Corn yield response to polymer and non-coated urea placement and timings

Poorly drained claypan soils can increase the importance of tillage and N management for corn (Zea mays L.) production. Field research in 2008, 2009 and 2010 (high rainfall years) near Novelty, MO (40° 1' N, 92° 11' W) sought to determine the effect of polymer-coated urea (PCU) placement [strip-tillage (ST) deep banded and no-till (NT) broadcast] and application timing (fall, early preplant and preplant) on red clover (Trifolium pratense L.) biomass and corn response compared to non-coated urea (NCU) and anhydrous ammonia (AA) in the presence and absence of nitrapyrin a nitrification inhibitor. Strip-tillage reduced clover dry weights 20% in 2008 and 2009 and early preplant ST reduced dry weights 40 to 45% in 2010 compared to NT. Corn plant population was 8,100 to 8,400 plants ha-1 greater with ST compared to NT. Preplant applications of AA plus nitrapyrin, AA, ST placement of PCU and NCU increased grain yields 1 to 1.2 Mg ha-1 compared to fall applications of these fertilizer sources. Fall and preplant ST placement of PCU increased grain yields 1.2 Mg ha-1 compared to NCU. Strip-till placement of PCU and NCU increased yields 2.1 to 3.2 Mg ha-1 over broadcast applications of these fertilizer sources. Strip-till placement of PCU synergistically increased yield over NCU and broadcast applications of PCU or NCU due to increased stands and possibly due to better plant utilization of the banded N fertilizer utility.