applied sciences  
Article  
Corn Cropping Systems in Agricultural Soils from the Bajio Region of Guanajuato: Soil Quality Indexes (SQIs)  
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or inadequate practices, such as excessive use of chemical fertilizers and herbicides, constant and deep plowing, and monoculture practices. Every year, approximately 12 million hectares of soil are lost due to degradation caused by the aforementioned conventional practices [1].  
To address this problem, Mexico has introduced the national program ENASAS (Estratea Nacional de Suelo para la Agricultura Sostenible--National Soil Strategy for Sustainable Agriculture). The main objective of this program is the conservation and care of agricultural soils, preventing and reversing processes that damage the soil and promoting sustainable agricultural practices [4].  
Corn is a crop native to Mexico and one of the most significant crops worldwide. In 2016, more than one billion tons of corn were produced on approximately 200 million hectares of cropland. Mexico is one of the top seven producers and is among the top ten consumers of this crucial grain [5]. The Bajio region of the State of Guanajuato, Mexico, covers an area of 1.2 million hectares devoted to agriculture [6], where a variety of grains are grown--including corn and sorghum. Despite its importance, this region has also suffered from soil deterioration and loss of soil fertility due to conventional and unsustainable agricultural practices [7].  
In this context, the concept of \"soil fertility\" has evolved to encompass a wide range of aspects, including chemical, physical and biological attributes, as well as their decline in soils [8]. This loss of fertility or deterioration of the soil has prompted studies to characterize and evaluate soil quality, using tools known as Soil Quality Indexes (_SQIs_). These _SQIs_ are based on biological and physicochemical indicators related to the problem to be analyzed, especially in agricultural soils that have experienced a decrease in fertility [9].  
Currently, similar studies have been carried out nationally and internationally, focusing on agricultural soils with different crops. These studies have used various indicators (soil organic carbon (SOC), organic matter (OM), pH, electrical conductivity (EC), cation exchange capacity (CEC), nitrogen (N), phosphorous (P), potassium (K)) and have highlighted the importance of assessing soil quality as the first step towards accurate, sustainable agriculture and effective agricultural management [9; 10; 11].  
Nowadays, _SQIs_ are an essential application tool in the agricultural field, both in terms of crop yield and economics. The reason for this is that, in order to grow and market high-quality products, it is essential to determine the quality level of agricultural soil. This plays an integral role in ensuring food security and economic stability.  
Considering the aforementioned, the main objective of this study was to establish an _SQI_ for agricultural soils under corn cultivation in the Bajio region of the State of Guanajuato, analyzing both physicochemical and biological indicators. It was proposed that the established _SQI_ would allow for the differentiation of soil quality according to the indicators selected in the minimum data set by means of a principal component analysis (PCA).