耕作方式对滨海盐渍土有机碳含量及团聚体特性的影响

为探明不同耕作措施对滨海盐渍土耕层土壤有机碳含量和团聚体特征的影响,本研究在江苏省东台市滨海滩涂农田区开展田间试验,选择玉米-大麦的旱-旱轮作方式,采用传统翻耕、深翻、少耕和免耕4种耕作方式,分别对耕层土壤的有机碳含量、土壤体积质量(容重)、水稳性团聚体含量和稳定性进行测定。结果表明:与传统翻耕相比,免耕措施利于促进土壤有机碳的积累,免耕能使土壤有机碳含量增加18%~32%;少、免耕措施能使0~10 cm土层0.25 mm团聚体增加10%~31%,并且能显著增加0~20 cm土层土壤平均重量直径和几何平均直径值;团聚体中有机碳含量表现为,除0.25~0.5 mm团聚体外,在5 mm至0.5~1 mm粒径之间,粒径愈小,有机碳含量愈高。     

长期深耕秸秆还田配施生物炭对砂姜黑土团聚体及小麦-玉米产量的影响

为探究耕作方式、秸秆还田和生物炭添加结合对土壤团聚体粒径分布、团聚体养分特征、养分库储量及小麦-玉米周年产量的影响,本研究采用3因素2水平试验设计,分别为耕作方式：常规旋耕（CT）,深翻耕作（DT）;秸秆处理：秸秆还田（S）、秸秆不还田（NS）;生物炭：生物炭添加（B）、无生物炭添加（NB）,共8个处理。结果表明：无生物炭添加时,旋耕秸秆还田显著提高了0~15 cm土层团聚体稳定性及土壤养分库储量,而深耕秸秆还田显著改善了>15~30 cm土层土壤团粒组成,提升土壤肥力,促进作物增产。相关性分析表明,砂姜黑土中作物产量的提升更依赖于深层（>15~30 cm）土壤物理结构的改善和土壤肥力的提升。配施生物炭后如DT-S-B（深耕秸秆还田配施生物炭）较CT-NS-NB（旋耕秸秆不还田无生物炭）处理尤其使>15~30 cm土层团聚体稳定性显著增强,>2 mm粒级团聚体比例、重量平均直径和几何平均直径值分别增加165.88%、62.37%和119.81%,显著提高>2 mm粒级团聚体有机碳、全氮和全磷含量,提高了>2 mm粒级团聚体有机碳和养分固持能力,降低了<2 mm粒级团聚体有机碳和养分固持能力,使>15~30 cm土层土壤有机碳库储量、全氮、全磷和全钾库储量分别显著提升37.41%、38.99%、41.26%和9.84%,促使2年作物周年产量平均增加22.96%,但在深耕秸秆还田的基础上配施生物炭在短期内增产效果不显著。综上,深耕秸秆还田配施生物炭能够显著改善黄淮海南部砂姜黑土深层土壤团聚体粒径分布和稳定性,提升了土壤肥力和作物周年产量,保障了农田高效绿色可持续生产。     

免耕对土壤团聚体特征以及有机碳储量的影响

以实施7年的中国科学院禹城综合试验站冬小麦夏玉米轮作免耕长期定位试验场为对象,研究免耕条件下土壤水稳性团聚体和有机碳储量的变化,为进一步评价免耕措施对黄淮海平原土壤结构和质量的影响提供科学依据。设置免耕(NT)、免耕秸秆不还田(NTRR)、常规耕作(CT)3种处理,分析土壤表层(0~20 cm)及深层(20~60 cm)水稳性团聚体分布特征、土壤有机碳以及团聚体有机碳的变化和相互关系。研究结果表明:由于减少了对土壤的破坏以及增加了秸秆还田和有机肥的施用,与常规耕作相比,NT和NTRR可提高表层土壤有机碳含量和储量、水稳性团聚体平均重量直径(MWD)和几何平均直径(GMD),以及大团聚体有机碳的含量和储量。其中,秸秆覆盖比施用有机肥对表层土壤有机碳储量和0.25~2 mm团聚体有机碳储量的提高具有更显著的作用。与表层不同,深层土壤有机碳和大团聚体有机碳的含量和储量表现为NT相似文献   

