秸秆还田模式对小麦-玉米轮作体系土壤有机碳固存的影响

为解决麦玉轮作体系小麦秸秆直接粉碎还田存在的弊端,基于多年麦玉秸秆还田定位试验,筛选高产-节本-地力提升为一体的还田模式。选择4种还田模式,即小麦玉米秸秆均不还田(WN-MN,CK1)、小麦玉米秸秆均粉碎还田(WC-MC,CK2)、小麦高留茬还田(WH-MN)和小麦高留茬-玉米粉碎还田(WH-MC)为研究对象,比较其产量表现、土壤有机碳贮量盈亏、碳库管理指数等指标,评价将小麦秸秆粉碎还田改成高留茬还田后形成的还田模式与两季秸秆均粉碎还田的优劣。结果表明,与WN-MN相比,WC-MC和WH-MC的土壤碳储量分别增加24.23%和16.05%;与试验开始前土壤有机碳储量相比,4种还田模式的土壤碳固持为–0.83~6.14 Mg·hm^–2;维持土壤初始碳储量水平的最小碳投入量为4.06 Mg·hm^–2·a^–1。各处理不稳定有机碳组分的含量随着土层加深呈下降趋势。与WN-MN相比,WC-MC、WH-MC和WH-MN显著增加了0~20 cm表层不稳定碳组分的含量;WC-MC和WH-MC也显著增加了各土层的碳库管理指数。2015—2016周年产量,WC-MC、WH-MC平均较其他两个处理分别增加了34.5%、20.1%;2016—2017周年产量,以WH-MC最高,较其他处理平均高出11.1%。小麦高留茬-玉米粉碎还田模式下土壤有机碳储量、不稳定有机碳组分、碳库管理指数和作物产量均较高,且节本增效,表明该模式有利于关中平原麦玉轮作体系粮食生产可持续发展。     

秸秆还田对黑土亚表层微生物群落结构的影响特征及原因分析

为明确切碎秸秆与秸秆颗粒对黑土亚表层土壤微生物群落结构的影响效应,从而评价不同秸秆还田方式对亚表层的培肥效果,该研究于2016-2018年在东北黑土区进行一次性玉米秸秆深埋还田试验,设置切碎秸秆低量(QS1)、切碎秸秆高量(QS5)、秸秆颗粒低量(KL1)与秸秆颗粒高量(KL5)4种秸秆还田处理,并与秸秆不还田(CK)进行对比,于每年玉米收获季对土壤理化指标及微生物菌群结构进行监测。结果表明,1)秸秆还田第1年,切碎秸秆处理显著提高土壤总磷脂脂肪酸含量及真菌摩尔百分数,其高量处理较CK最高增加71.0%和120.5%,而秸秆颗粒处理对细菌、革兰氏阳性菌和革兰氏阴性菌的摩尔百分数增幅更显著,其高量处理最高增加41.6%、29.7%和26.3%;还田第2年高量处理显著提高各菌群磷脂脂肪酸含量,且切碎高量处理的真菌摩尔百分数含量显著高于颗粒高量处理21.0%;还田第3年仅高量处理下的菌群结构有显著分异。2)还田初期切碎秸秆处理显著提高真菌:细菌比值,而低量还田则对革兰氏阳性菌和革兰氏阴性菌比有提高,随还田时间的增加,高量还田比值提高更显著,利于长期维持生态系统稳定性。3)秸秆高量还田可显著改变土壤理化因子水平,这是导致微生物群落结构分异的重要原因,其显著影响因子随还田年限而更替:第1年,土壤容重、酸碱度、全氮和碳氮比为显著(P<0.05)影响因素;第2年,土壤含水量、有机碳、碳氮比和土壤容重为极显著影响因素(P<0.01);第3年仅有机碳为显著因素(P<0.05)。切碎秸秆高量还田处理微生物群落结构分布与CK区分最为明显,对土壤真菌群落的调控能力更强,更适宜于东北黑土亚表层肥力的提升。     

