Influence of Cu2O and Cu Engineered Nanoparticles on Soil Properties and Nutrient Availability

The increasing use of nano-agrochemical formulations in agricultural systems has intensified concerns regarding their impact on soil properties and nutrient dynamics. This study aimed to compare the effects of engineered copper (I) oxide nanoparticles (Cu2O-ENPs) and engineered copper nanoparticles (Cu-ENPs) on chemical and physical properties, as well as on phosphorus (P) availability, in a volcanic soil (VS). Soil samples were incubated for one day with both types of ENPs at a 1% dose under controlled conditions, and changes in pH, electrical conductivity (EC), organic matter (OM), bioavailable copper (Cu), specific surface area (SSA), pore volume (PV) and pore diameter (PD), among other parameters, were evaluated. Additionally, to determine the impact of Cu-based ENPs on P availability, adsorption–desorption studies were conducted using batch systems in triplicate. The findings revealed that both Cu-based ENPs altered the soil’s chemical and physical properties. Notably, both types of ENPs increased the bioavailability of Cu2+, with a more pronounced effect observed for Cu-ENPs (720 ± 4.20 mg kg−1), indicating their higher dissolution rates. This phenomenon was associated with an increase in soil EC. Furthermore, Cu-based ENPs decreased SSA and PV, and PD in VS, with a higher effect for Cu2O-ENPs (SSA = 10.035 m2 g−1, PV = 0.009 cm3 g−1, and PD = 3.608 nm). The application of 1% Cu-based ENPs enhanced the adsorption of P in VS at pH = 4.5 and pH = 5.5, with a greater effect observed for 1% Cu-ENPs than with 1% Cu2O-ENPs. In contrast, 1% Cu2O-ENPs retained a higher amount of P in VS than 1% Cu-ENPs. Collectively, the results of this study provide novel insights into the contrasting effects of Cu2O-ENPs and Cu-ENPs in agricultural soils, underscoring the need for further investigation of ENPs to elucidate the underlying mechanisms and the long-term implications for soil health and agricultural productivity.