Late‐Split Nitrogen Applications Increased Maize Plant Nitrogen Recovery but not Yield under Moderate to High Nitrogen Rates

Abstract

N itrogen fertilizer is a high-cost input for maize production that is diffi cult to manage because efficient crop accumulation and utilization is dependent on agronomic, genetic, biological, and environmental factors. Within the wide spectrum of N fertilizer management decisions, a key interest has been improving the effi ciency with which N fertilizers are used by optimizing N rate and the timing of N application. One way to pursue increased N fertilizer effi ciency may be with the use of late-season, split N applications instead of the more common practice of N application near or shortly aft er planting (Scharf et al., 2002). Reasons that can motivate implementing late-season N applications include reducing work load during planting season, avoiding the frequently wet spring soil conditions, and allowing in-season assessment of N fertilizer needs (Scharf et al., 2002). Once N is applied to the soil it is vulnerable to losses from denitrifi cation and leaching, as well as volatilization and surface run-off if not injected (Raun and Johnson, 1999). When considering the potential benefi ts of late-season N applications, of prime interest are how the timing of N application impacts post-silking nitrogen accumulation (PostN), and the relationships between PostN and grain yield.Previous literature refl ects mixed results on the eff ects of the timing of sidedress N application. While Scharf et al. (2002) found no evidence of decreased grain yield when 100% of the N application was delayed until V11, Binder et al. (2000) reported a 12% reduction in maximum grain yield due to delaying sidedress application until V6 in a silty-clay soil. Similarly, Walsh et al. (2012) found a yield loss in six out of nine sites when sidedress was delayed until V10-VT. Th e latter authors attributed this yield decrease to irreversible yield loss due to early season N stress. Th ese studies indicate that a more feasible split-N application strategy would involve applying the majority of the N fertilizer early in the growing season and delaying a supplemental portion until the late-vegetative aBStractTh eoretically, N losses are reduced by synchronizing fertilizer additions with plant uptake requirements. We investigated the impacts of supplemental, late-season N applications on nitrogen fertilizer recovery effi ciency (NRE), and N accumulation and partitioning in maize (Zea mays L.) at silking (R1) and physiological maturity (R6). Also tested was whether modern hybrids responded diff erently to split-N applications compared to hybrids released 20 yr ago. We compared 3 to 4 N rates ranging from 0 to 245 kg N ha -1 applied either in a single application at V3, or split with the last 45 kg N ha -1 delayed until V12, over 3 yr. Two newer hybrids (2012 and 2014) and two 1990 era hybrids (1991 and 1995) were compared at all N treatment combinations. Additional plant N accumulation following latesplit N applications was already apparent at R1, particularly in stems. Late-split N application increased both whole-plant R6 N accumulation and N...

Can Late‐Split Nitrogen Application Increase Ear Nitrogen Accumulation Rate During the Critical Period in Maize?

“…To ensure that the older hybrids were not negatively affected by the use of a common plant density, an additional plant density experiment was also conducted in 2015 and 2016. That experiment, described further in Mueller et al (2017), found no hybrid × plant density interaction for grain yield and, therefore, it was concluded that the use of a single plant density would not materially alter the relative hybrid treatment results of this experiment. All hybrids were treated with in‐furrow insecticide at planting to mitigate differences in genetic insect resistance.…”

How do recommendation systems and nitrogen recovery efficiency work together?

“…Timing of nitrogen fertilizer applications plays a role in uptake. Depending on weather conditions, nitrogen uptake after silking can range from 22.4 to 40.8% of the total nitrogen uptake by the plant (Mueller et al, 2017).…”

“…Monitoring a measurement like NRE as a part of this system over time can help producers and consultants identify the external impact on nitrogen fertilizer applications. For example, Mueller et al (2017) found a yield response and an NRE improvement in the growing season where rainfall was limited in 32 days between the first and the second nitrogen applications compared with when rainfall was higher in other seasons.…”

“…Improving nitrogen management in cropping systems is important for the economic, environmental, and social goals of 4R Nutrient Stewardship. Increasing nitrogen recovery efficiency (NRE) is part of this [NRE = (nitrogen accumulation with fertilizer – nitrogen accumulation without fertilizer)/nitrogen rate; Mueller et al, 2017]. Corn grain yield increases with increased nitrogen application.…”

“…In‐field research has shown that NRE consistently improves with a late split nitrogen fertilizer application, but corn grain yield does not (Mueller et al, 2017). Further research is needed on the impact of combining source, rate, time, and placement changes in a single experiment and their impact on NRE.…”