and environmental sustainability. A nanohybrid construct like nanofertilizers (NFs) is an excellent alternative to overcome the negative impact of traditional chemical fertilizers. The NFs provide smart nutrient delivery to the plants and proves their efficacy in terms of crop productivity and environmental sustainability over bulky chemical fertilizers. Plants can absorb NFs by foliage or roots depending upon the application methods and properties of the particles. NFs enhance the biotic and abiotic stresses tolerance in plants. It reduces the production cost and mitigates the environmental footprint. Multitude benefits of the NFs open new vistas towards sustainable agriculture and climate change mitigation. Although supra-optimal doses of NFs have a detrimental effect on crop growth, soil health, and environmental outcomes. The extensive release of NFs into the environment and food chain may pose a risk to human health, hence, need careful assessment. Thus, a thorough review on the role of different NFs and their impact on crop growth, productivity, soil, and environmental quality is required, which would be helpful for the research of sustainable agriculture.

Sustainable Production of Tomato Plants (Solanum lycopersicum L.) under Low-Quality Irrigation Water as Affected by Bio-Nanofertilizers of Selenium and Copper

Under the global water crisis, utilizing low-quality water sources in agriculture for irrigation has offered an effective solution to address the shortage of water. Using an excess of low-quality water sources may cause serious risks to the environment, which threaten crop safety and human health. Three kinds of irrigation water (0.413, 1.44, and 2.84 dS m−1) were selected under foliar-applied bio-nanofertilizers of selenium (100 mg L−1) and copper (100 mg L−1) in individual and/or combined application. The nanofertilizers were tested on the production of tomato under greenhouse. After harvesting, the quality of tomato yield and soil biology was evaluated. Using saline water for irrigation caused many main features in this study such as increasing the accumulation of salts, soil organic matter, and CaCO3 in soil by 84.6, 32.3, and 18.4%, respectively, compared to control. The highest tomato yield (2.07 kg plant−1) and soluble solids content (9.24%) were recorded after irrigation with low water quality (2.84 dS m−1) and nano-Cu fertilization. The plant enzymatic antioxidants and soil biological activity were decreased in general due to the salinity stress of irrigation water. After 30 days from transplanting, all studied soil biological parameters (soil microbial counts and enzymes) were higher than the same parameters at harvesting (80 days) under different categories of water quality. The values of all soil biological parameters were decreased by increasing water salinity. This study was carried out to answer the question of whether the combined nanofertilizers of selenium and copper can promote tomato production under saline water irrigation. Further investigations are still needed concerning different applied doses of these nanofertilizers.