Li Na, He Hong-Zhou, Feng Ai-Xuan, Li Wei, Jiang Zhen-Mao, Wei Shi-Qiang
College of Resources and Environment, Southwest University, Chongqing 400715, China.
Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing 400715, China.
Huan Jing Ke Xue. 2019 Oct 8;40(10):4637-4646. doi: 10.13227/j.hjkx.201904230.
The western Chongqing region is the main grain-producing area in Chongqing. This region's soils are characterized by light-to-moderate cadmium (Cd) pollution. Two types of typical paddy soils in this area (acidic and calcareous purple soils) were selected for the development of safe rice production techniques using in situ field remediation experiments. These involved a low-Cd-accumulating rice variety (Changliangyou 772) grown either alone or in combination with heavy metal passivators (silicon-calcium fertilizer, iron powder, biochar, and straw organic fertilizer). The results showed that:① all of the passivators except for the Fe powder increased rice yields from both types of soils. Straw organic fertilizer showed the best results for the acidic purple paddy soil, with a rice-yield increase of 47.43%, while biochar performed best for the calcareous paddy soil, increasing yields by 23.95%; ② The low-accumulation rice variety alone could not meet the requirements of safe rice production in the acid purple paddy soil (pH=4.75); however, combined the with passivators (with the exception of the silicon-calcium fertilizer), Cd content in rice grains was reduced by 14.81%-54.88% to within the national safe food standard for rice (0.2 mg·kg, GB 2762-2017). The Cd content of rice grains varied between 0.012 and 0.030 mg·kg in the calcareous purple paddy soil (pH=7.77), under various treatments, which was far lower than the safety standard. The application of passivators (with the exception of biomass charcoal) further reduced the Cd content of rice by 26.67%-59.00% nevertheless; ③ The use of passivators altered Cd transportation and distribution in the rice plant. Taking the acidic soil as an example, silicon-calcium fertilizer inhibited the transport of Cd from the stems to the rice grains, Fe powder and biochar reduced the enrichment of Cd in roots and inhibited the transport of Cd from the stems to the rice grains, and straw organic fertilizer inhibited the transport of Cd from the roots to the stems; ④ The application of passivators promoted the transformation of soil Cd from labile forms into residual form, reduced the bioavailability of Cd in the soil, and, thus, reduced the accumulation of Cd in the rice plants. In the acidic soil, biochar showed the best effect, while straw organic fertilizer performed best in calcareous soils. ⑤ Silicon-calcium fertilizer and straw organic fertilizer significantly increased the pH and organic matter content of acid soils. Consequently, the soil available Cd content decreased by 39.45% and 34.69%, respectively, while no such effects were observed for the calcareous soil.
重庆西部地区是重庆的主要粮食产区。该地区土壤的特点是镉（Cd）污染程度为轻度至中度。选取了该地区两种典型的稻田土壤（酸性和石灰性紫色土），通过原位田间修复试验来开发安全水稻生产技术。试验涉及种植低镉积累水稻品种（长两优772），单独种植或与重金属钝化剂（硅钙肥、铁粉、生物炭和秸秆有机肥）结合种植。结果表明：①除铁粉外，所有钝化剂均提高了两种土壤的水稻产量。秸秆有机肥对酸性紫色稻田土壤效果最佳，水稻产量提高了47.43%，而生物炭对石灰性稻田土壤效果最佳，产量提高了23.95%；②单独种植低积累水稻品种不能满足酸性紫色稻田土壤（pH = 4.75）安全水稻生产的要求；然而，与钝化剂（硅钙肥除外）结合使用时，水稻籽粒中的镉含量降低了14.81% - 54.88%，降至国家水稻安全食品标准（0.2 mg·kg，GB 2762 - 2017）以内。在石灰性紫色稻田土壤（pH = 7.77）中，各种处理下水稻籽粒中的镉含量在0.012至0.030 mg·kg之间，远低于安全标准。不过，施用钝化剂（生物炭除外）进一步使水稻镉含量降低了26.67% - 59.00%；③使用钝化剂改变了镉在水稻植株中的运输和分布。以酸性土壤为例，硅钙肥抑制了镉从茎向水稻籽粒的运输，铁粉和生物炭减少了镉在根部的富集并抑制了镉从茎向水稻籽粒的运输，秸秆有机肥抑制了镉从根向茎的运输；④施用钝化剂促进了土壤镉从可交换态向残渣态的转化，降低了土壤中镉的生物有效性，从而减少了镉在水稻植株中的积累。在酸性土壤中，生物炭效果最佳，而秸秆有机肥在石灰性土壤中表现最佳。⑤硅钙肥和秸秆有机肥显著提高了酸性土壤的pH值和有机质含量。因此，土壤有效镉含量分别降低了39.45%和34.69%，而石灰性土壤未观察到此类效果。
