Generally,except for the second crop,mean As,Pb,Cr,Cu and Zn contents of BP in various crops increase with the increasing application times of chicken manure,mean Cd contents decrease.

• 除第2茬因产量稀释作用影响外；不同茬别所有处理菜心As、Pb、Cr、Cu、Zn平均含量随施用茬数增加而提高；Cd平均含量则下降.