水旱轮作条件下免耕土壤有机碳变化特征研究

采用野外调查与室内分析相结合的方法,研究了水旱轮作条件下免耕土壤有机碳的变化特点。结果表明,水作及旱作后,随免耕年限延长土壤有机碳在免耕5～6a达到最大值,与常规耕作差异显著;免耕0—5cm土层有机碳显著高于其他土层,具有一定的表聚现象;水旱轮作条件下土壤富里酸含量略高于胡敏酸,土壤碳氮比在10～16,有利于有机质矿化过程中养分的释放;有机碳密度与土壤有机碳变化趋势一致。研究水旱轮作免耕措施对土壤有机碳含量的影响,可为建立合理轮耕模式提供一定的理论基础,同时,也为该耕作方法的推广应用提供科学指导。

Change of Soil Organic Carbon Under No-tillage Paddy-Upland Rotation

Change of soil organic carbon under no-tillage paddy—upland rotation was studied through filed investigation and laboratory analysis.Results showed that with the increasing years of no-tillage,the maximum soil organic carbon occurred 5 to 6 years after water-cultivation and dry-cultivation.The content of soil organic carbon under no-tillage was significantly different from that under conventional tillage.The content of soil organic carbon within 5 cm of the surface soil was obviously higher than that in other soil layers,suggesting a certain surface accumulation phenomenon.The ontent of fulvic acid was found to be higher than the content of humic acid after water-cultivation and dry-cultivation.Ratios of soil carbon to nitrogen were from 10 to 16,which is favorable to nutrient release during organic matter decomposition.Change in organic carbon density was the same as that in soil organic carbon.The study may clarify the effect of no-tillage practices on the content of soil organic carbon and provide a theoretical basis for building a reasonable crop rotation model and a scientific guidance for promoting the use of farming methods.