Soils occupied by dryland pastures usually have low fertility but can exhibit a high spatial variability. Consequently, logical application of fertilisers should be based on an appropriate knowledge of spatial variability of the main soil properties that can affect pasture yield and quality. Delineation of zones with similar soil fertility is necessary to implement site-specific management, reinforcing the interest of methods to identify these homogeneous zones. Thus, the formulation of the objective Rasch model constitutes a new approach in pasture fields. A case study was performed in a pasture field located in a montado (agrosilvopastoral) ecosystem. Measurements of some soil properties (texture, organic matter, nitrogen, phosphorus, potassium, cation exchange capacity and soil apparent electrical conductivity) at 24 sampling locations were integrated in the Rasch model. A classification of all sampling locations according to pasture soil fertility was established. Moreover, the influence of each soil property on the soil fertility was highlighted, with the clay content the most influential property in this sandy soil. Then, a clustering process was undertaken to delimit the homogeneous zones, considering soil pasture fertility, elevation and slope as the input layers. Three zones were delineated and vegetation indices (normalized difference vegetation index, NDVI, and normalized difference water index, NDWI) and pasture yield data at sampling locations were employed to check their differences. Results showed that vegetation indices were not suitable to detect the spatial variability between zones. However, differences in pasture yield and quality were evident, besides some key soil properties, such as clay content and organic matter.

中文翻译：

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使用客观模型和多元技术绘制沙质牧场土壤中的管理区图

旱地牧场占据的土壤通常肥力低，但空间变异性高。因此，合理施用肥料应基于对可能影响牧场产量和质量的主要土壤特性的空间变异性的适当了解。划定具有相似土壤肥力的区域对于实施特定地点的管理是必要的，从而增强了识别这些同质区域的方法的兴趣。因此，客观 Rasch 模型的制定构成了牧场领域的新方法。案例研究是在位于 montado（农林牧）生态系统的牧场中进行的。测量一些土壤特性（质地、有机质、氮、磷、钾、阳离子交换容量和土壤表观电导率）在 24 个采样点被整合到 Rasch 模型中。根据牧场土壤肥力对所有采样地点进行分类。此外，强调了每种土壤性质对土壤肥力的影响，其中粘土含量是这种沙质土壤中影响最大的性质。然后，将土壤牧场肥力、海拔和坡度作为输入层，进行聚类过程以划定均质​​区。划定了三个区域，并利用采样地点的植被指数（归一化差异植被指数，NDVI，归一化差异水指数，NDWI）和牧草产量数据来检查它们的差异。结果表明，植被指数不适合检测区域之间的空间变异性。然而，除了一些关键的土壤特性，如粘土含量和有机质外，牧草产量和质量的差异也很明显。