不同耕作方式对土壤有机碳、微生物量及酶活性的影响

【目的】依托8年长期(2005~2012)固定道定位试验,研究不同耕作方式对土壤有机碳、土壤微生物量、土壤酶活性在0—90 cm土层的分布特征,为优化中国西北干旱区的耕作方式提供理论依据。【方法】试验包括固定道垄作(PRB)、固定道平作(PFT)与传统耕作(CT)三种耕作模式下的土壤有机碳土壤总有机碳(TOC)、颗粒有机碳(POC)、土壤微生物量碳(MBC)、土壤微生物量氮(MBN)、土壤微生物量磷(MBP)、蔗糖酶、过氧化氢酶、脲酶及小麦产量进行了测定和分析。【结果】在0—90 cm土层,不同耕作方式下的TOC、POC、MBC、MBN、MBP、蔗糖酶活性、脲酶活性均随着土层的增加呈下降趋势,过氧化氢酶活性呈先下降后增大的分布特征;在0—60 cm,固定道保护性耕作能够显著增加心土层作物生长带土壤有机碳储量,有机碳储量大小为PRBPFTCT;PRB、PFT较CT可以显著增加0—10 cm作物生长带TOC、POC、MBC、MBN、MBP含量、蔗糖酶、脲酶活性,其大小为PRBPFTCT;耕作方式对过氧化氢酶活性影响不显著;TOC、POC、MBC、MBN、MBP、蔗糖酶活性、脲酶活性、过氧化氢酶活性之间均达到了显著或极显著相关。【结论】PRB较PFT、CT能够提高耕作层(0—10 cm)土壤有机碳含量、土壤微生物量、土壤酶活性, 增加作物产量, 增大0—60 cm土层有机碳储量,耕作方式(PRB、PFT及CT)对10 cm以下土层土壤环境改善作用不明显。     

Changes in soil organic carbon fractions and bacterial community composition under different tillage and organic fertiliser application in a maize−wheat rotation system

ABSTRACT

The objective of this study was to assess the impact of different tillage and organic fertiliser regimes on soil carbon fractions and bacterial community composition within a maize–wheat cropping system. We conducted a six-year experiment on the Huang-Huai-Hai Plain of China. Six treatments were established: deep tillage (DT), shallow tillage (ST), no-tillage (NT), deep tillage with organic fertiliser (DTF), shallow tillage with organic fertiliser (STF), and no-tillage with organic fertiliser (NTF). Results indicated that during the winter wheat growing season, the highest contents of soil organic carbon (SOC) and easily-oxidised organic carbon (EOC) were in the STF treatment. During the summer maizegrowing season, the DTF treatment had the highest SOC and EOC contents. Compared with the other treatments, the NTF treatment had higher Chao1 and Shannon indices for bacteria; however, the relative abundance of Proteobacteria is highest in all treatments. A redundancy analysis (RDA) revealed that bacterial community composition was correlated with variation of the SOC, DOC, EOC, and microbial biomass carbon (MBC). Our results showed that combining the two components of the SOC fractions and bacterial community composition, STF practice in a maize–wheat rotation was a sustainable approach to optimising soil structure and improving soil quality.     

Long-term tillage and straw returning effects on organic C fractions and chemical composition of SOC in rice-rape cropping system

Understanding the different C pools and chemical composition of soil organic carbon (SOC) in cropping system is imperative for sustaining soil quality. This study examined the effects of tillage and straw returning practices on organic C fractions and chemical composition of SOC under a rice-rape system in central China. The field experiment consisted of conventional tillage (CT); conventional tillage with straw returning (CTS); no-tillage (NT); and no-tillage with straw returning (NTS) treatments. Compared to CT, NT significantly increased SOC stocks, SCMI and C fractions of 0–20 cm depth by 6–50%. The SOC, particulate organic carbon (POC), microbial biomass carbon (MBC), easily oxidizable carbon (EOC), dissolved organic carbon (DOC) contents of 0–20 cm depth were 16, 80, 24, 22 and 13%, respectively, higher under NTS treatment. Straw returning enhanced the relative contents of O-alkyl C, carbonyl C, alkyl C, A/O-A ratio, and aromaticity. The correlations of SOC with C fractions and SCMI were significant. O-alkyl C was positively correlated with C fractions and negatively correlated with carbonyl C and alkyl C. In conclusion, long-term tillage and straw returning significantly affected the fractions and chemical compositions of SOC, could be viable option for improving the soil quality in the rice-rape rotation system.     

