摘要
【目的】耕作措施对土壤有机碳(SOC)和全氮(TN)具有重要影响。本研究利用团聚体和密度联合分级方法,旨在揭示长期耕作对表层土壤团聚体内密度颗粒组分SOC及TN的影响,为深入理解黄土高原农田土壤碳氮提升机理提供依据。【方法】长期试验位于黄土高原东部边缘地区,开始于1999年,共设4个处理:少耕无覆盖(RT)、免耕覆盖(NT)、深松覆盖(SM)和传统翻耕(CT)。于2013年7月采集0—10 cm土层样品,首先通过干筛法筛分>2、1—2、0.25—1和<0.25 mm粒级团聚体,之后利用颗粒密度分组,将团聚体有机质分为轻组有机质(LF)、粗颗粒有机质(cPOM)、细颗粒有机质(fPOM)和矿质结合有机质(m-SOM)。【结果】(1)15年保护性耕作(包括NT和SM处理)显著提高了0—10 cm土层的SOC和TN含量,与CT相比,NT和SM处理的SOC含量分别提高了22.9%和21.8%,TN含量分别提高了35.2%和42.3%。不进行秸秆覆盖的少耕处理(RT)对SOC和TN无显著影响。(2)不同耕作措施改变了团聚体质量组成及其内部SOC和TN含量。NT和SM处理显著提高了1—2 mm和0.25—1 mm粒级的干筛大团聚体含量,相对地,降低了>2 mm和<0.25 mm粒级团聚体的含量。NT和SM处理不同程度提高了团聚体的SOC和TN含量,与CT相比,团聚体SOC平均提高了8.5%和9.5%,尤其对>1 mm粒级团聚体SOC含量提高幅度最大;团聚体TN平均提高了12.2%和24.1%,尤其对<0.25 mm微团聚体TN含量提高幅度最大。(3)fPOM和m-SOM组分对团聚体SOC和TN的贡献最大,对SOC的贡献率分别为27.3%—45.1%和25.0%—52.6%;对TN的贡献率分别为23.5%—34.7%和42.2%—64.3%。不同有机质组分对耕作的响应不同,cPOM和fPOM组分最为敏感。与CT相比,NT和SM处理显著提高了土壤所有粒级团聚体的cPOM和fPOM的SOC和TN含量,尤其对>2 mm团聚体cPOM和<2 mm团聚体fPOM的SOC和TN含量提升幅度最大。【结论】长期免耕和深松提高了团聚体中有机碳及全氮含量,尤其提高了团聚体中颗粒有机质的碳氮含量,有利于土壤碳氮的长效累积,是黄土高原坡耕地区值得推荐的耕作管理方式。
【Objective】Tillage management has essential effects on soil organic carbon(SOC)and total nitrogen(TN).Based on a combined soil aggregate size,particle density and size fractionation method,the study aimed at revealing effects of different tillage treatments on SOC and TN of physical fractions within different sizes of aggregates.This study provided theoretical basis for understanding mechanisms soil carbon and nitrogen sequestration and selecting optimized tillage management for loess hilly region of China.【Method】The long-term tillage experiment,started in 1999,was used for the study.The tillage treatments included:reduced tillage without mulch(RT),no-tillage(NT),sub-soiling with mulch(SM),and conventional tillage(CT).The soil samples from the 0-10 cm layer were collected to obtain physical fractions,including free light fraction(LF),coarse and fine particulate organic matter(cPOM and fPOM)and mineral associated organic matter(m-SOM)within four dry-sieving aggregate sizes(>2 mm,1-2 mm,0.25-1 mm and<0.25 mm),by applying a combined soil aggregate size,and particle density and size fractionation procedure.【Result】(1)15 years application of conservation tillage(including NT and SM)significantly increased SOC and TN contents in 0-10 cm layer.Compared to CT,NT and SM increased SOC content by 22.9%and 21.8%,and increased TN content by 35.2%and 42.3%,respectively.However,RT had no significant effects on SOC and TN contents.(2)Different tillage practices changed the mass distribution,SOC and TN contents of aggregates.Compared to CT,NT and SM improved the mass percentage of 1-2 mm and 0.25-1 mm size aggregates,relatively,increased the mass percentage of>2 mm and<0.25 mm aggregates.Moreover,conservation tillage enhanced SOC and TN contents across four sizes aggregates.Compared to CT,NT and SM averagely increased SOC content in aggregates by 8.5%and 9.5%and increased TN contents by 12.2%and 24.1%,respectively.The fPOM and m-SOM stored largest parts of aggregate SOC and TN,constituting 27.3%-45.1%and 25.0%-52.6%of aggregate SOC,23.5%-34.7%and 42.2%-64.3%of aggregate TN.Different physical fractions had different reflects to tillage managements.The cPOM and fPOM were the most sensitive fractions.Compared to CT,NT and SM led to higher contents of SOC and TN accumulated in cPOM and fPOM in all aggregates,especially cPOM in>2 mm aggregates and fPOM in<2 mm aggregates.【Conclusion】The long-term conservation tillage(included no-tillage and sub-soiling and mulch management)promoted SOC and TN sequestration in aggregates by increasing the storage of physical protected particulate organic matter in aggregates.Thus,the conservation tillage was a sustainable soil carbon and nitrogen enhancement management for dryland soils for the loess hilly region of China.
作者
李景
吴会军
武雪萍
王碧胜
姚宇卿
吕军杰
LI Jing;WU HuiJun;WU XuePing;WANG BiSheng;YAO YuQing;LÜ JunJie(School of Water Resources and Environment,Hebei GEO University/Hebei Province Collaborative Innovation Center for Sustainable Utilization of Water Resources and Optimization of Industrial Structure,Shijiazhuang 050031;Institute of Agricultural Resources and Regional Planning,Chinese Academy of Agricultural Sciences,Beijing 100081;College of Agronomy,Qingdao Agricultural University,Qingdao 266109,Shandong;Luoyang Academy of Agriculture and Forestry Sciences,Luoyang 471022,Henan)
出处
《中国农业科学》
CAS
CSCD
北大核心
2021年第2期334-344,共11页
Scientia Agricultura Sinica
基金
国家重点研发计划(2018YFD0200408、2016YFD0300804)
中央级公益性科研院所基本科研业务费专项(1610132019034、1610132019033)
河北地质大学博士科研启动基金(BQ2019039)
国家科技支撑计划(2015BAD22B03)。
关键词
保护性耕作
长期耕作
团聚体
有机碳
氮
密度分组
conservation tillage
long-term tillage
soil aggregate
organic carbon
nitrogen
density fraction
