,1,*, 李勇,1,*Effect of annual straw return model on soil carbon sequestration and crop yields in winter wheat-summer maize rotation farmland
LI Hao-Yu1, MENG Zhao-Liang1, PANG Dang-Wei2, CHEN Jin2, HOU Yong-Kun1, CUI Hai-Xing1, JIN Min1, WANG Zhen-Lin,1,*, LI Yong,1,*通讯作者:
收稿日期:2018-10-21接受日期:2019-01-19网络出版日期:2019-02-27
| 基金资助: |
Received:2018-10-21Accepted:2019-01-19Online:2019-02-27
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李昊昱, 孟兆良, 庞党伟, 陈金, 侯永坤, 崔海兴, 金敏, 王振林, 李勇. 周年秸秆还田对农田土壤固碳及冬小麦-夏玉米产量的影响[J]. 作物学报, 2019, 45(6): 893-903. doi:10.3724/SP.J.1006.2019.81078
LI Hao-Yu, MENG Zhao-Liang, PANG Dang-Wei, CHEN Jin, HOU Yong-Kun, CUI Hai-Xing, JIN Min, WANG Zhen-Lin, LI Yong.
农田土壤碳库约占陆地土壤碳库的8%~10%, 对农艺管理措施响应敏感[1], 促进农田土壤固碳对土质提升与作物增产有重要意义[2]。土壤团聚体的团聚作用被认为是有机碳固定的核心机制[3], 其稳定性与有机碳的长期固存密切相关[4]。秸秆还田是农田碳输入和驱动团聚体周转的重要因素[5]。因此, 研究秸秆还田对土壤团聚体及有机碳的影响对农田土壤固碳意义重大。
合理的秸秆还田能够改善土壤结构, 提高有机质含量, 促进大团聚体形成, 利于作物增产[6]。秸秆双季还田配施适量氮肥能够有效降低土壤容重, 增加总孔隙度, 是改良砂姜黑土的有效措施[7]; Zhao等[8]认为双季全量还田能够显著改善土壤结构, 提高土壤有机碳含量及周年产量, 单季还田则能够维持土壤有机碳初始水平; 在莱阳潮土区, 麦玉双季还田处理下作物籽粒品质优于小麦单季还田[9]; 同时, 许菁等[10]发现, 深松+秸秆还田能够显著增强小麦玉米光合能力, 提高单季和周年产量。然而, 也有研究表明秸秆还田对土壤团聚体和作物产量产生负面影响[11]。因此, 秸秆还田的效应与特定生态区、还田量、耕作方式及施氮量等配套农艺措施密切相关。
随着作物单产的提高以及秸秆综合利用技术的发展, 选择适宜的周年秸秆还田模式对于兼顾土质提升和秸秆资源的充分利用有重要意义。前人对黄淮海东部地区小麦玉米周年生产中秸秆还田技术的研究多集中于双季秸秆还田; 单季秸秆还田对土壤肥力、作物生产的影响仍需深入。此外, 大部分研究侧重于秸秆还田对耕层(0~20 cm)土壤结构和养分的影响, 较少关注更深层土壤碳库变化; 同时, 研究与该区常用耕作方式相结合的周年还田模式更具有现实推广意义。本试验分析不同周年秸秆还田模式对土壤容重、团聚体组成与稳定性、团聚体有机碳含量、土壤固碳能力以及小麦-玉米周年产量的影响, 旨在为现有耕作制度下提升土壤生产潜力和优化配套区域秸秆还田模式提供理论依据与技术支撑。
1 材料与方法
1.1 试验点概况
山东农业大学试验站(山东泰安, 36°09°N, 117°09°E)属于温带半湿润大陆性气候, 年平均气温13℃, 年平均降雨量697 mm, 是典型的冬小麦-夏玉米一年两熟区。试验开始前耕层(0~20 cm)土壤含有机质14.37 g kg-1、全氮1.24 g kg-1、速效磷9.60 mg kg-1、速效钾85.30 mg kg-1、硝态氮12.79 mg kg-1、铵态氮6.06 mg kg-1, pH 8.06。1.2 试验材料与设计
定位试验中设置双季秸秆不还田(NS)、夏玉米季秸秆还田(SS)、冬小麦季秸秆还田(WS)、双季秸秆还田(DS) 4个处理。采取随机区组设计, 3次重复, 小区面积为9 m × 3 m = 27 m2。田间操作见表1。Table 1
表1
表1试验设计
Table 1
| 代码 Code | 处理 Treatment | 田间操作 Field operation |
|---|---|---|
| NS | 秸秆双季不还田 No straw incorporation | 玉米、小麦秸秆全量移除。 All maize and wheat straws are removed. |
| SS | 夏玉米季秸秆还田 Summer maize-season straw incorporation | 玉米秸秆全量移除; 小麦秸秆经灭茬机粉碎后(约5~10 cm), 免耕覆盖还田。 Maize straws are removed fully. wheat straws are smashed (5-10 cm) and returned with no-tillage. |
| WS | 冬小麦季秸秆还田 Winter wheat-season straw incorporation | 玉米秸秆经灭茬机粉碎后(约5~10 cm), 旋耕还田; 小麦秸秆全量移除。 Maize straws are smashed (5-10 cm) and returned with rotary tillage. All wheat straws are removed. |
| DS | 秸秆双季还田 Double-season straw incorporation | 秸秆经灭茬机粉碎后(约5~10 cm), 玉米秸秆旋耕还田, 小麦秸秆免耕覆盖还田 All straws are smashed (5-10 cm); Maize straw was returned with rotary tillage and wheat straw with no-tillage. |
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供试冬小麦品种为济麦22, 种植密度为2.25×106 株 hm-2, 行距25 cm。于2016年10月9日、2017年10月8日播种(按照种植密度×130%播种), 三叶期查苗、定苗(根据种植密度要求, 每平方米留苗225株, 去弱留强)。各处理施肥量均为纯氮225 kg hm-2, 耕地时施入50%氮肥(尿素)、105 kg hm-2 P2O5 (过磷酸钙)和105 kg hm-2 K2O (氯化钾), 其余氮肥于拔节期开沟追施。供试夏玉米品种为郑单958, 种植密度为6.75×104株hm-2。于2017年6月11日、2018年6月9日播种, 各处理施肥量均为纯氮180 kg hm-2、120 kg hm-2 P2O5 (过磷酸钙)和96 kg hm-2 K2O (氯化钾), 50%氮肥和全部磷、钾肥于播种前施入, 其余氮肥于大喇叭口期追施。耕作方式为冬小麦季旋耕(10~12 cm), 夏玉米季免耕。其他管理措施同高产田。还田秸秆均为上季作物残茬 (表2)。
Table 2
表2
表2两年还田秸秆总量与性质
Table 2
| 秸秆类型 Straw type | 地上部秸秆还田量 The rate of straw returned to the field (kg hm-2) | 全氮 Total N (g kg-1) | 有机碳 Organic carbon (g kg-1) | 碳氮比 C/N |
|---|---|---|---|---|
| 小麦秸秆 Wheat straw | 22000 | 4.75 | 313.44 | 66.04 |
| 玉米秸秆 Maize straw | 16000 | 7.57 | 363.77 | 48.05 |
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1.3 样品采集
1.3.1 土壤容重样品采集 于2017年9月25日和2018年9月20日采集土壤容重样品, 从各小区随机选取5个点, 采用环刀法每10 cm一层, 测定0~40 cm土层容重。1.3.2 土壤团聚体样品采集 于2017年9月25日和2018年9月20日从各小区随机选取5个点, 使用分离式土壤原状土取样器(AWS-ETC-300E, 美国)采集具有代表性的原状耕层土壤(避免外力挤压, 以保持原来的结构状态), 分0~10 cm、10~20 cm、20~30 cm、30~40 cm 4个层次。运回室内(运输时避免震动和翻倒), 沿土壤的自然结构轻轻拨开, 将原状土剥成小土块, 防止外力作用而变形, 去除秸秆、根系残体与小石块, 于通风处自然风干。
1.3.3 土壤样品采集 于2017年9月25日和2018年9月20日从各小区随机选取5个点, 分别用土钻采集0~10 cm、10~20 cm、20~30 cm、30~40 cm土层土壤, 充分混合后, 经风干, 磨碎, 过60目筛, 测定土壤有机碳含量。
1.4 样品分析及方法
