Abstract:
A pot experiment with Cd-contaminated soil was conducted to study the effects of different nitrogen fertilizers and application rates on Cd uptake and grain yield of rice. Among four nitrogen fertilizers combined with same P and K fertilizers, urea produces the highest rice yield. Next is (NH
4)
2SO
4 and NH
4Cl, followed by NH
4NO
3, which produces the lowest yield. Among the four nitrogen fertilizers, NH
4Cl more significantly increases rice Cd content than urea, (NH
4)
2SO
4 and NH
4NO
3. It also facilitates Cd transfer from rice straw to grain. There is no significant difference in Cd contents in straw and grain among the other three nitrogen fertilizers treatment. While optimal rate of urea 0.2 g(N)·kg
-1 significantly lowers Cd content in rice grain, either zero N or high urea application rate significantly enhances grain Cd content. In Cd-contaminated paddy soils, using Cd-resistant rice cultivars in combination with optimized fertilization and water management practices considerably lowers grain Cd content below the maximum permissible level for pollution-free rice production.