Degradation of Great Lakes water quality and weather variability emphasize improved nitrogen (N) management strategies that synchronize N availability with corn (Zea mays L.) N uptake. Field studies were conducted at either Lansing or Richville, Michigan from 2014 to 2016 and included investigations of cover crops (radish [Raphanus sativus (L.) var. The Buster], forage oats [Avena sativa (L.) var. Magnum], or no cover crop), and N management strategies (starter N as in-furrow [IF] or sub-surface banded 5-cm beside and 5-cm below the seed furrow [5x5] followed by sidedress [SD] at V4, V10, or split 50/50, pre-plant incorporated N with or without enhanced efficiency N, poultry litter [PL] followed by V11 SD, and zero N). Assessments included cover crop biomass quantity and quality, soil NO3-N levels, corn grain production and profitability, soil basal CO2 respiration, and soil bacterial community composition (16S rRNA sequencing). Radish and oat cover crops (CC) seeded in August reduced autumn soil NO3-N levels 78 – 84% from the no CC control. The following year CC residues reduced N availability to a corn cash crop and reduced effectiveness of 5x5 starter N to maintain yield potential when full SD was applied at V11. Sidedress N delayed from V4 to V11 resulted in similar or reduced yield and profitability. Soil bacterial diversity at R1 was inversely proportional to corn grain yield and suggested bacterial relative abundance may increase indication of yield rather than diversity.
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