1.4.1 土壤团聚体分析 采用改进的湿筛法测定土壤团聚体含量, 取各处理50.0 g土样, 用于湿筛的分析, 采用土壤团聚体分析仪(TTF-100, 浙江舜龙), 一次可同时分析4个土样, 套筛孔径依次为5、2、1、0.5和0.25 mm。将土样倒入套筛中, 在水中稳定10 min, 然后按20次 min-1的频率上下振动3 min (上下筛动时套筛不能露出水面)。筛分结束后, 将留在筛子上的各级团聚体用去离子水流通过漏斗分别洗入铝盒, 澄清后倒去上清液, 40℃烘干至恒重, 在空气中平衡2 h后称量。磨碎过60目筛, 测定各粒级土壤团聚体有机碳含量。1.4.2 土壤有机碳含量测定 采用重铬酸钾-外加热法测定土壤有机碳含量。
1.4.3 产量相关性状测定 冬小麦成熟期在各小区内选取长势均匀一致的区域, 收获2.0 m×6行(共计3 m2, 不包括边行), 采用QKT-320A型小型种子脱粒机(河南省卫辉市种子机械制造厂)脱粒, 风干后调整含水量至12%测定籽粒产量。夏玉米成熟期在每个小区去除边行后, 随机收获双行玉米中的连续30穗, 人工脱粒, 风干后调整含水量至14%测定籽粒产量。
1.4.4 样品分析与计算公式
(1) 土壤不同粒级团聚体的质量百分比:
${{w}_{i}}=\frac{{{W}_{i}}}{50}\times 100$
式中, wi代表第i级团聚体的质量分数(%); Wi代表第i级团聚体的风干质量(g)。
(2) 土壤大团聚体数量:
${{R}_{0.25}}=\frac{{{W}_{i}}>0.25}{50}\times 100$
式中, R0.25代表大团聚体(>0.25 mm)数量(%), Wi>0.25代表>0.25 mm团聚体的重量。
(3) 平均重量直径(MWD):
$\text{MWD}=\frac{\sum\nolimits_{i=1}^{n}{\left( {{x}_{i}}\times {{w}_{i}} \right)}}{\sum\nolimits_{i-1}^{n}{{{w}_{i}}}}$
式中, xi为第i级团聚体的平均直径(mm), wi为第i级团聚体的质量比例(%)。
(4) 土壤有机碳储量:
$\text{SCS}=\frac{\text{SOC}\times \text{SBD}\times \text{H}}{10}$
式中, SCS代表土壤有机碳储量(t C hm-2); SOC代表土壤有机碳含量(g kg-1); SBD代表土壤容重(g cm-3); H代表土层深度(cm)。
(5) 土壤不同粒级团聚体的固碳能力:
CPCi = SSACi×wi
式中, CPCi代表第i级土壤团聚体固碳能力; SSACi代表第i级团聚体中土壤有机碳含量(g kg-1); wi代表第i级团聚体的质量分数(%)。
1.5 统计分析
对2018年样品进行分析, 采用Microsoft Excel2016整理数据, 用DPS 7.05进行统计方差分析, 用 LSD 法进行多重比较, 采用 SigmaPlot 12.5绘图。
2 结果与分析
2.1 土壤容重与团聚体分布
在0~40 cm土层中, 随土层加深, 容重增加, 大团聚体质量比例减少(表3)。与秸秆不还田相比, 各秸秆还田处理均不同程度降低了0~30 cm各土层的土壤容重, SS、WS和DS处理分别平均降低4.8%、2.7%和6.1%; 大团聚体质量比例平均分别提高12.8%、15.0%和12.9%, 说明秸秆还田能够有效地改善土壤结构。3种还田模式中, DS处理对容重的降低效果最显著。Table 3
表3
表3不同秸秆还田模式对0~40 cm土壤容重、团聚体分布及稳定性的影响
Table 3
| 处理 Treatment | 容重 SBD (g cm-3) | 大团聚体 质量比例 R0.25 (%) | 各粒级团聚体质量比例 Soil aggregate proportion (%) | 平均重量直径 MWD (mm) | |||||
|---|---|---|---|---|---|---|---|---|---|
| >5 mm | 5-2 mm | 2-1 mm | 1.0-0.5 mm | 0.05-0.25 mm | <0.25 mm | ||||
| 0-10 cm | |||||||||
| NS | 1.41 a | 73.50 b | 3.99 a | 15.43 a | 13.63 a | 20.54 a | 19.91 a | 26.50 a | 1.24 b |
| SS | 1.32 b | 81.95 a | 8.71 a | 16.39 a | 15.32 a | 25.43 a | 16.10 a | 18.05 b | 1.54 a |
| WS | 1.35 ab | 82.21 a | 6.37 a | 17.41 a | 13.10 a | 25.95 a | 19.37 a | 17.79 b | 1.44 ab |
| DS | 1.30 b | 84.55 a | 8.97 a | 17.19 a | 13.92 a | 25.88 a | 18.59 a | 15.45 b | 1.56 a |
| 10-20 cm | |||||||||
| NS | 1.49 a | 74.82 b | 3.13 a | 17.22 a | 15.13 a | 23.69 a | 15.66 a | 25.18 a | 1.29 b |
| SS | 1.42 ab | 80.29 b | 3.32 a | 16.52 a | 17.07 a | 28.32 a | 15.06 a | 19.71 a | 1.32 b |
| WS | 1.47 ab | 89.45 a | 5.82 a | 18.13 a | 21.13 a | 28.82 a | 15.56 a | 10.55 b | 1.54 ab |
| DS | 1.39 b | 88.49 a | 8.44 a | 24.63 a | 20.30 a | 25.19 a | 9.92 a | 11.51 b | 1.84 a |
| 20-30 cm | |||||||||
| NS | 1.51 a | 70.83 c | 3.25 a | 9.96 c | 11.73 b | 23.11 a | 22.80 a | 29.18 a | 1.02 b |
| SS | 1.46 ab | 75.14 bc | 3.42 a | 11.62 bc | 17.62 ab | 22.58 a | 19.90 a | 24.87 ab | 1.15 ab |
| WS | 1.50 ab | 80.40 ab | 1.56 a | 17.59 ab | 12.77 ab | 29.82 a | 18.66 a | 19.60 bc | 1.23 ab |
| DS | 1.44 b | 84.40 a | 2.25 a | 20.21 a | 20.38 a | 26.99 a | 14.57 a | 15.60 c | 1.42 a |
| 30-40 cm | |||||||||
| NS | 1.51 a | 76.84 a | 1.03 a | 5.69 a | 10.80 a | 38.60 a | 20.73 a | 23.16 a | 0.84 a |
| SS | 1.46 a | 72.64 a | 0.32 a | 3.29 a | 8.49 a | 38.49 a | 22.05 a | 27.36 a | 0.70 a |
| WS | 1.51 a | 72.42 a | 0.63 a | 4.83 a | 15.21 a | 31.47 a | 20.28 a | 27.58 a | 0.81 a |
| DS | 1.46 a | 71.31 a | 0.24 a | 2.70 a | 10.05 a | 26.12 a | 32.21 a | 28.69 a | 0.65 a |
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不同粒级团聚体分布如表3所示, 在0~40 cm各土层中, 1.0~0.5 mm粒级团聚体质量比例分别为24.5%、26.5%、25.6%和33.7%, 是土壤团聚体的优势粒级; 在0~10 cm土层中, 秸秆还田主要通过提高>5 mm、1.0~0.5 mm粒级团聚体质量比例来提高R0.25, 各处理平均提升100.8%和25.5%; 在10~20和20~30 cm土层中, R0.25的提升主要是由于5~2 mm (14.7%和64.5%)和1.0~0.5 mm (15.8%和14.6%)粒级团聚体的提升。所有土层中, 均以DS处理大团聚体提升幅度最大。同时, 与不还田处理相比, 各秸秆还田处理显著降低了0~30 cm各土层微团聚体质量比例, 平均分别降低35.5%、44.7%和31.5%。在30~40 cm各土层中, R0.25以及各团聚体分布处理间差异不显著。平均重量直径(MWD)是评价土壤团聚体稳定性的重要指标, 在0~10 cm、10~20 cm和20~30 cm土层中, 秸秆还田处理的MWD值显著高于无秸秆还田处理, 说明秸秆还田提高了土壤团聚体的稳定性。其中, DS处理提升效果最显著。在30~40 cm土层中, 各处理间无显著性差异, 说明秸秆还田对该土层土壤团聚体结构影响较小。
