田间管理措施对土壤有机碳含量影响的模拟研究

Modelling soil organic carbon dynamics in the major agricultural regions of China

利用农业生态系统生物地球化学模型(DNDC),选择6个典型的种植模式点,在特定的土壤和气候条件下运行模型,考察在其它投入条件不变的情况下,改变田间管理措施(秸秆还田、增施有机肥、改变化肥施用等)对土壤有机碳(SOC)含量影响的长期效应。研究结果表明,在众多的管理措施中,增加秸秆还田比例的固碳效应在众多的农田管理措施中体现最突出,以基本管理措施20年后有机碳含量为对照,当秸秆还田率增加到80%时,齐齐哈尔、平凉和芷江地区增加的SOC含量都在C 3 000 kg/hm2以上,北京郊区、江宁和盐亭地区每公顷则可以增加C10 000 kg以上。化肥增加SOC含量是通过增加作物还田残茬来实现的,与基本措施相比,除了华北和华东地区增施化肥使SOC含量显著增加外,其它地区均不明显。化肥施用量为本底值的50%配合秸秆还田率50%和化肥施用量为本底值的50%增施有机肥C 1 000 kg/hm2的两项措施,在各个地区都表现出比基本管理措施能存储更多的碳素,因此,在我国现在措施下,减少化肥的同时增加秸秆还田比例和增施有机肥是既增加土壤有机碳含量又减少化肥污染的"双赢"措施。

In China,the modernization of farming has led to the gradual replacement of traditional by manufactured fertilizers.Now,animal wastes are randomly disposed of and there is more ex-farm removal of crop residues which have impacted not only the crop yield but also the soil organic carbon（SOC）dynamics.China has about 120 million hectares of croplands,which are geographically divided into six agricultural regions based on their climate and cropping management.This paper reports a modelling study on long-term（20 years）impacts of present and alternative farming management practices on（SOC）dynamics.A well documented,process-based model,DNDC,was employed,depending on the local climate,soil and management conditions in the six regions.Modelled results indicated that,under the present management conditions,the SOC status in the three northern sites（i.e.,Qiqihar,Miyun and Pingliang）where upland crops dominated appeared more dynamic than that in the three southern sites（i.e.,Zhijiang,Jiangning and Yanting）where paddy rice dominated.During the simulated 20 years,the northern sites were either losing or gaining SOC at relatively high rates from-1 000 to 200 kg/（hm2·a）C;and the southern sites had relatively stable SOC contents with deviations ranging from-70 to 26 kg/（hm2·a）C.Increase in the fraction of above-ground crop residue incorporated in soil or application of manure effectively converted most of the tested sites into sinks of atmospheric carbon.Since crop residue and manure resources are available in most of the agricultural regions,adaptation of the management alternatives should be feasible in China.