SPATIO-TEMPORAL VARIABILITY OF SOIL NUTRIENTS IN THE ZUNHUA PLAIN, NORTHERN CHINA

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. In order to evaluate soil-nutrient changes, 124 samples in surface soil (0 to 20 cm) were collected in a 416.16 km2 plain region in Zunhua County of Hebei province in 1999 and compared to 1980 results from the Second National Soil Survey. The average contents of available potassium, available phosphorus, and organic matter in 1999 were significantly higher than in 1980 (p < 0.1%). The nugget-to-sill ratio of available potassium decreased from 56.5% in 1980 to 41.1% in 1999, while the nugget-to-sill ratio of available phosphorus increased from 45.5% in 1980 to 54.1% in 1999. The ratio of organic matter changed from 60% in 1980 to 32.3% in 1999. The ranges of available potassium and available phosphorus between the years of 1980 and 1999 were similar. The range of organic matter was 4.8 km in 1980, decreasing to 2.7 km in 1999. Thus, the effects of human activities linked with land, such as land use and tillage, on spatial variation differed for each of the three soil properties examined. [Key words: soil nutrients, variability, tillage, geostatistics, land use.]