2.2 土壤总有机碳含量和储量
不同秸秆还田模式均显著提高了0~30 cm各土层中有机碳含量(SOC)(图1)。与NS相比, DS提升幅度最大, 增幅为16.3%~20.8%; 各秸秆还田处理SOC在不同土层表现出不同趋势, 在0~10 cm土层表现为DS>SS>WS>NS; 而在10~30 cm土层中则表现为DS>WS>SS>NS。30~40 cm土层中, 各处理间SOC含量无显著性差异。从不同土壤层次来看, 秸秆还田处理下0~10 cm和10~20 cm土层中有机碳含量显著高于20~30 cm和30~40 cm土层, 说明秸秆还田主要促进表层有机碳积累。图1
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NS: 秸秆不还田; SS: 夏玉米季秸秆还田; WS: 冬小麦季秸秆还田; DS: 秸秆双季还田; SOC: 土壤有机碳含量; SCS: 土壤有机碳储量。
Fig. 1Effects of straw incorporation on SOC and SCS in 0-40 cm layers
NS: no straw incorporation; SS: summer maize-season straw incorporation; WS: winter wheat-season straw incorporation; DS: double-season straw incorporation; SOC: soil organic carbon content; SCS: soil carbon stock.
不同处理下土壤有机碳储量(SCS)表现为10~20 cm>0~10 cm>20~30 cm>30~40 cm。0~20 cm土层中SCS占0~40 cm土层SCS的63.6%, 表现出“上富下贫”的规律。与不还田相比, 各秸秆还田处理均显著提高了0~30 cm各土层中有机碳储量, 以DS处理最为显著, 分别提升6.6%、12.5%和14.6%。
2.3 团聚体有机碳含量
由表4可以看出, 0~40 cm各土层中有机碳含量均随团聚体粒级的减小逐渐减少。10~20 cm土层中各粒级团聚体有机碳含量最高, 其他土层依次为0~10 cm、20~30 cm和30~40 cm, 与SOC、SCS规律表现一致。与秸秆不还田处理相比, 各秸秆还田处理对所有粒级团聚体中有机碳含量均有不同程度的提高; 各处理效果总体表现为DS>WS>SS, DS处理下各粒级团聚体SOC平均分别提高12.5%、18.2%、16.4%、13.9%、12.4%和10.7%。Table 4
表4
表4不同秸秆还田模式对0~40 cm土层中各粒级团聚体关联有机碳含量的影响
Table 4
| 土层深度 Soil depth | 处理 Treatment | 不同粒级团聚体有机碳含量 Aggregate-associated SOC (g kg-1) | |||||
|---|---|---|---|---|---|---|---|
| >5 mm | 5-2 mm | 2-1 mm | 1.0-0.5 mm | 0.50-0.25 mm | <0.25 mm | ||
| 0-10 cm | NS | 6.30 a | 5.92 b | 5.88 b | 5.55 a | 5.53 a | 5.24 a |
| SS | 6.76 b | 6.54 ab | 6.24 ab | 5.89 a | 5.92 a | 5.43 a | |
| WS | 6.56 ab | 6.42 ab | 5.92 ab | 5.58 a | 5.61 a | 5.25 a | |
| DS | 6.87 a | 6.71 a | 6.41 a | 6.03 a | 5.93 a | 5.43 a | |
| 10-20 cm | NS | 7.05 a | 6.19 b | 6.10 b | 5.93 a | 5.73 a | 5.43 a |
| SS | 7.11 a | 6.59 ab | 6.44 ab | 6.13 a | 5.96 a | 5.67 a | |
| WS | 7.42 ab | 6.63 ab | 6.51 ab | 6.29 a | 5.96 a | 5.64 a | |
| DS | 7.77 a | 7.02 a | 6.92 a | 6.37 a | 5.95 a | 5.85 a | |
| 20-30 cm | NS | 4.92 c | 3.75 a | 3.72 c | 3.57 c | 3.34 b | 3.18 a |
| SS | 5.36 b | 4.64 a | 4.02 bc | 3.79 bc | 3.58 b | 3.20 a | |
| WS | 5.40 b | 4.71 a | 4.48 ab | 4.03 b | 3.94 ab | 4.09 a | |
| DS | 5.93 a | 4.01 a | 4.94 a | 4.74 a | 4.53 a | 4.05 a | |
| 30-40 cm | NS | — | 2.50 a | 2.30 b | 2.18 b | 2.07 a | 1.96 a |
| SS | — | 2.66 a | 2.61 ab | 2.27 b | 2.12 a | 1.87 a | |
| WS | — | 2.74 a | 2.80 ab | 2.71 a | 2.57 a | 2.51 a | |
| DS | — | 2.87 a | 2.93 a | 2.81 a | 2.38 a | 2.35 a | |
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2.4 土壤团聚体固碳能力
各土层土壤固碳能力为10~20 cm≈0~10 cm> 20~30 cm>30~40 cm (表5)。与不还田处理相比, 秸秆还田显著提高了0~30 cm各土层土壤总固碳能力, 平均分别提升7.2%、8.7%和21.4%。在0~10 cm土层, 秸秆还田主要提高了>5 mm和1.0~0.5 mm粒级土壤团聚体的固碳能力, 平均分别提高0.30 g kg-1和0.42 g kg-1; 其中DS处理效果最显著。在10~20 cm土层, 与不还田处理相比, >5 mm和5~2 mm粒级团聚体固碳能力显著提高, 平均分别提高0.24 g kg-1和0.39 g kg-1。在20~30 cm土层, 各秸秆还田处理则主要提高了5~2 mm、2~1 mm和1.0~0.5 mm粒级团聚体固碳能力, 平均分别提高0.43 g kg-1、0.34 g kg-1和0.30 g kg-1。但秸秆还田降低了0~30 cm土层中0.50~0.25 mm和<0.25 mm粒级团聚体固碳能力, 平均分别降低0.11 g kg-1和0.38 g kg-1。总体来看, DS处理下土壤固碳能力增幅最大, 说明双季秸秆还田最利于土壤有机碳的固定。Table 5
表5
表5不同秸秆还田模式对0~40 cm土层土壤固碳能力的影响
Table 5
| 土层深度 Soil depth | 处理 Treatment | 总固碳能力 TCPC (g kg-1) | 不同粒级团聚体固碳能力 Aggregate-associated CPC (g kg-1) | |||||
|---|---|---|---|---|---|---|---|---|
| >5 mm | 5-2 mm | 2-1 mm | 1-0.5 mm | 0.5-0.25 mm | <0.25 mm | |||
| 0-10 cm | NS | 5.60 b | 0.22 a | 0.95 a | 0.83 a | 1.10 b | 1.12 a | 1.37 a |
| SS | 6.07 a | 0.54 a | 1.10 a | 0.98 a | 1.53 a | 0.94 a | 0.98 ab | |
| WS | 5.79 ab | 0.42 a | 1.13 a | 0.75 a | 1.44 ab | 1.10 a | 0.96 b | |
| DS | 6.15 a | 0.61 a | 1.13 a | 0.89 a | 1.60 a | 1.07 a | 0.84 b | |
| 10-20 cm | NS | 5.87 c | 0.22 a | 0.95 b | 0.94 a | 1.50 a | 0.98 a | 1.28 a |
| SS | 6.17 b | 0.28 a | 1.05 ab | 1.03 a | 1.70 a | 0.98 a | 1.13 ab | |
| WS | 6.37 ab | 0.51 a | 1.31 ab | 0.47 a | 1.70 a | 0.82 a | 0.57 c | |
| DS | 6.61 a | 0.59 a | 1.66 a | 1.41 a | 1.63 a | 0.58 a | 0.74 bc | |
| 20-30 cm | NS | 3.51 c | 0.19 a | 0.35 b | 0.43 b | 0.82 b | 0.75 a | 0.97 a |
| SS | 3.82 c | 0.19 a | 0.55 ab | 0.76 ab | 0.84 b | 0.67 a | 0.82 a | |
