As the global population grows, the demand for food increases and puts a strain on food production systems and agricultural productivity, causing soil degradation. Soil quality indexes (SQIs) have been developed to maintain and improve soil quality. However, due to the variety of soils and SQIs, analyzing and comparing results has historically been difficult. Therefore, in this study, we carried out a systematic review with meta-analysis focused on soil quality studies of agricultural soils under intensive agriculture using the unified weighted additive SQI methodology (SQI_U). Sixty-five observations of agricultural soil quality were analyzed. Chemical indicators were the most prevalent in the SQI_Us, followed by physical and biological indicators. Conventional soil management had negative effects on soil quality (–7.55%). From the factors analyzed, the minimum database had a significant effect on the soil quality results, but not the number of indicators that made up the SQI_U. The SQI_U made up of chemical–biological indicators (CB) presented negatively overestimated measurements of soil quality (–32.53%), exaggerating the degradation of the analyzed soils. The indicators that correlated most strongly with the size of the effect on agricultural soil quality were the cation exchange capacity (CEC) and microbial biomass carbon (MBC). The SQI_U is a feasible tool to interpret the quality of agricultural soils around the world, as it makes it possible to obtain a simple and generalized view of soil conditions.

The Bajío—Mexico’s central lowlands—is a region of economic importance because of its agricultural industry. Over time, agricultural practices have led to soil deterioration, loss of fertility, and abandonment. In this study, six agricultural soils were analyzed: AGQ, CTH, CTJ, JRM, CRC, and CYI, and used to develop a soil quality index (SQI) that includes the use of physicochemical, biological, and ecophysiological indicators to differentiate soil quality. Principal component analysis (PCA) was used, reducing the indicators from 46 to 4, which represents 80.4% of data variability. It was implemented the equation of additive weights using the variance of the principal components as a weight factor for the SQI. The developed SQI was according to the indicators WHC, SLT, N-NO3−, and qCO2, differentiating the quality of soils from the agricultural management in low quality (JRM < CYI < AGQ) and moderate quality (CTJ < CRC < CTH). The use of biological and ecophysiological indicators added to the PCA and the equation of additive weights allowed establishing an SQI with a minimum of indicators, sensitive to agricultural management, facilitating its interpretation and implementation for the Mexican Bajío region and soils in similar conditions around the world.

The increasing production of biosolids (BS) as a result of urban wastewater treatment generates pollution problems in their management and final disposal, and a better management is needed for their disposal. The composting of BS is an alternative process for obtaining a product with potential application as an organic amendment in the recovery of agricultural soils. As a biotechnological contribution, this study analyzed a composting process with BS, bovine manure (BM) and rice husks using four treatments T1 (C/N = 24); T2 (C/N = 34); T3 (C/N = 44); T4 (C/N = 54) for 120 days, in order to develop compost quality indexes (CQIs) through the analysis of 18 physicochemical, biological and ecophysiological indicators. Subsequently, three methodologies—successfully used on soils—were implemented for the development of the CQIs called “unified”, “additive” and “nemoro”. The indicators that comprised the CQIs were nitrification index (NI) and synthetic enzymatic index (SEI). The CQIs made it possible to differentiate the quality of the compost according to the treatments applied. The treatments used resulted in composts considered phytonutritious whose average quality value depending on the CQI developed was considered high (CQI_w = 0.62), moderate (CQI_a = 0.56) and low (CQI_n = 0.30). The developed CQIs can be applied to determine the quality of BS composting systems reducing the cost of monitoring.

Soil degradation and the use of urban biosolid wastes to soil restoration have an economic, social-environmental and health impact. Therefore, there is interest worldwide in the use and comparison of methodologies to establish soil quality indexes (SQIs) based on physical, chemical, and biological indicators of soils. Considering that more than 60% of the territory in the Bajío region of Mexico in the State of Guanajuato is affected by some type of soil degradation, three methodologies for the establishment of SQIs—additive, weighted and unified weighted indexes—were compared in this study to evaluate the short-term effects—30 days—of the addition of biosolids as soil improvers. The methodologies were applied in experiments on carbon (C) and nitrogen (N) mineralization dynamics in a sodic agricultural soil. The ammonium indicator (N-NH4+) was established as the one that is most related to the quality of the soil. The additive and unified weighted indexes differentiated the level of soil quality with respect to time and treatment. The developed SQIs can be used for short-term assessment of the quality of agricultural soils under amendment addition treatments with biosolids or similar organic products.

The growing demand for quality food has intensified agricultural practices, thus deteriorating soil fertility. In response, reclamation techniques such as minimum, zero, or no tillage have been applied, especially in the Bajio region of the State of Guanajuato, Mexico. However, a reliable tool to evaluate the effectiveness of these techniques remains elusive. This study evaluated the effect of zero tillage and conventional tillage by developing a Soil Quality Index (SQI) from eight agricultural soils in the Bajio region. A set of 26 physicochemical indicators was used, reducing them by means of principal component analysis (PCA). Subsequently, the SQI methodology called “unified weighted” was applied. The resulting SQI_u included key indicators such as C/N, SND, ESP, and Fe. Although significant differences in soil quality were observed among the samples tested, the SQI_u was unable to discern soil quality under the different tillage schemes. This may be attributed to the limited application time of zero tillage, which might not be sufficient to achieve significant recovery of SQI indicators. Nevertheless, the SQI_u could be useful as a monitoring tool to evaluate the progress of soil recovery under zero tillage, both in the studied area and in similar contexts at the national or international level.

Agriculture is a sector of great importance for Mexico’s economy, generating employment and contributing significantly to the country’s gross domestic product. The Bajio stands out as one of the most productive agricultural regions in Mexico. However, intensive agricultural practices in this area have caused a progressive deterioration and loss of soil fertility. This study focused on evaluating the quality of soils used for agriculture in the Bajio region of the State of Guanajuato, Mexico. This evaluation, utilised soil quality indexes (SQIs) based on a total of 27 physicochemical, biological and enzymatic indicators. These indicators were selected by means of a principal component analysis (PCA), which allowed for the identification of a minimum set of data. The SQIs developed in this study categorised soils into different quality levels, ranging from low to high, mainly based on the values observed in the biological indicators (SMR and qCO₂), which comprised the established SQIs. The inclusion of these biological indicators provides the developed SQIs with greater sensitivity to detect minor disturbances in agricultural soils due to human activity, compared with SQIs consisting only of physicochemical indicators. The developed SQIs can be used to ensure high-quality food production in soils used for corn cultivation under similar conditions, both nationally and internationally.