深松和秸秆还田对旋耕农田土壤有机碳活性组分的影响

土壤有机碳(soil organic carbon,SOC)及其活性组分能够敏感响应耕作方式变化及有机物输入。为对比长期旋耕农田进行深松后土壤有机碳各活性组分及比例变化,该研究基于连续7a的旋耕转变为深松和秸秆管理长期定位试验,对比了旋耕无秸秆还田处理(rotary tillage with straw removal,RT)、旋耕秸秆还田处理(rotary tillage with straw return,RTS)、旋耕转变为深松无秸秆还田处理(rotary tillage conversion to subsoiling with straw removal,RT-DT)、旋耕转变为深松秸秆还田处理(rotary tillage conversion to subsoiling with straw return,RTS-DTS)下土壤有机碳(soil organic carbon,SOC)、颗粒有机碳(particulate organic carbon,POC)、易氧化有机碳(readily oxidizable organic carbon,ROC)、微生物生物量碳(microbial biomass carbon,MBC)、溶解性有机碳(dissolved organic carbon,DOC)、活性有机碳(labile organic carbon,LOC)在土壤有机碳中比例的变化及各组分间的相互关系。研究结果表明,耕作方式从旋耕转变为深松和秸秆还田对SOC及其各活性组分均产生显著影响,耕作方式转变、秸秆还田及两者的交互效应是影响SOC及其活性组分的主要因素。秸秆还田显著提高了RTS处理和RTS-DTS处理的SOC含量,分别比RT和RT-DT处理高6.1%~15.6%和19.1%~32.3%。并且转变耕作方式后RTS-DTS处理比于RTS处理SOC含量提高16.9%~20.0%。同时,RTS-DTS处理的POC含量比RTS处理高13.6%~53.8%;但RT-DT和RTS-DTS处理的土壤ROC含量较RT和RTS处理都呈下降趋势,RTS-DTS处理的ROC含量比RTS处理下降4.6%~10%;MBC含量降低23.8%~30.6%。虽然秸秆还田显著提高了各处理的DOC含量,但RTS转变为RTS-DTS处理后,其3个土层的DOC含量下降了8%~41%。相比于RT和RTS处理,RT-DT和RTS-DTS处理0~30 cm各土层中LOC在SOC中的比例显著下降。相关性分析结果表明,除POC与ROC之间无显著性相关关系外,SOC及各组分间均呈显著(P<0.05)或极显著(P<0.01)的相关关系。耕作方式转变为深松和秸秆还田提高了SOC含量的同时,显著降低了SOC中的活性有机碳组分,这更有利于SOC的有效积累,促进土壤碳库的稳定固存。     

耕作方式对华北农田土壤固碳效应的影响

研究不同耕作方式对华北农田土壤固碳及碳库管理指数的影响,可为探寻有利于农田固碳的耕作方式提供科学依据。该研究在中国农业大学吴桥实验站进行,试验于2008年设置了免耕秸秆不还田(NT0)、翻耕秸秆不还田(CT0)、免耕秸秆还田(NT)、翻耕秸秆还田(CT)和旋耕秸秆还田(RT)5个处理。研究测定分析了土壤容重、有机碳、易氧化有机碳含量及不同耕作方式下的碳库管理指数。通过对不同耕作方式下0～110cm土壤的分析,结果表明,随着土层的加深,土壤有机碳含量不断下降,NT显著增加了表层(0～10cm)土壤有机碳含量,而>10～50cm有机碳含量较其他处理(NT0除外)有所下降,深层(>50～110cm)处理间差异不明显;土壤容重与有机碳含量呈显著的负相关关系(P<0.01);0～30cm土层有机碳储量以NT最高,CT与其无明显差异,二者较CT0分别高出13.1%和11.0%,而至0～50cm土层,CT的碳储量最高,但与NT无显著差异(P<0.05);与CT0相比,NT0降低了各层土壤易氧化有机碳含量,而NT则在0～10cm土层表现为增加;RT、CT分别显著增加了0～10、>10～30cm土层的碳库管理指数。结果表明,秸秆还田可改善土壤质量,提高农田碳库管理指数,同时碳库管理指数受耕作方式的影响也较大,尤其是CT和RT;NT通过减少土壤扰动、增加有机质的输入,可提高上层土壤有机碳的储量。     

