Spectral data of tropical soils using dry-chemistry techniques (VNIR, XRF, and LIBS): a dataset for soil fertility prediction - Tavares, Tiago Rodrigues; Molin, José Paulo; Nunes, Lidiane Cristina; Alves, Elton Eduardo Novais; Krug, Francisco José; Carvalho, Hudson Wallace Pereira de (Data in Brief, 2022)