Arable soils polluted by heavy metals pose serious threat to the quality and safety of agricultural products as well as human health. It is of great significance to carry out pilot studies of the crop rotation and soil fallowing for remediation of heavy metal polluted farmlands and for guarantee of green developments in agriculture. Based on results from in situ investigations and consensus of professional forums, this paper offers a comprehensive summary of the progress and achievements of the pilot studies on crop rotation and fallow of arable soils in Hunan Province, analyzes existing problems and provides countermeasures to tackle the problems, providing some bases for decision making in regulating future pilot programs of crop rotation and fallowing of farmlands located in regions polluted with heavy metals in China. The pilot study was successful in implementing fallowing of soils with an area of 0.6673×104 hm2 for remediation within the 13 counties or districts in the cities of Changsha, Zhuzhou, Xiangtan in 2016. Further progress was accomplished in 2017 when additional farmlands of medium to severe heavy metal pollution with an area of 0.6667×104 hm2 were made fallowing village by village for the purpose of remediation. Through fallowing practices for remediation, the cadmium contents of rice (Oryza sativa) were within the limits of the safety standards, the efficacy of cadmium reduction in agricultural produces was significant, acidification of soils was effectively alleviated, and the bio-available cadmium concentrations seemed to decline overall. Good practices and exploratory measures were adopted in the pilot studies, including crop rotation and fallowing, block-wise remediation, formation of merged "fallowing, remediation and nurturing of agro-business" technical model, establishment of non-engineering path of using agricultural practices as the main adjustment and control while allowing active cultivation and remediation run side by side, exploration of alternating rice and green manure. The pilot studies also established a system of rules and regulations: emphasizing the controlling importance of government, enhancing the management of accomplishment and efficiency, stressing implementation of the policy of allowance, ensuring the availability of funds, highlighting the voluntary nature of fallowing by farmers, strengthening processes supervision, striking exploration of viable organization schemes, and nurturing businesses. Some problems were discovered during the pilot studies: severe conflicts between the needs for quality and safety of agricultural produces versus the continuous decline of quality of arable soils, no adequate scientific supports in regulating crop rotation and fallowing of heavy metal polluted areas, lack of mature infrastructures and managements. These suggested countermeasures are offered in the paper: better hierarchy design of the rules and regulations governing the crop rotation and soil fallowing of regions polluted by heavy metals; more scientific research in crop rotation and soil fallowing; accelerating the implementation of infrastructures and management mechanisms in crop rotation and soil fallowing especially the mechanism of funding; policy of ecological subsidy and its management.%土壤重金属污染严重威胁农产品质量安全和人体健康,开展重金属污染区耕地轮作休耕制度试点工作对重金属污染农田土壤治理修复和保障农业绿色发展具有重要意义.文章在实地调研考察和专题研讨的基础上,系统地总结了湖南省重金属污染地区耕地轮作休耕制度试点工作进展和成效,分析了存在的问题,并提出相应的对策建议,为开展中国重金属污染地区耕地轮作休耕制度试点工作提供决策依据.试点工作取得如下的进展:2016年长沙、株洲、湘潭等3市13县区实施治理式休耕面积10.01万亩(0.6673×104 hm2),2017年以整村推进方式新增并落实10万亩(0.6667×104 hm2)中度至重度重金属污染休耕耕地.通过治理式休耕,大面积水稻(Oryza sativa)镉含量达标,农产品降镉效果明显,土壤酸化得到有效缓解,土壤有效态镉含量总体上呈现降低的趋势.建立了轮作休耕模式,包括实行分区治理,形成"休治培"三融合技术模式,建立以农艺调控为主、边生产边修复的非工程性技术路径,探索了水稻与绿肥的轮作模式.建立了建设机制与体制:突出政府责任主体,强化绩效管理;突出补贴政策保障,强化资金落实;突出农民自愿休耕,强化过程监管;突出组织模式探索,强化产业培育.试点工作中也发现了若干问题:农产品质量安全与耕地质量下降的矛盾仍然十分突出;重金属污染区休耕制度的科技支撑明显不足,体制机制还不够完善.文章提出了若干对策建议:加强重金属污染区轮作休耕制度顶层设计;加强重金属污染区轮作休耕的科学技术研究;加快推进重金属污染区轮作休耕制度的体制机制建设,如资金保障机制、生态补偿制度和管理机制等.
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