Analysis and Comparison in Stabilities and Related Influence Factors for Several Common Methods Used in Soil Property Mapping

Total 870 soil samples were collected from the north of Henan Province over a 27 955 km2 area.Two subgroups with 435 samples were respectively used in soil property map-making,i.e.the content of exchangeable cations(CEC) and the total nitrogen(TN).The difference of map-making results between two subgroups was calculated.The stability among Kriging method,inverse distance weight method(IDW) and polygon value represented by point value method(PRP) were compared and its' influencing factors were discussed.The results showed that:(i) RMSE(Root Mean Square Error)and R(correlation coefficient) between measured data and predicted data could not represent the stability of map-making,namely,the returning probability of the spatial pattern of soil properties.And the result was differential in precision validation when using different ways.(ii) The stability of Kriging and IDW were significantly superior to the PRP.The area with relative difference lower than 0.3 didn't achieved 20% of the total area in Kriging and IDW mapping methods,but it achieved 51.57% in PRP mapping method.The area with a high difference level was scattered in the difference map when using the former two methods,but it was centralized and showed by big polygons when using PRP.(iii) The stability of soil property map-making results was disturbed by both sample distribution and high variability of soils in local area.Sample distribution was much important in keeping stability in Kriging method than that in IDW and PRP methods.In the two latter ways high variability among data values showed much impressive effects.