长期免耕旱作对冬小麦生长季土壤剖面有机碳含量的影响

依托21a长期免耕秸秆还田定位试验，探究长期免耕加秸秆还田的田间管理方式对冬小麦生长季0−60cm土层内土壤有机碳（SOC）和土壤活性有机碳（MBC、POC、DOC）的影响。试验共设长期免耕秸秆还田（NT）与常规耕作（CT）两种耕作模式，分析0−60cm土层内土壤总有机碳（SOC）、土壤微生物量碳（MBC）、土壤颗粒有机碳（POC）、土壤可溶性碳（DOC）含量的变化。结果表明，在0−20cm土层，NT处理SOC含量显著高于CT处理，其中0−5cm和5−10cm土层平均SOC含量分别增加了81.2 %和52.9 %，冬小麦不同生育期内土壤SOC含量变化不显著；在0−30cm土层内，与CT处理相比，NT显著改变了土壤MBC、POC及DOC在播种前、越冬前、拔节期、开花期和成熟期5个生育阶段的分布情况，且显著提高了5个生育阶段内土壤活性有机碳的含量（P＜0.05），其中0−5cm土层内，土壤MBC、POC及DOC含量在各个时期相较于CT处理分别增长60.8%～161.4%、71.8%～141.1%和21.9%～104.4%。0−60cm土层内，两种耕作方式下的SOC、MBC、POC、DOC均随着土壤深度的增大呈下降趋势。说明长期免耕可提高耕作层土壤有机碳含量和小麦生长季活性有机碳的水平，这为旱地土壤有机碳的高效固存提供了理论依据。     

外源有机碳对黑土有机碳及颗粒有机碳的影响

为了阐释外源有机碳在土壤有机碳运转中的作用机制,以黑土为供试材料,进行了5年的室外培养试验,并结合室内全土及颗粒组分单独矿化培养试验,研究了不同外源有机碳对黑土有机碳(SOC)、颗粒有机碳(POC)含量及其矿化特征的影响。试验包括单施化肥、牛粪配施化肥、鸡粪配施化肥、秸秆配施化肥和树叶配施化肥5个处理。结果表明:(1)单施化肥黑土SOC的损失主要来源于POC的损失,外源有机碳有利于SOC和POC的累积,与对照相比,禽畜粪便处理的SOC和POC平均增加幅度分别为16.6%和27.8%,植物残体处理的SOC和POC平均增加幅度分别为27.0%和46.4%;(2)一级动力学方程能较好地描述SOC和POC的矿化动态(R~20.9),且POC比SOC易矿化,POC的60d累积矿化量是SOC的3倍以上;(3)禽畜粪便处理和植物残体处理的POC平均矿化率分别为31.5%和29.8%,禽畜粪便处理的POC更易矿化;(4)外源有机碳有效降低了黑土有机碳的矿化,尤其是牛粪,其SOC矿化率为1.9%,比对照低了3.4%,其POC矿化率为24.8%,比对照低17.4%;(5)外源有机碳在黑土中的碳累积能力表现为树叶秸秆牛粪鸡粪。     

土壤颗粒有机碳和矿质结合有机碳对4种耕作措施的响应

以陕西关中平原中部耕作定位试验为研究对象,研究深松、旋耕、免耕和统耕作4种耕作方式在秸秆还田和不还田条件下对土壤颗粒有机碳和矿质结合态有机碳的影响。结果表明,相对于传统耕作,深松、旋耕和免耕处理都使土壤颗粒碳(POC)含量增加,但在秸秆还田下相应增加幅度更大,在0-10cm土层颗粒碳增加20.71%～69.25%,表现出深松>旋耕>免耕>传统耕作的顺序,而对其他10-20cm,20-30cm,30-40cm土层的颗粒碳影响较小。在同一种耕作模式下,秸秆还田的与无秸秆还田的相比,深松、旋耕、传统耕作使土壤POC增加了9.17%～26.61%,其中以传统耕作措施的提高幅度最大。在秸秆不还田条件下,各耕作处理矿质结合态有机碳的差异较小,但在秸秆还田条件下,旋耕促进了土壤矿质结合态有机碳(MOC)的增加,比对照(传统耕作)提高了22.98%。从土壤有机碳的角度考虑,深松和旋耕并结合秸秆还田是较适合于当地土壤条件的耕作模式。     

