Abstract:

In recent years, biochar as a soil amendment has been widely used in soil carbon sequestration and emission mitigation, fertility improvement, and heavy metal pollution control. Although biochar can effectively reduce the bioavailability of heavy metals such as Cd in the soil-rice system, there is relatively little research on the impact of biochar application on the uptake of trace elements by rice. The effect of applying wheat straw biochar (20 t·hm^-2 and 40 t·hm^-2) on the content of trace elements Fe, Mn, Cu, and Zn in different parts of rice was studied through field experiments, in order to provide case support for better understanding of the impact of biochar on the uptake and accumulation of trace elements in rice. Results showed that the Fe, Cu, and Zn contents in various parts of rice are as following order: root>straw>grain. Fe content in rice roots is much higher than that in other parts, while the Mn content in straw is much higher than that in roots, and the grain part is the lowest. Compared with the dosage of 20 t·hm^-2, 40 t·hm^-2 biochar treatment can better reduce the Fe content in rice grains, straw, and roots, with a decrease of 56.7%, 13.0%, and 39.4%, respectively; The application of 40 t·hm^-2 biochar treatment reduced the Mn content in rice grains and straw by 35.6% and 43.7%, respectively. In addition, only 40 t·hm^-2 biochar treatment significantly reduced the Cu content in rice roots by 47.2%, while only 20 t·hm^-2 biochar treatment significantly reduced the Zn content in rice straw by 17.6%. The above results indicate that the application of biochar has a various effects on the trace element Fe, Mn, Cu, and Zn content in rice. The application of biochar is more conducive to reducing the content of Fe and Mn in various parts of rice, and the impact on Cu and Zn content is relatively small, which is related to the application amount of biochar. Attention should be paid to the impact of high dosage of biochar on the absorption of trace elements in rice.

Key words: biochar, heavy metal, rice, uptake and accumulation, in-situ passivation