| WS | 4.21 b | 0.08 a | 0.81 a | 0.54 b | 1.21 a | 0.77 a | 0.80 a | |
| DS | 4.73 a | 0.14 a | 0.99 a | 1.01 a | 1.30 a | 0.65 a | 0.64 a | |
| 30-40 cm | NS | 2.13 b | — | 0.14 a | 0.23 a | 0.87 a | 0.41 a | 0.48 a |
| SS | 2.17 b | — | 0.09 b | 0.22 a | 0.94 a | 0.46 a | 0.47 a | |
| WS | 2.59 a | — | 0.13 a | 0.40 a | 0.82 a | 0.57 a | 0.68 a | |
| DS | 2.57 a | — | 0.08 b | 0.33 a | 0.74 a | 0.73 a | 0.69 a | |
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2.5 秸秆还田量与SBD、SOC、SCS、MWD和CPC间的关系
作物地上部秸秆还田量(SIR)与0~30 cm土壤SOC、SCS、MWD和CPC之间显著正相关(表6), 表明地上部秸秆还田总量是促进SOC和SCS提高、团聚体稳定性和土壤固碳能力增强的主要因素之一, 与0~30 cm土层SBD呈显著负相关, 说明秸秆还田量对降低土壤容重有一定影响。土壤有机碳作为土壤团聚过程中的胶结剂, 其含量影响着土壤团聚体的稳定性。在0~10 cm、10~20 cm和20~30 cm土层中, SOC与MWD值呈显著正相关, 说明较高的SOC促进了团聚体稳定性的提高; 同时SOC与SBD呈显著负相关。SCS与SBD相关性不显著, 与SOC显著正相关, 说明SOC是决定SCS的主要因素。SOC、SCS和MWD均与0~30 cm土壤CPC呈显著正相关, 表明土壤固碳能力的提升与有机碳含量、储量的提高和团聚体稳定性的增强密不可分。Table 6
表6
表6作物地上部还田量与SBD、SOC、SCS、MWD和TCPC之间的相关系数
Table 6
| 土层深度 Soil depth | 指标 Indictor | 秸秆还田量 SIR | 土壤容重 SBD | 平均重量直径 MWD | 土壤有机碳含量 SOC | 土壤有机碳储量 SCS |
|---|---|---|---|---|---|---|
| 0-10 cm | SBD | -0.75* | ||||
| MWD | 0.81** | -0.63* | ||||
| SOC | 0.79* | -0.56** | 0.59* | |||
| SCS | 0.41 | -0.05 | 0.26 | 0.80* | ||
| TCPC | 0.75** | -0.93** | 0.66* | 0.61* | 0.05 | |
| 10-20 cm | SBD | -0.70** | ||||
| MWD | 0.72** | -0.49 | ||||
| SOC | 0.81** | -0.56* | 0.72** | |||
| SCS | 0.58* | -0.12 | 0.89** | 0.89* | ||
| TCPC | 0.82** | -0.26 | 0.69** | 0.80** | 0.80* | |
| 20-30 cm | SBD | -0.70* | ||||
| MWD | 0.83** | -0.53 | ||||
| SOC | 0.57* | -0.45** | 0.71* | |||
| SCS | 0.41* | -0.19 | 0.62* | 0.96** | ||
| TCPC | 0.85** | -0.58* | 0.87** | 0.79** | 0.69 | |
| 30-40 cm | SBD | -0.56 | ||||
| MWD | -0.77** | 0.35 | ||||
| SOC | -0.02 | 0.19 | 0.28 | |||
| SCS | 0.12 | 0.37 | 0.33 | 0.98** | ||
| TCPC | 0.59* | -0.13 | -0.25 | 0.23 | 0.20 |
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2.6 冬小麦-夏玉米产量
秸秆还田显著提高了冬小麦、夏玉米的籽粒产量(表7), 两年规律表现一致, 虽然2017—2018年小麦产量整体下降, 但秸秆还田对产量的提升作用依然显著。3种还田模式中, 以DS处理增产效果最为显著, 小麦、玉米两年平均每公顷增产1297.15 kg和1175.03 kg; 周年总产对秸秆还田响应显著, SS、WS、DS处理两年分别平均增产4.4%、8.1%和14.3%。SS主要提高了夏玉米产量, WS则主要提高了冬小麦籽粒产量, DS处理下小麦、玉米增产均衡, 说明秸秆还田主要影响当季作物的籽粒产量。Table 7
表7
表7不同秸秆还田模式对冬小麦和夏玉米产量的影响
Table 7
| 处理 Treatment | 冬小麦产量 Wheat yield (kg hm-2) | 夏玉米产量 Maize yield (kg hm-2) | 周年产量Annual yield (kg hm-2) | 周年增产 Yield increases of annual crop (kg hm-2) | 小麦增产 Yield increases of wheat (kg hm-2) | 增产比例 Ratio of yield increases (%) | 玉米增产 Yield increases of maize (kg hm-2) | 增产比例 Ratio of yield increases (%) |
|---|---|---|---|---|---|---|---|---|
| 2016-2017 | ||||||||
| NS | 8320.20 b | 9257.65 b | 17577.85 d | — | — | — | — | — |
| SS | 8610.80 b | 9975.31 ab | 18586.11 c | 1008.26c | 290.60 c | 28.8 | 717.66 b | 71.2 |
| WS | 9902.50 a | 9763.41 ab | 19665.91 b | 2088.06 b | 1582.30 b | 75.8 | 505.76 b | 24.2 |
| DS | 10340.80 a | 10491.05 a | 20831.85 a | 3254.00 a | 2020.60 a | 62.1 | 1233.40 a | 37.9 |
| 2017-2018 | ||||||||
| NS | 7186.20 b | 9505.57 c | 16691.77 c | — | — | — | — | — |
| SS | 7303.93 ab | 9897.48 b | 17201.41 bc | 509.64 b | 117.73 b | 23.1 | 391.91 b | 76.9 |
| WS | 7696.10 a | 9729.75 bc | 17425.85 b | 734.08 b | 509.90 ab | 69.5 | 224.18 b | 30.5 |
| DS | 7759.90 a | 10622.24 a | 18382.14 a | 1690.37 a | 573.70 a | 33.9 | 1116.67 a | 66.1 |
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3 讨论
3.1 秸秆还田对土壤容重和团聚体分布的影响
土壤容重是土壤重要的物理性质之一, 能够有效调节土壤水肥热状况[12]。多数研究表明, 秸秆还田对降低土壤容重起积极作用[13], 本试验结果与前人研究一致(表3)。究其原因, 可能由于秸秆具有密度低的特点, 还田后对土壤起到一种“稀释作用”, 从而降低单位体积土壤的质量[14]。土壤团聚体是由矿物颗粒和有机物形成的不同尺度的多孔结构单元[15], 良好的土壤结构是作物高产的基础。Foute等[16]研究表明, 大量的秸秆输入是大团聚体比例和团聚体稳定性提高的主要原因。本研究结果表明, 与未还田处理相比, 秸秆还田对土壤团聚体的影响趋势大致相同, 即大团聚体质量比例增加, 微团聚体质量比例减小, 团聚体稳定性增强(表3)。其中, 双季秸秆还田处理效果最显著, 这与前人研究一致[15,17]。本试验条件下, 在0~30 cm土层, SOC与MWD呈显著正相关(表6)。秸秆腐解产生的有机物质如多糖和有机酸, 不仅为微生物提供更多的生存环境, 同时促进土壤微团聚体、土壤矿物质和粗颗粒有机物胶结为大团聚体, 提高团聚体的稳定性[18]。
3.2 秸秆还田对土壤总有机碳的影响
