Abstract:

Currently, research on soil health of cropland primarily focuses on the assessment of farmland/facility vegetable plots at the county level. There is a dearth of soil health assessment focusing on cropland conservation projects, and the related research is still in the preliminary stage. Three different types of farmland soils from ecological conservation projects implemented in Chongming District were used to examine the impact of various types of conservation measures on farmland soil health. A secondary index with three primary indicators of soil environment, nutrients, and biology, six secondary indicators of soil acidity, heavy metals, organic matter, nitrogen, and phosphorus, and three additional indicators of soil environment, nutrients, and biology was used. The findings showed that the heavy metal content in the soil from two non-chemical projects was significantly lower than that in the control site; seven heavy metals, with the exception of Zn, decreased from 0.830 to 0.951 times in comparison with the control site; the content of Cd and Cr was significantly lower than that of the paddy soil at the control site (P<0.05); the As content in the earthworm project soil (8.660 mg·kg^-1) was significantly lower than that in the soils from the two no-chemical and the biofertilizer projects (P<0.05). The fertility of available potassium in the soil at all sites was the highest with a mean value of 216.137 mg·kg^-1, reaching the first level, while effective phosphorus and total nitrogen were both at the second level; the soil from the biofertilizer project had the highest soil nitrogen (83.104 mg·kg^-1), phosphorus (223.218 mg·kg^-1), and potassium content (1.614 mg·kg^-1); the organic matter content was the highest in the soil from two chemical-free projects. Compared to the two-free and vermicomposting studies, The density of actinomycetes in the soil of biological bacterial fertilizer project was the highest (3.328×10⁸ ind·g^-1), which was statistically significant (P<0.05). The densities of earthworms in the soil of the earthworm project and the two-free project were 2.853 and 1.231 times greater than that of the control, respectively. The two-free project had the greatest soil health index (0.843), followed by the earthworm project (0.834), and the biofertilizer project (0.826), all of which were in sub-health status. The three ecological conservation projects on arable land improved the soil health level from unhealthy to sub-healthy, with soil nutrients being the main factor, indicating that Chongming Eco-Island farmland’s soil health should be improved by raising the level of nutrients in the soil.

Key words: eco-conservation project, soil, soil-health index, soil environment, soil nutrients, soil biology

摘要：

目前国内外学者对耕地土壤健康的研究主要以分析县域层次上的农田/设施菜田地块的土壤健康评估，缺乏以耕地保育工程为主体的土壤健康评价，对耕地保育工程为主体的研究仍处于初步探索阶段。为探究不同耕地保育措施类型对农田土壤健康的影响，以在崇明区实施的3种耕地生态保育工程农田土壤为研究对象，构建了包含土壤环境、土壤养分和土壤生物3个一级指标，土壤酸碱度、土壤重金属、土壤有机质、土壤氮磷钾、土壤微生物和土壤动物等6个二级指标，以及17个三级指标的土壤健康度评价指标体系，开展土壤健康度评价。结果表明：两无化工程土壤重金属含量明显低于对照点，除Zn外其他7项重金属比对照点下降了0.830-0.951倍，其中Cd、Cr含量显著低于对照水田土壤（P<0.05）；蚯蚓工程土壤As含量均值为8.660 mg·kg^-1，显著低于生物菌肥及两无化工程（P<0.05）。所有点位土壤中速效钾肥力最高，平均值为216.137 mg·kg^-1，达到一级水平，而有效磷和全氮均为二级水平；生物菌肥工程土壤氮磷钾含量均为最高，均值分别达到83.104、223.218和1.614 mg·kg^-1；两无化工程土壤有机质含量均值最高，达到24.85 g·kg^-1。生物菌肥工程土壤放线菌密度最大，为3.328×10⁸ ind·g^-1，显著高于两无化、蚯蚓工程（P<0.05）。蚯蚓和两无化工程土壤蚯蚓密度分别是对照的2.853倍和1.231倍。两无化工程土壤健康度指数最高，达0.843；其次是蚯蚓工程，为0.834；生物菌肥工程最低，三者均为亚健康状态。3种耕地生态保育工程土壤健康度等级由不健康提升为亚健康，影响健康度的最主要指标为土壤养分。崇明生态岛农田土壤健康度提升应重点着眼于提升土壤养分水平。

关键词: 生态保育工程, 土壤, 土壤健康度, 土壤环境, 土壤养分, 土壤生物