Spatial characteristics and changes of soil organic matter for cultivated land in suburban area of Xi'an from 1983 to 2009

Geographical information system technology and geostatistics were used to analyze the spatial variability, impact factors, and soil quality grade changing patterns of soil organic matter (SOM) in Chang'an District, Hu County, and Zhouzhi County in the past 26 years, based on 3 100 topsoil samples using the "S-shape" method of the Cultivated Land Productivity Investigation and Quality Evaluation Project of Shaanxi Province (2007-2009). A global positioning hand-held receiver was used to record sampling site locations. SOM contents satisfied the normal distribution after Box-Cox transformation (p=0.42) with the Kolmogorov-Smironov (K-S) test. The results showed that SOM contents were low, ranged from 5.80 to 34.90g/kg, concentrated at >10-20 g/kg with an average of 15.95 g/kg which was increased by 26.76% compared with that in 1983(12.58 g/kg). The study can provide a scientific guidance for cultivated land maintenance and regional agricultural production in the suburban area of Xi'an.