关键词: 重金属污染区, 轮作休耕, 植物移除, 体制机制, 对策建议

Abstract:

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.

Key words: heavy metal polluted region, crop rotation and fallowing, phyto-remediation, infrastructure and mechanism, suggested countermeasures