Lightly polluted paddy soil was selected and a two-factor pot experiment was conducted in Wuxue County, Hubei Province, to clarify the cadmium reduction effects of applying nano-silicon and active-silicon under different cadmium pollution conditions. Three levels of cadmium (Cd1, no cadmium added, low cadmium; Cd2, add 5 mg/kg cadmium, medium cadmium; Cd3, add 10 mg/kg cadmium, high cadmium) and three levels of silicon fertilizer (Si0, no silicon fertilizer applied; Si1, 20 mg/pot nano-silicon sprayed on leaves; Si2, 20 mg/pot nano-silicon sprayed on leaves+120 mg/kg active-silicon applied on soil) were set for a total of nine treatments. The results showed that with the increase of soil cadmium concentration, the biomass of rice roots, stems and leaves decreased, the number of effective panicles decreased, and the yield significantly decreased. Compared with Cd1 treatment, the rice yield of Cd2 and Cd3 treatments decreased by 7.1% and 20.0%, respectively. Applying silicon fertilizer could reduce the cadmium content in roots, stems, and leaves, promote the accumulation of dry matter in roots and aboveground parts, increase the number of effective panicles, and thereby increase rice yield. Compared with Si0 treatment, the rice yield of Si1 and Si2 treatments increased by 12.3% and 15.4%, the cadmium content in brown rice decreased by 26.0% and 42.3%, the cadmium content in milled rice decreased by 25.2% and 42.0%, respectively. Si1 and Si2 treatments could reduce the transport of cadmium from chaff to brown rice and milled rice. The cadmium reduction effect of Si2 treatment is better than that of Si1 treatment. In summary, under medium and high cadmium stress, spraying nano-silicon on rice leaves and applying active-silicon to the soil have significant effects on increasing yield and reducing cadmium, which can be further studied as an effective measure for cadmium reduction in cadmium polluted paddy fields.