保护性耕作对麦-豆轮作土壤有机碳全氮及微生物量碳氮的影响

通过设置在甘肃省定西市李家堡镇的保护性耕作措施长期定位试验,共设4个处理（T：传统耕作;NT：免耕无覆盖;TS：传统耕作＋秸秆还田;NTS：免耕＋秸秆覆盖）,采用春小麦豌豆双序列轮作（即小麦→豌豆→小麦和豌豆→小麦→豌豆,本文中所指春小麦地、豌豆地分别指2008年种植春小麦、豌豆的轮作次序）,于2008年3月中旬对春小麦、豌豆双序列轮作下的土壤有机碳、全氮、土壤微生物量碳及土壤微生物量氮含量进行了采样测定。结果表明,经过7a的轮作后,两种轮作次序下,0-30cm土层中土壤有机碳、全氮、土壤微生物量碳、土壤微生物量氮含量均有在免耕＋秸秆覆盖、传统耕作＋秸秆还田处理较免耕不覆盖、传统耕作处理高的趋势,且其含量均随着土壤深度的增加而降低。其中,土壤微生物量碳含量在两种轮作次序下的排序均为：免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉免耕不覆盖（NT）〉传统耕作（T）;而土壤微生物量氮含量在春小麦地和豌豆地的排序则分别表现为：免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉传统耕作（T）〉免耕不覆盖（NT）和免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉免耕不覆盖（NT）〉传统耕作（T）。同时,微生物量碳、微生物量氮与有机碳和全氮均呈显著正相关,说明提高土壤有机质、全氮含量的保护性耕作模式有利于土壤微生物量碳与氮的积累。     

Neoformation of pedogenic carbonate and conservation of lithogenic carbonate by farming practices and their contribution to carbon sequestration in soil

Land use change, tillage practices and straw incorporation are known to affect soil organic carbon (SOC) as well as soil inorganic carbon (SIC) turnover in agricultural soils. SOC and SIC, particularly pedogenic carbonates (PC), were assessed in a semi‐humid region of China to a depth of 160 cm. δ¹³C values were used to calculate the percentage of PC and lithogenic carbonates (LC) in the total SIC. Over the 39‐y period of intensive agriculture including 14 y of tillage × straw experiment, three treatments, i.e ., tillage with wheat and maize straw return (TWM), tillage with wheat straw return (TW), and wheat and maize straw return with no‐tillage (WM) showed an increase of PC compared to a native plantation plot (NP). The significantly higher SOC stock via no‐tillage was limited to top 1 m soil and there was no significant difference between tillage and no‐tillage treatments at 0–160 cm depth. The changes of SOC caused by the tillage and maize straw addition were negligible compared to the gain in PC. Tillage, crop residues incorporation and irrigation played an important role in the turnover of PC and LC. SIC accumulation resulted from combination of neoformation of PC and conservation of LC. Neoformation of silicatic PC sequestered at least 0.49, 0.47, and 0.29 Mg C ha⁻¹ y⁻¹ in TWM, TW, and WM treatments, respectively, with reference to NP plot. We concluded that to evaluate the long term impacts of land use and farming practices on soil C storage, change of pedogenic and lithogenic carbonates and soil organic carbon in deeper soil profiles should be integrated on regional and global scales.     

Influence of dry–wet cycles on the interrelationship between aggregate,particulate organic matter,and microbial community dynamics

