Secondary and micronutrient application effects on corn fertilized for different yield goals under highly weathered soil conditions

Highly weathered soils have low native fertility; thus, optimum nutrient management is critical, especially for a high-input crop such as corn (Zea mays). Field studies were established in Plains and Tifton, GA, to assess secondary nutrient (SN; Mg, Ca, and S) and micronutrient (MN; B, Zn, Mn, Fe, Cu, and Mo) application effects on corn fertilized with primary nutrients (PN; N, P, and K) to achieve 12.5 Mg ha-1 (low) and 25.1 Mg ha-1 (high) yields. Both Plains and Tifton have Ultisol soil. However, the Tifton soil has a 30-cm top sandy layer, and the Plains soil has no top sandy layer. Differences in corn nutrient concentrations were observed at the V5-V7 stage but not in biomass accumulation. The 12.5 Mg ha-1 target grain yield from applying the low PN was exceeded at both locations (by 19.0%-26.6% in Plains and 6.3%-19.7% in Tifton), irrespective of the SN or MN application. However, the 25.1 Mg ha-1 target grain yield from applying the high PN rate was not achieved, with yields of 16.9-17.7 Mg ha-1 in Plains and 15.7-17.1 Mg ha-1 in Tifton obtained. The SN and/or MN application increased corn yield (by 2.3%-13.6%) across all conditions, but the differences were statistically significant under just the low PN rate in Tifton. Overall, the results showed that SN and MN could be yield-limiting factors of corn in the Ultisol soils tested in the study, and also 12.5 Mg ha-1 corn yield can be achieved with lower PN rates than currently recommended. Differences in nutrient concentrations were observed at the V5-V7 stage, but they did not affect corn biomass. Corn yield increased by 2.3%-13.6% from secondary (SN) and/or micronutrient (MN) applications. The yield goal of 12.5 Mg ha-1 from applying the recommended primary nutrients (PNs) was exceeded by 6.3%-26.6%. The yield goal of 25 Mg ha-1 from applying the PNs was not achieved, regardless of SN or MN applications.