[Effects of intercropping Sedum plumbizincicola in wheat growth season under wheat-rice rotation on the crops growth and their heavy metals uptake from different soil types].

A pot experiment with heavy metals- contaminated black soil from Heilongjiang Province, alluvial soil from Henan Province, and paddy soil from Zhejiang Province was conducted to study the effects of intercropping Sedum plumbizincicola in wheat growth season under wheat (Triticum aestivum) - rice (Oryza sativa) rotation on the growth of the crops and their heavy metals uptake, aimed to explore the feasibility of simultaneous grain production and heavy metals-contaminated soil phytoremediation in main food crop production areas of this country. Comparing with monoculture T. aestivum, intercropping S. plumbizincicola increased the soil NaNO3 -extractable Zn and Cd significantly, with the increment of extractable Zn in test paddy soil, alluvial soil, and black soil being 55%, 32% and 110%, and that of extractable Cd in test paddy soil and black soil being 38% and 110%, respectively. The heavy metals concentration in T. aestivum shoots under intercropping S. plumbizincicola was 0.1-0.9 times higher than that under monoculture T. aestivum, but the intercropping had little effects on the rice growth and its heavy metals uptake. Though the Cd concentration in rice grain after S. plumbizincicola planting was still higher than 0.2 mg kg(-1) (the limit of Cd in food standard), it presented a decreasing trend, as compared with that after monoculture T. aestivum. Therefore, intercropping S. plumbizincicola in wheat growth season under wheat-rice rota- tion could benefit the phytoremediation of heavy metals-contaminated soil, and decrease the food-chain risk of rotated rice.

[Effects of Sedum plumbizincicola--Oryza sativa rotation and phosphate amendment on Cd and Zn uptake by O. sativa].

In a pot experiment, hyperaccumulator Sedum plumbizincicola and low-cadmium accumulating Oryza sativa cultivar "Zhongxiang No. 1" were planted in rotation on a heavy metals-polluted soil, and calcium magnesium phosphate (Ca-P) and rock phosphate (P-R) were amended, aimed to study the effects of the rotation and phosphate amendment on the growth of the two plants and the zinc- and cadmium accumulation in their shoots. After the amendment of 50 g P-R x kg(-1), the Zn and Cd uptake by S. plumbizincicola was 11.5 mg x pot(-1) and 0 x 79 mg x pot(-1), respectively, being significantly higher than that after the amendment of 4 g Ca-P x kg(-1). After the planting of S. plumbizincicola, the Zn and Cd concentrations in "Zhongxiang No. 1" increased, but the amendment of Ca-P decreased the accumulation of Zn and Cd in rice shoot significantly. The rotation with S. plumbizincicola and the amendment of Ca-P and P-R could immobilize the Zn and Cd in the contaminated soil as indicated by the quantitative change of NH4OAc-extractable Cd and Zn, and the efficiency of amendment with Ca-P was better than that of amendment with P-R. Field trial showed that amendment with Ca-P could not only increase the rice yield, but also reduce the Zn and Cd accumulation in rice shoot to a certain extent.