黄土高原区长期施用有机肥对土壤肥力及小麦产量的影响

黄土高原区长期定位试验麦秸、玉米秸、绿肥、厩肥及化肥等培肥物质对土壤养分及小麦产量的影响结果表明,长期施用有机肥可明显提高土壤有机质、全量养分和速效养分含量,提高土壤酶活性,改善土壤有机无机复合体、土壤水分、物理形状和土壤团聚度,提高调节土壤水、肥、气、热等能力,其中秸秆增产效果最显著。     

黄土高原丘陵沟壑区土壤物理性质对苜蓿 种植年限的响应

西部黄土高原丘陵沟壑区是中国乃至世界上水土流失最严重的区域,以禾谷类作物单播为主的传统农业生产系统和过度耕作是引致水土流失的最主要原因。紫花苜蓿作为优良豆科牧草,在区域生态环境建设和产业结构调整中发挥着重要作用。因此,本研究通过设置在陇中黄土高原半干旱区的长期定位试验,以苜蓿草地(3 a、10 a、12 a)和农田(马铃薯地)为主要研究对象,探讨了土壤物理性质对于苜蓿种植年限的响应,为黄土高原雨养农业系统紫花苜蓿适宜种植年限的选择及苜蓿草地的可持续利用提供科学依据。结果表明,随着紫花苜蓿种植年限的加长,土壤表层呈容重降低、孔隙度增加的变化趋势,而下部土层变化不明显。苜蓿种植可以提高耕层0~30 cm土壤0.25 mm水稳性团聚体含量、平均重量直径(MWD)和几何平均直径(GMD),同时降低团聚体破坏率(PAD),且随种植年限的延长效果愈加明显。苜蓿种植一定年限后土壤总有机碳(TOC)和易氧化有机碳(ROOC)与农田差异明显,其中种植苜蓿土壤易氧化有机碳占总有机碳的比例为44%~57%,农田土壤易氧化有机碳比例占52%~68%,表明种植苜蓿不仅提高了土壤总有机碳含量,且改变了土壤有机碳的组成比例。与农田相比,苜蓿种植可改善土壤水分入渗性能,表现为随种植年限的延长呈现先增加后降低的趋势。黄土高原沟壑区种植苜蓿可以改善土壤有机质形态和物理结构,提高土壤渗透能力,但苜蓿种植年限以10 a为宜,10 a之后应该进行轮作换茬以维持雨养农业系统的可持续发展。     

Soil aggregation,aggregate stability,organic carbon and nitrogen in different soil aggregate fractions under forest and shrub vegetation on the Loess Plateau,China

Revegetation has been reported as one of the most effective counter measures to reduce soil and water erosion on the Loess plateau in China. Soil aggregate stability and the distribution of organic carbon and nitrogen in different aggregate fractions would be affected by different plant communities. The objectives of this study were to elucidate the effects of different plant communities on soil aggregate stability and the distribution of organic carbon and nitrogen in different aggregate fractions in order to prove that the different plant covers enhance soil aggregate stability.     

黄土台塬不同土地利用方式下土壤碳组分的差异

为探讨土地利用方式对土壤碳固定的影响,以乔木、灌木、草和农田等不同植被类型,纯林和混交两种栽培模式的黄土台塬为对象,进行了土壤碳组分研究。结果表明,不同利用方式下林地和天然草地在0—100 cm土层总碳,轻组、重组、可溶性有机碳以及轻组有机碳分配比例(LFOC/SOC)均不同程度高于耕地,而其有机无机复合度(HFOC/SOC)则低于耕地,灌木林地和天然草地这种趋势尤为突出;各种土地利用方式间,土壤总碳和HFOC/SOC在0—20cm差异显著,总碳在60—100 cm也差异明显,轻组、重组及可溶性有机碳在0—40 cm,而无机碳则在40—100 cm差异明显;LFOC/SOC和DOC/SOC在各土层均存在一定差异。土壤总碳、有机碳以及各组分有机碳之间呈极显著正相关,而无机碳则与其呈负相关。轻组和可溶性有机碳均与粗颗粒、易氧化有机碳以及2—0.25 mm团聚体有机碳的相关性高于与细颗粒、稳态有机碳和2 mm团聚体有机碳;而重组有机碳则与之相反。轻组有机碳较有机碳、总碳、重组以及可溶性有机碳能更敏感地反映利用方式之间的差异,可作为土壤质量变化的评价指标。     

