A re-examination of optimum foliar magnesium levels in corn

Reliable tissue leaf standards for N, P, and K are available for corn, although standards for some other nutrients have not been well defined. Published ear leaf Mg sufficiency ranges are generally about 0.20 to 0.40% of dry leaf weight, critical values range from 0.15% to 0.25%, and the current standard most widely used with DRIS is 0.24%. However, in maximum yield studies, yields over 18 t/ha have been obtained with ear leaf Mg levels ranging from 0.13 to 0.18%. A field study was initiated to determine whether providing additional Mg to plants grown under ’maximum yield’ conditions would result in increased tissue Mg and yield, or whether optimum or sufficient Mg levels should be redefined. Ear leaf Mg was increased by foliar-applied Mg in two years of the study, and by soil-applied Mg in the third.