The increased focus on soil quality (SQ) aims to conserve land resources and arrest land degradation. However, there are several unknowns regarding which indicators can most effectively indicate specific SQ outcomes and ecosystem functioning. For the first time, this study aims to integrate the soil morphological properties and earthworm population with physical and chemical properties and propose a comprehensive soil quality index (SQI) to evaluate SQ across a land-use – soil type – climate gradient. Soil profile data (n = 47) covering semi-arid, sub-humid, and humid climates, three soil types (Inceptisols, Vertisols, and Alfisols) and three major land-use systems (grassland, plantation, and annual field crops) were used in this study. As a novel approach, we used a combination of expert opinion and principal component analysis to select 12 soil quality indicators (five morphological, two physical, three chemical, and two biological properties) and developed four thematic SQ indices, viz., morphological quality index (SQI), physical quality index (SQI), chemical quality index (SQI), and biological quality index (SQI) from the respective SQ indicators using the weighted additive index method. The thematic SQ indices were integrated to create SQI for surface and subsurface soils. The SQI showed a strong relationship with SQI and SQI and a moderate relationship with SQI, indicating that the thematic SQ indices can be employed to evaluate soil quality in resource-limited regions or countries. The SQI differentiated the effects of climate, soil type, and land use management on soil quality and showed a strong correlation with crop yield, enabling the comparison of production systems. The integration of the earthworm population to SQI is a crucial advancement in SQ assessment, and the SQI adds a new dimension. The proposed SQI could be a potential precursor for emerging consensus towards a generalised and comprehensive SQI, which can be effectively used for SQ monitoring across varied land use, soil types, and climate regions.

中文翻译：

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一种集土壤形态、物理、化学、生物特性于一体的新型综合土壤质量指数


对土壤质量（SQ）的日益关注旨在保护土地资源并阻止土地退化。然而，关于哪些指标可以最有效地表明特定的 SQ 结果和生态系统功能，还存在一些未知数。本研究首次将土壤形态特征和蚯蚓种群与物理和化学特征相结合，并提出了综合土壤质量指数（SQI）来评估跨土地利用-土壤类型-气候梯度的SQ。土壤剖面数据 (n = 47) 涵盖半干旱、半湿润和湿润气候、三种土壤类型（初始土、变性土和化土）和三种主要土地利用系统（草地、种植园和一年生大田作物）本研究中使用。作为一种新颖的方法，我们采用专家意见和主成分分析相结合的方法，选择了 12 个土壤质量指标（5 个形态指标、2 个物理指标、3 个化学指标和 2 个生物指标），并制定了 4 个主题 SQ 指数，即形态质量指数使用加权相加指数法从各个SQ指标中得出（SQI）、物理质量指数（SQI）、化学质量指数（SQI）和生物质量指数（SQI）。整合专题 SQ 指数以创建表层和地下土壤的 SQI。 SQI 与 SQI 和 SQI 表现出较强的相关性，与 SQI 呈中等相关性，表明主题 SQ 指数可用于评价资源有限地区或国家的土壤质量。 SQI区分了气候、土壤类型和土地利用管理对土壤质量的影响，并显示出与作物产量的密切相关性，从而可以对生产系统进行比较。 将蚯蚓种群纳入 SQI 是 SQ 评估的一个重要进步，并且 SQI 增加了一个新的维度。拟议的 SQI 可能是达成普遍和全面的 SQI 共识的潜在先驱，可有效用于不同土地利用、土壤类型和气候区域的 SQ 监测。