Many predictive soil mapping (PSM) methods encounter two problems. One is how to construct a similarity index that can indicate not only the similarity of an environmental covariate between sites but also the directional difference of the covariate itself between sites and predict the soil property values beyond the range of sample values. Another is how to determine which soil samples should be used when estimating the soil property value at an unknown site. We propose a new asymmetrical environmental contrast index between an unknown site and a sample site to address the first problem, based on which we developed an enhancive predictive coefficient (EPC)-based soil mapping (EPSM) method. EPC integrates the contrasts of associated environmental principal component covariates by the weights of the covariates influencing a certain soil property. A member recruiting process was programmed to determine the calculating samples for an unknown site after conducting an uncertainty threshold (ut) test for all the sample sites. We applied the EPSM method to five data groups with different numbers and distributions of sample sites for prediction. The results showed that the EPSM method performs better than the soil-land inference model (SoLIM) method regardless the value of ut and thus can be used to estimate the soil property values well at most unknown sites. The method is especially valid when the unknown sites are spatially far from the sample sites and when sample sites are limited in number or spatially distributed at a local area. Our study suggests that the EPSM method is an effective PSM method that can be widely used in soil mapping.

许多预测性土壤测绘（PSM）方法遇到两个问题。一种方法是构建一个相似性指数，该指数不仅可以指示站点之间环境协变量的相似性，而且可以指示站点之间协变量本身的方向差异，并预测超出样本值范围的土壤属性值。另一个是在估算未知地点的土壤特性值时如何确定应使用哪种土壤样品。我们提出了一个未知地点与样本地点之间的新的不对称环境对比度指数，以解决第一个问题，在此基础上，我们开发了基于增强预测系数（EPC）的土壤测绘（EPSM）方法。EPC通过影响特定土壤属性的协变量的权重来整合相关环境主成分协变量的对比。ut）测试所有示例站点。我们将EPSM方法应用于五个具有不同样本站点数量和分布的数据组，以进行预测。结果表明，无论ut的值如何，EPSM方法的性能均优于土壤土地推断模型（SoLIM），因此可用于估计大多数未知地点的土壤特性值。当未知位置在空间上远离样本位置并且样本位置数量有限或在局部区域空间分布时，该方法特别有效。我们的研究表明，EPSM方法是一种有效的PSM方法，可广泛用于土壤测绘。