耕作与秸秆还田方式对稻田N2O排放、水稻氮吸收及产量的影响

保护性耕作是改善农田土壤肥力的重要举措,然而其对作物氮吸收与产量的作用尚不明确。为此,本试验于2016—2017年稻季在湖北省武穴市花桥镇,设置常规翻耕与免耕两种耕作方式以及前茬作物秸秆全量还田与不还田两种秸秆还田方法,研究耕作与秸秆还田方式对稻田土壤N2O排放、根系酶活性、水稻氮吸收与产量的影响。结果表明,耕作方式显著影响土壤N2O排放,但不影响根系硝酸还原酶与谷氨酰胺合成酶活性、水稻氮吸收与产量。与翻耕处理相比,免耕处理2016年和2017年土壤N2O排放量分别显著提高了12.5%~18.2%和21.1%~38.6%。秸秆还田显著影响土壤N2O排放量、根系酶活性、水稻氮吸收与产量。相对于秸秆不还田处理,秸秆还田处理2016年和2017年土壤N2O排放量分别显著提高了38.5%~45.5%和13.1%~29.5%。秸秆还田处理相对于不还田处理根系硝酸还原酶与谷氨酰胺合成酶活性分别显著增加了6.7%~45.9%和9.0%~46.7%,水稻氮吸收量提高了12.5%~26.0%,产量增加了9.4%~12.6%。本文认为,虽然秸秆还田提高了水稻氮吸收与产量,但也促进了土壤N2O的排放,因此在评估保护性耕作稻田温室效应时应加强对温室气体(CH4和N2O)排放和土壤碳固定影响的长期监测,以期为发展低碳稻作提供理论依据和技术支撑。

Effects of tillage and straw returning methods on N2O emission from paddy fields,nitrogen uptake of rice plant and grain yield

Conservation tillage is an important practice to improve agricultural soil fertility. However, the effects of this practice on crop nitrogen uptake and grain yield remain unknown. Here, a 2-year field experiment was conducted to investigate the effects of different tillage (conventional intensive tillage CT] and no-tillage NT]) and straw returning methods (preceding crop straw returning S] and removal NS]) on soil N₂O emission, root nitrate reductase and glutamine synthetase activities, nitrogen uptake of rice plants and grain yield in the 2016 and 2017 rice growing seasons at Huaqiao town, Wuxue county, Hubei province. The tillage practices and straw returning methods had significant effects on the N₂O emission from paddy soil. Compared with CT treatment, NT treatment enhanced the N₂O emission by 12.5%-18.2% in 2016 and 21.1%-38.6% in 2017. S treatments increased the soil N₂O emission by 38.5%-45.5% in 2016 and 13.1%-29.5% in 2017 as compared with NS treatments. Straw returning methods had significant effects on root nitrate reductase and glutamine synthetase activities, as well as on nitrogen uptake of rice plants and grain yield. Compared with NS treatments, S treatments had 6.7%-45.9% higher root nitrate reductase activity and 9.0%-46.7% higher root glutamine synthetase activity, resulting in 12.5%-26.0% higher nitrogen uptake of rice plants and 9.4%- 12.6% greater grain yield. Our results indicate that straw returning significantly increases nitrogen uptake and grain yield, and also promotes soil N₂O emissions, suggesting that the effects of long-term NT and straw returning on global warming potential and soil carbon sequestration should be taken into account when assessing the global warming potential of these practices.