Optimal Indicators for Microtopography-oriented Soil Quality Assessment in Semiarid Regions of the Loess Plateau, China

This study was aimed to identify optimal indicators for microtopography-oriented soil quality assessment. Twenty-two soil physicochemical and biological parameters were investigated at 93 sampling points in five different microtopographic units in semiarid regions of the Loess Plateau, where the principal functions of eroded agriculture soils are related to productivity and anti-erosion ability. The selection of soil quality indicators was accomplished using a combination of sensitivity analysis, principal component analysis, and stepwise regression. The indicators used for microtopographyoriented soil quality assessment were found to be moderately sensitive with no high sensitivity. Moderately sensitive soil quality indicators including the levels of sucrase activity (SA), available phosphorus (AP), total nitrogen (TN), soil organic matter (SOM), and urease (UA) are the major objectives of soil quality restoration and regulation in the study area. The 22 soil physicochemical and biological parameters indicative of soil quality were grouped into seven soil quality factors; SOM, water-holding capacity, total phosphorous (TP), total potassium (TK), soil water content, capillary porosity, and AP. Optimal indicators for microtopography-oriented soil quality assessment in the study area were identified as; SOM, TN, SA, UA, AP, TP, CaCO3, APA, and TK. Among these, the SOM level was the key indicator for characterizing soil quality in relation to microtopography in the semiarid loess region. This study provides reference information for the conservation of agricultural soils and improvement of low-yield farmlands in semiarid regions of the Loess Plateau. This will enable better agricultural decisions by the residents and aid decision making by the government according to local conditions.