Analysis of Spatial Variability of Plough Layer Compaction by High-Power and No-Tillage Multifunction Units in Northeast China

In this study, we addressed the problem of the spatial variability of plough layer compaction by high-power and no-tillage multifunction units in the management of maize planting in the Great Northern Wilderness in China. A comprehensive field experiment involving high-power and no-tillage multifunction units for 165 acres of maize was conducted and analyzed using GIS. Firstly, the test area was divided into four areas, and points were set at equal horizontal distances to collect data on the compactness, water content, porosity and fatigue of the plough layer at different depths. Secondly, the GIS kriging difference method was used to analyze the impact of longitudinal compaction of the plough layer profile at each depth in different test areas. Thirdly, the GIS kriging difference method was used to analyze the lateral spatial distribution of plough layer compaction. Finally, the spatial longitudinal and transverse variabilities of the plough layer were summarized, and the effect of the high-power and no-tillage multifunction units on the physical ecology of the soil in the plough layer was investigated. The results show that the physical properties of the plough layer can be significantly affected by compaction after spreading in the middle tillage period. The surface soil was most affected, with the greatest change in compactness and porosity; the rate of change of soil compactness reached 143.49% and the rate of change of soil porosity reached 40.57%. With the increase in soil depth, the rate of change of soil compactness and porosity gradually decreased. The greatest variation in soil moisture content was found in the middle layer and reached a maximum of 13.78% at a depth of approximately 20 cm. The results of the spatial variability analysis show that the mean values of c/(c + c) for the spatial semi-variance functions of compactness, water content and porosity of the tilled soil in the longitudinal space of each test area before compaction were approximately 15%, 19% and 20%, respectively; after compaction, the mean values were approximately 33%, 23% and 30%, respectively; the mean values of c/(c + c) for the spatial semi-variance functions of compactness, water content and porosity change of the tilled soil were approximately 24%, 14% and 12%, respectively. The mean values of c/(c + c) for the spatial semi-variance functions of compactness, water content and porosity of the soil at each depth in the lateral space before compaction were approximately 80%, 71% and 78%, respectively, and after compaction the mean values were approximately 40%, 23% and 24%, respectively, with the mean values of c/(c + c) along the east–west direction being approximately 8%, 27% and 18%, and the mean values of c/(c + c) along the north–south direction being approximately 9%, 0% and 20%. The results show that compaction by high-power and no-tillage multifunction units led to a decrease in the spatial variability of soil physical parameters at each depth of tillage in the black soil layer in the longitudinal space, while the spatial variability of the soil physical parameters at each depth of tillage in the black soil layer in the transverse space increased. Moreover, the degree of influence of compaction by high-power and no-tillage multifunction units on soil physical parameters was higher in both vertical and horizontal spaces. This study can provide a theoretical reference for the analysis of the impact of large units on the compaction of black soil layers from the perspective of GIS.