Changes in microelement availability in a paddy field exposed to long-term atmospheric CO2 enrichment

Purpose The stimulations of plant growth and soil nutrient availability by elevated carbon dioxide (CO2) concentration have been demonstrated in a series of experiments. However, the long-term response of microelement availability to elevated CO2 in paddy ecosystems without micronutrient fertilizer inputs is a matter of debate. Methods Changes of microelement availability in paddy field were investigated by performing a situ experiment under the Free Air CO2 Enrichment (FACE) platform that lasted for a decade. Results Elevated CO2 stimulated the dry matter production of rice and enhanced accumulation of iron (Fe), manganese (Mn), and zinc (Zn) in the stem and panicle. High CO2 concentration led to significant reductions in Fe, Mn, and Zn concentrations in soil solution at jointing and/or pre-filling stages, which were the vigorous growth periods for rice. A significant increase for Fe concentration in the surface water was observed at the vegetative stage, under elevated CO2 condition. Additionally, the contents of Zn extracted by diethylene triamine pentoacetic acid (DTPA) increased significantly in 0-10 cm soil treated by elevated CO2. Conclusions Our study provides an improved understanding on changes of microelements availability in paddy field. The results demonstrated that high CO2 concentration promoted the accumulation of micronutrients in rice plants, but had no significant and positive effects on the availability of Fe and Mn in soil following a decade of CO2 fumigation.