Abstract:

The spatial autocorrelation analysis of soil pH and six nutrient indexes (organic matter, available phosphorus, available potassium, total nitrogen, total phosphorus and total potassium) in Dulan County of Qinghai Province was conducted, and their spatial aggregation and isolation were further analyzed. Based on the results of this study, we hope to improve the utilization rate of farmland soil and fertilizer in Dulan County and lay a foundation for precision agriculture. After field sampling, soil samples were tested according to existing effective standards such as NY/T 1121. The spatial distribution pattern and spatial aggregation of cropland soil indexes in the study area were analyzed by combining global spatial autocorrelation and local spatial autocorrelation. The results showed that the average values of soil pH, organic matter, available phosphorus, available potassium, total nitrogen, total phosphorus and total potassium were 8.12, 17.90 g/kg, 19.00 mg/kg, 123.00 mg/kg, 0.80 g/kg, 0.80 g/kg and 17.85 g/kg, respectively. Global spatial autocorrelation under the Inverse_Distance weight, pH, organic matter, total phosphorus and total potassium showed positive spatial autocorrelation. Available phosphorus, available potassium and total nitrogen showed negative spatial autocorrelation. The results were the same in Contiguity_Edges_Only and Contiguity_Edges_Coeners weights. There were positive spatial autocorrelation between pH, organic matter, available potassium, total nitrogen, total phosphorus and total potassium. The available phosphorus showed negative spatial autocorrelation. Local spatial autocorrelation could intuitively obtain the specific locations of aggregation areas and isolated areas of soil content distribution of different indicators of cropland in the study area through LISA aggregation map. Altitude was negatively correlated with available phosphorus, available potassium, total nitrogen, total phosphorus and total potassium. Slope was negatively correlated with available phosphorus, total nitrogen and total phosphorus. The effect of slope aspect on the spatial pattern of soil nutrients was relatively small in the study area. In global spatial autocorrelation analysis, different spatial weights had great influence on the analysis results. According to the local spatial autocorrelation analysis, the low-content areas of total nitrogen, total phosphorus and total potassium were distributed in Chawusu Town and Xiariha Town in the eastern part of Dulan County, namely, “low-low” aggregation areas, and “high-high” aggregation areas were found in Balong Township and Xiangride Town in the central part of Dulan County. In the eastern part of Dulan County, the content of organic matter was relatively high in the towns of Chawusu and Xiariha, showing the “high-high” aggregation areas, and the “low-low” aggregation area appeared in the town of Zongjia. There were significant differences in the correlation between different topographic factors and soil nutrients.

Key words: plough layer, spatial autocorrelation, soil nutrient content, land parcel scale, Dulan County