Historical trends in the nitrogen requirement of corn over 45 years in Ohio

The average annual corn (Zea mays L.) grain yield in Ohio has increased since the 1970s, yet the respective roles of corn hybrids and optimal nitrogen (N) fertilization in contributing to this historical trend remain unclear. This study evaluated trends in the agronomically optimal nitrogen rate (AONR) and corn grain yield at agronomically optimal nitrogen rate (YAONR) when corn followed corn (CC) or soybean [Glycine max (L.) Merr.] (SC) in the crop rotation within two eras of corn hybrid development. The two eras were associated with different technological development phases, including 1976–1995 (pre-transgenic era) and 1996–2021 (transgenic era). A total of 431 rainfed corn fertilizer N rate response trials were conducted in 31 Ohio counties over 45 years. From 1976 to 2021, AONR did not significantly increase, while YAONR increased by 96.1 kg per ha per year, a 52% increase over 45 years. Unfertilized (0 kg N per ha) corn yield gains were similar to annual yield gain at AONR, and th..., , # Historical trends in the nitrogen requirement of corn over 45 years in Ohio

Dataset DOI: [10.5061/dryad.3bk3j9kxg](10.5061/dryad.3bk3j9kxg)

## Description of the data and file structure

Ohio State University Corn Nitrogen Rate Data (1976-2021)

Ohio corn N rate dataset published in Fulford et al., 2025: [https://doi.org/10.1002/agj2.70049](https://doi.org/10.1002/agj2.70049)

Dataset contains two data files:

1) Experimental_Design: Data related to the experimental design of each trial. One observation per trial. (431 observations x 18 variables)

2) Crop_Data: Crop N fertilizer applied and total corn grain yields. One observation per plot or per N rate. (5,778 observations x 7 variables)

Periods (.) in datasheets indicate missing information. Questions about these data or the use of these data should be directed to Steve Culman: [[e-mail]](mailto:[e-mail])

### Files and variables

**Description:** Two data files: Experimental_Des...,