Effects of metal oxide nanoparticles on soil water retention curve and tensile strength

Generally, nanotechnology plays an very important role in various applied scientific fields. Iron and magnesium nanoparticles (NPs) can cause positive or negative changes in soil physical and mechanical properties, especially in long periods. The aim of this study was to investigate the multi-year effects of NPs on soil water retention and aggregate tensile strength. A wheat farm loamy soil was amended with 1%, 3%, and 5% (weight/weight) of magnesium oxide (MgO) and iron oxide (Fe₃O₄) NPs in three replications and incubated for three years. Water contents were measured at different matric suctions of 0, 10, 20, 40, 60, 100, 300, 1 000, and 15 000 cm. The van Genuchten model was fitted to the moisture data. Tensile strength was measured on the 2–4 mm aggregates at matric suctions of 300 (i.e., field capacity) and 15 000 (i.e., permanent wilting point) cm. The results showed that the levels of 1% and 3% Fe₃O₄ NPs significantly increased water retention, compared to the no NP application control and 5% MgO NPs, which is probably due to the increase of adsorption surfaces in the treated soils. Water contents at field capacity and permanent wilting point in the 5% MgO NP treatment decreased compared to those of the other treatments, due to the increased soil vulnerability and reduced soil fine pores. The application of Fe₃O₄ NPs did not have any significant effect on soil tensile strength. Based on the results of this study, soil physical and mechanical properties could be affected by NP application.