摘要:合理耕作方式对农业可持续生产和减缓全球气候变化有重要意义。为评价耕作方式转变对农田温室气体排放的影响，本研究针对连续16年的长期旋耕小麦/玉米农田进行不同的轮耕处理，采用原位静态箱-气相色谱法分析了小麦季农田土壤3种温室气体CH4、CO2、N2O排放规律。试验共设3个处理：在前期旋耕基础上分别进行翻耕处理（XF）和深松处理（XS），另外保持旋耕（X）作为对照。试验结果表明：CO2排放通量在耕作后1周有明显排放峰，XF处理显著低于X和XS处理；N2O排放通量在耕作和灌溉施肥后有明显排放峰，XS处理显著高于XF和X处理；两种气体排放通量在越冬期出现最低值。CH4从耕作后到越冬期有持续明显的吸收过程，其中XS处理的吸收通量显著高于XF和X处理。农田土壤在冬小麦生长季表现为CO2的源，累积排放量为XS（5 241 kg·hm-2）> X（5 160 kg·hm-2）> XF（4 840 kg·hm-2），XS与X处理间差异不显著，均显著高于XF；N2O的源，累积排放量表现为XS（4.38 kg·hm-2）> XF（2.39 kg·hm-2）> X（2.26 kg·hm-2），XS与XF处理间差异不显著，均显著高于X处理；CH4的汇，累积吸收量为XS（6.14 kg·hm-2）> XF（5.64 kg·hm-2）> X（3.70 kg·hm-2）。将累积温室气体换算为CO2当量，对增温效应的贡献表现为XF（5.32 t·hm-2） < X（5.66 t·hm-2） < XS（6.23 t·hm-2），三者之间差异达显著水平。经翻耕处理后，0~10 cm土壤有机质含量明显低于X处理，而10~20 cm土壤有机质升高，表层有机质降低可能是翻耕处理CO2的排放减少的主要原因。不同耕作处理后小麦产量差异明显，X处理冬小麦产量最高，且显著高于XS处理，XF处理与X和XS处理差异均不显著。综合考虑耕作方式对温室气体排放和冬小麦产量的影响，短期内旋耕-翻耕可能是较适宜的轮耕模式，旋耕深松模式不利于控制温室气体排放，但未来需要加强对不同轮耕模式长期效应研究。
关键词:冬小麦/
旋耕/
翻耕/
深松/
温室气体/
产量
Abstract:Under long-term rotary tillage, soil bulk density, carbon decomposition and nutrient in sub-surface soil in the shallow plow layer significantly increase, but wheat growth and soil carbon sequestration become limited. However, subsoiling and deep plowing can break the bottom of the plow layer and reduce soil bulk density, which are conducive for good growth of plant root and absorption of nutrients to ensure high crop yield. The objectives of this study were to analyze changes in greenhouse gases emission and wheat yield after 16 years (2001-2016) of rotary tillage (X) treatment and conversion into other tillage treatments, including rotary tillage-deep plowing (XF) and rotary tillage-subsoiling (XS) treatments in 2016, and to determine the best rational tillage strategy. Carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4)emission fluxes in the three tillage treatments were sampled and measured using static chamber-gas chromatography. Soil temperature at the 0 cm depth, soil gravimetric moisture content, soil bulk density at different depths and other related factors were monitored during wheat growth period and winter wheat yield analyzed after harvest. The experimental results showed prominent high fluxes of CO2 and N2O one week after the three tillage treatments and during harvest, with minimum emission fluxes of CO2and N2O during winter period. Compared with XF treatment, X and XS treatments significantly increased CO2 emission fluxes from the start of the three tillage treatments to the end of October. Compared with X and XF treatments, N2O fluxes under XS treatment were significant high after tillage treatment, fertilization and irrigation. CH4 fluxes fluctuated from November 2016 to February 2017, and became more stable from March 2017. From January 2017 to the harvest season, soil uptake of CH4 under XS treatment was higher than those under XF and X treatments. The fields under the three tillage treatments during winter wheat growth were the sources of CO2 and N2O. The cumulative fluxes of the three tillage treatments served as CH4 sink. In winter wheat fields, cumulative CO2 emission was in order of XS > X > XF, with total CO2 emissions of 5 241 kg·hm-2, 5 160 kg·hm-2 and 4 840 kg·hm-2, respectively. Cumulative N2O emission was in order of XS > XF > X, with total N2O emissions of 4.38 kg·hm-2, 2.39 kg·hm-2 and 2.26 kg·hm-2, respectively. Cumulative CH4 sink was in order of XS > XF > X, with total CH4 absorptions of 6.14 kg·hm-2, 5.64 kg·hm-2 and 3.70 kg·hm-2, respectively. The contribution of cumulative greenhouse gases to CO2-equivalents was expressed as XS > X > XF, which were 6.23 t·hm-2, 5.66 t·hm-2 and 5.32 t·hm-2, respectively. Using deep plowing and subsoiling, soil organic matter decreased in the 0-10 cm soil depth, but increased in the 10-20 cm soil depth. Soil organic carbon was the main source of CO2. Reduction in soil organic matter led to reduction in CO2. Winter wheat grain yield under X treatment was higher than that under XS and XF treatments. Considering the changes in soil physical properties, greenhouse gas emission and wheat yield, XF treatment was the most suitable tillage practice. However, more and longer research work was needed to determine an ideal tillage treatment to ensure future ecological benefits and grain yield.
Key words:Winter wheat/
Rotary tillage/
Deep plowing tillage/
Subsoiling tillage/
Greenhouse gases/
Yield
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