The precise and efficient evaluation of cultivated land soil quality is fundamental to ensuring regional land sustainability. In order to address issues of indicator redundancy and method applicability in soil quality assessment, the present study focused on the plough layer soils of Fugu County on the Loess Plateau. The employment of membership function (MF), linear scoring (SL), and non-linear scoring (NSL) methods in conjunction with the total data set (TDS) and minimum data set (MDS) was undertaken to identify the optimal model for quantitative soil assessment. The cross-validation process was facilitated by employing grey relational analysis (GRA). Furthermore, an obstacle factor diagnostic model was employed to elucidate the primary constraints and their degree within the plough layer soil. The results demonstrated that: 1) The levels of soil organic matter (SOM) and available nutrients were found to be generally low, with SOM and available phosphorus (AP) demonstrating strong variability and available potassium (AK) exhibiting moderate variability. 2) The minimum data set (MDS) was constructed via principal component analysis (PCA). The MDS comprised available zinc (Zn), AK, and selenium (Se), accounting for 76.04% of the variance in the ten initial indicators. 3) An analysis of the scoring methods employed revealed that the SL method yielded results that exhibited a high degree of consistency with the nationally recommended MF method (r = 0.981). This finding is in alignment with the GRA validation, thereby confirming the robustness of the SL method in this particular region. Conversely, the NSL method exhibited systematic overestimation and was therefore deemed unsuitable. 4) The quality of the soil in the study area was found to be predominantly medium to low. The obstacle factor analysis indicated that basic soil fertility limitation was the primary constraint, with soil organic matter (SOM), available phosphorus (AP), and selenium (Se) identified as the key obstacle factors. The secondary factor, AK, demonstrated a propensity to amplify these limitations. The present study provides a scientific basis for evaluating the quality of the plough layer soil and informs targeted strategies for its improvement in the Fugu region.