关键词: 再生稻, 双季稻, CH₄, 水稻产量

Abstract:

【Objective】In order to explore the ecologically sustainable rice planting model, the yield potential and CH₄ emission characteristics of traditional double-cropping rice and emerging ratoon rice in the middle and lower reaches of the Yangtze River were compared, so as to provide a scientific basis for selecting a green and ecologically sustainable rice farming model.【Method】In 2017-2018, relying on the research base of Hongshuo Eco-Agricultural Machinery Company in Datonghu District, Yiyang City, Hunan Province, two models of double-cropping rice and ratoon rice were set up, and the yield potential, CH₄ emission dynamics and CH₄ seasonal cumulative emission were compared and analyzed to evaluate unit yield CH₄ emissions from paddy fields.【Result】During the experiment, from the aspect of yield, the yield of early rice was 7.37 t·hm ^-2, and the yield of main crop was 8.84 t·hm ^-2. Main crop yield increased by 19.95% compared with early rice; the late rice yield was 6.82 t·hm ^-2, and the ratoon crop was 3.39 t·hm ^-2. Compared with the late rice, the ratoon crop yield was reduced by 50.29%. In the two crops, the total yield of double-cropping rice was 14.19 t·hm ^-2, and the total yield of ratoon rice was 12.22 t·hm ^-2; in terms of CH₄ emission dynamics, double-cropping rice was highly polluted in the tillering and full-heading. In addition to strong emissions in the tillering and full-heading, the ratoon rice also appeared small peak when applying budding fertilizer. However, the emission range of the overall double-cropping rice (-0.06 to 1.30 μmol·m ^-2·s ^-1) was higher than that of the ratoon rice (- 0.01 to 0.70 μmol·m ^-2·s ^-1); from the seasonal cumulative emission of CH₄ in paddy fields, the cumulative emission of CH₄ in double-cropping rice was higher than that in ratoon rice. The cumulative emission range of main crop was from 23.90 to 266.59 kg·hm ^-2, and the ratoon crop was from 0 to 4.61 kg·hm ^-2. The cumulative emission range of early rice was from 35.57 to 251.29 kg·hm ^-2, and the late rice was from10.74 to 321.59 kg·hm ^-2. CH₄ seasonal cumulative emissions of double-cropping rice showed: A-B stage (two leaves-one heart to late-tillering) > B-C stage (late-tillering to full-heading) > C-D stage (full-heading to mature), and cumulative emissions of double-cropping rice during the whole growth period was up to 922.35 kg·hm ^-2. The cumulative emission of methane from ratoon rice was B-C stage>A-B stage>C-D stage, and the cumulative emission of methane during the whole growth period was 609.74 kg·hm ^-2. Compared with the double-cropping rice control, ratoon rice methane cumulative emissions decreased by 33.89%. Finally, by evaluating the unit yield methane emissions, the methane emission per unit yield of early rice was0.069 kg·kg ^-1, and the methane emission per unit yield of main crop was 0.062 kg·kg ^-1, which was 10.14% lower than that of early rice. The methane emission per unit yield of late rice was 0.061 kg·kg ^-1, the methane emission per unit of ratoon crop was0.018 kg·kg ^-1, and the ratoon crop was reduced by 70.49%, compared with the late rice. In the two crops, the methane emission per unit yield of double-cropping rice was 0.065 kg·kg ^-1, and the methane emission per unit yield of ratoon rice was 0.050 kg·kg ^-1, which was 23.08% lower than that of double-cropping rice.【Conclusion】Therefore, in terms of methane emissions per unit yield, expanding the cultivation of ratoon rice was a good strategy in the main producing areas of the double-cropping rice in the middle and lower reaches of the Yangtze River.

Key words: ratoon rice, double-cropping rice, CH₄, rice yield