# A global meta-analysis of yield-scaled N2O emissions and its mitigation efforts for maize, wheat and rice Author: Zhisheng Yao, Haojie Guo, Yan Wang, Yang Zhan, Tianli Zhang, Rui Wang, Xunhua Zheng, Klaus Butterbach-Bahl Any correspondence has to be send to ## Description of the Data and file structure Note: There are six sheets in the dataset. The variable name, unit, and description for each column of each sheet are shown below. The empty cells in this Excel file mean that data are not available. Variable List: #### Sheet1: Overview | Column | Name | Unit | Description | | :----- | :----------- | :--- | :----------------------------------- | | A | Full Name | None | Full name of collected parameters. | | B | Abbreviation | None | Abbreviation of collected parameter. | #### Sheet2: Maize | Column | Name | Unit | Description | | :----- | :----------------------------- | :--------- | :------------------------------------------------ | | A. | Number | None | Number of References used in the meta-analysis. | | B. | Reference | None | References used in the meta-analysis. | | C. | Location | None | Location of the experimental site. | | D. | Country | None | Country of the experimental site. | | E. | Continent | None | Continent of the experimental site. | | F. | Longitude | None | Longitude of the experimental site. | | G. | Latitude | None | Latitude of the experimental site. | | H. | Category | None | Category of the experimental site. | | I. | Observation period | None | Observation period. | | J. | Climate | None | Climate of the experimental site. | | K. | MAT | °C | Mean annual temperature. | | L. | Category | None | Category of Mean annual temperature . | | M. | MAP | mm | Mean annual precipitation. | | N. | Category | None | Category of Mean annual precipitation. | | O. | Sand | % | Sand content of soil. | | P. | Silt | % | Silt content of soil. | | Q. | Clay | % | Clay content of soil. | | R. | Soil texture | None | Soil texture of soil. | | S. | SOC | g C kg-1 | Description:Soil organic C of soil. | | T. | Category | None | Category of Soil organic C. | | U. | TN | g N kg-1 | Total N of soil. | | V. | Category | None | Category of Total N . | | W. | C/N ratio | None | C/N ratio of soil. | | X. | Category | None | Category of C/N ratio. | | Y. | Soil pH | None | pH of soil. | | Z. | Category | None | Category of Soil pH. | | AA. | BD | g cm-3 | Bulk density of soil. | | AB. | Category | None | Category of BD. | | AC. | Crop type | None | Crop type of experiment. | | AD. | Replicates | None | Replicates of experiment. | | AE. | N type | None | N type of experiment. | | AF. | Category | None | Category of N type. | | AG. | N rate | kg N ha-1 | N rate of experiment. | | AH. | Category | None | Category of N rate. | | AI. | N fertilizer management | None | N fertilizer management of experiment. | | AJ. | Optimized timing and placement | None | Optimized timing and placement. | | AK. | Straw return | Unit:None | Straw return. | | AL. | Water regime | None | Water regime. | | AM. | Tillage type | None | Tillage type. | | AN. | Plastic-film mulching | None | Plastic-film mulching | | AO. | Cumulative N2O fluxes | kg N ha-1 | Cumulative nitrous oxide fluxes of experiment. | | AP. | SE | kg N ha-1 | Standard error of Cumulative N2O fluxes. | | AQ. | SD | kg N ha-1 | Standard deviation of Cumulative N2O fluxes. | | AR. | Grain yield | Mg ha-1 | Grain yield of experiment. | | AS. | SE | Mg ha-1 | Standard error of Grain yield. | | AT. | SD | Mg ha-1 | Standard deviation of Grain yield. | | AU. | Yield-scaled N2O emission | g N Mg-1 | Yield-scaled N2O emission of experiment. | | AV. | SE | g N Mg-1 | Standard error of Yield-scaled N2O emission. | | AW. | SD | g N Mg-1 | Standard deviation of Yield-scaled N2O emission. | | AX. | PFPN | kg kg -1 | partial factor productivity of N. | | AY. | ANE | kg kg -1 | agronomic N efficiency. | | AZ. | EFd | % | Direct N2O emission factor. | #### Sheet3: Wheat | **Column** | **Name** | **Unit** | **Description** | | :--------- | :----------------------------- | :--------- | :------------------------------------------------ | | A. | Number | None | Number of References used in the meta-analysis. | | B. | Reference | None | References used in the meta-analysis. | | C. | Location | None | Location of the experimental site. | | D. | Country | None | Country of the experimental site. | | E. | Continent | None | Continent of the experimental site. | | F. | Longitude | None | Longitude of the experimental site. | | G. | Latitude | None | Latitude of the experimental site. | | H. | Category | None | Category of the experimental site. | | I. | Observation period | None | Observation period. | | J. | Climate | None | Climate of the experimental site. | | K. | MAT | °C | Mean annual temperature. | | L. | Category | None | Category of Mean annual