INFLUENCE OF NITROGEN FERTILIZER AND STRAW RETURNING ON CH4 EMISSION FROM A PADDY FIELD IN CHAO LAKE BASIN, CHINA.

In the rice paddy ecosystem, application of nitrogen fertilizer and straw to soil methanogenic bacteria provides abundant methanogenic substrates, which significantly influences methane (CH₄) emission from paddy fields. The effects of nitrogen fertilizer and straw returning on CH₄ emissions in rice paddy fields were studied during a two year of the field experiment in Chao lake basin, China. The experiment consisted of 4 treatments: Control (CK), Traditional fertilizer (CT), Optimized fertilizer (CO) and CO with straw-return (CO + SR). The cumulative effects of straw-returning practices on greenhouse gas emission in a rice-wheat rotation system were determined, along with an estimation of CH₄ in a rice growing season. According to our results, The CH₄ emission fluxes from paddy field showed three different peak trends; Compared to CK, CT, CO, and CO + SR increased seasonal CH₄ emission by 36.6%, 45.8% and 42.0% in 2013 and by 42.0%, 48.5% and 80.1% in 2014, respectively. Anaerobic decomposition of wheat straw accelerates the decline of soil redox potential (Eh) after flooding, thereby providing suitable environmental conditions for the growth of methanogens and promoting CH₄ production in the subsequent rice season. The CH₄ emission fluxes of CK, CT, CO, and CO + SR were significantly correlated with soil temperatures at 5 cm depth. Therefore, our findings show that application rates of nitrogen fertilizer and straw returning to a paddy field could significantly affect the CH₄ emissions in China. [ABSTRACT FROM AUTHOR]