Aggregate dynamics and their relationship to the microbial community have been suggested as key factors controlling SOM dynamics. Dry–wet (DW) cycles are thought to enhance aggregate turnover and decomposition of soil organic matter (SOM), particularly in tilled soils. The objective of this study was to evaluate the effects of DW cycles on aggregate stability, SOM dynamics, and fungal and bacterial populations in a Weld silt loam soil (Aridic Paleustoll). Samples, taken from 250 μm sieved air-dried soil (i.e. free of macroaggregates > 250 μm), were incubated with ¹³C-labeled wheat residue. In one set of soil samples, fungal growth was suppressed using a fungicide (Captan) in order to discern the effect of dry–wet cycles on fungal and bacterial populations. Aggregate formation was followed during the first 14 d of incubation. After this period, one set of soil samples was subjected to four DW cycles, whereas another set, as a control, was kept at field capacity (FC). Over 74 d, total and wheat-derived respiration, size distribution of water stable aggregates and fungal and bacterial biomass were measured. We determined native and labeled C dynamics of three particulate organic matter (POM) fractions related to soil structure: the free light fraction (LF), and the coarse (250–2000 μm) and fine (53–250 μm) intra-aggregate POM fraction (iPOM). In the fungicide treated soil samples, fungal growth was significantly reduced and no large macroaggregates (> 2 mm) were formed, whereas without addition of fungicide, fungi represented the largest part of the microbial biomass (66%) and 30% of the soil dry weight was composed of large macroaggregates. During macroaggregate formation, labeled free LF-C significantly decreased whereas labeled coarse iPOM-C increased, indicating that macroggregates are formed around fresh wheat residue (free LF), which is consequently incorporated and becomes coarse iPOM. The first drying and wetting event reduced the amount of large macroaggregates from 30 to 21% of the total soil weight. However, macroaggregates became slake-resistant after two dry-wet cycles. Fine iPOM-C was significantly lower in soil after two dry–wet cycles compared to soil kept at FC. We conclude that more coarse iPOM is decomposed into fine iPOM in macroaggregates not exposed to DW cycles due to a slower macroaggregate turnover. In addition, when macroaggregates, subjected to dry–wet cycles, became slake-resistant (d 44) and consequently macroaggregate turnover decreased, fine iPOM accumulated. In conclusion, differences in fine iPOM accumulation in DW vs. control macroaggregates are attributed to differences in macroaggregate turnover.     

Effects of part and whole straw returning on soil carbon sequestration in C3–C4 rotation cropland

Long‐term no‐tillage management and crop residue amendments to soil were identified as an effective measure to increase soil organic carbon (SOC). The SOC content, SOC stock (SOCs), soil carbon sequestration rate (CSR), and carbon pool management index (CPMI) were measured. A stable isotopic approach was used to evaluate the contributions of wheat and maize residues to SOC at a long‐term experimental site. We hypothesized that under no‐tillage conditions, straw retention quantity would affect soil carbon sequestration differently in surface and deep soil, and the contribution of C3 and C4 crops to soil carbon sequestration would be different. This study involved four maize straw returning treatments, which included no maize straw returning (NT‐0), 0.5 m (from the soil surface) maize straw returning (NT‐0.5), 1 m maize straw returning (NT‐1), and whole maize straw returning (NT‐W). The results showed that in the 0–20 cm soil layer, the SOC content, SOCs, CSR and CPMI of the NT‐W were highest after 14 years of no‐tillage management, and there were obvious differences among the four treatments. However, the SOC, SOCs, and CSR of the NT‐0.5 and NT‐W were the highest and lowest in 20–100 cm, respectively. The value of δ¹³C showed an obviously vertical variability that ranged from –22.01‰ (NT‐1) in the 0–20 cm layer to –18.27‰ (NT‐0.5) in the 60–80 cm layer, with enriched δ¹³C in the 60–80 cm (NT‐0.5 and NT‐1) and 80–100 cm (NT‐0 and NT‐W) layers. The contributions of the wheat and maize‐derived SOC of the NT‐0.5, NT‐1 and NT‐W increased by 11.4, 29.5 and 56.3% and by 10.7, 15.1 and 40.1%, relative to those in the NT‐0 treatment in the 0–20 cm soil layer, respectively. In conclusion, there was no apparent difference in total SOC sequestration between the NT‐0.5, NT‐1, and NT‐W treatments in the 0–100 cm soil layer. The contribution of wheat‐derived SOC was higher than that of maize‐derived SOC.     

