Early Season Nitrogen Fertilizer Recovery by Corn within a Furrow‐Irrigated Production System

Core Ideas At‐planting fertilizer‐N recovery was influenced by rate and application method. Large amounts of at‐planting fertilizer‐N was not recovered by the corn crop prior to the V6 growth stage. At‐planting fertilizer‐N recovery efficiency ranged from 0.8 to 18.4% at the V6 growth stage. Corn (Zea mays L.) is an important row crop in the mid‐South where irrigation and N fertilization is required to produce optimal yields. Producers typically split season‐total fertilizer‐N recommendations between at‐planting (30%) and sidedress (70%) applications. The research objective was to investigate the influence of at‐planting N rate and application method on fertilizer‐N recovery efficiency (FNRE) and mass fertilizer‐N recovery (MFNR) in a furrow‐irrigated corn production system measured at the V6 growth stage. At‐planting N rates consisted of 0, 33, 67, and 100 kg N ha‐¹ as ¹⁵N labeled‐urea and were applied using incorporated, surface broadcast, and water‐furrow application methods. Surface broadcast or incorporation of at‐planting N at rates of 34 and 67 kg N ha‐¹ resulted in greater FNRE and MFNR than fertilizer‐N applied directly to the water‐furrow. Fertilizer‐N applied either broadcast or incorporated and the 67 kg N ha‐¹ rate resulted in the highest biomass production at the V6 growth stage. For all treatments, at least 58% of the total‐N (TN) uptake at the V6 growth stage was derived from soil‐N regardless of N rate or application method. The results of this study highlight the importance of fertilizer‐N placement and producers should avoid surface applying at‐planting N to the bottom of the water‐furrow which has limited availability to corn at early growth stages. Results suggest that producers growing furrow‐irrigated corn on silt loam soils should incorporate N applied at‐planting into the soil and only apply up to 67 kg N ha‐¹ to simultaneously optimize early season FNRE and MFNR.