Medeiros, A. and Haag, H. 1990. Critical level of phosphorus in cotton varieties: III. concentration of phosphorus in the leaves and petioles correlated with time of sampling . Anais da Escola Superior de Agricultura Luiz de Queiroz. 47, 1 (Jan. 1990), 107–133. DOI:https://doi.org/10.1590/S0071-12761990000100007.