稻草高茬-紫云英联合还田改善土壤肥力提高作物产量

研究旨在探讨稻草留高茬套种绿肥、稻草-绿肥联合还田下的生产及土壤肥力特征,为南方稻区综合利用稻草和绿肥提供理论及技术支撑。2012—2016年设置定位试验,研究高茬稻草-绿肥联合还田下的绿肥和水稻产量、土壤碳氮库活性及其他养分特征。试验包括5个处理:冬闲+稻草不还田(CK),冬闲+稻草全量还田(RS),冬种紫云英+稻草不还田(MV),冬种紫云英+稻草低茬全量还田(MV+LRS),冬种紫云英+稻草高茬全量还田(MV+HRS),各处理施用等量化肥。结果表明:稻草-绿肥联合还田提高绿肥产草量及其含氮量,与MV相比,分别增加了13.1%和6.8%(MV+LRS)、32.2%和5.2%(MV+HRS);增加水稻产量,以MV+HRS处理最高,4 a平均产量较RS、MV增加556.8和412.8 kg/hm2。2013和2015年,MV+HRS处理水稻产量高于MV+LRS。稻草-绿肥联合还田培肥地力效果明显,土壤有机质、全氮含量均比CK、RS和MV增加;且联合还田下有效养分提升更为全面。与稻草和绿肥单独应用相比,稻草-绿肥联合还田还能提升土壤微生物量氮及可溶性有机碳氮含量。可见,稻草-绿肥联合还田能够改善绿肥生长、提高水稻产量、提升土壤肥力;其中,高茬稻草与绿肥联合还田下的紫云英和水稻产量最高,土壤肥力也优于低茬处理,是综合利用稻草和绿肥资源的较好方式。     

Effects of different quality plant residues on soil carbon accumulation and aggregate formation in a tropical sandy soil in Northeast Thailand as revealed by a 10‐year field experiment

Particulate organic matter (POM) plays important role in soil organic carbon (SOC) retention and soil aggregation. This paper assesses how quality (chemical composition) of four different‐quality organic residues applied annually to a tropical sandy loam soil for 10 years has affected POM pools and the development of soil aggregates. Water‐stable aggregate size distribution (>2, 0·25–2, 0·106–0·25 mm) was determined through wet sieving. Density fractionation was employed to determine POM (light—LF, and heavy—HF fractions, 0·05–1 mm). Tamarind leaf litter showed the highest SOC (<1 mm) accumulation, while rice straw showed the lowest. LF‐C contents had positive correlations with high contents of C and recalcitrant constituents, (i.e. lignin and polyphenols) of the residues. Dipterocarp, a resistant residue, showed the highest LF‐C, followed by the intermediate residues, tamarind, and groundnut, whereas HF was higher in groundnut and tamarind than dipterocarp residues. Rice straw had the lowest LF‐ and HF‐C contents. Tamarind had the highest quantity (51 per cent) of small macroaggregates (0·25–2 mm), while dipterocarp had the most (2·1 per cent) large macroaggregates (>2 mm). Rice straw had the lowest quantities of both macroaggregates. Similar to small‐sized HF (0·05–0·25 mm), small macroaggregates had positive correlation with N and negative correlation with C/N ratios, while large macroaggregates had positive correlations with C and recalcitrant constituents of the residues. Tamarind, with intermediate contents of N and recalcitrant compounds, appears to best promote small macroaggregate formation. Carbon stabilized in small macroaggregates accounted for the tamarind treatment showing the largest SOC accumulation. Copyright © 2010 John Wiley & Sons, Ltd.     

秸秆颗粒化高量还田快速提高土壤有机碳含量及小麦玉米产量

针对黄淮海地区秸秆还田难度大不利于土壤快速培肥的问题,探讨秸秆颗粒化高量还田快速提高土壤有机碳的可行性。采用2a的田间定位试验,设置秸秆不还田(CK)、秸秆颗粒12 000 kg/hm~2(KL1)、秸秆颗粒36 000 kg/hm~2(KL3)、粉碎秸秆12 000 kg/hm~2(FS1)、粉碎秸秆36 000 kg/hm~2(FS3)5种用量30～40 cm还田处理,研究了颗粒化秸秆高、低量还田对土壤有机碳、养分元素比例平衡以及小麦-玉米产量的影响。结果表明,秸秆还田2a内对20～40、40～60 cm土层有机碳含量影响显著,其中FS1提升幅度最低,分别为7.2%(20～40cm)、5.9%(40～60cm),KL3提升幅度最高,分别为12.3%(20～40 cm)、11.1%(40～60 cm)。与粉碎还田相比,秸秆颗粒化还田能在还田1a显著提高土壤有机碳含量,KL3较FS320～40、40～60 cm土壤有机碳分别提高1.7%、1.3%,KL1较FS120～40、40～60 cm分别提高0.8%、0.7%。另外,高量还田具有大幅提高有机碳的优势,FS3较FS1分别提高20～40 cm土壤有机碳1.7%～3.9%、40～60 cm土层有机碳0.7%～3.8%,KL3较KL1分别提高20～40 cm有机碳2.4%～4.7%、40～60 cm土层1.3%～5.1%。秸秆颗粒高量还田(KL3)在各生长季均具有较高的有机碳累积速率,且总体均值最高。秸秆颗粒化高量还田能在一定程度上提高土壤碳氮比(RCN)、碳磷比(RCP)、碳钾比(RCK),促使土壤养分比向高肥力方向转化。该试验中秸秆颗粒化高量还田连续4个生长季增产4.57%、11.40%、10.87%、8.87%,增产效果显著。综上可见,秸秆颗粒36000kg/hm~2深埋还田最有利于黄淮海地区土壤有机碳的提高,在解决土壤"碳饥饿"等问题、保障农业可持续发展上具有重要意义。     

