长期保护性耕作对麦-玉两熟农田土壤碳氮储量及固碳固氮潜力的影响

Effects of Long-term Conservation Tillage on Soil Organic Carbon and Nitrogen Storages,Soil Carbon Sequestration Potential and Nitrogen Fixation Potential in Wheat-Maize Crop System

在收集整理2005—2014年连续10a黄淮海平原长期定位保护性耕作试验结果的基础上,整合分析长期保护性耕作下麦—玉两熟农田表土有机碳和全氮储量的变化特征及不同耕作措施的固碳潜力和固氮潜力。结果表明,土壤碳氮储量密切相关,变化趋势也基本一致,10a间,不同年份不同耕作处理和有无秸秆还田各处理间土壤碳氮储量呈明显的动态变化,秸秆还田各处理的土壤碳氮储量均显著高于无秸秆还田处理。2009年,PC(常规翻耕秸秆还田)、PZ(免耕秸秆还田)、PS(深松秸秆还田)、PH(耙耕秸秆还田)和PR(旋耕秸秆还田)的碳储量分别比AC(常规翻耕无秸秆还田)、AZ(免耕无秸秆还田)、AS(深松无秸秆还田)、AH(耙耕无秸秆还田)和AR(旋耕无秸秆还田)高6.45%,13.51%,32.52%,34.42%和37.94%,PC、PZ和PS的氮储量与AC、AZ和AS的最大差值分别为1.56t/hm2,2.50t/hm2和1.57t/hm2;各保护性耕作措施的土壤碳氮储量均显著高于常规耕作AC,PZ处理的土壤有机碳和氮储量呈先低于其它处理,2009年以后高于其它处理的趋势。各处理固碳潜力由高到低依次为PZ>PS>PC>AZ>AC>AS,固氮潜力由高到低依次为PZ>PC>PS>AZ>AC>AS,秸秆还田各处理的固碳潜力和固氮潜力均显著高于无秸秆还田处理,各保护性耕作措施的固碳潜力和固氮潜力也均显著高于常规耕作,PZ处理的固氮潜力和固氮潜力均最高,说明秸秆还田和保护性耕作措施能提高土壤的固碳潜力和固氮潜力,PZ更有效。长期保护性耕作下,黄淮海平原麦—玉两熟农田表土有机碳储量、氮储量、固碳潜力和固氮潜力总体呈上升趋势,秸秆还田更有利于增加表土碳氮储量,PZ处理效果最佳。

By collecting the results of the long-term located conservation tillage experiments for 10 consecutive years（2005—2014）in the Huang-Huai-Hai Plain in North China,this study did integration analysis of the variation of topsoil organic carbon and total nitrogen storages,soil carbon sequestration potential and nitrogen fixation potential in wheat-maize crop system under long-term conservation tillage.The results showed that the storages of soil carbon and nitrogen were closely related,and their changing trends were basically the same.Soil organic carbon and nitrogen storages showed obvious dynamic changes in different years between 2005—2014,which were higher in straw-returning treatments than no straw-returning treatments.In 2009,the organic carbon storages of PC（conventional tillage with straw-returning）,PZ（no tillage with straw-returning）,PS（subsoil tillage with straw-returning）,PH（harrow tillage with straw-returning）and PR（rotary tillage with strawreturning）were respectively 6.45%,13.51%,32.52%,34.42%and 37.94% higher than AC（conventional tillage without straw-returning）,AZ（no tillage without straw-returning）,AS（subsoil tillage without straw-returning）,AH（harrow tillage without straw-returning）and AR（rotary tillage without straw-returning）.The maximum differences between nitrogen storages of PC,PZ and PS and those of their corresponding no straw-returningtreatments（AC,AZ and AS）were 1.56t/hm2,2.50t/hm2 and 1.57t/hm2,respectively.The conservation tillage induced higher soil organic carbon and nitrogen storages than conventional tillage.The storages of soil organic carbon and nitrogen of PZ were lower than those in other treatments at first and showed an opposite tendency after 2009.In all treatments,the soil carbon sequestration potential decreased in order of PZ〉PS〉PC〉AZ〉AC〉AS,and the soil nitrogen fixation potential decreased in order of PZ〉PS〉PC〉AZ〉AC〉AS.The soil carbon sequestration potential and nitrogen fixation potential of treatments with straw-returning were significantly higher than treatments without straw-returning,and conservation tillage led to higher soil carbon sequestration potential and nitrogen fixation potential than conventional tillage.The carbon sequestration potential and nitrogen fixation potential of PZ were both the highest,suggesting that conservation tillage,especially PZ,could improve the soil carbon sequestration potential and nitrogen fixation potential.The results showed that the topsoil organic carbon and nitrogen storages,soil carbon sequestration potential and nitrogen fixation potential in wheat-maize crop system generally increased under long-term conservation tillage,and straw-returning improved topsoil carbon and nitrogen storages.Therefore,PZ showed the best improvement effects on topsoil organic carbon and nitrogen storages,soil carbon sequestration potential and nitrogen fixation potential in wheat-maize crop system.