Can integrated rice-duck farming reduce CH4 emissions?

Integrated rice-duck farming (IRDF) has proven to decrease methane (CH4) emissions due to increased dissolved oxygen caused by duck bioturbation. The duck bioturbation, however, also causes many bubbles of CH4 that were overlooked in previous studies. Therefore, it is uncertain whether IRDF could decrease CH4 emissions. We hypothesize that the effect of IRDF on CH4 emissions is related with the intensity of duck bioturbation. We simulated duck's disturbance (trampling and foraging) by stirring and aerating the surface soil in flooded rice fields. Three treatments were disturbed with an interval of 12 h (D12), 24 h (D24), and 48 h (D48), respectively, with non-disturbance as the control (CK). CH4 emissions as bubbles during the disturbance period (CH4-A) were investigated. Besides, CH4 emissions were investigated every 2 h (CH4-B), which lasted for 4 days during the rice elongation stage. Compared with CK, D12, D24, and D48 decreased CH4-B emissions by 17.1%, 14.0%, and 10.1%, respectively. However, the CH4-A emissions under D12, D24, and D48 were equivalent to 14.2%, 14.0%, and 11.9% of CH4 emissions under CK, respectively. On the whole, simulated duck bioturbation had limited effects on the reduction of total CH4 emissions.