绿洲灌区小麦免耕秸秆还田对后作玉米产量性能指标的影响

产量性能是决定作物生长发育和产量形成的关键因素,研究前茬秸秆处理方式对后茬作物产量性能指标的影响,对于建立高效种植制度、优化栽培措施具有重要指导意义。2009—2012年,在甘肃河西绿洲灌区,通过田间定位试验,研究了前茬小麦不同秸秆还田和耕作措施(NTSS:25 cm高茬收割立茬免耕;NTS:25 cm高茬等量秸秆覆盖免耕;TIS:25 cm高茬等量秸秆翻耕;CT:不留茬翻耕对照)对后作玉米产量性能指标的影响,以期为优化试区玉米种植模式提供依据。结果表明,与CT相比,前茬小麦秸秆还田降低了后作玉米大喇叭口期之前的叶面积指数(LAI)与光合势(LAD),但增大了吐丝期之后的LAI与LAD,延缓了衰老,以NTSS、NTS延缓衰老作用突出;NTSS、NTS和TIS处理玉米全生育期的平均叶面积指数(MLAI)比CT分别提高12.8%、19.1%和7.0%,总光合势分别提高12.9%、18.6%和6.8%,免耕秸秆还田(NTSS和NTS)提高MLAI和LAD的效果最好。免耕秸秆还田提高了玉米全生育期的平均净同化率(MNAR),以NTSS提高作用明显,较CT高10.7%;但净同化率(NAR)表现为吐丝期之前增大,吐丝期之后降低。NTSS、NTS提高了后作玉米的籽粒产量,比CT分别高13.0%、15.6%,TIS比CT提高7.9%,NTS增产效应最大。不同秸秆还田及耕作方式下,玉米籽粒产量与MLAI、穗数(EN)、穗粒数(KNE)呈极显著正相关性,与收获指数(HI)呈显著正相关性,但与MNAR无显著相关性。MLAI、EN、KNE增加、HI提高是前茬小麦免耕秸秆还田提高后作玉米产量的主要原因。前茬秸秆免耕还田优化后茬玉米主要产量性能指标的效果最好。因此,前茬小麦25 cm秸秆覆盖免耕还田是绿洲灌区优化后作玉米产量性能指标及获得高产的可行栽培措施。     

Long‐term cropping systems and tillage management effects on soil organic carbon stock and steady state level of C sequestration rates in a semiarid environment

A calcareous and clayey xeric Chromic Haploxerept of a long‐term experimental site in Sicily (Italy) was sampled (0–15 cm depth) under different land use management and cropping systems (CSs) to study their effect on soil aggregate stability and organic carbon (SOC). The experimental site had three tillage managements (no till [NT], dual‐layer [DL] and conventional tillage [CT]) and two CSs (durum wheat monocropping [W] and durum wheat/faba bean rotation [WB]). The annually sequestered SOC with W was 2·75‐times higher than with WB. SOC concentrations were also higher. Both NT and CT management systems were the most effective in SOC sequestration whereas with DL system no C was sequestered. The differences in SOC concentrations between NT and CT were surprisingly small. Cumulative C input of all cropping and tillage systems and the annually sequestered SOC indicated that a steady state occurred at a sequestration rate of 7·4 Mg C ha⁻¹ y⁻¹. Independent of the CSs, most of the SOC was stored in the silt and clay fraction. This fraction had a high N content which is typical for organic matter interacting with minerals. Macroaggregates (>250 µm) and large microaggregates (75–250 µm) were influenced by the treatments whereas the finest fractions were not. DL reduced the SOC in macroaggregates while NT and CT gave rise to higher SOC contents. In Mediterranean areas with Vertisols, agricultural strategies aimed at increasing the SOC contents should probably consider enhancing the proportion of coarser soil fractions so that, in the short‐term, organic C can be accumulated. Copyright © 2010 John Wiley & Sons, Ltd.     

