do Amaral, L.R. and Molin, J.P. 2012. Optical sensor to support nitrogen fertilization recommendation for sugarcane crops. Pesquisa Agropecuaria Brasileira. 46, 12 (Feb. 2012), 1633–1642. DOI:https://doi.org/10.1590/S1678-3921.pab2011.v46.9781.