temperature . | | M. | MAP | mm | Mean annual precipitation. | | N. | Category | None | Category of Mean annual precipitation. | | O. | Sand | % | Sand content of soil. | | P. | Silt | % | Silt content of soil. | | Q. | Clay | % | Clay content of soil. | | R. | Soil texture | None | Soil texture of soil. | | S. | SOC | g C kg-1 | Soil organic C of soil. | | T. | Category | None | Category of Soil organic C. | | U. | TN | g N kg-1 | Total N of soil. | | V. | Category | None | Category of Total N . | | W. | C/N ratio | None | C/N ratio of soil. | | X. | Category | None | Category of C/N ratio. | | Y. | Soil pH | None | pH of soil. | | Z. | Category | None | Category of Soil pH. | | AA. | BD | g cm-3 | Bulk density of soil. | | AB. | Category | None | Category of BD. | | AC. | Crop type | None | Crop type of experiment. | | AD. | Replicates | None | Replicates of experiment. | | AE. | N type | None | N type of experiment. | | AF. | Category | None | Category of N type. | | AG. | N rate | kg N ha-1 | N rate of experiment. | | AH. | Category | None | Category of N rate. | | AI. | N fertilizer management | None | N fertilizer management of experiment. | | AJ. | Optimized timing and placement | None | Optimized timing and placement. | | AK. | Straw return | None | Straw return. | | AL. | Water regime | None | Water regime. | | AM. | Tillage type | None | Tillage type. | | AN. | Plastic-film mulching | None | Plastic-film mulching | | AO. | Cumulative N2O fluxes | kg N ha-1 | Cumulative nitrous oxide fluxes of experiment. | | AP. | SE | kg N ha-1 | Standard error of Cumulative N2O fluxes. | | AQ. | SD | kg N ha-1 | Standard deviation of Cumulative N2O fluxes. | | AR. | Grain yield | Mg ha-1 | Grain yield of experiment. | | AS. | SE | Mg ha-1 | Standard error of Grain yield. | | AT. | SD | Mg ha-1 | Standard deviation of Grain yield. | | AU. | Yield-scaled N2O emission | g N Mg-1 | Yield-scaled N2O emission of experiment. | | AV. | SE | g N Mg-1 | Standard error of Yield-scaled N2O emission. | | AW. | SD | g N Mg-1 | Standard deviation of Yield-scaled N2O emission. | | AX. | PFPN | kg kg -1 | partial factor productivity of N. | | AY. | ANE | kg kg -1 | agronomic N efficiency. | | AZ. | EFd | % | Direct N2O emission factor. | #### Sheet4: Rice | **Column** | **Name** | **Unit** | **Description** | | :--------- | :----------------------------- | :--------- | :------------------------------------------------ | | A. | Number | None | Number of References used in the meta-analysis. | | B. | Reference | None | References used in the meta-analysis. | | C. | Location | None | Location of the experimental site. | | D. | Country | None | Country of the experimental site. | | E. | Continent | None | Continent of the experimental site. | | F. | Longitude | None | Longitude of the experimental site. | | G. | Latitude | None | Latitude of the experimental site. | | H. | Category | None | Category of the experimental site. | | I. | Observation period | None | Observation period. | | J. | Climate | None | Climate of the experimental site. | | K. | MAT | °C | Mean annual temperature. | | L. | Category | None | Category of Mean annual temperature . | | M. | MAP | mm | Mean annual precipitation. | | N. | Category | None | Category of Mean annual precipitation. | | O. | Sand | % | Sand content of soil. | | P. | Silt | % | Silt content of soil. | | Q. | Clay | % | Clay content of soil. | | R. | Soil texture | None | Soil texture of soil. | | S. | SOC | g C kg-1 | Soil organic C of soil. | | T. | Category | None | Category of Soil organic C. | | U. | TN | g N kg-1 | Total N of soil. | | V. | Category | None | Category of Total N . | | W. | C/N ratio | None | C/N ratio of soil. | | X. | Category | None | Category of C/N ratio. | | Y. | Soil pH | None | pH of soil. | | Z. | Category | None | Category of Soil pH. | | AA. | BD | g cm-3 | Bulk density of soil. | | AB. | Category | None | Category of BD. | | AC. | Crop type | None | Crop type of experiment. | | AD. | Replicates | None | Replicates of experiment. | | AE. | N type | None | N type of experiment. | | AF. | Category | None | Category of N type. | | AG. | N rate | kg N ha-1 | N rate of experiment. | | AH. | Category | None | Category of N rate. | | AI. | N fertilizer management | None | N fertilizer management of experiment. | | AJ. | Optimized timing and placement | None | Optimized timing and placement. | | AK. | Straw return | None | Straw return. | | AL. | Water regime | None | Water regime. | | AM. | Tillage type | None | Tillage type. | | AN. | Plastic-film mulching | None | Plastic-film mulching | | AO. | Cumulative N2O fluxes | kg N ha-1 | Cumulative nitrous oxide fluxes of experiment. | | AP. | SE | kg N ha-1 | Standard error of Cumulative N2O fluxes. | | AQ. | SD | kg N ha-1 | Standard deviation of Cumulative N2O fluxes. | | AR. | Grain