Influence of different rates of gypsum application on methane emission from saline soil related with rice growth and rhizosphere exudation

• Higher EC levels result in higher amount of organic acids exudation by plants.
• The highest root exudation was observed under the addition of gypsum 0.5 ton ha− 1.
• The addition of gypsum 0.5 ton ha− 1 is not enough to suppress CH4 emission.
• The lowest CH4 emission was observed under the addition gypsum 2 ton ha− 1.
• Methane emission is influenced by both carbon availability and SO4 level of soil.

The effect of different rate of gypsum fertilizer addition on rice plant performance and methane (CH4) emission was evaluated for saline paddy rice soil by a pot experiment for 30 days. There were four treatments; control, gypsum 0.5 (G0.5), 1 (G1), and 2 (G2) ton ha− 1 with 3 replications. Gypsum application led to a significant decrease in pH and an increase in EC. Although no significant improvement in rice growth was observed between control and gypsum fertilizer treatments, the addition of gypsum fertilizers significantly improved the potassium ion concentration except G2 and significantly decreased the sodium ion concentration of plants. The addition of gypsum G0.5 and G1 resulted in higher concentration and larger species of organic acids of rice rhizosphere exudates. Furthermore, the addition gypsum fertilizer G0.5 and G1 enhanced CH4 emission compared to control while lowest CH4 emission was observed in G2. The highest CH4 emission in G0.5 might be due to the highest availability of organic carbon which was contributed from the rhizosphere exudates of rice plants. The lowest CH4 emission in G2 might be due to its lower above dry matter yield, lowest pH value, and excessive sulfate (SO42 -) concentration in the soil.