Pre‐Plant and In‐Season Nitrogen Combinations for the Northern Corn Belt

Abstract

S pring pre-plant N applications are considered a bestmanagement practice in conventionally tilled, poorly drained, medium-to fine-textured soils throughout the northern Corn Belt (Vetsch and Randall, 2004). Corn (Zea mays L.) yield potential is affected by a multitude of agronomic practices (e.g., fertility management), cultivars, and the environment (Evans and Fischer, 1999). Recent data project more frequent heat waves (i.e., >5°C above climatic normal) and increasing air temperatures (1.5-2.0°C) over the next 30 yr that may affect spring frost dates in the northern hemisphere and increase precipitation intensity during winter and spring months (>50.8 mm in 48 h) (Hayhoe et al., 2007; Karl et al., 2009). Warmer spring temperatures may shift corn planting dates earlier than currently recommended (Lauer et al., 1999). Weather variability may increase risk of early applied N losses (i.e., volatilization, leaching, and denitrification) and require reexamination of N management strategies (Scharf et al., 2002). Optimal soil fertility management includes adjusting strategies to account for the proper placement, time, source, and rate (e.g., 4R) of N adapted to site-or region-specific environments (Roberts, 2007). Rapid corn N uptake does not occur until the V10 growth stage (Bender et al., 2013). Delayed sidedress (SD) N applications (e.g., after V10) may help mitigate the time lapse between N application and uptake but further research is needed to refine current grower practices. Pre-plant incorporation (PPI) is a one-pass N strategy where 100% of the N inputs are applied up to planting time and incorporated. A large percentage of Michigan corn land area is grown on calcareous soils with a soil pH > 7.2, which can increase NH 3 volatilization losses, increase N immobilization, and reduce the efficiency of surface-applied urea containing N fertilizers (Havlin et al., 2014). In Michigan studies, blending polymer-coated urea (PCU) with urea (75:25, PCU/urea blend ratio) has improved efficiency of urea containing fertilizers. For example, when April and May precipitation were above average, PCU/urea broadcast 2 to 4 wk before planting and incorporated improved corn yield up to 1.38 Mg ha-1 relative to 100% urea PPI (Franzen, 2017). In the same studies a PCU/ urea blend extended N activity in dry soils, which increased corn grain yield 1.07 Mg ha-1 relative to a V4 to V6 surface

Comparing nitrogen timing and sidedressing placement strategies on corn growth and yield in Michigan

“…However, N mobility and availability from preplanting incorporation (PPI) may be limited under dry soil conditions and reduce early‐season growth relative to starter fertilizer placed 2 inches below and 2 inches to the side of the seed (the 2 × 2 treatment) (i.e. subsurface N placement) (Chaidhary & Prihar, 1974; Khosla, Alley, & Davis, 2000; Rutan & Steinke, 2018). In Michigan, Rutan and Steinke (2018) reported that PPI application reduced yield relative to subsurface N placement when deficit cumulative April to June rainfall occurred but resulted in similar yields when cumulative May to June precipitation was above normal.…”

Soybean seeding rate and fertilizer effects on growth, partitioning, and yield

“…Benefits to increased plant size may include greater photosynthetic capacity and a larger root system able to support or initiate BNF and soil nutrient uptake earlier, but yield‐limiting factors including plant lodging and disease severity (e.g., white mold [ Sclerotinia sclerotiorum ]) must be accounted for (Ball et al., 2000; Salvagiotti et al., 2008; De Souza Jaccoud‐Filho et al., 2016; Tamagno et al., 2018). Subsurface banded fertilizer applications have previously been observed to increase early‐season DM and nutrient accumulation in corn ( Zea mays L.) (Niehues, Lamond, Godsey, & Olsen, 2004; Rutan & Steinke, 2018). As soybean growers respond to a changing climate and plant earlier in the season due to warmer air and soil temperatures, similar benefits may exist in soybean production (Hankinson et al., 2015).…”

“…A quadratic model describing yield and net return response to seeding rate was fit to the data and suggested maximum grain yield was achieved at 364,300 seeds ha −1 while net economic return was maximized at 265,300 seeds ha −1 . Growers often identify grain yield potential as a greater risk factor instead of profitability (Rutan & Steinke, 2018). Without improvements to commodity prices, results from this study suggest growers may want to consider incrementally decreasing seeding rates to <321,200 seed ha −1 for increased profitability instead of maximizing yield.…”

Integrating corn nitrogen management strategies and cover crops following winter wheat

“…When following radish, PL maintained corn yield potential with full SD delayed until V11 as compared with the current 2×2 starter N rate. Characteristics of PL including increased at‐plant N rate or slower availability likely helped increase N supply until the V11 SD timing (Rutan and Steinke, 2018). Growers who prefer to utilize an oat CC may have to consider N placement in relation to residues.…”