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Abstract

Introduction: Traditional methods to determine the agronomic optimum nitrogen rate (AONR) for corn (Zea mays L.) rely on grain yield data, limiting in-season decision-making for nitrogen (N) management. Vegetation indices (VIs) derived from satellite imagery can serve as proxies for grain yield and help estimate in-season AONR, enabling timely sidedress applications. This study aimed to (1) quantify how VI–yield relationships vary during the vegetative period across fields with different tillage systems and crop residue; (2) determine whether VI–N response curves can be used to estimate AONR (AONRvi); and (3) assess the accuracy of AONRvi relative to yield-based AONR (AONRy).

Methods: Three rainfed on-farm field trials with contrasting tillage systems and four to five N rates were conducted in Indiana in 2021. PlanetScope imagery (3-m resolution) was used to calculate 16 VIs (8 NIR-based and 8 RGB-based) across multiple growth stages. Linear regressions between yield and VIs were used to assess strength of their relationship, followed by VI–N response curves to estimate AONRvi.

Results and Discussion: During the vegetative period, VI–yield relationships were generally weak (R2 ≤ 0.31) and varied across fields, with fewer significant relationships under higher crop residue conditions. Of the VI–N response curves evaluated, 17% met selection criteria for estimating AONRvi, with lower proportions observed in higher-residue systems. Mid-vegetative period imagery (V10–V11) produced the smallest deviations from AONRy for NIR-based indices, although no single VI consistently performed best across fields and timings. These results indicate that 3-m satellite imagery has potential to detect crop N response under commercial field conditions, but its reliability for estimating in-season AONR depends on management context, image timing, and spectral domain.

Document Type

Article

Publication Date

2026

Notes/Citation Information

© 2026 Morales-Ona, Mizuta, Camberato, Nielsen, Miao, Cammarano, Mandrini and Quinn. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Digital Object Identifier (DOI)

https://doi.org/10.3389/fpls.2026.1731400

Funding Information

The author(s) declared that financial support was received for this work and/or its publication. This work was supported by the USDA Natural Resources Conservation Service (NRCS) through the Conservation Innovation Grant (CIG) (Grant No. NR213A750013G005) and by the USDA National Institute of Food and Agriculture (NIFA) through the Multi-State Hatch project S1090 (Project No. KY006151-7008110-S1090). Ana Morales-Ona was supported by the Indiana Corn Marketing Council through the Gary Lamie Scholarship.

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