免耕对华北地区潮土碳库特征的影响

以实施7年的中国科学院禹城综合试验站冬小麦-夏玉米轮作免耕长期定位试验场为对象,系统研究免耕条件下土壤总碳(TC)、有机碳(SOC)、无机碳(SIC)的变化,为进一步评价免耕措施对华北地区潮土碳库的影响提供数据支持。研究设置免耕秸秆覆盖(NTRC)、免耕施用有机肥(NTRR)、常规耕作(CT)3种处理,分析表层(0-20cm)及深层(20-60cm)土壤TC、SOC及SIC的变化特征和影响因素。主要结果为:NTRC和NTRR能够增加0-20cm土层TC含量及储量,但降低20-60cm土层TC含量及储量,0-60cm总碳储量表现为NTRC>CT>NTRR;与CT相比,NTRC能够显著增加0-20cm而降低20-60cm土层SOC含量及储量,NTRR增加了0-5cm土层SOC含量及储量,在5-60cm则呈降低趋势,0-60cm土层SOC储量表现为CT>NTRC>NTRR;NTRC增加了0-60cm土层SIC储量,而NTRR则影响较小。TC与SOC呈显著正相关(P<0.05),而与SIC呈显著负相关(P<0.05),说明总碳的变化趋势与SOC一致,与SIC相反。     

有机培肥与耕作方式对稻麦轮作土壤团聚体和有机碳组分的影响

为了明确不同外源有机物和耕作方式对土壤地力培育的影响,以水稻-小麦轮作系统为对象,通过2个年度(2016—2018年)大田试验研究了外源有机物(秸秆和有机肥)和耕作方式及其交互作用[稻麦秸秆还田配合旋耕(SR),稻麦秸秆还田配合翻耕(SP),秸秆不还田、增施有机肥配合旋耕(MR),秸秆不还田、增施有机肥配合翻耕(MP),秸秆不还田、不施用有机肥、旋耕深度15 cm(CKR)]对土壤团聚体和有机碳组成的短期影响。结果表明:SR处理能够降低水稻季土壤容重并增加总孔隙度。相比CKR,小麦季SR处理显著增加0.05mm水稳性团聚体含量,增加量为7.2%。此外,外源有机物和耕作对土壤有机碳活性组分具有显著影响。其中,易氧化有机碳(EOC)主要受耕作与有机物交互作用影响,酸水解有机碳(LPIc和LPII_c)主要受耕作措施的影响, SR处理的土壤EOC和LPI_c含量比CKR提高0.3～2.6 g·kg~(-1)。颗粒有机碳(POC)主要受外源有机物的影响,并且秸秆还田处理POC平均含量高于增施有机肥处理,增加量为0.75g·kg~(-1)。短期内,外源有机物和耕作及其交互作用对稳定性有机碳(黑碳和矿物结合态有机碳)的影响较小。综上,秸秆还田配合旋耕有助于提高土壤水稳性团聚体和活性有机碳的含量(EOC、LPI_c和POC)。     