长期施肥土壤不同粒径颗粒的固碳效率

【目的】探讨不同施肥措施土壤有机碳在不同粒级颗粒中的分配及变化情况,可揭示各级颗粒中有机碳与外源有机碳输入之间的定量关系。【方法】依托南方红壤连续20年长期定位施肥试验,依据外源有机碳累积输入梯度选择不施肥(CK)、氮磷钾化肥配施(NPK)、氮磷钾化肥与秸秆配施(NPKS)、轮作条件下氮磷钾化肥与有机肥配施(NPKMR)、氮磷钾化肥与有机肥配施(NPKM)、单施有机肥(M)、增量氮磷钾化肥与增量有机肥配施(1.5NPKM)7个处理,并采用物理分组方法将土壤颗粒分为砂粒(53~2000μm)、粗粉粒(5~53μm)、细粉粒(2~5μm)和粘粒(2μm)4个组分。【结果】与不施肥相比,长期施肥均能显著增加土壤总有机碳及各级颗粒中的有机碳的储量,其中以施用有机肥的效果最明显。不同施肥处理各级颗粒中以粘粒的有机碳储量最高,平均为16.26 t/hm~2。施用有机肥和秸秆还田均能显著增加砂粒中有机碳的分配比例,降低粘粒有机碳的分配比例而对粗粉粒和细粉粒无显著影响。土壤砂粒所占的质量百分比及其与粗粉粒、细粉粒和粘粒的比值均与粗粉粒、细粉粒和粘粒组分中有机碳的浓度呈显著正相关关系表明小颗粒(粗粉粒、细粉粒和粘粒)中有机碳的固持和富集促进了大颗粒(砂粒)的形成与稳定。各级颗粒之间,施用有机肥处理的土壤粘粒组分的固碳速率最快,为0.29~0.52 t/(hm~2·a),其次为砂粒[0.30~0.40 t/(hm~2·a)]而粗粉粒和细粉粒的固碳速率基本相当为0.09~0.16t/(hm~2·a)。分析结果还表明土壤总有机碳及各级颗粒有机碳与外源有机碳的输入呈显著正线性相关关系,其中土壤总固碳效率为10.57%而各级颗粒之间,粘粒和砂粒组分的固碳效率(4.25%和3.60%)相当于粗粉粒和细粉粒(1.73%和1.00%)的2倍以上。【结论】南方红壤各级颗粒中有机碳均没有出现饱和现象,有机碳主要在土壤粘粒和砂粒组分中富集,细颗粒中有机碳的富集会促进大粒径土壤颗粒的形成而粘粒是土壤固碳效率最重要的矿物颗粒组成部分。表明长期配施有机肥不仅是红壤有机质提升的重要措施,也是改善红壤结构的重要途径。     

菜地土壤有机碳分级以及总量变化的动态特征研究

Fertilisers significantly affect crop production and crop biomass inputs to soil organic carbon（SOC）. However, the long-term effects of fertilisers on C associated with aggregates are not yet fully understood. Based on soil aggregate and SOC fractionation analysis, this study investigated the long-term effects of organic manure and inorganic fertilisers on the accumulation and change in SOC and its fractions, including the C concentrations of free light fraction, intra-aggregate particulate organic matter（POM） and intra-aggregate mineral-associated organic matter（MOM）. Long-term manure applications improved SOC and increased the concentrations of some C fractions. Manure also accelerated the decomposition of coarse POM（cPOM） into fine POM（fPOM） and facilitated the transformation of fPOM encrustation into intra-microaggregate POM within macroaggregates. However, the application of inorganic fertilisers was detrimental to the formation of fPOM and to the subsequent encrustation of fPOM with clay particles, thus inhibiting the formation of stable microaggregates within macroaggregates. No significant differences were observed among the inorganic fertiliser treatments in terms of C concentrations of MOM, intra-microaggregate MOM within macroaggregate（imMMOM） and intra-microaggregate MOM（imMOM）. However, the long-term application of manure resulted in large increases in C concentrations of MOM（36.35%）, imMMOM（456.31%） and imMOM（19.33%） compared with control treatment.     

