Zotarelli, Lincoln, Eduardo Garcia Cardoso, Jorge Luiz Piccinin, Segundo Urquiaga, Robert Michael Boddey, Eleno Torres, and Bruno José Rodrigues Alves. 2003. “Calibration of a Minolta SPAD-502 Chlorophyll Meter for Evaluation of the Nitrogen Nutrition of Maize”. Pesquisa Agropecuaria Brasileira 38 (9):1117-22. https://doi.org/10.1590/S1678-3921.pab2003.v38.6680.