土壤有机碳能够有效地调控土壤的物理、化学和生物过程, 是评价土壤质量的重要指标之一[19]。本试验研究结果表明, 与未还田处理相比, 秸秆还田显著提高了0~30 cm各土层土壤有机碳含量和储量(图1), 与前人研究一致[17,20]。Stewart等[21]认为, 当农田土壤有机碳含量未饱和时, 秸秆还田才能够提高SOC含量。本研究表明, 在黄淮海平原小麦玉米轮作中, 双季秸秆还田处理的SOC和SCS高于单季还田处理高于未还田处理, 说明该区域农田土壤中有机碳含量和储量尚未达到饱和。因此, 秸秆还田仍是黄淮海东部提升地力的有效措施。农田土壤有机碳主要取决于有机物料输入与输出的平衡[22]。本研究结果表明, 在0~30 cm土层中, 秸秆还田量与SOC呈显著正相关(表6)。小麦秸秆还田量虽大, 但对SOC的提升作用不如玉米秸秆还田, 其原因可能为冬小麦季播前旋耕使得玉米秸秆与土壤接触紧密, 为土壤微生物提供了附着点和营养源, “刺激”了微生物活性, 加速了玉米秸秆的腐解[23,24]; 而小麦秸秆为免耕覆盖还田, 表层秸秆只能经风化等物理过程初步降解[25], 只有与土壤接触的下层秸秆才能由微生物快速分解, 导致SS处理下0~10 cm土层SOC和SCS高于WS处理。同时, 小麦秸秆的C/N要高于玉米秸秆, 腐解速率较低[26]。综上所述, 农田土壤有机碳的积累主要取决于秸秆还田量、还田秸秆性质及其腐解速率。
3.3 秸秆还田对土壤团聚体有机碳及固碳能力的影响
有研究表明, 土壤表层有机碳约90%储存在团聚体中, 团聚体的团聚作用对实现农田土壤固碳具有重要意义[27]。本实验条件下, 土壤团聚体中有机碳含量均随团聚体粒径的增大而增加(表4), 说明大团聚体是有机碳的主要载体[28]。同时, 秸秆还田也提高了团聚体的固碳能力, 尤其是>5 mm、5~2 mm、1~0.5 mm粒级土壤团聚体(表5)。秸秆腐解释放的有机碳受土壤大团聚体的物理保护, 并在其中进行化学转化和结构稳定, 进而影响微生物群落和功能的进化与匹配, 最终将有机碳固定在土壤中[29]。团聚体的固碳效应以及大团聚体的形成是有机碳与团聚体共同作用的结果, 二者相辅相成, 共同促使土壤质量良性化发展。三种秸秆还田处理中, 以双季秸秆还田对土壤团聚体稳定性与固碳能力改善效果最显著, 可能是秸秆还田量差异造成的[30]。3.4 秸秆还田对作物产量的影响
本试验研究结果表明, 与不还田相比, 无论何种还田模式, 两年度小麦-玉米周年产量均得到了提升(表7), 与前人研究结果相符[31]。秸秆还田能够优化土壤结构, 补充和平衡土壤养分, 最终提升作物产量。两种单季还田模式均产生了对还田当季作物明显的增产效应, 其原因可能与秸秆分解特性有关。玉米秸秆主要在越冬期前和拔节后快速腐解[32], 伴随着养分的释放, 越冬前秸秆还田有利于培育冬前壮苗, 拔节后秸秆的快速腐解使得土壤水肥供应更加充足, 进而提高小麦产量。在夏玉米生长季, 秸秆还田补充了土壤中的有机质与养分, 从而为籽粒发育提供充足的碳源[33], 达到玉米增产的目的。4 结论
秸秆还田能够显著提高耕层(0~30 cm)有机碳含量, 优化土壤团聚体组成, 提高团聚体稳定性与固碳能力, 协同提高小麦玉米产量。双季还田模式是当前黄淮海区域土质提升和作物增产的最佳措施; 单季秸秆还田能维持较高的土壤生产力, 同时提供大量秸秆的饲料化、能源化和原料化多元利用。参考文献 原文顺序
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被引期刊影响因子
[本文引用: 1]
[本文引用: 1]
DOI:10.1111/gcb.12384URLPMID:24038905 [本文引用: 1]
Sequestration of atmospheric carbon (C) in soils through improved management of forest and agricultural land is considered to have high potential for global CO2 mitigation. However, the potential of soils to sequester soil organic carbon (SOC) in a stable form, which is limited by the stabilization of SOC against microbial mineralization, is largely unknown. In this study, we estimated the C sequestration potential of soils in southeast Germany by calculating the potential SOC saturation of silt and clay particles according to Hassink [Plant and Soil 191 (1997) 77] on the basis of 516 soil profiles. The determination of the current SOC content of silt and clay fractions for major soil units and land uses allowed an estimation of the C saturation deficit corresponding to the long-term C sequestration potential. The results showed that cropland soils have a low level of C saturation of around 50% and could store considerable amounts of additional SOC. A relatively high C sequestration potential was also determined for grassland soils. In contrast, forest soils had a low C sequestration potential as they were almost C saturated. A high proportion of sites with a high degree of apparent oversaturation revealed that in acidic, coarse-textured soils the relation to silt and clay is not suitable to estimate the stable C saturation. A strong correlation of the C saturation deficit with temperature and precipitation allowed a spatial estimation of the C sequestration potential for Bavaria. In total, about 395 Mt CO2-equivalents could theoretically be stored in A horizons of cultivated soils - four times the annual emission of greenhouse gases in Bavaria. Although achieving the entire estimated C storage capacity is unrealistic, improved management of cultivated land could contribute significantly to CO2 mitigation. Moreover, increasing SOC stocks have additional benefits with respect to enhanced soil fertility and agricultural productivity.
[本文引用: 1]
[本文引用: 1]
[本文引用: 1]
[本文引用: 1]
DOI:10.1016/j.still.2015.10.013URL [本文引用: 1]
