Abstract:A field experiment was conducted in cadmium contaminated paddy rice field to investigate the effects of combined application of nitrogen and silicon on growth and cadmium accumulation in hybrid rice cultivar Gangyou725. In the present study, three nitrogen (0, 90, 180 kg/hm2) and/or silicon (0, 150, 300 kg/hm2) levels were applied, dry matter weight, nitrogen accumulation in rice shoot, rice yield and its component factors, cadmium content and accumulation amount in rice root and shoot and cadmium content in polished rice were investigated. The results showed that under 3 nitrogen application levels, silicon could improve the root dry matter weight significantly. But it only improved the shoot dry matter weight at 0 and 90 kg/hm2 nitrogen treatments. Under the three nitrogen treatments, the nitrogen accumulation in shoot of the rice was increasing with the silicon levels applying in the field. The yield component factors were significantly affected by combined application of nitrogen and silicon. Treatment with 150 kg/hm2 silicon could increase the effective panicle numbers under the same nitrogen levels, but decrease the 1000–grain weight compared to the treatments with 0 kg/hm2 silicon treatment. Under 0 kg/hm2 nitrogen treatment, applying 150 and 300 kg/hm2 silicon improved the spikelets per panicle significantly compared to the 0 kg/hm2 silicon treatment. Under each nitrogen level, rice yield was higher in 150 and 300 kg/hm2 silicon treatments compared with 0 kg/hm2 silicon treatment, but the effect was not significant under 180 kg/hm2 nitrogen treatment. The cadmium contents in root, stem, panicle and the cadmium accumulation amount were lower in treatment with 150 and 300 kg/hm2 silicon treatments than those in 0 kg/hm2 silicon treatment under each nitrogen level, but the cadmium content in 150 and 300 kg/hm2 silicon treatments was higher than in 0 kg/hm2 silicon treatment. The cadmium contents in polished rice were decreased significantly by the silicon under the three nitrogen levels, there was no difference between the two silicon treatments under 180 kg/hm2 nitrogen treatment. Based on the rice yield and cadmium content in panicle, combined application of 180 kg/hm2 with 150 kg/hm2 silicon could both improve rice yield and decrease cadmium in polished rice.