Field experimental data of crop yields, nutrient concentrations, and harvest indices from around the world

Estimates of cropland nutrient budgets and nutrient use efficiencies at national to global scales have generally relied on average nutrient concentrations for quantifying nutrients removed in crops and by-products. Calculation of crop nutrient removal requires estimates of the yield of crop products (e.g. grain or beans) and crop residues (e.g. straw or stover) and the nutrient concentration of these components. Data for yields of crop products are often readily available, but those of crop residues are not. The harvest index can be used to estimate the quantity of crop residue from available data on crop product yields. Nutrients removed in harvested crops are the major source of nutrient losses. The availability of more locally relevant crop coefficients can improve the granularity of estimates for nutrient budgets and use efficiencies.  To aid this, field experimental data were collated for major crops from August 2020 to improve estimates of crop harvest index and nutrient concentrations of crop products and crop residues. This dataset contains available data from published scientific articles or theses. Articles were manually checked for relevant data (generally as summary statistics) and transferred into a standardised format. Initially, these articles were selected based on relevance to maize, rice, soybeans and wheat and for nitrogen, phosphorus, potassium and sulphur. It is envisioned this dataset will increase in scope over time, in terms of included nutrients and crops to further improve crop nutrient budgets and use efficiency estimates across the world.

Methods
Data acquisition

Data were collated from published articles or theses found in scientific literature following the method described by Ludemann et al. (2022). Terms used in Ovid (https://ovidsp.ovid.com/), CAB Abstracts (https://www.cabdirect.org/) and Google Scholar (https://scholar.google.com/) were as follows: (nitrogen OR phosphorus OR potassium OR sulphur OR sulfur) AND ("triticum aestivum" OR wheat OR maize OR "Zea mays" OR corn OR soybean OR "Glycine max" OR rice OR "oryza sativa") AND ("nutrient concentration" OR "nutrient content").  In September 2020 this search led to over 18,000 articles. The list of articles was manually filtered to include crop product and/or crop residue nutrient concentration and/or harvest index data of relevance to maize, rice, soybeans and wheat.  Thereafter, citation alerts were continually tracked, with data from any new articles added to the combined dataset. It is envisioned that this database will be updated with data from new articles over time.

In January 2025 data for Potatoes were added.

Data from the articles were manually converted into a standardized Excel format (Microsoft Office, Microsoft, Redmond, Washington, USA). Where data were unavailable in the publications as tables, data were extracted from figures using the GetData Graph Digitizer software (version 2.26, http://www.getdata-g raph-digitizer.com/).  To improve interoperability, the original Excel data file was converted to a comma-delimited CSV file using R code from: https://github.com/ludemannc/meta_analysis_crop_nutrient_dryad.git and a meta-data file was created to support this file.