Hi there. You could looking for more informations on site of Brazilian Agricultural Research Corporation (EMBRAPA, the portal is: https://www.embrapa.br/en/international). We've an unit that make research on Corn (https://www.embrapa.br/milho-e-sorgo) where you could find some data for you.
Concentration (mg/100 g) of mineral nutrients in maize (average of five samples) is listed hereunder:
P 299.6 ± 57.8
K 324.8 ± 33.9
Ca 48.3 ± 12.3
Mg 107.9 ± 9.4
Na 59.2 ± 4.1
Fe 4.8 ± 1.9
Cu 1.3 ± 0.2
Mn 1.0 ± 0.2
Zn 4.6 ± 1.2
Ref: Bressani, R., Breuner, M. and Ortiz, M.A. 1989. Contenidodefibraacidoy neutro-detergente y de minerales menores en maíz y su tortilla. Arch. Latinoam. Nutr., 39: 382-391.