Abstract
From 1993, we have conducted trials with the same set of old to newer soybean cultivars to determine the impact of plant breeding on seed yield, physiological and agronomic characteristics, and seed composition. Since 1993, global atmospheric [CO2] increased by 47 ppm. The objective of our current analysis with this data set was to determine if there were changes in soybean seed yield, quality or phenology attributable to elevated atmospheric CO2 concentration (eCO2), temperature or precipitation. Additionally, we estimated genetic gain annually. Over 23 years, there was a significant increase in atmospheric [CO2] but not in-season average maximum or minimum temperatures, or average in-season precipitation. Seed yield was increased significantly by eCO2, higher precipitation and higher minimum temperatures during flowering and podding. Yield decreased with higher minimum temperatures during vegetative growth and seed filling. Seed oil and also seed protein plus oil concentrations were both reduced with eCO2. Phenology has also changed, with soybean cultivars spending less time in vegetative growth, while time to maturity remained constant. Over the 23 years of the study, genetic improvement rates decreased as [CO2] increased. Newer cultivars are not better adapted to eCO2 and soybean breeders may need to intentionally select for favourable responses to eCO2 in the future.
Highlights
Atmospheric carbon dioxide concentration has increased from 270 ppm, at the beginning of the industrial revolution (~1830), to 404 ppm at the present day (2016) [1,2]
Our study estimated that soybean seed yield increased by the Mauna Loa, CO
Our study estimated that soybean seed yield increased by 4.3
Summary
Atmospheric carbon dioxide concentration has increased from 270 ppm, at the beginning of the industrial revolution (~1830), to 404 ppm at the present day (2016) [1,2]. 66% of total CO2 accumulation has occurred since the 1950s [3]. Estimated that even with serious carbon emission reductions, [CO2 ] will reach 480 ppm by 2050 [4]. CO2 absorbs long-wave radiated energy resulting in increased air temperature (T). This is referred to as the Greenhouse Effect. Since the beginning of the industrial revolution, global temperatures have risen by 0.9 ◦ C and are predicted to continue to rise ~2.0 ◦ C by 2050 [4]
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