Skip to main content
ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Soil, Water & Air Resources Research » Research » Publications at this Location » Publication #289933
Title: Growth response of soybean to elevated carbon dioxide and soil moisture levels

Author
item MADHU, MADAGOWDA - Central Soil And Water Conservation Research And Training Institute
item Hatfield, Jerry

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2013
Publication Date: 7/8/2013
Citation: Madhu, M., Hatfield, J.L. 2013. Growth response of soybean to elevated carbon dioxide and soil moisture levels. Journal of Experimental Botany. 105:657-669.

Interpretive Summary: Plants are being grown under constantly changing climate and some of the changes represent long-term trends and other short-term episodic events. The changes in carbon dioxide in the atmosphere represent a long-term trend with the current carbon dioxide levels expected to increase to nearly 500 ppm by the middle of the century. However, changes in rainfall are expected to become more variable within a growing season and among years. There is little understanding of how these changes will affect soybean growth in the future and the implications of climate change on plant growth. We conducted a study in a controlled environment in which we could manage the soil water to represent environments with limited water, adequate soil water, and excess soil water under two carbon dioxide conditions representing the conditions expected within the next 10 years and those expected by the end of the century. The high levels of carbon dioxide decreased the growth rate and the size of the plant across all of the soil water conditions; however, the higher carbon dioxide levels increased the amount of plant biomass in the reproductive structures of the plant. These observations indicate that continued exposure to increased carbon dioxide may not be beneficial to vegetative development of soybean and will alter the amount of plant material in the reproductive components. This information will be of interest to agronomists, plant physiologists, and geneticists in terms of evaluating the impact of a changing climate on soybean growth and development.

Technical Abstract: Climate change due to increasing atmospheric [CO2] concentration has been predicted to alter the plant structure and growth behavior leading to change in patterns of soil moisture and nutrient use. The objectives of this study were to investigate phenology of crop, growth behavior, dry matter assimilation and leaf C and N content of soybean plants under two [CO2] levels (380 and 800 µmol mol-1) with three soil moisture levels established as amounts replaced per day (low: 5mm day-1; normal: 7.5mm day-1 and high: 10 mm day-1) and two genotypes of soybean with different seed treatments (S 21-N6: Untreated; S 21-N6: Treated) in controlled rhizotron environment. Soybean seeds were planted in each soil monolith at 60 cm row spacing. [CO2] treatment was imposed at 50% seedling emergence and soil moisture treatments imposed at 15 DAP by watering twice during the week. Destructive sampling was done at 29, 44, and 58 DAP to monitor different growth parameters and dry matter accumulation at different plant components. At early crop growth stage, phenology of soybean crop was influenced by [CO2] levels, soil moisture, and genotypes. Slow growth rate and altered crop phenology of soybean plants under elevated [CO2] compared to plants under ambient [CO2]. Growth parameters, e.g., plant height, number of leaves and leaf area per plant were higher under ambient [CO2] with normal soil moisture condition at 29 and 44 DAP, but at 58 DAP all these parameters were higher under elevated [CO2] with normal soil moisture condition. Plants under elevated [CO2] with low soil moisture level had higher SLA at 44 and 58 DAP indicating thinner leaves. Dry matter assimilation in different components of plants viz., leaf, stem, and total dry biomass followed the similar trend as that of the growth parameter of soybean plants. Significant interactions of [CO2] and soil moisture levels were observed for plant height (29 & 44DAP), number of leaves (29 and 58DAP), leaf area per plant (29DAP) and dry matter accumulation in different components of plants (29 and 58DAP). Low leaf C and N content with high C:N ratio was observed in plants under elevated [CO2]. Number and dry weight of pods showed significant response to elevated [CO2] with normal soil moisture level. Elevated [CO2] produced 54.7% and 6.86% higher number of pods and dry weight of pods, respectively, over ambient [CO2]. Pods dry weight was significantly higher under plants with normal soil moisture condition which produced 27.7% and 36.8% higher over low and high soil moisture condition. Genotypes not responding significantly to [CO2] and soil moisture levels will be at a disadvantage under the changing climate.