Study on forms of Pb in Purple Soil - Rice Plant System and Plant Response.
Zhou Yong (Sichuan Academy of A-gricultural Sciences .Chengdu 610066).Tu Cong and Qing Changle(.Dcpt. of Soil Science, Southwest Agricultural U-niversity, Chongqing 630716)
The form and availability of Pb and its ef- feet on rice in acideaeutral anti calcareous purple soils were studied. Significant injury was found in rice growing in acid and calcareous purple soils at 1000 and 2000 rng/kg Pb,respectively. However,no significant injury was found in neutral purple soil at Ph up to 4000mg/kg. Ph content in different parts of plant ricf was significantly related to Ph added in soil and in orders of acid purple soilcalcareous purple soil neutral purple soil ,and roots rice straw brown rice. Pb was mostly remained in roots, accounting for more than 90% of Pb absorbed by rice. The addition of Pb increased the proportion of more available Pb fractions. and reduced that of residual fraction. Plant responses to Pb were more sensitive in soil with higher exchangeable and / or carbonate or weakly bound Pb. Available Pb may unify the critical concentration of Pb in various soils.