Agricultural intensification, an inevitable process to feed the ever-increasing population, affects soil quality due to management-induced changes. To measure the soil quality in terms of soil functioning, several attempts were made to develop a soil quality index (SQI) based on a set of soil attributes. However, there is no universal consensus protocol available for SQI, and the role of soil biological indicators in SQI is meagre. Therefore, the present work aims to develop a unitless soil biological quality index (SBQI) scaled between 0 and 10, which would be a major component of SQI in the future. The long-term organic manure amended (OM), integrated nutrient management enforced (INM), synthetic fertilizer applied (IC), and unfertilized control (control) soils from three different predominant soil types of the location (Tamil Nadu state, India) were chosen for this. The soil organic carbon, microbial biomass carbon, labile carbon, protein index, dehydrogenase activity, and substrate-induced respiration were used to estimate the SBQI. Five different SBQI methods, viz. simple additive (SBQI1 and SBQI2), scoring function (SBQI3), principal component analysis-based statistical modelling (SBQI4), and quadrant-plot-based method (SBQI5), were developed to estimate the biological quality as a unitless scale. All five methods have the same resolution to discriminate the soils and INM ≈ OM > IC > control is the relative trend being followed in all the soil types based on the SBQIs. All five methods were further validated for their efficiency in 25 farmers' soils of the location and proved that these methods can scale the biological health of the soil. Among the five SBQIs, we recommend SBQI5, which relates the variables to each other to scale the biological health of the soil.

中文翻译：

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半干旱热带地区土壤生物质量指标的建立

农业集约化是养活不断增长的人口的必然过程，由于管理引起的变化而影响了土壤质量。为了从土壤功能方面衡量土壤质量，已进行了一些尝试，以基于一组土壤属性来开发土壤质量指数（SQI）。但是，尚无适用于SQI的通用共识协议，土壤生物学指标在SQI中的作用微不足道。因此，目前的工作目的是开发一个尺度在0到10之间的无单位土壤生物质量指数（SBQI），它将成为未来SQI的主要组成部分。修改了长期使用的有机肥（OM），实施了综合养分管理（INM），施用了化肥（IC）和该地点三种不同主要土壤类型（泰米尔纳德邦，为此选择了印度）。用土壤有机碳，微生物生物量碳，不稳定碳，蛋白质指数，脱氢酶活性和底物诱导的呼吸来估算SBQI。五个不同的SBQI方法，即。开发简单的添加剂（SBQI1和SBQI2），评分函数（SBQI3），基于主成分分析的统计模型（SBQI4）和基于象限图的方法（SBQI5），以无单位规模估算生物质量。这五种方法具有相同的分辨率来区分土壤和INM 开发了基于主成分分析的统计模型（SBQI4）和基于象限图的方法（SBQI5）以无单位规模估算生物质量。这五种方法具有相同的分辨率来区分土壤和INM 开发了基于主成分分析的统计模型（SBQI4）和基于象限图的方法（SBQI5）以无单位规模估算生物质量。这五种方法具有相同的分辨率来区分土壤和INM ≈  OM  >  IC  > 控制是所遵循基于所述SBQIs所有土壤类型的相对趋势。进一步验证了这五种方法在该位置的25个农民土壤中的效率，并证明这些方法可以扩展土壤的生物健康状况。在这五个SBQI中，我们建议使用SBQI5，该变量相互关联以衡量土壤的生物健康状况。