集约农田管理措施对桓台县域土壤有机碳储量的影响

Effect of intensive farming practice on soil organic carbon stock in Huantai County

优化农田管理措施,在增加土壤肥力、确保粮食高产稳产的同时,也可以提升农田土壤有机碳(SOC)储量。本研究以华北第一吨粮县山东桓台县的集约化农田为对象,分析化肥、有机肥和秸秆还田等农田管理措施对全县土壤有机碳库的影响。研究分别在点位和区域尺度对生物地球化学模型DNDC进行了校验;进而设置未来5种农田管理情景,以2011年为基准年,对未来30 a桓台县农田耕层土壤(0~20 cm)的SOC变化进行了模拟预测。预测结果显示,在保持2011年农田管理措施不变情景下[化肥氮500 kg(N)∙hm^(−2)、秸秆还田比例90%],10 a、20 a和30 a后SOC含量分别增加28.1%、39.2%和44.9%,说明在当前气候条件下,以桓台县为代表的华北农田秸秆还田对增加土壤有机质仍有较大空间;另一方面,秸秆还田下土壤有机质不是线性增加,即呈现出土壤有机质的饱和趋势。在5种农田管理情景中,年均400 kg(N)∙hm^(−2)的氮肥施用量、90%的秸秆还田比例和40 kg(N)∙hm^(−2)的有机肥施用量情景,能够最大程度地提高农田耕层SOC含量,30 a后可达16.2 g∙kg^(−1)。研究结果可为评价华北平原农田土壤有机碳库的变化提供科学依据,并为农田管理措施优化及相应政策的制定提供参考。

Agriculture is an important source of greenhouse gas(GHG)emissions and an important approach for carbon stock enhancement in terrestrial ecosystems.Optimization of farming practices can not only improve the utilization efficiencies of chemical fertilizer,but also increase the soil organic carbon(SOC)and hence improve soil fertility with the prerequisite of high and stable grain yield,and mitigate the greenhouse effect via increased SOC.The study chose the intensive farmland of Huantai County in Shandong Province,the first county to achieve 1000 kg of grain per mu(15 tons per hectare)in North China,to analyze the impacts of farming practices including fertilization,organic manure application,and crop straw incorporation,on SOC stock in the whole county.A biogeochemical model,DeNitrification-DeComposition(DNDC),was validated at the plot and regional scales for its applicability to SOC simulation.Five scenarios of farming practices were set,with full consideration of the natural and social conditions of Huantai County.With 2011 as the baseline year,the SOC changes in farmland soil within 30 years after 2011 were simulated.The simulation using the DNDC model showed that,under the scenario of maintaining the farming practices of 2011(annual average chemical fertilizer of 500 kg(N)∙hm^(−2) and 90%crop straw incorporation),the SOC content increased by 28.1%,39.2%,and 44.9%,respectively,at 10,20,and 30 years after 2011.This indicates that there is still room for soil organic matter to increase under current climate conditions,mainly due to crop straw incorporation in Huantai County.However,the increase in SOC is not linear,the increasing rate declines over time,and SOC saturation will occur for the farmland soil in Huantai County.Among the five farming practice scenarios,an annual average chemical fertilizer application rate of 400 kg(N)∙hm^(−2),straw incorporation ratio of 90%,and animal manure application rate of 40 kg(N)∙hm^(−2) can maximize farmland SOC content,reaching 16.2 g∙kg^(−1) at 30 years after 2011.These results can provide a scientific basis for evaluating the farmland SOC pool in the North China Plain and provide technical support for the optimization of farming practices and policy improvement.