种植制度对水稻籽粒铅、镉含量的影响

为比较不同种植制度对水稻籽粒铅、镉含量及变化的影响,从2016年开始,在衡阳和岳阳地区实施为期3 a的大田定位试验,探究稻-稻-紫云英、稻-稻-冬闲和稻-稻-油菜3种不同种植制度下,水稻籽粒中铅和镉含量的高低及其变化趋势。结果表明,各种植制度的水稻籽粒铅、镉含量变化呈现出先升高后降低的趋势。实施种植制度3 a后,相比于稻-稻-冬闲,稻-稻-油菜种植制度显著降低了早稻和晚稻籽粒镉含量,平均降低幅度分别为23.90%和47.30%,稻-稻-紫云英和稻-稻-冬闲之间没有显著差异;相比于其他种植制度,稻-稻-紫云英种植制度会显著提高早稻和晚稻籽粒中铅含量,平均提高幅度分别为50.42%和80.49%,稻-稻-冬闲和稻-稻-油菜之间没有显著差异。研究发现,与种植第一年相比,3 a后稻-稻-油菜种植制度能够显著提高衡阳和岳阳的土壤pH(增幅分别为8.60%和10.33%),并显著降低土壤有效态铅含量(衡阳地区除外)和有效态镉含量,稻-稻-紫云英种植制度会增加土壤的有效态铅含量(增幅分别为17.51%和13.32%)。从季别来看,湖南地区水稻品种早39在晚稻季收获的籽粒镉含量要显著高于早稻季118.93%～429.11%,而在早稻季收获的籽粒铅含量要显著高于晚稻季10.71%～59.20%。综合考虑,在南方重金属污染的多熟制地区,应选择稻-稻-油菜种植制度作为主流的种植制度。

Effect of cropping system on Cd and Pb content in rice grains

To compare the effects of different cropping systems on the concentrations of Pb and Cd in rice grains and changes thereof, a three-year field positioning experiment that began in 2016 was carried out in Hengyang and Yueyang. The levels and trends of Pb and Cd in rice grains were studied under three different cropping systems(Rice-Rice-Astragalus sinicus, Rice-Rice-Winter fallow, and RiceRice-Rape). The results showed that the content of Pb and Cd in rice grains first increased and then decreased. Three years after the implementation of the cropping system, compared with the Rice-Rice-Winter fallow cropping system, the Rice-Rice-Rape system significantly reduced the Cd content in the early and late rice grains, with average reductions of 23.90% and 47.30%, respectively. There was no significant difference between the Rice-Rice-Astragalus sinicus and the Rice-Rice-Winter fallow cropping systems. Compared with other cropping systems, the Rice-Rice-Astragalus sinicus cropping system significantly increased the Pb content in the early and late rice grains, with average increases of 50.42% and 80.49%, respectively. There was no significant difference between the Rice-Rice-Winter fallow and Rice-Rice-Rape systems. Compared with the first year of planting, the Rice-Rice-Rape cropping system can significantly improve the soil pH of Hengyang and Yueyang(by 8.60% and 10.33%, respectively), and significantly reduce the soil available Pb content(except for that of Hengyang)and available Cd content. The Rice-Rice-Astragalus sinicus cropping system can increase the soil available Pb content(by 17.51% and 13.32%, respectively). From the perspective of season, the Cd content of Zhongzao 39 in the late rice grains was significantly higher than that of early rice(118.93%~429.11%), while the content of Pb in the early rice grains was significantly higher than that of the late rice grains(10.71%~59.20%). In summary, the Rice-Rice-Rape cropping system should be selected as the main cropping system in heavy metal polluted areas of south China.