Effects of land use and topographical attributes on soil properties in an agricultural landscape

Knowledge about soil properties associated with land use and topographical attributes is vital for modelling soil-landscape relationships and establishing sustainable on-field management practices. Our study focuses on an arable area in south-western China, where paddy fields and vegetable growing are dominant land uses. These are representative of millions of hectares of farmland in south-western China. Samples from 120 sites were collected according to a gridded sampling scheme and analysed. Land-use map units were delineated at a scale of 1 : 2000 from field survey. Topographical indicators (elevation, aspect, slope) were extracted from a digital elevation model with a resolution of 2m. One-way and two-way analyses of variance and Pearson correlations were adopted to investigate the effects of land use and topographical variables on the selected soil properties: pH, organic matter (OM), ammonium-nitrogen (N), available phosphorus (P), available potassium (K), exchangeable calcium (Ca), and exchangeable magnesium (Mg). Statistically significant differences were found for OM, P, Ca, Mg, and pH between the land-use types and elevation gradient as well as slope classes. Mean contents of OM and P in paddy fields (lower and flat locations) were lower than in vegetable lands (higher and steep places) (P < 0.05). Mean values of Ca, Mg, and pH in paddy fields were higher than in vegetable lands (P < 0.05). Further analysis combining with management practice demonstrated that the redistribution of pH, OM, N, P, Ca, and Mg was mainly controlled by the interactive effects of topography and land use. Therefore, interactions between topography and land-use types need to be considered in regional soil properties inventory assessments.