Spatial variation of soil quality limiting indicators in the North China

The identification of cultivated land obstacle indicators and their spatial distribution are preconditions to soil quality and productivity improvement. This study takes the North China as the objective, using principal component analysis (PCA), entropy TOPSIS and obstacle degree (OD) models to establish a systematic evaluation framework to identify the major limiting indicators. Results reveal that 17.0% of the cultivated land faces severe obstacles, 32.1% and 41.9% experience moderate and slight obstacles, respectively. Only 9.0% of the land shows no significant obstacles. Soil pH and the available potassium content (AK) emerged as the most critical limiting indicators, severely affecting 42.0% and 27.2% of the land, respectively. Other indicators like soil total nitrogen (TN), organic matter (OM) content and cultivated-layer thickness (CLT) exhibited slight obstacles, while AP and BD showed no significant limitations. Spatial analysis highlighted that the pH, AP and BD present notable obstacle incidences, followed by OM and TN. Furthermore, spatial overlap of multiple obstacle indicators was also revealed, 87.1% of the area were limited by more than 3 indicators in the North China. The systematic framework proposes an effective tool for guiding the accurate regional cultivated land quality improvement.