Reducing tillage intensity and retaining residues are important components of conservation agriculture but in small holder systems in developing countries where crop residues have alternate uses such as fodder and fuelwood, recycling or external additions of organic matter may be a possible option. Information on impacts of long term reduced tillage on soil carbon, labile organic carbon fractions and their depth distribution is scant in drylands of semi arid regions. The effect of tillage intensity (CT—conventional tillage; RT—reduced tillage and MT—minimum tillage) and sources of nitrogen (100% OS: 100% of recommended N through organic source; 50% OS +50%IOS: 50% N through organic source and 50% N through inorganic source and 100% IOS: 100% N through inorganic source) on crop yields, soil organic carbon and C fractions in an Alfisol was assessed at the end of a 10 year long term experiment. Finger millet yields decreased significantly with reduction in tillage intensity (29%). Among N sources, highest yields were recorded with substitution of 50% of the N through organic source. After 10 years, the soil organic carbon (SOC) in 0–20cm soil layer with MT was 11% higher than with CT. The labile fractions of carbon, viz. particulate organic carbon (POC), microbial biomass carbon (MBC) and permanganate oxidizable carbon (KMnO4-C) under MT were 47%, 16% and 43% higher, respectively, in comparison to CT in the 0–20cm soil layer. The total carbon (TC) and total organic carbon (TOC) with MT were higher by 28% and 27% over CT and higher by 20% and 20% with 100%OS over 100% IOS. Labile carbon fractions revealed differential sensitivity and POC, MBC and KMnO4-C are sensitive indicators to detect short term management effects. Reducing tillage intensity and applying various N sources enhanced SOC marginally and the C sequestration rate varied from 62 to 186kgha611yr611. Based on the study it can be recommended for substitution of 50% of the recommended N with organic source as it increases crop yields and soil carbon and could be a potential alternative for residue retention for crops which have fodder value. Reducing the tillage intensity can enhance the SOC in semi arid rainfed systems but lower crop yields under MT is a concern which needs to be addressed in order to make these systems acceptable to the farming community.
DOI:10.1016/j.still.2014.07.014URL [本文引用: 1]
The importance of soil organic carbon (SOC) and nitrogen (N) sequestration in agricultural soils as climate-change-mitigating strategy has received robust attention worldwide in relation to soil management. This study was conducted to determine the temporal effects of different tillage systems and residue management on distribution, storage and stratification of SOC and N under wheat (Triticum aestivum L.) – maize (Zea mays L.) cropping systems in the North China Plain (NCP). Four tillage systems for winter wheat established in 2001 were: moldboard plow tillage with maize residues removed (PT0), moldboard plow tillage with maize residues incorporated (PT), rotary tillage with maize residues incorporated (RT), and no-till with maize residues retained on the soil surface (NT). Compared with PT0 and PT, significantly higher SOC and N concentrations were observed in the surface layer (0–10cm depth) under NT and RT. In 2004, the SOC stocks were lower (P<0.05) under NT and RT than under PT and PT0, however, the opposite trend was observed in 2012. Compared with 2001, the net profile (0–30cm) SOC sequestration rate was 10.60, 13.95, 13.65, and 14.92Mgha611 in 2012 under PT0, PT, RT, and NT, respectively. As for SOC stocks in the 0–50cm profile, no significant differences (P<0.05) were observed among NT, RT, and PT. The trends in N stocks in profile (0–30, 0–50cm depth) were NT>RT>PT>PT0 in both years. Compared with other treatments, SOC and N stocks were the lowest (P<0.05) under PT0. Therefore, crop residues play an important role in SOC and N management, and improvement of soil quality. The higher SOC stratification was observed under NT and RT than under PT and PT0, whereas the C:N ratio was higher (P<0.05) under PT and PT0 than under NT and RT systems. Therefore, the notion that NT leads to higher SOC stocks than plowed systems requires cautious scrutiny. Nonetheless, some benefits associated with NT present a greater potential for its adoption in view of the long-term environmental sustainability under wheat–maize double-cropping system in the NCP.
