Abstract:

A pot experiment was conducted to study effects of phosphorus and silicon on migration of Pb in the soil-tobacco system and to explore approaches to reducing Pb activity in soil and Pb concentration in tobacco leaf. Results show that phosphorus application made exchangeable and carbonate-bound Pb transformed into Fe-Mn oxide-bound and residual Pb in non-rhizospheric soil and silicon application made exchangeable Pb transformed into Fe-Mn oxide-bound Pb. Combined application of phosphorus and silicon made exchangeable Pb transformed into Fe-Mn oxide-bound, organic-bound and residual Pb. Though tobacco roots tend to activate Pb in the rhizosphere, the application of P, Si and P+Si in combination reduced the content of exchangeable Pb in the rhizosphere by 46.05%, 14.24% and 48.76%, respectively, and hence reduction of Pb uptake of tobacco by 44.02%，44.04%，and 65.65%, respectively, thus lowering the concentration of Pb in tobacco leaf by 63.06%, 60.37%, and 83.24%, respectively. P application restricted the transportation of Pb from soil to tobacco leaf by reducing the mobility index of Pb from soil to root (I_Msoil-root) and that from root to stem (I_Mroot-stem) as well. Si application and combined P and Si application restricted the transportation of Pb from soil to tobacco leaf by reducing I_Msoil-root, I_Mroot-stem and I_Mstem-leaf, (the mobility index of Pb from stem to leaf). Application of P and Si is an effective measure to reduce Pb concentration in tobacco leaf, and combined application of P and Si is more effective than the application of merely P or Si.

Key words: phosphorus, silicon, Pb, tobacco, rhizosphere, migration