Porous silica nanocarriers have the potential to improve agricultural crop productivity. However, the impacts of nanoencapsulated pesticides on soil health and plant growth, and how they compare with conventional pesticide...

Biostimulation by addition of nitrogen (N) and phosphorus (P) for enhancement of biodegradation of petroleum hydrocarbons in contaminated soils is a common practice in sub-Arctic (cold) regions. Based on the data reported in 58 peerreviewed papers on hydrocarbon degradation in northern region soils, there was no identifiable optimal nutrient dose, although applied doses ranged over 3 orders of magnitude. Microcosm slurry biodegradation experiments conducted over a range of N (41 to 1350 mg/kg) and P (46 and 115 mg/kg) doses, using a northern site soil spiked with Arctic diesel, also showed comparable results. While addition of nutrients improved degradation extents, the degradation extents were not dependent on N and P doses. Biodegradation rate constants for C 10 −C 16 and C 16 −C 24 hydrocarbon fractions, however, showed the highest enhancements for the lowest N dose. Microbial community composition analysis based on 16S rRNA sequencing of DNA extracted from microcosms amended with only diesel, only nutrients, and both diesel and nutrients revealed that diesel enriched hydrocarbon degraders such as Pseudomonadaceae and Burkholderiaceae. Overall, our results and analyses show limited benefits of biostimulation of hydrocarbon degradation with high nutrient doses, and low nutrient doses are generally more or equally effective.

No abstract

Porous silica nanocarriers have the potential to improve agricultural crop productivity. However, the impacts of nanoencapsulated pesticides on soil health and plant growth, and how they compare with conventional pesticide have not been systematically elucidated. In this study, we investigated how applying azoxystrobin encapsulated in porous hollow SiO2 nanocarriers to agricultural soil impacted the soil microbial community and plant development, using Solanum lycopersicum grown in the laboratory in soil microcosms. The data show that plant growth was heavily inhibited by the non-encapsulated pesticide treatment compared to that with encapsulated pesticide yielding 3.85-fold less plant biomass, while the soil microbial community experienced few to no changes regardless of the treatment. There was a 2.7-fold higher azoxystrobin uptake per unit dry plant biomass after 10 days of exposure for the non-encapsulated pesticide treatment when compared to that of nanoencapsulated pesticide, but only 1.5-fold increase in total uptake. After 20 days of exposure, however, the total uptake and uptake per unit of dry biomass were 3-fold and 10-fold higher, respectively, for the nanopesticide treatment. The differences in uptake can be attributed to phytotoxicity caused by the high the bioavailability of the non-encapsulated pesticide. The nanocarrier promoted slow release of the pesticide over days, which prevented phytotoxicity, and allowed healthy plant growth.

Porous silica nanocarriers have the potential to improve agricultural crop productivity. However, the impacts of nanoencapsulated pesticides on soil health and plant growth, and how they compare with conventional pesticide have not been systematically elucidated. In this study, we investigated how applying azoxystrobin encapsulated in porous hollow SiO2 nanocarriers to agricultural soil impacted the soil microbial community and plant development, using Solanum lycopersicum grown in the laboratory in soil microcosms. The data show that plant growth was heavily inhibited by the non-encapsulated pesticide treatment compared to that with encapsulated pesticide yielding 3.85-fold less plant biomass, while the soil microbial community experienced few to no changes regardless of the treatment. There was a 2.7-fold higher azoxystrobin uptake per unit dry plant biomass after 10 days of exposure for the non-encapsulated pesticide treatment when compared to that of nanoencapsulated pesticide, but only 1.5-fold increase in total uptake. After 20 days of exposure, however, the total uptake and uptake per unit of dry biomass were 3-fold and 10-fold higher, respectively, for the nanopesticide treatment. The differences in uptake can be attributed to phytotoxicity caused by the high the bioavailability of the non-encapsulated pesticide. The nanocarrier promoted slow release of the pesticide over days, which prevented phytotoxicity, and allowed healthy plant growth.