桓台县冬小麦和夏玉米秸秆长期还田的生态效益分析

山东省桓台县作为江北第一个"吨粮县",1980年以来农业集约化得到了快速发展。随着燃料需求的减少以及畜牧养殖与作物生产的分离,作物秸秆处理已日益成为当地农民和技术人员面临的巨大挑战。该地区冬小麦和夏玉米秸秆从1980年开始,还田比例逐步增加,到2010年两季秸秆接近全部还田。我们查阅年鉴数据,结合长期定位试验,收集相关数据计算和分析桓台地区1980—2014年期间的作物和秸秆产量、秸秆养分含量、土壤养分及有机碳状况、温室气体排放和氮淋溶等,并对秸秆还田的农田生态效应进行系统评估。研究发现,到2014年,两季秸秆还田对N、P、K养分的贡献率(即还田秸秆养分量与还田秸秆和肥料养分总量的比值)分别为19.3%、15.8%和59.8%。随着秸秆还田量的增加,土壤有机碳(SOC,0—20 cm)含量从(7.8±1.6)g/kg(1980年)增加到(11.0±2.3)g/kg(2014年),土壤碱解氮、速效磷和速效钾分别提高了134.0%、138.5%和62.2%。秸秆还田可以降低农田氮素损失,2010年代全县县域内减少温室气体排放量为24528 Mg CO_2-eq a~(-1),氨挥发和氮淋溶分别减少156.4 Mg N hm~(-2)和287.4 Mg N hm~(-2)。综上,秸秆还田能显著改善农学和环境效益,提高土壤固碳减排潜力,降低氮素投入量并减少氮素损失。今后农业生产中,在直接还田基础上,秸秆综合利用可以进一步优化(如进行堆肥或替代畜牧饲料等),从而增加秸秆还田的经济和环境效应。

Ecological impacts of winter wheat and summer maize straw incorporation in Huantai County, Shandong Province

Huantai was the first county in northern China which achieved an average grain yield of 15 t/hm² from 1990, and has experienced a rapid agricultural intensification process since 1980s. Crop straw management has been an increasing challenge for local farmers and technicians as fuel demand decreased and uncoupling of animal husbandry with crop production. Huantai county initiated the program of crop straw incorporation to cropland since 1980s and by the 2010s, 100% of crop straw had been recycled. We collected crop production within the period of 1980-2014, and the corresponding parameters of straw and soil nutrients and soil organic carbon (SOC) contents, greenhouse gas (GHG) emissions and nitrogen (N) leaching, to quantify the ecological impacts of crop straw incorporation. The study found that crop straw incorporation contribution increased to 19.3%, 15.8% and 59.8% of N, phosphorous (P), and potassium (K) in total nutrients input (chemical fertilizer+straw) in 2014, respectively. In 2014, the SOC content (0-20 cm) for the whole county increased from 7.8±1.6 g/kg to 11.0±2.3 g/kg; meanwhile, soil available N, available P and available K increased by 134.0%, 138.5% and 62.2%, respectively, compared with that of 1982. During 2010s, global warming potential of N₂O, ammonia volatilization and N leaching were reduced at 24528 Mg CO₂-eq a^-1, 156.4 Mg N hm^-2 and 287.4 Mg N hm^-2, respectively. In the future, besides direct incorporation, other measures such as compost and replacement of animal husbandry feedstuffs, maybe introduced to further improve the economic and environmental benefits of straw incorporation.