生物质炭施用和不同水分管理对水稻生长和Cd吸收的影响

Effects of the biochar application and water management on the rice growth and Cd accumulation

向实际Cd污染土壤中添加不同质量比（0.5%、1%和2%）的生物质炭,并结合不同水分管理方式,研究该处理对Cd污染土壤的修复效果。结果表明,添加生物质炭提高了淹水处理中水稻各生育期土壤溶液p H值和可溶性有机碳（DOC）质量浓度及土壤p H值,且增幅随生物质炭添加量增加而升高;旱作处理中仅2%生物质炭添加量处理显著提高了各生育期土壤溶液p H值和DOC质量浓度,但所有处理均提高了土壤p H值;生物质炭显著降低了土壤Cd生物有效性,下降幅度达5.09%~68.7%。施用生物质炭后,水稻的株高、稻米产量和水稻总生物量均有显著提高。淹水条件下施用生物质炭显著降低了水稻籽粒中Cd质量比（下降幅度为36.9%~73.4%）,而在旱作条件下则增加了水稻籽粒中Cd质量比,这可能与不同水分条件下生物质炭的分解及其携带的Cd有关。研究表明,采用1%生物质炭施用量和淹水的农业措施可有效降低土壤有效态Cd含量和水稻籽粒中Cd含量。

The present paper is to introduce its study on the effects of the biochar application and water control on the rice growth and Cd accumulation in Cd contaminated soil. As is known,biochar is a kind of newly material for restoring the contaminated soil,though little is known about its repair mechanism with different agronomic measures for the heavy metal contaminated soil. The effects of biochar dosages（ 0. 5%,1% and 2%）and water management on the growth of rice and Cd accumulation in rice have been studied in the pot experiments. The results of our experiments show that the addition of biochar tends to increase p H value and DOC content in the soil solution of different rice growth stages under the waterflooding condition, and the increased rate in correspondence with the dosages of biochar. However,only 2% dosage treatment under the dry farming condition could increase p H value and DOC content in the soil solution.When biochar is applied,it can be found that the soil＇s p H value can be found increasing from 5. 06 to 5. 81 under the waterflooding condition and from 5. 13 to 6. 28 under the dry farming condition. At the same time,bioavailable Cd contents in the soils with different treatments tend to decrease significantly by a factor of5. 09% to 68. 7%. Biochar can thus be found functioning significantly in promoting rice growth in Cd contaminated soil,including promoting the rice plant growth,the rice grain yield and the rice biomass. The rice yield and the whole plant biomass under the treatment with 2% biochar have been found increased about twice as much as that of the contrast group under the waterflooding condition. What is more,the application of biochar helps to reduce the Cd content in rice grain significantly. Under the waterflooding condition,Cd content in the rice grain can be decreased by73. 4%,66. 2% and 36. 9% through the treatment of 0. 5%BCW,1% BCW and 2% BCW,respectively. Cd contents in the rice grain by 0. 5% BCW and 1% BCW treatments can be made to reach the national food standard（ GB 2762—2005）. Nevertheless,biochar may help to increase Cd content in the rice grain under the dry farming condition,which is likely to be involved with the easy release of Cd by biochar under such dry condition.Thus,it can be concluded that adding 1% of biochar to the waterflooding can effectively decrease the soil bioavailable Cd content and Cd content in the rice grain.