Both Zn biofortification and nutrient distribution pattern in cherry tomato plants are influenced by the application of ZnO nanofertilizer.

A pot experiment was conducted to determine the influence of commercial nanoparticles (ZnO-NPs) at different doses for use as nanofertilizer on nutrient uptake and its distribution in cherry tomato (Solanum lycopersicum L var. cerasiforme) plants in an acidic (soil pH 5.5) and calcareous soil (soil pH 8.5) from the Mediterranean area. We determined crop yield; macro- (N, P, K, Mg, S and Ca) and micro-nutrient (B, Cu, Fe, Mn, Na and Zn) concentrations in the different parts of the crop (root, stem, leaves and tomato fruits) and the extent of nutrient translocation to the aerial part of the plant. The concentrations of macronutrients N, P, K and Mg in tomato fruits grown in both soils can be considered adequate in terms of nutritional requirements. However, the Ca concentration in tomato fruits grown in the calcareous soil did not reach the required concentration to be considered sufficient. This effect was related to the characteristics of this calcareous soil. Although different concentrations of ZnO-NPs did not affect Fe and Na concentrations in tomato fruit, B concentration in tomato fruits increased with the application of ZnO-NPs. In addition, Cu concentration decreased with the application of ZnO-NPs compared to treatments without any Zn application (Nil-ZnO NP) in the calcareous soil. Manganese concentrations decreased with ZnO-NPs application in both soils. The effect of the application of ZnO-NPs depends on soil characteristics. Zinc applied as a nanofertilizer in the form of ZnO-NPs can be used to increase the crop yield and to obtain an adequate Zn biofortification in cherry tomato crop. The Zn concentrations in tomato fruits reached ranges of 4.5-4.8 mg Zn kg-1 in the acidic soil and 2.5-3,5 mg Zn kg-1 in the calcareous soil. Nutrient concentrations in these fruits following biofortification are adequate for human consumption.

Effect of ageing of bare and coated nanoparticles of zinc oxide applied to soil on the Zn behaviour and toxicity to fish cells due to transfer from soil to water bodies.

This study evaluated the influence of ageing of ZnO nanoparticles (NPs) applied to soil on the potential availability and chemical speciation of Zn, and also of their toxicity to aquatic organisms due to transfer of contaminants from soil to water. To this end, soil samples were spiked with two types of bare nanoparticles: b1ZnO NPs (rod- and elongated-shaped) and b2ZnO NPs (near-spherical shaped) and ZnO NPs coated with (3-aminopropyl)triethoxysilane (cZnO NPs) within the 0-800 mg Zn kg-1 soil dose range, and were left to age for 0, 30, 60 and 90 days. The available concentration and speciation of Zn in soil were determined by the DGT (diffusive gradients in thin films) technique and sequential extraction procedures, respectively. The toxicity of the aqueous extracts from the ZnO NP-treated soils was assessed in vitro in established fish cell lines (RTG-2). The highest distribution percentages of the applied Zn occurred in the organically complexed (OC), followed by the exchangeable (EXC) fraction, for all NP types, applied doses and incubation times. The toxicity of NPs depended on their intrinsic properties: b1ZnO NPs affected the membrane function, reductase enzyme activity and, to a lesser extent, reactive oxygen species (ROS) levels of fish cells, whereas b2ZnO NPs and cZnO NPs affected mainly ROS generation. Ageing increased Zn soil availability, but toxicity to fish cells showed no trend over time. The particle dissolution of ZnO NPs did not explain the observed toxicity, hence a nanoparticles-specific effect should be assumed. The findings of this study seem to indicate that the transfer of ZnO NP from contaminated soils to aquatic ecosystems should be addressed.

Joint effects of zinc oxide nanoparticles and chlorpyrifos on the reproduction and cellular stress responses of the earthworm Eisenia andrei.

The co-exposure of soil organisms to ZnO nanoparticles (ZnO NPs) and pesticides is likely to take place in agricultural soils. However, the impacts of co-exposure on terrestrial ecosystems are virtually unknown. In this paper, Eisenia andrei was exposed for a 28-day period to serial concentrations of ZnO NPs and/or the organophosphate insecticide chlorpyrifos (CPF) in natural soil, and was evaluated for single and joint effects. Zn and CPF accumulation in earthworm tissue was also determined. In the single assay, ZnO NPs and CPF caused statistical significant effects on survival and growth, but mainly on reproduction. Significant reductions in fecundity and fertility were detected with EC50 values of 278 and 179 mg Zn/kg for ZnO NPs, and of 50.75 and 38.24 mg/kg for CPF, respectively. The most notable effect on biomarkers was the reduction in acetylcholinesterase (AChE) activity caused by CPF, which reflected the neurotoxicity of this compound. The results of the combined assay indicated that co-exposure to ZnO NPs and CPF increased adverse effects in E. andrei. According to the independent action model, the binary mixtures showed a synergism (a stronger effect than expected from single exposures) on earthworm reproduction, which became up to 84% higher than the theoretically predicted values. Zn, and especially CPF accumulation, were influenced by the co-exposure. These results underpin the need to consider the effects of mixtures of NPs and organic chemicals on soil to adequately make ecological risk assessments of NPs.

Zinc application in conjunction with urea as a fertilization strategy for improving both nitrogen use efficiency and the zinc biofortification of barley.

BACKGROUND: Intensive cropping systems have caused widespread Zn deficiency, low nutritional quality of cereals and environmental problems. The aim of the microplot field experiment reported in this paper was to assess the option of using Zn in conjunction with urea fertilization in order to reduce N rate and to maintain the yield level and grain quality but minimizing environmental risks. Barley (Hordeum vulgare L.) was cultivated in a calcareous soil under semi-realistic conditions. Combinations of four Zn levels, applied by spraying aqueous solutions of ZnSO4 , and three N levels, applied by spreading granular urea, were tested. RESULTS: Zn and N showed a synergistic effect, increasing yield and Zn content in all plant parts and protein content in grain. A low Zn dosage of 5 kg ha-1 was sufficient to significantly increase the amount of bioavailable Zn in soil and significantly raise its concentration in plant material and also the protein content in grain. The remobilization of Zn from leaf tissue to grain was dependent on the availability of Zn and was only crucial when its bioavailability was low. CONCLUSIONS: A Zn dosage of 5 kg ha-1 enhanced the agronomic efficiency of N by 15.5 kg grain kg-1 N. The Zn applied to the soil permitted a reduction in the rate of N with only a small decrease in barley grain yield and nutritional value. However, due to the interannual variability in rainfall, which is characteristic of Mediterranean climates, further studies will be necessary to confirm and extend these results. © 2019 Society of Chemical Industry.