Impact of smart combinations of graphene oxide and micro/nanosized sulfur particles on soil health and plant biomass accumulation

Background: Elemental sulfur (S-0) is a cost-efficient fertilizer and the least rapidly utilizable source of S for soil microorganisms and plants. Its bacterial-mediated oxidation to sulfates is dependent on particle size. Finely formulated (micronized, nanosized) S-0 exerts enhanced oxidation rate and benefit due to nutrient availability and crop nutrition efficiency. Graphene oxide (GO) affects soil properties both negatively and positively. A pot experiment was carried out with lettuce using soil supplemented with S-0 in different composition, applied alone or in combination with GO. The following variants were tested: control, GO, micro-S-0, micro-S-0 + GO, nano-S-0, nano-S-0 + GO. Results: Nanosized S-0 improved most of enzyme activities (dehydrogenase, arylsulfatase, N-acetyl-beta-D-glucosaminidase, beta-glucosidase, phosphatase). However, respirations induced by D-glucose, protocatechuic acid, L-arginine were decreased. GO mitigated negative to neutral effect of micro-S-0 in the soil pH, dehydrogenase and urease activity. Furthermore, micro-S-0 positively affected basal respiration and respirations induced by D-trehalose and N-acetyl-beta-D-glucosamine. Nano-S-0 + GO improved plant biomass yield and enzyme activities. However, nano-S-0 + GO significantly decreased all substate-induced respirations. Conclusions: The benefit of soil treatment with nano-/micro-sized S-0 and its combination with GO on soil biological parameters was partially demonstrated.