Abstract: By comparing the current soil organic matter（SOM） content data of 5 704 cultivated soil samples in Ningbo City with the past data， temporal\|spatial variation of SOM in Ningbo City during 50 years were studied. The results showed that SOM content of the cultivated soils changed greatly over 50 years. From the first general detailed soil survey in 1958 to the second general detailed soil survey in 1980s， the mean content of organic matter increased from 22.4 g·kg-1 to 34.8 g·kg-1 by 55%， and the difference was significant （P<0.01）. But， the mean SOM content decreased to 31.0 g·kg-1 significantly （P<0.05） by 10.9% from 1980s to 2008. The SOM distribution showed that the water net plain area had higher organic matter contents than the hilly area， and the valley plain area had higher contents than the coastal plain area. The history of cultivation and hydrology and climate change caused by increasing elevation were main factors affecting the spatial variability of SOM.

Key words: soil organic matter, temporal\, spatial variability, Ningbo City