Table 1. Definitions of reported variables, corresponding to columns of the dataset (Data Citation 1).

Variable	Definition
Row	An index, numbered 2–1153, to aid in sorting the dataset.
Study	Name of the study in which the plants were grown.
Data_Type	Indicates whether samples are raw data for use in analyses (‘RawData’), or duplicate samples used for technical validation (‘Validation’).
City	City in which samples were grown.
State	State in which samples were grown.
Country	Country in which samples were grown.
Year	Year in which samples were grown.
Crop	Crop species grown. Either wheat (Triticum aestivum), soybean (Glycine max), sorghum (Sorghum bicolor), corn (Zea mays), rice (Oryza sativa), or field peas (‘peas,’ Pisum sativum).
Elevated_CO2_Target_ppm	Target concentration for elevated [CO2] treatments, in parts per million (ppm).
Elevated_CO2_Achieved_ppm	Daytime average [CO2] in elevated [CO2] treatments, in ppm.
Ambient_CO2_ppm	Daytime average [CO2] in ambient (control) [CO2] treatments, in ppm.
FACE_Ring_Diameter_m	Diameter of FACE rings, in meters.
SampleCode	A unique number or character string identifying each sample.
Replicate	Denotes the experimental replicate, sometimes called ‘block’ in the accompanying literature, in which samples were grown.
Ring	Denotes the specific FACE ring in which samples were grown.
Plot	Location within a FACE ring in which samples were grown. This may differ among paired samples within a replicate.
Temperature_Qualitative	Temperature at which crops were grown; either ‘Ambient,’ for most crops, or ‘Elevated’ by 2 °C for some rice samples.
Water_Qualitative	Studies used up to two irrigation treatments. For studies using two irrigation treatments, ‘Wet’ and ‘Dry’ refer to samples that received more and less water, respectively. For studies that did not vary irrigation, this is ‘NA.’
Precipitation_mm	Water crops received as precipitation during the growing season, in mm.
Irrigation_mm	Water crops received as irrigation during the growing season, in mm.
Total_Water_mm	Sum of precipitation and irrigation; the total amount of water available to crops during the growing season, in mm.
Nitrogen_Application_Qualitative	Studies used up to three levels of nitrogen fertilizer application per cultivar. ‘Low’ means no nitrogen applied to crops, ‘Medium’ means some nitrogen fertilizer applied to crops, and ‘High’ is reserved for greater amounts of nitrogen application than ‘Medium’ samples. ‘High’ nitrogen applications vary among rice cultivars.
Nitrogen_Application_Quantitative	Amount of nitrogen applied to crops as fertilizer, in kg N ha−1.
Phosphorus_Application_Quantitative	Amount of phosphorus applied to crops as fertilizer, in kg P ha−1.
Potassium_Application_Quantitative	Amount of potassium applied to crops as fertilizer, in kg K ha−1.
Sowing_Timing_Qualititative	Time of sowing (TOS) was an independent variable for the wheat experiments. ‘TOS1’ represents late autumn planting, typical for the region, and ‘TOS2’ represents a mid-winter planting. In general, ‘TOS2’ crops matured under hotter, drier conditions. For all other crops this is ‘NA.’
Sowing_Timing_Quantitative	Date that crops were sown (mm/dd/yy). For rice, we present the date that seedlings were transplanted into hills in the field; seeds were planted in seedling trays approximately one month prior28,43.
Cultivar	Cultivar grown.
CO2_Treatment	Denotes whether a sample was grown at ambient [CO2] (‘aCO2’) or elevated [CO2] (‘eCO2’).
N_percent	Nitrogen concentration of sample, in percent of dry mass.
P_percent	Phosphorus concentration of sample, in percent of dry mass.
K_percent	Potassium concentration of sample, in percent of dry mass.
Ca_percent	Calcium concentration of sample, in percent of dry mass.
Mg_percent	Magnesium concentration of sample, in percent of dry mass.
Zn_ppm	Zinc concentration of sample, in ppm of dry mass.
Fe_ppm	Iron concentration of sample, in ppm of dry mass.
S_ppm	Sulfur concentration of sample, in ppm of dry mass.
B_ppm	Boron concentration of sample, in ppm of dry mass.
Mn_ppm	Manganese concentration of sample, in ppm of dry mass.
Cu_ppm	Copper concentration of sample, in ppm of dry mass.
Phy_Ext1_Precip1	First of two precipitation measurements of phytic acid phosphorus from the first of up to three phytic acid extractions, in mg g−1.
Phy_Ext1_Precip2	Second of two precipitation measurements of phytic acid phosphorus from the first of up to three phytic acid extractions, in mg g−1.
Phy_Ext1_Avg	Average of the two phytic acid phosphorus measurements from the first of up to three phytic acid extractions, in mg g−1.
Phy_Ext2_Precip1	First of two precipitation measurements of phytic acid phosphorus from the second of up to three phytic acid extractions, in mg g−1.
Phy_Ext2_Precip2	Second of two precipitation measurements of phytic acid phosphorus from the second of up to three phytic acid extractions, in mg g−1.
Phy_Ext2_Avg	Average of the two phytic acid phosphorus measurements from the second of up to three phytic acid extractions, in mg g−1.
Phy_Ext3_Precip1	First of two precipitation measurements of phytic acid phosphorus from the third of up to three phytic acid extractions, in mg g−1.
Phy_Ext3_Precip2	Second of two precipitation measurements of phytic acid phosphorus from the third of up to three phytic acid extractions, in mg g−1.
Phy_Ext3_Avg	Average of the two phytic acid phosphorus measurements from the third of up to three phytic acid extractions, in mg g−1.
Phy_Grand_Avg	Sample phytic acid phosphorus concentration in mg g−1. This is the average of the results from the first two extractions if they differed by less than 15%, otherwise a third extraction was performed and the two extractions in best agreement were averaged to generate this value.