Corn 15-nitrogen uptake and partitioning in response to fertilizer application rate and timing

Authors: SPACKMAN, JARED - University Of Idaho; FERNÁNDEZ, FABIAN - University Of Minnesota; PAIAO, GABRIEL - University Of Minnesota; Venterea, Rodney - Rod; COULTER, JEFFREY - University Of Minnesota

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2024
Publication Date: 5/9/2024
Citation: Spackman, J., Fernández, F., Paiao, G., Venterea, R.T., Coulter, J. 2024. Corn 15-nitrogen uptake and partitioning in response to fertilizer application rate and timing. Agronomy Journal. 1-16. https://doi.org/10.1002/agj2.21577.
DOI: https://doi.org/10.1002/agj2.21577

Interpretive Summary: Nitrogen fertilizer is needed to optimize corn production but also can lead to environmental pollution when all of the nitrogen is not used by the crop. Therefore, determining the appropriate amount of nitrogen fertilizer to apply, and when to apply it, are important decisions that influence the efficiency of fertilizer use and any potential environmental impacts. This study used isotope-labelled fertilizer to track the fate of the applied nitrogen in an effort to better determine how much of the total crop nitrogen uptake originated from the applied fertilizer versus nitrogen released from the soil organic matter. Field experiments were conducted at six sites in Minnesota over two consecutive years, with the corn at each site receiving different amounts of nitrogen fertilizer. The fertilizer was applied either at planting or in a “split application” where one-third was applied at planting and the remainder applied several weeks later when the crop had developed to stage V4. The results showed that crop uptake of fertilizer nitrogen was greatest closest to the time of fertilizer application but decreased over time as soil-derived nitrogen became the more dominant source. Split application significantly improved the uptake of fertilizer-derived nitrogen but did not improve the total amount of nitrogen that the crop utilized during the entire growing season. Fertilizer N use efficiency ranged from 3 to 43% at the end of the first year with the majority of the nitrogen contained in the corn grain. This study showed that application of fertilizer ensures adequate nitrogen availability to the developing crop, but ultimately the soil organic matter contributed more than 60% of the crop’s total nitrogen uptake. This study has important implications for managing nitrogen for corn production and will be of interest to producers and scientists interested in increasing the efficiency of fertilizer use and decreasing its environmental impacts.

Technical Abstract: Nitrogen (N) fertilizer applications near the time of planting are important for U.S. upper Midwest corn (Zea mays L.) production but wet springs may result in significant N fertilizer loss. Split applications may avoid wet conditions and improve fertilizer uptake and use efficiency, but the relative contribution of N from the soil and fertilizer is poorly understood. A field study with six sites in Minnesota, USA received 15N-labeled urea fertilizer in the first year and unlabeled urea in the second year to determine the effect of N rate and application timing on corn uptake and accumulation patterns of fertilizer-derived N (FDN) and soil-derived N (SDN) over two consecutive growing seasons. The percentage of total N uptake as FDN was greatest closest to the time of fertilizer application but decreased over time as SDN became the dominant N source. A split application (45 kg N ha-1 at planting, 90 kg N ha-1 at V4) significantly improved FDN uptake over the 135 kg N ha-1 preplant treatment but did not improve total N uptake in the first year at any site. Fertilizer N use efficiency (F15NUE) using the isotopic method was 2.8 to 43.3% across all sites at the end of the first year with the majority partitioned to the grain. At the end of the second year, approximately 2.2% of the first-year applied FDN was recovered in aboveground biomass. Fertilization ensures adequate N availability to the developing crop, but ultimately SDN contributes >61% of the total N uptake.