Evaluation of Pre-Plant and in-Season Nitrogen Management Strategies on Grain Yield in the Northern Corn Belt.

Volatile spring weather conditions and earlier corn (Zea mays L.) planting both emphasize improved nitrogen (N) management strategies that reduce opportunities for N loss. In-season N applications offer flexibility to synchronize N availability with corn uptake but further validation of pre-plant and in-season N strategies is required in the Northern Corn Belt. Field experiments were initiated in 2014 to investigate corn yield response to N management programs involving multiple N-placements and timings applied at a single N rate at two Michigan locations. Nitrogen management programs were grouped into three strategies utilizing broadcast pre-plant incorporated (PPI) N, starter N applied in-furrow (7.8 kg N ha^-1), or starter N sub-surface banded 5 cm beside and 5 cm below the furrow (44.8 kg N ha^-1). Treatment combinations within the in-furrow and banded starter N strategies included sidedress at V4-6, V10-12, or 50/50 (split) V4-6 and V10-12. Pre-plant incorporated strategies involved 100% urea, 25/75 mix of urea with polymer-coated urea, and poultry litter applied at 2.24 Mg ha^-1 plus sidedress N V10-12. Treatments were arranged in a randomized complete block with four replications including a zero-N control. Two years of data indicated a significant effect of year on treatment means when analyzed by site. At site 1, the in-furrow starter N strategy with delayed sidedress N application at V10-12 decreased mean grain yield 7-8% as compared to V4 or split sidedress N timings in 2014 but similar yields were obtained in 2015. At site 2, the sub-surface banded starter N strategy with delayed sidedress N application at V10-12 decreased mean grain yields 5-6% as compared to other sidedress N timings but with similar yields in 2015. Two-year data suggest that under both wet and dry soil conditions opportunities for positive yield gains were reduced when utilizing a V10-12 sidedress N application.