Lower methane and nitrous oxide emissions from rice-aquaculture co-culture systems than from rice paddies in southeast China,

Abstract

Rice paddies and rice-aquaculture co-culture systems are important sources of methane (CH4) and nitrous oxide (N2O) to the atmosphere. Due to the growing human demand of aquaculture protein and the rapid development of green agriculture, rice-aquaculture co-culture systems have been increasingly developed from rice paddies in southeast China. However, the strength of CH4 and N2O emissions from rice-aquaculture co-culture systems remains poorly quantified, in particular the contribution of these emissions from different functional cultivation areas. Here, a two-year parallel field experiment was conducted to examine the changes in CH4 and N2O fluxes following the conversion from rice paddies to rice-crayfish co-culture systems in southeast China. Over the two-year period, annual CH4 and N2O fluxes from rice-crayfish co-culture systems averaged 4.59 mg m-2 h-1 and 39.50 μg m-2 h-1, amounting to 391.9 kg ha−1 and 3.46 kg ha−1, respectively. The conversion from rice paddies to rice-crayfish co-culture systems significantly reduced CH4 and N2O emissions by 14% and 31%, respectively. The emission factors of N2O were estimated to be 1.25–1.61% in the rice-crayfish co-culture system. Relative to rice planted areas, CH4 and N2O fluxes from crayfish ditched culture areas were three times higher and 50% lower, which contributed 26% and 5% to the total CH4 and N2O emissions from rice-crayfish co-culture systems, respectively. Our results highlight that the conversion of paddy rice monoculture to rice-crayfish co-culture systems can benefit low greenhouse gas emissions and high ecosystem economic profits as a potential option to sustain agricultural development and achieve carbon neutrality.