yield | Mg ha-1 | Grain yield of experiment. | | AS. | SE | Mg ha-1 | Standard error of Grain yield. | | AT. | SD | Mg ha-1 | Standard deviation of Grain yield. | | AU. | Yield-scaled N2O emission | g N Mg-1 | Yield-scaled N2O emission of experiment. | | AV. | SE | g N Mg-1 | Standard error of Yield-scaled N2O emission. | | AW. | SD | g N Mg-1 | Standard deviation of Yield-scaled N2O emission. | | AX. | PFPN | kg kg -1 | partial factor productivity of N. | | AY. | ANE | kg kg -1 | agronomic N efficiency. | | AZ. | EFd | % | Direct N2O emission factor. | #### Sheet5: Potential mitigation strategies | Column | Name | Unit | Description | | :----- | :------------------------------- | :--------- | :--------------------------------------------------- | | A. | Number | None | Number of References used in the meta-analysis. | | B. | Reference | None | References used in the meta-analysis. | | C. | Crop type | None | Crop type of experiment. | | D. | C\_Cumulative N2O fluxes | kg N ha-1 | Cumulative N2O fluxes of control soil. | | E. | T\_Cumulative N2O fluxes | kg N ha-1 | Cumulative N2O fluxes of experimental soil. | | F. | ln RR\_Cumulative N2O fluxes | None | Response ratio of Cumulative N2O fluxes. | | G. | C\_Grain yield | Mg ha-1 | Grain yield of the control soil. | | H. | T\_Grain yield | Mg ha-1 | Grain yield of the experimental soil. | | I. | ln RR\_Grain yield | None | Response ratio of Grain yield. | | J. | C\_Yield-scaled N2O emission | g N Mg-1 | Yield-scaled N2O emission of the control soil. | | K. | T\_Yield-scaled N2O emission | g N Mg-1 | Yield-scaled N2O emission of the experimental soil. | | L. | ln RR\_Yield-scaled N2O emission | None | Response ratio of Yield-scaled N2O emission. | | M. | Potential mitagation strategies | None | Potential mitagation strategies. | #### Sheet6: References | Column | Name | Unit | Description | | :----- | :-------- | :--- | :----------------------------------- | | A | Number | None | Number of references. | | B | Reference | None | References used in the meta-analysis | ## Sharing/Access information Data was derived from the following sources: We identified a total of 608 published experimental studies covering 30 countries and 724 sites, including 236 experiments for maize, 190 for wheat and 298 for rice. Collect the yield-scaled N2O emissions, grain yields, total cumulative N2O emissions, and other key information, including geographical location (country, longitude and latitude), general climate (tropical, subtropical and temperate), mean annual air temperature (MAT) and precipitation (MAP), soil properties (e.g., soil texture, soil organic C (SOC), total N content (TN), soil C/N ratio, soil pH and bulk density (BD)), management practices (e.g., straw return, tillage and N fertilizer type and rate). And recorded in our full dataset. ## Code/Software None

Maintaining or even increasing crop yields while reducing nitrous oxide (N2O) emissions is necessary to reconcile food security and climate change, while the metric of yield-scaled N2O emission (i.e., N2O emissions per unit of crop yield) is at present poorly understood. Here we conducted a global meta-analysis with more than 6000 observations to explore the variation patterns and controlling factors of yield-scaled N2O emissions for maize, wheat, and rice and associated potential mitigation options. Our results showed that the average yield-scaled N2O emissions across all available data followed the order wheat (322 g N Mg-1, with the 95% confidence interval (CI): 301-346) > maize (211 g N Mg-1, CI: 198-225) > rice (153 g N Mg-1, CI: 144-163). Yield-scaled N2O emissions for individual crops were generally higher in tropical or subtropical zones than in temperate zones, and also showed a trend towards lower intensities from low to high latitudes. This global variation was better explained by climatic and edaphic factors than by N fertilizer management, while their combined effect predicted more than 70% of the variance. Furthermore, our analysis showed a significant decrease in yield-scaled N2O emissions with increasing N use efficiency or in N2O emissions for production systems with cereal yields > 10 Mg ha-1 (maize), 6.6 Mg ha-1 (wheat) or 6.8 Mg ha-1 (rice), respectively. This highlights that N use efficiency indicators can be used as valuable proxies for reconciling trade-offs between crop production and N2O mitigation. For all three major staple crops, reducing N fertilization by up to 30%, optimizing the timing and placement of fertilizer application or using enhanced-efficiency N fertilizers significantly reduced yield-scaled N2O emissions at similar or even higher cereal yields. Our data-driven assessment provides some key guidance for developing effective and targeted mitigation and adaptation strategies for the sustainable intensification of cereal production.