Abstract:

The objective is to understand the spatial variation of total nitrogen and its main influencing factors in plough layer soil of northwest Hubei Province. The geostatistics, stepwise regression method and GIS technology were used in the study. The results show that: (1) the average nitrogen content of Shiyan City is 1.12 g/kg, and the total nitrogen content of plough layer soil is relatively high, with a variation coefficient of 0.49 among the 701 sampling sites, the degree of variation is moderate; (2) the best model for spatial variability of soil total nitrogen is Gaussian model, and the nugget effect value is 48.09%; total nitrogen has strong spatial variability and is affected by the sharing of random factors and structural factors; (3) the total nitrogen content of the plough layer soil in Shiyan City has obvious difference in spatial distribution, areas in the south, west, southwest and southeast have high total nitrogen content, but areas in the east, northeast and northwest have low total nitrogen content, the north-south direction variation is the most obvious and the difference is large; (4) total nitrogen has a positive correlation with organic matter, elevation, and effective soil thickness, and has a negative correlation with soil pH; there is more total nitrogen in plough layer soil such as clay, brown soil, paddy fields, alluvial deposits of rivers and lakes, quaternary alluvial deposits, double cropping and rice planting soils, there is less total nitrogen in sandy soil, purple soil, purple rock weathering materials, fruit planting soil, wheat soil, and soil under sprinkler irrigation; (5) the influence degree of ten factors on total nitrogen is ranked as soil environment > soil parent material > maturity > biodiversity > crop species > soil texture > soil type > terrain > land use mode > irrigation method, and the first five factors are the dominant factors affecting the spatial differentiation of total nitrogen. In future agricultural production, it is necessary to appropriately increase the application amount of nitrogen fertilizer in the river valley and mountain valley, the double cropping area, the red sandstone weathering and the purple rock weathering zone, and the areas with less organic matter content area. Biodiversity needs to be protected and the impact of human activities on soil quality should be highlighted, and crop rotation could be adopted to improve the quality and production capacity of cultivated land.

Key words: Northwest Hubei, Plough Layer Soil, Soil Total Nitrogen, Semi-variogram, Total Nitrogen Spatial Differentiation, Variance Analysis, Stepwise Regression