长期施用有机肥对稻麦轮作体系土壤有机碳氮组分的影响

【目的】 以湖北武汉地区长期稻麦轮作制度下施肥试验地作为研究对象,研究了长期不同施肥处理对耕层土壤有机碳、全氮及活性碳氮组分的影响,为优化稻麦轮作体系下施肥措施,实现土壤固碳减排,培肥土壤提供理论依据。 【方法】 长期施肥试验开始于1981年,试验处理包括不施肥 (CK)、施化学氮肥 (N)、施化学氮磷肥 (NP)、施化学氮磷钾肥 (NPK)、单施有机肥 (M) 及有机无机肥配施处理 (NPKM)。收集2017年小麦收获后耕层 (0—20 cm) 土壤,测定各小区土壤中的有机碳 (SOC)、全氮 (TN)、微生物量碳氮 (MBC、MBN)、水溶性碳 (DOC)、热水溶性有机碳 (HWSC)、颗粒有机碳氮 (POC和PON)、轻组有机碳氮 (LFOC和LFON) 及氯化钾浸提氮 (KEN,即水溶性无机氮) 的含量并分析各指标间的关系。 【结果】 1) 除KEN外,长期施用有机肥显著增加耕层土壤的各碳氮组分含量,特别是有机无机肥配施处理。2) 各活性有机碳组分占SOC的百分比由高到低排序为POC > LFOC > HWSC > MBC > DOC,各氮组分占TN的百分比由高到低排序为PON > LFON > MBN > KEN,其中POC占SOC的24.04%～37.64%,PON占TN的12.09%～20.24%,且有机肥处理下POC/SOC、PON/TN显著高于其余处理。3) 通过对土壤有机碳及各活性有机碳的对施肥的敏感性分析可得,各活性碳敏感性指数均显著高于SOC,且DOC的敏感性最高。4) 通过各组分间相关性分析可知,除KEN外,各碳、氮组分间显著正相关,其中DOC与SOC、PON与TN关系更为紧密,表明DOC及PON可较好地反应出SOC、TN的变化情况。 【结论】 在湖北稻麦轮作地区,长期有机无机肥配施处理显著增加了土壤碳库及氮库,促进了土壤碳、氮的积累,尤其是颗粒有机碳和有机氮 (POC和PON)。水溶性碳 (DOC) 对施肥反应最为敏感,可作为指示该地区有机物早期变化的指示物。      

保护性耕作对黑土有机碳组分和玉米产量的影响

  目的  探究不同保护性耕作措施对黑土有机碳组分的影响,对于保持黑土生态稳定性及其高肥力水平具有重要意义。  方法  以农田黑土为研究对象,玉米为供试作物,采用随机区组设计,设置传统翻耕（CT）、传统翻耕 + 秸秆还田（CTSI）、免耕（NT）、免耕 + 秸秆还田（NTSI）、深松（ST）和深松 + 秸秆还田（STSI）,共6个处理,采用密度分组法,研究不同保护性耕作措施对耕层土壤（0 ~ 20 cm）有机碳组分含量、结构特征及玉米产量的影响。  结果  与CT处理相比,不同保护性耕作处理土壤总有机碳含量均显著提高（P < 0.05）。ST处理轻组有机碳、粗颗粒有机碳和细颗粒有机碳组分含量均较CT处理显著增加（P < 0.05）,与不还田相比,秸秆还田处理有机碳各组分含量均增加,NTSI处理较CTSI处理显著提高轻组有机碳含量,STSI处理较CTSI处理显著提高粗颗粒有机碳和细颗粒有机碳含量。主成分分析表明,与CT处理相比,NT、NTSI、ST和STSI处理均能提高轻组有机碳多糖和碳水化合物官能团的相对含量;保护性耕作措施较CT处理不仅增加了粗颗粒有机碳和细颗粒有机碳组分活性官能团相对含量,还增加了稳定性官能团相对含量,有利于土壤稳定性结构的形成,促进碳的固存。耕作与秸秆还田显著影响了玉米产量,ST较CT和NT处理分别显著提高了22.37%和21.42%（P < 0.05）,秸秆还田处理有利于玉米产量提升,STSI处理增产效果最佳;相关性分析表明,粗颗粒有机碳能有效指示土壤有机碳的变化,其与细颗粒有机碳在维持和提升玉米产量中具有重要贡献。  结论  采用深松结合秸秆还田的保护性耕作措施对于稳定与提高黑土有机碳含量、固持土壤碳库和增加玉米产量具有重要作用。     

