Input data set: N-Fertilizer 5crops (ISIMIP4)

Description:

Annual nitrogen fertilizer application rate for each of the five LUH3 crop functional types, i.e. for both annual and perennial C3 and C4 crops as well as for nitrogen-fixing crops. Rates are given in kg N ha⁻¹ yr⁻¹ over the crop season, on the ISIMIP 0.25° and 0.5° grids, with an annual time step.

The rate applies per hectare of the respective crop type, not per hectare of grid cell. To obtain a nitrogen mass, multiply by that crop type's area, which is provided by the companion landuse-5crops dataset. Grid cells that contain no area of a crop type carry a missing value for that crop type's rate.

Rates are derived from the LUH3 fertilizer input at its native 0.25° resolution and remapped mass-conservatively: since a rate is defined per hectare of crop type rather than grid cell, the nitrogen mass and the crop area are remapped separately and then divided back into a rate.

Users needing one rate per ISIMIP crop group rather than per crop functional type should use n-fertilizer-15crops instead.

Time step: annual

Spatial resolution: 0.25° × 0.25° (15arcmin) and 0.5° × 0.5° (30arcmin), global

Unit: kg ha⁻¹ yr⁻¹ (crop season), nitrogen

Format: NetCDF4-classic

Period (ISIMIP4b): 1850–2021 for histsoc and 1850soc; 2022–2100 for 2021soc, ssp1vlsoc-noadapt and ssp3hsoc-noadapt
Period (ISIMIP4a): 1850–2025 for all scenarios, published as two files split at the 1900/1901 boundary

Filenames carry the resolution as 15arcmin or 30arcmin.

A method description covering both n-fertilizer-5crops and n-fertilizer-15crops can be found here: https://docs.google.com/document/d/1Q77KZniheAL9G8Iyegcjk-WU5GDlmKeB3EMwLF9z9Ng/edit?usp=sharing

Derived from the CMIP7 input4MIPs UofMD Land-Use Harmonization (LUH3) dataset, using the multiple-management fertilizer rates together with the multiple-states crop-type area fractions.
Project page: https://luh.umd.edu/

Historical: UofMD-landState-3-1-2
SSP1-VL: UofMD-landState-vl-3-1-1
SSP3-H: UofMD-landState-h-3-1-1

All three were taken at input4MIPs publication version v20260408.

Chini, L. and Hurtt, G.: Land-Use Harmonization 3 v1.2 for CMIP7 Historical (LUH3 v1.2), source_id UofMD-landState-3-1-2, https://doi.org/10.5281/zenodo.19261724 — used for histsoc, 1850soc, 1901soc and 2021soc

Chini, L. and Hurtt, G.: Land-Use Harmonization 3 Future Scenario VL v1.1 for ScenarioMIP (LUH3-VL v1.1), source_id UofMD-landState-vl-3-1-1, https://doi.org/10.5281/zenodo.19353397 — used for ssp1vlsoc-noadapt

Chini, L. and Hurtt, G.: Land-Use Harmonization 3 Future Scenario H v1.1 for ScenarioMIP (LUH3-H v1.1), source_id UofMD-landState-h-3-1-1, https://doi.org/10.5281/zenodo.19354835 — used for ssp3hsoc-noadapt

References for the LUH methodology:
Hurtt et al. (2020), Geoscientific Model Development, https://doi.org/10.5194/gmd-13-5425-2020
Chini et al. (2021), Earth System Science Data, https://doi.org/10.5194/essd-13-4175-2021

The rates are not resolved sub-nationally. The underlying LUH3 product assigns one value per country, crop functional type and year, and only a few large countries split into several sub-national values. The spatial detail visible in the delivered grids therefore reflects where a crop functional type is grown, not local variation in how intensively it is fertilized: two grid cells in the same country with the same crop mix carry the same rate, however far apart they are.

Application rates are capped at 500 kg N ha⁻¹ yr⁻¹. This is the same bound LUH applies in its own scenario harmonization; the historical reconstruction carries no such bound and passes three national values above it through into every scenario. The cap affects 0.03–0.11 % of global nitrogen mass.

The pre-industrial scenarios are zero everywhere. 1850soc (ISIMIP4b) and 1901soc (ISIMIP4a) contain zero for every variable in every year. This is intended, not a missing or failed file: synthetic nitrogen fertilizer did not exist at either base year, as the Haber-Bosch process was industrialised around 1913, so holding the forcing at that level gives a no-fertilizer counterfactual. In the LUH3 source, application rates are exactly zero through 1910 and first become non-zero between 1910 and 1920.

The two resolutions do not give the same global totals. The 0.5° product is conservatively remapped from the native 0.25° grid and renormalized over the land area of each coarser cell, so a global nitrogen total computed from a 30arcmin file exceeds the same total from the 15arcmin file by about 1 %, concentrated in coastal cells. Use the 15arcmin files when the global mass matters.

2021soc differs between the two rounds. Under ISIMIP4b it holds the 2021 rate fixed across the 2022–2100 future window; under ISIMIP4a it holds the same rate fixed across the full 1850–2025 historical period, as a present-day baseline.

Under ISIMIP4a the value for 2025 repeats 2024, the last observed year.