| High heavy metal content in animal manures commonly occurs in the world since microelement additives are widely used in intensive animal production. Successive field trials in Brassica parachinensis (BP) were conducted to investigate the influence of successive application of chicken manure (at the rate of) on the yield and heavy metal content of BP. The application rate of chicken manure was calculated by its N content and ranged from N 0～450 kg·hm-2. The results indicate that compared to single application of inorganic fertilizers, chicken manure decreases the yield of BP in the first and the third crop, increases that in the second crop. Combinations of chicken manure and inorganic fertilizers increase the yield in the fourth yield. Mean yields of all treatments in various crops are greatly different. The second crop is significantly higher than all other crops. In terms of mean heavy metal contents of BP of four crops in various treatment, As and Zn contents increase with applying chicken manure, Cr and Cd contents decrease, Pb contents don't change considerably，and Cu contents increase with applying chicken manure and inorganic fertilizers together. 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. Hence, mass application for one crop or repeated application of chicken manure should be avoided in crop production. |
