Amendment of Agricultural Soil with Metal Nanoparticles: Effects on Soil Enzyme Activity and Microbial Community Composition

Abstract

Several types of engineered nanoparticles (ENPs) are being considered for direct application to soils to reduce the application and degradation of pesticides, provide micronutrients, control pathogens, and increase crop yields. This study examined the effects of different metal ENPs and their dissolved ions on the microbial community composition and enzyme activity of agricultural soil amended with biosolids. The activity of five extracellular nutrient-cycling enzymes was measured in biosolid-amended soils treated with different concentrations (1, 10, or 100 mg ENP/kg soil) of silver (nAg), zinc oxide (nZnO), copper oxide (nCuO), or titanium dioxide (nTiO) nanoparticles and their ions over a 30-day period. At 30 days, nZnO and nCuO either had no significant effect on soil enzyme activity or enhanced enzyme activity. In contrast, Ag inhibited selected enzymes when dosed in particulate or dissolved form (at 100 mg/kg). nTiO either had no significant effect or slightly decreased enzyme activity. Illumina MiSeq sequencing of microbial communities indicated a shift in soil microbial community composition upon exposure to high doses of metal ions or nAg and negligible shift in the presence of nTiO. Some taxa responded differently to nAg and Ag. This work shows how metal ENPs can impact soil enzyme activity and microbial community composition upon introduction into soils amended with biosolids, depending on their type, concentration, and dissolution behavior, hence providing much needed information for the sustainable application of nanotechnology in agriculture.

Effects of Nanoparticles on Plant Growth-Promoting Bacteria in Indian Agricultural Soil

“…Perturbations in microbial community structure due to these nanoparticles have also been reported in other soils [86][87][88]. These studies have used a wide range of concentrations of silver nanoparticles from 0.01 µg/g to 1815 µg/g of soil and varying exposure times, of one day to one year [39,72,[82][83][84][85]89]. Two of these studies have also described bacterial communities recovering after 21 to 50 days following an initial shift [35,84].…”

“…The preliminary nature of the work does not permit definite conclusions to be drawn with respect to diversity. However, changes in soil bacterial diversity have been described in earlier studies in the presence of silver nanoparticles [38,[82][83][84][85].…”

Impact of silver nanoparticles (AgNP) on soil microbial community depending on functionalization, concentration, exposure time, and soil texture

“…Because of the spatial structure imposed by soil particles resulting in local variations in oxygen availability over small distance [81], both aerobic and anaerobic conditions can be found in the same soil sample. Thus, AgNO 3 control could act as substrate for nitrate reducing bacteria, such as gamma-Proteobacteria or Acidobacteria [63,82,83], which were less sensitive to AgNP or Ag + in form of AgNO 3 [78,84,85] and promoted their increase due to nitrate utilization via denitrification and/or dissimilatory nitrate reduction [81,83] resulting in new nitrogen sources for the ammonia-oxidizing and nitrogen fixing bacteria.…”

Relationship between enantioselective transformation of racemic quizalofop‐ethyl and soil bacterial diversity: A destructive approach

“…The composition of bacterial communities in restored soil differed significantly ( P < .05) from those in native soil and changed with restoration time. A decrease in the abundance of soil microorganisms also occurred in response to other disturbances, including chloroform fumigation, fire, pesticides, heavy metal ions, or engineered nanoparticles in the soils …”

“…A decrease in the abundance of soil microorganisms also occurred in response to other disturbances, including chloroform fumigation, 18 fire, 24 pesticides, 23 heavy metal ions, 25,26 or engineered nanoparticles in the soils. 27,28 Griffiths et al reported random changes in the dominant bacteria that occurred after the chloroform fumigation. 18 In this study, all microorganisms were reduced or eliminated from the autoclaving, as indicated by no detectable MBC or extractable trace DNA in the autoclaved soil.…”