Key nutrients for high yield corn production were identified based on nutrient harvest index values and the removal of a given nutrient. Total nutrients required to produce 12.0 Mg ha-1 of corn included 23,000, 286, 114, 202, 59, 26, 1.4, 0.6, 0.5, 0.1, 0.08 kg ha-1 of DW, N, P2O5, K2O, Mg, S, Fe, Mn, Zn, Cu, and B, respectively. Four nutrients were found to have relatively high harvest index values: P (79%), Zn (62%), N (58%), and S (57%). These results suggest that a high proportion of total uptake for these nutrients are removed annually and may ultimately lead to soil depletion without accurate maintenance fertilizer applications.
A ten day period (V10-V14) resulted in the maximum rates of dry weight production and nutrient assimilation on a per day basis for dry weight (432 kg), N (8.8 kg), P2O5 (2.4 kg), K2O (6.1 kg), Mg (2.2 kg), S (0.6 kg), Zn (14.7 g), Mn (18.2 g), B (3.5 g), Fe (99.6 g), and Cu (1.5 g). While timing of nutrient acquisition varied considerably among nutrients, some required season- long availability – with more than one-half of total uptake occurred post-flowering for Zn, S, P, and Cu. Additionally, micronutrients demonstrated more narrow periods of rapid nutrient uptake than macronutrients, especially Zn and B, when greater than two-thirds of nutrient uptake occurred during less than one-third of the growing season. This reexamination of nutrient use provides opportunities to further improve fertilization rate and application timings as growers continue to achieve greater yields.