Tillage effects on soil aggregation,organic carbon fractions and grain yield in Eum‐Orthic Anthrosol of a winter wheat–maize double‐cropping system,Northwest China

Conservation tillage has been applied in vast semi‐arid regions of the Guanzhong Plain, Northwest China. The tillage effects on soil aggregation, organic carbon (OC) stabilization and grain yield on this plain have not been fully elucidated. A 9‐year field experiment was established from 2002 on a silty clay loam soil (Eum‐Orthic Anthrosol) growing winter wheat–maize in a double‐cropping system. Six conservation tillage treatments were applied by different combinations of rotary tillage (RT), subsoiling (SS) and no‐till (NT), with or without finely chopped straw retention. Conventional tillage (CT) acted as the control. Results showed that in the surface (0–10 cm) soil, the proportion of water‐stable aggregates (WSA) <0.05 mm was 18% less while that for WSA >2 mm was 98% more under NT treatments compared with CT. Additionally, the oxidizable OC content in WSA 0.25–2 mm was 27% greater under NT treatments compared with CT. The OC stocks increased under SS by 17%, RT by 16% and NT by 15% relative to CT. Grain yield (wheat + maize) showed similar increasing trends in all the tillage treatments compared with CT. Both OC stocks and grain yield were larger in treatments with than without straw retentions. These results indicate that NT is beneficial for OC accumulation in WSA but is limited in its ability to improve soil structure in this region. SS plus straw retention (fine‐chopped or as a mulch) is an effective practice to improve soil structural stability, OC accumulation and soil productivity of Eum‐Orthic Anthrosols in Northwest China.     

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。     

Long‐term non‐flooded mulching cultivation influences rice productivity and soil organic carbon

A field experiment was conducted for 10 years to examine the long‐term effects of non‐flooded mulching cultivation on rice yield and soil organic carbon on Chengdu Plain, south‐west China. Compared with traditional flooded cultivation (TF), non‐flooded plastic film mulching (PM) resulted in a 14% higher average rice (Oryza sativa L.) yield. However, non‐flooded straw mulching (SM) decreased the average rice yield by 11% compared with TF. After 10 years, PM led to similar or higher (SM) soil organic carbon (SOC) and total soil N (TN) in the top 5 cm of the soil profile compared with TF. No differences were found among the three cultivation systems in SOC or total N at 5–12 and 12–24 cm soil depths. Small macroaggregates (0.25–2 mm) were predominant in the top 5 cm of the soil (58–63% of whole soil) across the three cultivation systems. However, the proportion of large macroaggregates (>2 mm) from SM and PM was significantly larger than from TF in the top 5 cm of the soil. Non‐flooded mulching cultivation led to increased C and N contents in large macroaggregates and mean weight diameter of aggregates in the 0–5 cm soil depth. This suggests that non‐flooded mulching cultivation increased soil aggregation concomitant with soil C stabilization within the improved soil structure.     