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DOI:10.1016/j.still.2017.09.012URL [本文引用: 1]
Straw return is a widely recognized strategy for increasing soil organic carbon (SOC) sequestration and improving soil quality and crop productivity. A 4-year-long field experiment established in 2008 was conducted to investigate the effects of the combined return of maize and wheat straw on the SOC stock at a soil depth of 0-20 cm in an intensive summer maize (Zea mays L.)-winter wheat... [Show full abstract]
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DOI:10.1016/j.fcr.2012.10.010URL [本文引用: 1]
There is considerable interest in using straw for industrial fibre or biofuel (ethanol) production. Removing straw from farm fields could have detrimental effects on soil quality. The objective of this work was to evaluate the role of above-ground vs. below-ground crop residues on soil organic C content, soil microbiological and physical properties, and crop yields. In a barley (Hordeum vulgare L.), field pea (Pisum sativa L.), wheat (Triticum aestivum L.), canola (Brassica napus L.) crop rotation from 2007 to 2010, we varied straw inputs by removing or retaining straw, with or without N fertilization, and also by fallowing some treatments in some years. Grain yields were unaffected by straw management or crop residue input, probably due to soil moisture deficits in three of the four years. Soil nitrate accumulation was consistently higher in fallow and N-fertilizer treatments, and grain N uptake was reduced after three years of retaining straw on the surface, indicating probable net N immobilization. The coarse (>0.5mm) light fraction of soil organic matter was reduced by fallowing the preceding year or disking in the straw, and was significantly correlated with the most recent input amounts of straw or total residue (root plus straw) dry matter (DM). The fine light fraction did not correlate with those residue inputs. Soil aggregation was indicated by mean weight diameter and was not affected by straw management. Non-rhizosphere soil microbial biomass C and glucosidase enzyme activity were consistently lowest in the control (no cropping) treatment and the treatment with straw incorporated by disking, but the amounts of C and N mineralized were not affected by straw treatments. Non-rhizosphere soil MBC was strongly correlated with cumulative total residue DM input. However, because crop yields did not vary much with straw management, they did not correlate with soil quality parameters. Therefore, varying above- and below-ground crop residue inputs, as well as tillage (disking in straw), over four years affected some early indicators of soil quality but not crop yields.
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DOI:10.1038/srep36602URLPMID:27812038 [本文引用: 1]
Abstract In this study, a fixed-site field experiment was conducted to study the influence of different combinations of tillage and straw incorporation management on carbon storage in different-sized soil aggregates and on crop yield after three years of rice-wheat rotation. Compared to conventional tillage, the percentages of >2090009mm macroaggregates and water-stable macroaggregates in rice-wheat double-conservation tillage (zero-tillage and straw incorporation) were increased 17.22% and 36.38% in the 0-15090009cm soil layer and 28.93% and 66.34% in the 15-30 cm soil layer, respectively. Zero tillage and straw incorporation also increased the mean weight diameter and stability of the soil aggregates. In surface soil (0-15090009cm), the maximum proportion of total aggregated carbon was retained with 0.25-0.106090009mm aggregates, and rice-wheat double-conservation tillage had the greatest ability to hold the organic carbon (33.64090009g kg -1 ). However, different forms occurred at higher levels in the 15-30090009cm soil layer under the conventional tillage. In terms of crop yield, the rice grown under conventional tillage and the wheat under zero tillage showed improved equivalent rice yields of 8.77% and 6.17% compared to rice-wheat double-cropping under zero tillage or conventional tillage, respectively.
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DOI:10.1007/s11104-012-1199-2URL [本文引用: 1]
Plants and earthworms are key ecosystem engineers and important regulators of soil aggregation and C dynamics, yet research to date has mainly considered their impacts in isolation thereby ignoring potential interactions between these organisms. We conducted a microcosm experiment under greenhouse conditions to assess the impacts of plants (Brachiaria decumbens) and earthworms (Pontoscolex corethrurus) on soil structure and C stabilization. Aggregate stability was assessed by wet-sieving. Large macroaggregates (> 2 mm) were also visually separated according to origin (e.g., earthworms, roots) and then further fractionated into particle size fractions to assess aggregate composition and C distribution. Earthworms increased aboveground biomass of B. decumbens by nearly 30 %. The presence of plant roots increased aggregate stability (mean weight diameter) by 2.6 %. While earthworms alone had no simple impacts on aggregation, a significant interaction revealed that earthworms increased aggregate stability in the presence of roots by 6 % when compared to microcosms without plants. Additionally, the presence of roots increased the C concentration of coarse particulate organic matter in earthworm casts, while earthworms increased C storage in microaggregates and the silt and clay fraction within root-derived aggregates. These findings suggest that plants and earthworms are intimately linked in soil aggregate formation and that both organisms need be considered simultaneously for proper management of soils.
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DOI:10.1007/s003740000229URL [本文引用: 1]
Earthworms are generally considered to fit the definition of ecosystem engineers. The casts they produce are recognised to have a great importance in the regulation of soil processes. Lifetimes and degradation rates of these structures remain poorly known. In this study, the dynamics of disappearance and the changes in the physical properties of the surface casts of the anecic earthworm Martiodrilus carimaguensis were assessed in a native savanna and an intensive pasture. In both systems, casts were composed of superposed layers deposited by earthworms over a period of at least a few days. The half-life of casts ranged between 265months and 1165months in the pastures (trampled and protected, respectively), and 565months in the savanna. Some dry casts remained at the soil surface for more than 165year after having been excreted. The disappearance of casts was mostly attributed to rain-drop impact and the effect of animal trampling. The bulk density of fresh casts was higher (+17%, P 0.05) to that of the surrounding soil, in the savanna and the pasture, respectively. Fresh cast aggregates were of larger size than bulk soil aggregates (about +70% in both systems, P< 0.05). Bulk density and the size of cast aggregates decreased with cast ageing (from –29% to –24% for bulk density, and from –68% to –80% for size, in the pasture and the savanna, respectively). Macroinvertebrates were observed digging into casts, and were assumed to be partly responsible for the physical degradation of casts with time.
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DOI:10.1016/j.fcr.2017.12.003URL [本文引用: 1]
Inappropriate fertilization has negative effects on soil quality and utilization of soil water storage. The effects of maize straw incorporation at low (LS 450062kg62ha 611 ), medium (MS 900062kg62ha 611 ), and high (HS 13,50062kg62ha 611 ) rates combined with chemical fertilizers on soil properties, maize yield and water-use efficiency (WUE) compared with chemical fertilizers (CK) were researched over 5 years under semi-humic conditions in dark loessial soil. The duration of decreased soil bulk density after straw incorporation depended on the straw incorporation rate; compared with CK, only HS treatment significantly decreased soil bulk density from the fourth year of the experiment and onward. Annual straw incorporation had cumulative effects on the build-up of soil enzyme activity. Soil fertility and enzyme activities were significantly improved with increasing straw incorporation rate over time. Straw incorporation rate decided the duration of increased crop yield and WUE; compared with CK, MS and HS treatments had 8.0–39.5% higher maize yield and 6.2–36.8% higher WUE in the five experimental years, whereas LS treatment significantly increased maize yield after the second fertilization year and significantly enhanced WUE after the fifth fertilization year. After the fourth fertilization year, MS treatment had no significant difference with HS treatment on maize yield and WUE. The rational straw incorporation treatment is MS in terms of improving dryland soil fertility, crop product and WUE.
