Nitrogen Fertilizer Timing, Leaching Risk, and Long-Term Yield Stability in KBS Cropping Systems: The Synchrony Challenge
Academic Level at Time of Presentation
Graduate
Major
AGRICULTURE
List all Project Mentors & Advisor(s)
Dr. Oliver Freeman
Presentation Format
Poster Presentation
Abstract/Description
Aligning nitrogen (N) fertilizer supply with peak crop demand — termed N synchrony — is critical for improving nitrogen-use efficiency and minimizing reactive N losses in corn production. This study evaluated the impact of N-application timing on long-term yield stability across four contrasting management systems (Conventional T1, No-Till T2, Reduced-Input T3, Organic T4) using 35 years (1989–2024) of data from the Kellogg Biological Station (KBS) LTER Main Cropping System Experiment, encompassing 852 plot-years across a corn–soybean–wheat rotation, with N synchrony analyses and regression modeling conducted on corn phases of the rotation (n=192 corn plot-years). Cumulative Growing Degree Days (GDD; base 10°C) from planting to N application anchored timing physiologically, while a leaching window was defined as precipitation exceeding 20 mm within 48 hours of application, consistent with reported thresholds for rapid nitrate movement in loam soils. Yield stability was quantified with the coefficient of variation (CV) and tested for variance stationarity (Levene's test) between 1989–2004 and 2005–2024, and ordinary least-squares regression incorporated GDD at application, N rate, post-application rainfall, management system, and total May–August precipitation as a covariate, and treatment-by-rainfall interaction terms, with the full interaction model explaining 44.7% of corn yield variance (Adj. R² = 0.416). Seasonal precipitation was the dominant yield driver (+10.8 kg ha⁻¹ mm⁻¹, p< 0.001), indicating that unadjusted leaching-risk analyses may overestimate N-loss impacts by confounding them with the general yield benefit of wetter growing seasons, while the Reduced-Input system (T3), which receives substantially lower N rates than conventional management, exhibited a significant positive interaction with post-application rainfall (+68 kg ha⁻¹ mm⁻¹, p=0.0008), suggesting that moderate precipitation helps move N into the root zone rather than leaching it below. The No-Till system (T2) experienced an 11.1% yield reduction in high-risk leaching years and a CV decline from 29.95% to 18.57% across study periods, reflecting progressive yield stability gains under maturing no-till management, and these results collectively demonstrate that N-rate intensity, rather than timing alone, primarily governs system-specific responses to weather-driven synchrony disruptions, providing practical guidance for designing climate-resilient nitrogen management strategies in Midwestern corn production.
Keywords: Corn, Nitrogen synchrony, Yield stability, Leaching risk, Growing degree days, Kellogg Biological Station, Long-term ecological research
Spring Scholars Week 2026
Sigma Xi Poster Competition
Nitrogen Fertilizer Timing, Leaching Risk, and Long-Term Yield Stability in KBS Cropping Systems: The Synchrony Challenge
Aligning nitrogen (N) fertilizer supply with peak crop demand — termed N synchrony — is critical for improving nitrogen-use efficiency and minimizing reactive N losses in corn production. This study evaluated the impact of N-application timing on long-term yield stability across four contrasting management systems (Conventional T1, No-Till T2, Reduced-Input T3, Organic T4) using 35 years (1989–2024) of data from the Kellogg Biological Station (KBS) LTER Main Cropping System Experiment, encompassing 852 plot-years across a corn–soybean–wheat rotation, with N synchrony analyses and regression modeling conducted on corn phases of the rotation (n=192 corn plot-years). Cumulative Growing Degree Days (GDD; base 10°C) from planting to N application anchored timing physiologically, while a leaching window was defined as precipitation exceeding 20 mm within 48 hours of application, consistent with reported thresholds for rapid nitrate movement in loam soils. Yield stability was quantified with the coefficient of variation (CV) and tested for variance stationarity (Levene's test) between 1989–2004 and 2005–2024, and ordinary least-squares regression incorporated GDD at application, N rate, post-application rainfall, management system, and total May–August precipitation as a covariate, and treatment-by-rainfall interaction terms, with the full interaction model explaining 44.7% of corn yield variance (Adj. R² = 0.416). Seasonal precipitation was the dominant yield driver (+10.8 kg ha⁻¹ mm⁻¹, p< 0.001), indicating that unadjusted leaching-risk analyses may overestimate N-loss impacts by confounding them with the general yield benefit of wetter growing seasons, while the Reduced-Input system (T3), which receives substantially lower N rates than conventional management, exhibited a significant positive interaction with post-application rainfall (+68 kg ha⁻¹ mm⁻¹, p=0.0008), suggesting that moderate precipitation helps move N into the root zone rather than leaching it below. The No-Till system (T2) experienced an 11.1% yield reduction in high-risk leaching years and a CV decline from 29.95% to 18.57% across study periods, reflecting progressive yield stability gains under maturing no-till management, and these results collectively demonstrate that N-rate intensity, rather than timing alone, primarily governs system-specific responses to weather-driven synchrony disruptions, providing practical guidance for designing climate-resilient nitrogen management strategies in Midwestern corn production.
Keywords: Corn, Nitrogen synchrony, Yield stability, Leaching risk, Growing degree days, Kellogg Biological Station, Long-term ecological research