Seed quality under elevated CO₂ differs in soybean cultivars with contrasting yield responses

Abstract

Reduced grain and seed nutrient content in crops grown under elevated CO2 concentrations (eCO2) have raised concerns about future food security. Studies have reported that different seed elements responded differently to eCO2. Additionally, the nutrient response to eCO2 varied across species and cultivars. This study investigated the response of seed quality in two soybean cultivars (HS93‐4118 and Loda) previously shown to have different yield responses to eCO2. We show that seed quality responded differently to eCO2 for the two cultivars and that elements were differentially impacted. The strongest declines under eCO2 were observed for Al, Ca, Fe, and Se while P and Mn were unaffected. Seed protein content increased under eCO2 for the two cultivars. Oil content, however, showed a negative relationship with yield and declined under eCO2. Using path analysis, we show that eCO2 reduced the seed content for some elements through increasing seed yield, effectively diluting the elemental concentrations, while other elements were reduced in a yield‐independent manner. Despite the decline in the seed concentration for some elements, the overall yield per hectare of elements, protein, and oil under eCO2 increased because of greater seed yield. We quantified the economic impact of altered seed composition and show that the decline in oil content with increasing soybean yield at eCO2 could adversely impact profits.

Nutrient Challenges in a Changing Atmosphere: Investigating Biomass Growth and Mineral Concentration Changes in Soybean Plants under Elevated CO2

“…Despite the higher yield, Loda exhibited a consistent reduction in both macro-and micronutrient concentrations at 70 and 126 DAP. Previous studies have demonstrated a strong yield increase for Loda under eCO (Bishop et al, 2015;Sanz Sáez et al, 2017;Digrado et al, 2024). This trend was evident across multiple growth stages, highlighting the challenge of nutrient dilution in high-yielding cultivars under future atmospheric conditions.…”

“…Two atmospheric eCO 2 were used across eight chambers, four at ambient (~410 ppm) and four elevated (ambient + 200 ppm CO 2 ) during daylight hours. Three soybean cultivars (Clark, Flyer, and Loda) were chosen based on their different yield and/or nutrient accumulation responses under eCO 2 : Loda had high strong yield response; Flyer showed decreased Zn accumulation in seeds; and Clark showed no change in Zn in seeds (Myers et al, 2014;Sanz Sáez et al, 2017;Soba et al, 2020;Digrado et al, 2024). Chambers were set up in a randomized complete block design (n = 4), and each chamber contained four plants from each of the three cultivars.…”

“…A study by Bishop et al, (2015) examining the impact of eCO 2 on nine cultivars of soybean (including Clark) reported a significant impact of genotype by year interaction on seed yield, however. Previous studies have also shown the complexity of yield and nutrient concentration responses in soybean cultivars grown under different environmental stresses, geographical locations, and during different years (Köhler et al, 2019;Digrado et al, 2024). For example, a recent study found that when soybean plants were grown in eCO 2 and elevated temperature there no observed yield gains or nutrient losses (Köhler et al, 2019).…”

“…Consequently, the concentration of CO 2 in the Earth's atmosphere has reached unprecedented levels on a global scale (Friedlingstein et al, 2023). There are several studies providing evidence of increased leaf area index, biomass and yield because of increasing atmospheric CO 2 concentrations (eCO 2 ) in C 3 plants (Ferris et al, 1999;Dermody et al, 2006;Digrado et al, 2024). This increase in biomass is caused by the enhanced rate of photosynthesis with simultaneous decrease in stomatal conductance which drives the increase in water-use efficiency (WUE) in C 3 plants, resulting in a "fertilization" effect (Drake et al, 1997;Long et al, 2006;Loladze, 2014;Myers et al, 2014;Ainsworth & Long, 2021).…”