Spatial variability of soil organic matter and relation with natural quality of farm land

The present study researches exact interpolation and variability character of soil organic matter by Cokriging method which uses soil sample data in typical types of farm. Taking Chini town of Huadu County, Guangzhou City as an example, this study examines the quantitative relationship between soil organic matter and natural quality of farm land. The results show that the precision of Cokriging interpolation with soil organic matter and farm type variable by spherical model is the highest. In research areas, it is a distribution pattern of soil organic matter that low levels are in the surrounding hills and reservoirs, and high levels are in plains nearby the two sides of Bajiang River and Piedmont alluvial plains of south-west hills. The areas with high levels are paddy-intensive. In research areas the soil organic matter content in vegetable fields is well-distributed with strong spatial correlation and its distribution in irrigated fields is quite different with large spatial variability. Soil organic matter is isotropous in north-south and northeast-southwest direction with stronger spatial correlation, and is anisotropic in the southeast-northwest and east-west direction with larger spatial variability. There is a very significant relevance with interpolation result of soil organic matter and grade index of natural quality of farm land. Correlation of natural quality index of vegetable farm with that of farm land is most significant, then the paddy field, last the dry land.