Abstract: The spatial distribution of soil organic matter (SOM) and the affecting factors were studied based on the GIS technology in typical oil-sewage irrigation area of Shen-Fu, China. The results were followed the SOM content decreased from upper to lower reaches along ShenFu wastewater irrigation ditch and there was a negative correlation between the SOM content and the distance to the ditch. The mean content of SOM in surface layer was 1.7 fold more than that of subsurface layer in ShenFu irrigation area. The spatial distribution of the SOM content was affected significantly by land use type, sewage irrigation style, and irrigation duration. The coefficient of variance for SOM in paddy field was bigger than that in glebe. Along wastewater current in the ditch, the SOM content decrease gradually, but in lower reaches the SOM content was higher. The SOM content increased with sewage irrigation duration prolonged. Compared to the short duration in sewage irrigation area, the SOM contents of surface layer and subsurface layer in paddy irrigated 36-50 years increased by 71%-136% and 151%-187% respectively, and that of surface layer in glebe land after being irrigated for 16 years was 3.2%-3.6%.

Key words: Forest ecological benefits, Consociation equation set, Excessiveness identification, Three steps least square estimatation