生物炭及秸秆长期施用对紫色土坡耕地土壤团聚体有机碳的影响

依托紫色土坡耕地长期施肥试验观测平台,研究生物炭、秸秆对紫色土坡耕地团聚体有机碳分布的影响。长期施肥试验处理包括不施肥(CK)、无机氮磷钾肥(NPK)、秸秆还田(RSD)、生物炭与无机氮磷钾配施(BCNPK)、秸秆与无机氮磷钾配施(RSDNPK)。利用湿筛法,进行土壤团聚体粒径分组,随后测定各粒径团聚体含量及其有机碳含量,并计算团聚体平均质量直径(MWD)和几何平均直径(GMD)。结果表明,RSD、RSDNPK和BCNPK处理的表层SOC含量比CK处理增加43.1%～90.5%,SOC储量提高65.1%～74.3%,其中RSDNPK处理、BCNPK处理较NPK处理SOC显著增加25.2%～33.1%(P0.05), SOC储量显著提高23.2%～30.0%(P0.05)。团聚体MWD和GMD均为RSD处理RSDNPK处理BCNPK处理NPK处理CK处理; RSD处理0.25～2 mm的团聚体含量高达45.5%,较CK处理提高57.7%;秸秆和生物炭配施处理(RSDNPK处理和BCNPK处理)0.25～2mm的团聚体含量为41.3%～45.7%,而0.053mm粒径团聚体含量却降低54.1%～55.4%。NPK处理、RSD处理与CK处理的增长趋势相似,呈随团聚体粒径减小,团聚体有机碳含量先增大后减小,继而再增大的趋势;而RSDNPK、BCNPK处理则呈随粒径减小团聚体有机碳含量增加的趋势。生物炭和秸秆的施用能显著提升土壤有机碳含量,增强土壤结构稳定性,但生物碳的施用对提升土壤有机碳含量效果优于秸秆的施用,秸秆的施用对稳定土壤结构效果更优,因此生物炭和秸秆的施用可作为紫色土耕地土壤肥力维持和提升的有效管理措施。     

不同施肥措施对旱地采煤塌陷区复垦土壤结构及玉米品质的影响

研究不同施肥措施对复垦土壤结构及玉米品质的影响,以期深入理解采煤塌陷区复垦土壤有机碳固持机制。采集复垦1年的定位试验各处理耕层(0—20 cm)土样以及玉米籽粒,分析土壤水稳性团聚体(>2,0.25~2,0.053~0.25 mm)及粉黏粒组分(<0.053 mm)中有机碳(SOC)及全氮(TN)含量、玉米籽粒蛋白质、淀粉和脂肪含量的变化。试验设不施肥(CK)、施化肥(NPK)、单施有机肥(M)和有机无机肥配施(MNPK)4个处理。结果表明,同CK相比,NPK处理显著提高TN含量、玉米籽粒产量、淀粉和脂肪含量,增幅分别为11.23%,98.53%,1.16%和12.71%;M处理显著提高SOC、TN、>2 mm和0.25~2 mm团聚体中有机碳含量、籽粒产量、蛋白质、淀粉和脂肪含量,增幅分别为44.77%,13.23%,52.73%,60.22%,255.15%,23.28%,1.67%和12.71%;MNPK处理显著提高SOC、TN、各粒径团聚体及粉黏粒组分中SOC和TN含量(除0.25~2 mm团聚体中TN含量)、玉米籽粒产量、蛋白质、淀粉和脂肪含量,增幅分别为46.21%,29.08%,39.23%(>2 mm-C),49.07%(0.25~2 mm-C),110.41%(0.053~0.25 mm-C),40.35%(<0.053 mm-C),22.48%(>2 mm-N),43.29%(0.053~0.25 mm-N),33.33%(<0.053 mm-N),211.37%,35.34%,0.48%和25.18%。表明当养分投入量相同时,有机无机肥配施(MNPK)有利于采煤塌陷区复垦土壤团聚体对有机碳的物理保护,增加土壤有机碳累积,提升土壤肥力,提高作物产量,改善作物品质。     

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。     

麦茬管理对夏玉米幼苗生长及产量的影响

试验研究麦茬在不同处理条件下(烧茬、低茬、低茬覆盖和高茬覆盖)对夏玉米“农大108”幼苗生长及产量的影响结果表明,麦秸覆盖促进玉米幼苗根系发育,但焚烧麦茬对其产生抑制。幼苗前期麦秸覆盖对株高的影响不明显,而后期明显促进,但株高受留茬高度的影响最大,焚烧麦秸抑制了株高生长。幼苗(23d龄内)新展叶叶绿素含量均以烧茬处理最高、高茬覆盖处理最低,出苗23d后麦秸覆盖玉米叶片叶绿素含量显著提高,低茬覆盖尤为显著。高茬覆盖、低茬和烧茬籽粒产量差异不明显,低茬覆盖籽粒产量最高(10.68t/hm~2),比其他处理提高9.65％,差异显著。麦秸覆盖尤其是低茬覆盖夏玉米生物量大、抗倒伏、穗粒重高、农事操作方便,有较大推广价值。