长期保护性耕作提高土壤大团聚体含量及团聚体有机碳的作用

【目的】团聚体形成被认为是土壤固碳的最重要机制。本文以河南豫西地区长期耕作试验为研究对象,研究了长期保护性耕作对土壤团聚体性质及土壤有机碳(SOC)含量的影响,为探讨土壤固碳机理,优化黄土高原坡耕地区农田耕作管理措施,实现土壤固碳减排、培肥土壤提供理论依据。【方法】长期耕作试验开始于1999年,试验处理有免耕覆盖(NT)、深松覆盖(SM)和翻耕(CT)。利用湿筛法筛分第3年(2002年)和第13年(2011年)0—10cm和10—20 cm土层中,2000、250~2000、53~250和53μm级别的水稳性团聚体,计算团聚体平均质量直径(MWD),并测定了各级别团聚体的有机碳(SOC)含量。【结果】1)连续13年免耕覆盖和深松覆盖显著提高了土壤表层0—10 cm的SOC含量,分别比翻耕增加了33.47%和44.48%。2011年免耕覆盖和深松覆盖SOC含量较2002年上升了1.92%和8.59%,翻耕下降了18.97%。2)与翻耕相比,免耕覆盖和深松覆盖2000μm团聚体含量显著提高了40.71%和106.75%;53~250μm团聚体含量显著降低了19.72%和22.53%;团聚体平均质量直径显著提高了20.55%和39.68%,显示了土壤结构的明显改善。3)免耕覆盖和深松覆盖显著提高了表层土壤所有团聚体有机碳的含量,尤其以2000μm团聚体提升最多。与翻耕相比,2000μm团聚体有机碳分别提高了40.0%和27.6%。4)免耕覆盖和深松覆盖下表层土壤大团聚体有机碳含量随耕作年限增加,微团聚体有机碳随耕作年限降低。2000μm的土壤团聚体有机碳含量2011年较2002年分别升高了23.93%和7.12%,53~250μm微团聚体有机碳含量分别下降了19.58%和13.27%。【结论】长期保护性耕作(包括免耕覆盖和深松覆盖)可显著提高表层土壤大团聚体含量,降低微团聚体含量,提高团聚体的水稳性,改善土壤结构。同时可增加土壤团聚体有机碳含量,提高土壤肥力。长期保护性耕作在河南豫西丘陵地区是一种较为合理的耕作方式。     

Tillage effects on soil properties at different levels of fertilizer application in Punjab, Pakistan

The effects of cropping systems and management practices on soil properties provide essential information for assessing sustainability and environmental impact. Tillage and fertilizer rates were evaluated for their effects on soil bulk density (BD), penetration resistance, soil organic carbon (SOC) concentration and availability of macronutrients on a sandy clay loam (fine-loamy, mixed, hyperthermic Typic Haplargids, USDA; Luvic Yermosol, FAO) in a semi-arid region of Pakistan. Wheat (Triticum aestivum L.) and cotton (Gossypium hirsutum L.) were double-cropped from 1996 to 1998. Tillage treatments were minimum till (MT), conventional till (CT), and deep till (DT). Low, medium and high fertilizer rates were applied to wheat and cotton. BD was affected neither by tillage nor fertilizer rates. Soil penetration resistance was lower for DT than CT and MT. Tillage methods affected soil P concentration but did not affect N and K concentrations. However, fertilizer application significantly increased soil P and K concentrations. Concentrations of N, P, K and SOC were greater in the plough layer than sub-soil. Grain yield of wheat was significantly negatively correlated with penetration resistance and was positively correlated with soil P and K concentrations. Yield of cotton was significantly negatively correlated with soil BD. These data provide an experimental basis to re-evaluate recommendations for fertilizer rates and tillage methods for production of wheat and cotton in Punjab. Further, there is a strong need to establish long-term experiments to study agronomic and environmental effects of tillage methods, fertilizer rates, and cropping systems on productivity and environment quality.     

Influence of Residue Management and Tillage Systems on Carbon Sequestration and Nitrogen,Phosphorus, and Potassium Dynamics of Soil and Plant and Wheat Production in Semi-arid Region

