Abstract/Summary

Rice fields are a major source of the greenhouse gases, nitrous oxide (N2O) and methane (CH4). Organic fertilizers could potentially replace inorganic fertilizers to meet the nitrogen requirement for rice growth, yet the simultaneous effects of organic fertilizers on N2O and CH4 emission and yield in paddy fields are poorly understood and quantified. Experimental field plots were constructed in conventional double-cropped rice paddy-fields in the Pearl River Delta, China. A no fertilizer control (CK) plus five fertilizer treatments were applied: fresh organic fertilizer (FOF), successively composted organic fertilizer (SOF), chemical composted organic fertilizer (COF), chemical composted organic fertilizer with inorganic fertilizer (COIF), and chemical fertilizer (CF). Following all treatments, the paddy field soil was a N2O sink (-196 to -381 g N ha-1) and simultaneously a CH4 source (719 to 2178 kg ha-1). Compared with CF, the effect of organic fertilizers on N2O emission was not significant. In contrast, the total CH4 emission of the whole year in FOF, COF, SOF, and COIF increased by 157% (P < 0.05), 132% (P < 0.05), 125% (P < 0.05) and 37% (P > 0.05), respectively. The result demonstrates COIF can maintain rice yield and not significantly increase CH4 emissions from paddy-fields characterized by a prolonged period of flood inundation. An important next step is to up-scale these field-based measurements to larger rice cultivation areas to quantify the regional and national-scale impact on greenhouse gas emission and help determine best practice for fertilizer use.