Optimization of Soil Sampling for Layered Amelioration Trials Through Homogeneous Land Unit Mapping in Sandy Agricultural LandscapesSari Widya Utami, Fajar Hidayanto, Banti Fadillah and Muhamad Faqih HidayatullahBIO Web Conf., 197 (2025) 05001DOI: https://doi.org/10.1051/bioconf/202519705001