Spatio-temporal Variability of Soil Nitrogen in North China Plain Using Geostatistical Analysis

Large changes in land use and land management, which have had a tremendous impact on soil nutrients, have occurred in north China in recent years. Soil nitrogen is more influenced by human activities as the fertilizer application. We compared soil nitrogen in Yucheng County of Shandong province in 2003 to 1980 results from the Second National Soil Survey. The average contents of total nitrogen in 2003 were significantly higher than in 1980. Soil nitrogen increased from 0.68 to 0.84 mg/kg. Spatial variability of soil nitrogen was medium and characterized by coefficients of variation (CV) 22% and 28% in 1980 and 2003, respectively. Then geostatistical analysis was used to find the spatio-temporal variability of soil nitrogen. The results showed that the spatial distribution of soil nitrogen changed greatly between 1980 and 2003. Soil nitrogen showed increasing trends in Yucheng. And Zhangzhuang, Fangsi and Shiliwang towns showed the highest increase in soil nitrogen. The increase in soil nitrogen was contributed to increased application of chemical fertilizer. Among these towns in Yucheng, these with most obviously increase of soil nitrogen had the higher application of chemical fertilizers.