Worldwide Maize and Soybean Yield Response to Environmental and Management Factors Over the 20th and 21st Centuries

• Published in: Journal of geophysical research. Biogeosciences Vol. 126; no. 11
• Main Authors: Lin, Tzu‐Shun, Song, Yang, Lawrence, Peter, Kheshgi, Haroon S., Jain, Atul K.
• Format: Journal Article
• Language: English
• Published: 01.11.2021
• Subjects: crop growth; environmental and management factors; ISAM model; maize; scenarios; soybean
• ISSN: 2169-8953; 2169-8961
• DOI: 10.1029/2021JG006304

A land process model, Integrated Science Assessment Model, is extended to simulate contemporary soybean and maize crop yields accurately and changes in yields over the period 1901–2100 driven by environmental factors (atmospheric CO2 level ([CO2]) and climate), and management factors (nitrogen input and irrigation). Over the twentieth century, each factor contributes to global yield increase; increasing nitrogen fertilization rates is the strongest driver for maize, and increasing [CO2] is the strongest for soybean. Over the 21st century, crop yields are projected under two future scenarios, RCP4.5‐SSP2 and RCP8.5‐SSP5; the warmer temperature drives yields lower, while rising [CO2] drives yields higher. The adverse warmer temperature effect of maize and soybean is offset by other drivers, particularly the increase in [CO2], and resultant changes in the phenological events due to climate change, particularly planting dates and harvesting times, by 2090s under both scenarios. Global yield for maize increases under RCP4.5‐SSP2, which experiences continued growth in [CO2] and higher nitrogen input rates. For soybean, yield increases at a similar rate. However, in RCP8.5‐SSP5, maize yield declines because of greater climate warming, extreme heat stress conditions, and weaker nitrogen fertilization than RCP4.5‐SSP2, particularly in tropical and subtropical regions, suggesting that application of advanced technologies, and stronger management practices, in addition to climate change mitigation, may be needed to intensify crop production over this century. The model also projects spatial variations in yields; notably, the higher temperatures in tropical and subtropical regions limit photosynthesis rates and reduce light interception, resulting in lower yields, particularly for soybean under RCP8.5‐SSP5. Plain Language Summary A land surface model is used to estimate changes in global maize and soybean yields in response to changes in environmental conditions (climate (temperature and precipitation) and carbon dioxide concentration ([CO2])), and agricultural management activities (irrigation, nitrogen application, and dynamic planting time decisions) over the 20th and 21st centuries. Estimated current crop yields compare well with the observed crop yields circa 2000. We then project how maize and soybean resources may change in the future under two climate and socio‐economic assumptions: a high‐end emission pathway (RCP8.5‐SSP5) and a mitigated emission pathway (RCP4.5‐SSP2). We find that future increase in [CO2] drives yield higher and alleviates the negative climate impacts on soybean productivity. The maize yield increases under the mitigated emission pathway because of earlier planting dates and the continued [CO2] growth and nitrogen application. However, under the high‐end emission pathway with greater warming and lower nitrogen application, the maize yield reduces by 14% by the end of this century, suggesting that climate change mitigation and improved agricultural technologies and practices may be needed to intensify crop production over this century. Crops’ exposure to heat stress during grain formation is represented by canopy temperature and is projected to increase by the 2090s. Key Points Over the twentieth century, the global maize and soybean yields driven by environmental and management factors increase Projected future [CO2] increase has a positive effect, and warmer climate has a negative effect on soybean yield by the 2090s Projected maize yield is increased by 20% under RCP4.5‐SSP2 but is decreased by 14% under RCP8.5‐SSP5 by the end of the 21st century