Abstract:

To investigate the effect of sowing date on methane (CH₄) emissions from rice field and its comprehensive benefits, a field experiment with different sowing dates of Japonica rice (Nanjing 9108) was carried out in 2019 and 2020 rice growing seasons for selecting the optimum sowing date to achieve high yield of rice and reduction of CH₄ emission from paddy fields. Experiment treatments included the control (I), and treatment II, which delayed seeding and transplanting by 10 days compared with I. A transparent static closed chamber-laser greenhouse gas analyzer technique was used to measure the CH₄ flux. Physicochemical properties and enzyme activities of rhizosphere soils were analyzed at the key rice growth stages, and the yield of rice was measured after harvest. According to the difference between output and input, the economic benefit of rice production was calculated, and then the comprehensive benefit of rice production based on CH₄ reduction was calculated. The results showed that the seasonal dynamics of CH₄ emission fluxes of treatments I and II had the same tendency, with a gradual increase, reaching a maximum value and then decreasing. In 2019 and 2020 rice growing seasons, the cumulative amount of CH₄ emissions of treatment II decreased by 15.4% (P=0.006) and 26.3% (P=0.160), respectively, relative to treatment I. The CH₄ fluxes of treatments I and II were positively correlated with soil DOC, NO₃^--N, catalase activity, and urease activity, while negatively correlated with NH₄⁺-N content. In 2019 and 2020, compared with treatment I, the rice yield of treatment II decreased by 17.9% (P=0.004) and 40.2% (P=0.000), respectively. Meanwhile, the comprehensive benefits of treatment II reduced by 40.2% (P=0.000) and 60.0% (P=0.000), respectively. Overall, our study reveals that a 10-day delay in sowing reduced CH₄ emissions from rice field, but also reduced rice yield and the comprehensive benefits of rice production.

Key words: paddy field, CH₄ emission, sowing date, yield, comprehensive benefit

摘要：

为研究播期对稻田甲烷（CH₄）排放及其综合效益的影响,以优选最佳播期实现水稻丰产和稻田CH₄减排,于2019、2020年以粳稻（南粳9108）为试验材料,开展了分期播种试验。试验设两个不同播期,延期播种（Ⅱ期）的播种和移栽时间均比对照（Ⅰ期）延迟了10 d。采用透明箱-高精度气体分析仪观测CH₄通量;在水稻关键生育期,取水稻根际土测定土壤理化性质及酶活性;收获时进行水稻测产;根据产出与投入的差值计算水稻产量经济效益,进而计算基于CH₄减排的水稻生产综合效益。结果表明,2019、2020年水稻生长季,Ⅰ期和Ⅱ期稻田CH₄排放通量季节变化趋势一致,均呈逐渐增长,达到峰值后再下降趋势。2019、2020年的稻田CH₄累积排放量,Ⅱ期比Ⅰ期分别减小了15.4%（P=0.006）和26.3%（P=0.160）。Ⅰ期和Ⅱ期的稻田CH₄排放通量与土壤DOC含量、NO₃^--N含量、土壤转化酶和脲酶活性均呈正相关关系,与土壤NH₄⁺-N含量呈负相关关系。2019、2020年,Ⅱ期的水稻产量比Ⅰ期分别降低了17.9%（P=0.004）和40.2%（P=0.000）,Ⅱ期水稻生产综合效益比Ⅰ期分别减小了40.2%（P=0.000）和60.0%（P =0.000）。研究表明,延期播种10 d降低了粳稻稻田CH₄排放,同时也降低了水稻产量和水稻生产综合效益。

关键词: 稻田, CH₄排放, 播期, 产量, 综合效益