DOI:10.1007/s10533-007-9140-0URL [本文引用: 1]
Current estimates of soil C storage potential are based on models or factors that assume linearity between C input levels and C stocks at steady-state, implying that SOC stocks could increase without limit as C input levels increase. However, some soils show little or no increase in steady-state SOC stock with increasing C input levels suggesting that SOC can become saturated with respect to C input. We used long-term field experiment data to assess alternative hypotheses of soil carbon storage by three simple models: a linear model (no saturation), a one-pool whole-soil C saturation model, and a two-pool mixed model with C saturation of a single C pool, but not the whole soil. The one-pool C saturation model best fit the combined data from 14 sites, four individual sites were best-fit with the linear model, and no sites were best fit by the mixed model. These results indicate that existing agricultural field experiments generally have too small a range in C input levels to show saturation behavior, and verify the accepted linear relationship between soil C and C input used to model SOM dynamics. However, all sites combined and the site with the widest range in C input levels were best fit with the C-saturation model. Nevertheless, the same site produced distinct effective stabilization capacity curves rather than an absolute C saturation level. We conclude that the saturation of soil C does occur and therefore the greatest efficiency in soil C sequestration will be in soils further from C saturation.
DOI:10.1007/s00374-011-0579-8URL [本文引用: 1]
Changes in total organic C ( C T ), water-soluble organic C ( C WS ), microbial biomass C ( C MB ), C mineralization, particulate organic C ( C P ), labile organic C ( C L ), C management index (CMI), and C storage in surface Hapli-Ustic Cambisol (0-20cm) under straw incorporation after both 2- and 10-year durations were investigated in a maize ( Zea mays L.) field experiment in northeast China, in order to examine the effectiveness of these active C fractions and CMI as early indicators for total C change. The treatments included straw removal (0%S), 50% of straw incorporation (50%S), and 100% of straw incorporation (100%S). Under the straw incorporation, C T concentration and C storage did not significantly change under 2-year duration, while were significantly increased under 10-year duration. However, C MB , total C mineralization ( C TM ), C P , and C L , and CMI were significantly increased under the straw incorporation even after only 2-year duration, and the responses were more significant after 10-year duration. There were positive correlations between all these C indicators with each other. Our findings demonstrate that the measured active C fractions (except for C WS ) and CMI can provide an early indication of change in total soil organic C induced by straw incorporation.
DOI:10.1111/gcb.12517URLPMID:24395454 [本文引用: 1]
Straw return has been widely recommended as an environmentally friendly practice to manage carbon (C) sequestration in agricultural ecosystems. However, the overall trend and magnitude of changes in soil C in response to straw return remain uncertain. In this meta-analysis, we calculated the response ratios of soil organic C (SOC) concentrations, greenhouse gases (GHGs) emission, nutrient contents and other important soil properties to straw addition in 176 published field studies. Our results indicated that straw return significantly increased SOC concentration by 12.8 ± 0.4% on average, with a 27.4 ± 1.4% to 56.6 ± 1.8% increase in soil active C fraction. CO2 emission increased in both upland (27.8 ± 2.0%) and paddy systems (51.0 ± 2.0%), while CH4 emission increased by 110.7 ± 1.2% only in rice paddies. N2O emission has declined by 15.2 ± 1.1% in paddy soils but increased by 8.3 ± 2.5% in upland soils. Responses of macro-aggregates and crop yield to straw return showed positively linear with increasing SOC concentration. Straw-C input rate and clay content significantly affected the response of SOC. A significant positive relationship was found between annual SOC sequestered and duration, suggesting that soil C saturation would occur after 12 years under straw return. Overall, straw return was an effective means to improve SOC accumulation, soil quality, and crop yield. Straw return-induced improvement of soil nutrient availability may favor crop growth, which can in turn increase ecosystem C input. Meanwhile, the analysis on net global warming potential (GWP) balance suggested that straw return increased C sink in upland soils but increased C source in paddy soils due to enhanced CH4 emission. Our meta-analysis suggested that future agro-ecosystem models and cropland management should differentiate the effects of straw return on ecosystem C budget in upland and paddy soils.
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DOI:10.1016/S0038-0717(00)00179-6URL [本文引用: 1]
Soil disturbance from tillage is a major cause of organic matter depletion and reduction in the number and stability of soil aggregates when native ecosystems are converted to agriculture. No-till (NT) cropping systems usually exhibit increased aggregation and soil organic matter relative to conventional tillage (CT). However, the extent of soil organic matter changes in response to NT management varies between soils and the mechanisms of organic matter stabilization in NT systems are unclear. We evaluated a conceptual model which links the turnover of aggregates to soil organic matter dynamics in NT and CT systems; we argue that the rate of macroaggregate formation and degradation (i.e. aggregate turnover) is reduced under NT compared to CT and leads to a formation of stable microaggregates in which carbon is stabilized and sequestered in the long term. Therefore, the link between macroaggregate turnover, microaggregate formation, and C stabilization within microaggregates partly determines the observed soil organic matter increases under NT.
DOI:10.2134/jeq2007.0509URLPMID:18689740 [本文引用: 1]
Compared with open (treeless) pasture systems, silvopastoral agroforestry systems that integrate trees into pasture production systems are likely to enhance soil carbon (C) sequestration in deeper soil layers. To test this hypothesis, total soil C contents at six soil depths (0-5, 5-15, 15-30, 30-50, 50-75, and 75-125 cm) were determined in silvopastoral systems with slash pine (Pinus elliottii) + bahiagrass (Paspalum notatum) and an adjacent open pasture (OP) with bahiagrass at four sites, representing Spodosols and Ultisols, in Florida. Soil samples from each layer were fractionated into three classes (250-2000, 53-250, and <53 microm), and the C contents in each were determined. Averaged across four sites and all depths, the total soil organic carbon (SOC) content was higher by 33% in silvopastures near trees (SP-T) and by 28% in the alleys between tree rows (SP-A) than in adjacent open pastures. It was higher by 39% in SP-A and 20% in SP-T than in open pastures in the largest fraction size (250-2000 microm) and by 12.3 and 18.8%, respectively, in the intermediate size fraction (53-250 microm). The highest SOC increase (up to 45 kg m(-2)) in whole soil of silvopasture compared with OP was at the 75- to 125-cm depth at the Spodosol sites. The results support the hypothesis that, compared with open pastures, silvopastures contain more C in deeper soil layers under similar ecological settings, possibly as a consequence of a major input to soil organic matter from decomposition of dead tree-roots.
DOI:10.1016/j.catena.2015.08.008URL [本文引用: 1]
61Effect of annual straw return rate on soil organic carbon and crop yield was studied.61The 50% annual straw return rate increased soil organic carbon and crop yield most.61The 50% annual straw return rate could be a suitable option in a rice–wheat rotation.
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