Reducing the tillage and application of mulch are important strategies for soil and water conservation and sustainability of agricultural systems. Soil can be a source or sink for carbon (C) depending on management strategies and plays a major role in the global C cycle. These interacting practices can alter nutrient movement and availability to the crops, reduce water loss, slow down organic-matter (OM) decomposition, and thus enhance C sequestration. A 2-year field study was conducted to quantify the tillage and mulching effect on soil organic C (SOC), OM, nitrogen (N), phosphorus (P), and potassium (K) at two depths (i.e., 0–15 and 15–30 cm deep) in the soil profile and N, P, and K concentrations (g kg^?1) in plant shoots at harvest on a Typic Calciargids in wheat–maize rotation. The four tillage systems used were zero tillage (ZT), minimum tillage (MT), conventional tillage (CT), and deep tillage (DT), and four mulch rates [control, 2 (M₂), 4 (M₄), and 6 (M₆) Mg ha^?1 year^?1 wheat (Triticum aestivum L.) straw] were applied in combination with each tillage system, keeping recommended rates of fertilizers. There was a linear positive response of mulch application on SOC for both years, but it was more pronounced during the second year. Greater values were found in ZT and the lowest in CT at all depths, although greater SOC content was found in upper layers than in deeper ones. Greater shoot N, P, and K concentrations were found in MT, CT, and DT, whereas the lowest concentration was found in ZT. Mulch application has no effect on N, P, and K concentrations in shoots. The soil N concentration was not affected by tillage and mulch, yet greater soil N content was found at 0–15 cm than 15–30 cm deep. There was significant effect of tillage on soil P and K during one year as greater P and K concentrations were found under MT, CT, and DT compared to ZT. More N, P, K, and OM concentrations were found at 0–15 cm deep than at 15–30 cm deep during the whole study period. Mulch effect was significant on K, and significantly greater amounts were found at greater levels of mulch application. The increases in the soil OM were 34.5, 35.75, and 24% at 0–8, 8–16, and 16–24 cm deep respectively from the first year to the second year. Tillage effect on soil organic-matter content was not significant. Tillage increased grain production for both years. For the first year, 22.9 and 27% greater yields were found in CT and DT, whereas in the second year yields were 10.6, 17.9, and 57% greater, respectively, in MT, CT, and DT as compared to ZT. Grain production was increased at a result of mulch application by 12.9, 20.3, and 10.6% during the first year and 11.45, 23.74, and 10.9% during the second year as compared to control (i.e., without mulch). Results show the importance of mulch application and crop residue retention. Both can increase the SOC content and water-holding capacity, which will result in improved production and soil physical health over long and continuous use of mulch.     

中国黄土高原区轮耕对土壤团聚体、有机碳氮含量的影响

In rain-fed semi-arid agroecosystems, continuous conventional tillage can cause serious problems in soil quality and crop production, whereas rotational tillage (no-tillage and subsoiling) could decrease soil bulk density, and increase soil aggregates and organic carbon in the 0-40 cm soil layer. A 3-year field study was conducted to determine the effect of tillage practices on soil organic carbon (SOC), total nitrogen (TN), water-stable aggregate size distribution and aggregate C and N sequestration from 0 to 40 cm soil in semi-arid areas of southern Ningxia. Three tillage treatments were tested: no-tillage in year 1, subsoiling in year 2, and no-tillage in year 3 (NT-ST-NT); subsoiling in year 1, no-tillage in year 2, and subsoiling in year 3 (ST-NT-ST); and conventional tillage over years 1-3 (CT). Mean values of soil bulk density in 0-40 cm under NT-ST-NT and ST-NT-ST were significantly decreased by 3.3% and 6.5%, respectively, compared with CT, while soil total porosity was greatly improved. Rotational tillage increased SOC, TN, and water-stable aggregates in the 0-40 cm soil, with the greatest effect under ST-NT-ST. In 0-20 and 20-40 cm soils, the tillage effect was confined to the 2-0.25 mm size fraction of soil aggregates, and rotational tillage treatments obtained significantly higher SOC and TN contents than conventional tillage. No significant differences were detected in SOC and TN contents in the >2 mm and <0.25 mm aggregates among all treatments. In conclusion, rotational tillage practices could significantly increase SOC and TN levels, due to a fundamental change in soil structure, and maintain agroecosystem sustainability in the Loess Plateau area of China.     

Particulate and Mineral-Associated Organic Carbon in Aggregates as Affected by Biowaste Compost Applications in a Mediterranean Vegetables Cropping System

This study was conducted to assess the influence of biowaste compost on soil aggregation and soil organic carbon (SOC) stabilization, in a conventional tillage agro-ecosystem. Four treatments were involved: biowaste compost (Com), fertilizers nitrogen, phosphorus and potassium (NPK) (Min), biowaste compost plus mineral N (ComN) and unfertilized control (Cnt). Compared to the control, after four years, the amount of macroaggregates decreased by 23% and 69% for Com and ComN, while SOC stock increased by 17% and 10%, respectively. Most part of the SOC increases were stored in free-microaggregates and were made up for more than 70% by mineral-associated organic carbon (MOC), while no significant variation of particulate organic C (POC) was observed. Therefore, the biowaste compost application rates and time that were practiced in the studied agro-ecosystem were effective for C sequestration, but not enough to improve the macroaggregation and the POC protection.