Corn Nitrogen Management Following Daikon Radish and Forage Oat Cover Crops

Abstract

Core Ideas: Daikon radish and forage oat cover crops following winter wheat sequestered residual autumn soil NO 3 –N levels. Nitrogen availability to the ensuing corn crop may be reduced when preceded by radish or oat cover crops. When using radish or oat cover crops, increased 5×5 starter rates (> 45 kg N ha‐1) may be required if full SD is delayed until V11. Radish and oat cover crops preceding corn did not provide a subsequent N fertilizer replacement value but may still be effectively utilized as soil conservation tools. Cover crops (CC) preceding corn ( Zea mays L.) may influence subsequent nitrogen (N) availability, but it is not clear whether N strategies require adjustment. Field studies conducted in 2015 to 2016 evaluated the effects of a daikon radish [ Raphanus sativus (L.)], forage oat [ Avena sativa (L.)], and no CC following winter wheat [ Triticum aestivum (L.)] on soil chemical properties, corn growth, grain yield, and profitability. Nitrogen management strategies were equalized to 179 kg N ha –1 and included pre‐plant incorporated (PPI) N, poultry litter (PL) PPI (61 kg N ha –1 ) plus sidedress (SD) N V11, starter N (45 kg N ha –1 ) subsurface banded (5 cm below and 5 cm beside the seed, 5×5) followed by V4, V11, or V4 plus V11 SD, and a zero N control. Cover crops reduced autumn soil NO 3 –N levels 78 to 84% relative to no CC but occasionally reduced N during critical corn uptake periods. Cover crops did not increase soil base cation availability to the ensuing corn crop. When 5×5 starter was followed by full SD at V11, CCs reduced yield 3.2 to 3.9% and profitability 11.8 to 13.2% compared with no CC indicating reduced efficacy and possibly greater 5×5 requirements to maintain yield potential until SD time. In the zero N control, CCs reduced grain yield 11.8 to 14.2% and increased yield response to N 63 to 79% suggesting reduced N availability. Radish and oat CCs provided a trap crop for autumn residual N, but N management strategies may need to account for reduced N availability.