黄土高原不同植物群落土壤团聚体中有机碳和酶活性研究

以黄土高原延河流域森林区3种典型植物群落为研究对象,研究了3种植物群落土壤团聚体中有机碳的含量、组分及土壤酶活性,分析了有机碳与酶活性的关系。结果表明:(1)3种植物群落,土壤团聚体各种形态有机碳和酶活性均表现为0~10 cm土层含量高于10~20 cm土层,辽东栎群落0~10 cm土层土壤多酚氧化酶活性却低于10~20 cm土层。(2)土壤团聚体有机碳含量在植物群落间表现为:辽东栎群落人工刺槐群落狼牙刺群落,酶活性在植被群落间的高低表现则不一致。土壤有机碳含量和酶活性在团聚体间均表现为随团聚体粒级的增大而增大,或先增大再减小的趋势。(3)蔗糖酶、纤维素酶以及β-D葡糖苷酶活性与各种形态有机碳均呈显著的正相关关系,多酚氧化酶和过氧化物酶与有机碳含量相关性不显著。(4)辽东栎群落和狼牙刺群落土壤团聚体蔗糖酶、纤维素酶、以及β-D葡糖苷酶活性在团聚体中表现为:|0.25 mm团聚体||2~0.25 mm团聚体||5~2 mm团聚体||5 mm团聚体|,其多酚氧化酶和过氧化物酶以及人工刺槐群落各种土壤酶活性均表现为2~0.25 mm粒级团聚体中最大。(5)β-D葡糖苷酶活性增大,能促进土壤各种有机碳含量增加;土壤蔗糖酶活性和β-D葡糖苷酶活性的提高有助于土壤活性有机碳含量增加;土壤多酚氧化酶活性的增大,有利于土壤腐殖质碳的积累。     

黄土高原典型植被根系对土壤团聚体及其有机碳组分的影响

为探究植被根系作用下不同粒径团聚体内碳组分含量的相对变化及其主要影响因素,以黄土高原地区自然生长的直根系植物铁杆蒿(Artemisia gmelinii Web.)和须根系植物长芒草(Stipa bungeana Trin.)典型植被为研究对象,以退耕1年撂荒地为对照样地(CK),测定各粒径团聚体质量占比及其土壤有机碳(SOC)、颗粒态有机碳(POC)、矿物结合态有机碳(MAOC)含量,分析土壤基本理化性质和根系特征参数与不同粒径团聚体碳组分特征间的相互关系。结果表明:(1)与撂荒地相比,铁杆蒿和长芒草样地均显著提高POC和MAOC含量,POC含量变化幅度均大于MAOC。铁杆蒿和长芒草样地显著提高各粒径团聚体碳组分含量,＞0.25 mm大团聚体中POC和MAOC含量增幅较微团聚体更大,分别为7.44~8.26倍和3.76~4.37倍。(2)大团聚体有机碳含量与POC、MAOC均为极显著相关,小团聚体有机碳含量与POC显著相关,微团聚体有机碳含量与MAOC显著相关。团聚体对POC的包裹和对MAOC的结合作用共同存在,同时二者以不同的影响方式作用于团聚体有机碳变化,继而影响土壤总有机碳,其中,小团聚体有机碳含量是最主要的影响因素。(3)土壤团聚体碳组分与植被根系参数显著相关,根表面积密度(RSAD)和根生物量密度(RWD)是影响团聚体碳组分的主要因素,其解释方差分别为50.5%,17.0%。通过碳组分对各粒径土壤团聚体有机碳的影响,植物根系能够有效提升土壤有机碳含量并改善土壤质量。该研究结果为黄土高原地区土壤固碳与植被恢复提供参考。     

黄土高原半干旱区不同土地利用下的土壤有机碳、碳组分和土壤营养

Cropland (CP), native grassland (NG) and two shrub land treatments which were converted from cropland in 1985:seabuckthorn (Hippophae rhamnoides L. ) (ST), and branchytamarisk (Tamarix ramosissima) (BT) were investigated to evaluate effects of land use conversion on soil organic carbon (SOC) and soil nutrients in the semi-arid region of the Loess Plateau of China. Total organic carbon (TOC), light fraction organic carbon (LFOC), heavy fraction organic carbon (HFOC), total N (TN), nitrate nitrogen (NO₃^--N) and nitrite nitrogen (NO₂^--N), ammonium nitrogen (NH₄⁺-N), total P, and available P (AP) were measured. The results showed that SOC in NG, ST and BT were 12.7%, 27.7% and 34.8% higher than that of the cropland, respectively. LFOC, light fraction (LF) dry matter, ratio of TOC to TN (C/N) and the ratio of TOC to AP (C/P) were higher in the shrub land or native grassland than in the cropland. Cropland had the highest TN, the sum of NO₃^--N and NO₂^--N, TP and AP due to the use of chemical fertilizers. TOC significantly correlated with LFOC, HFOC and C/N. LFOC significantly correlated with dry matter of the LF and C/N. TN, the sum of NO₃^--N and NO₂^--N and AP were significantly negatively correlated with TOC and LFOC. Therefore, land use conversion from cropland to shrub land, or maybe grassland, contributed to SOC sequestration and improved soil nutrients stabilization.     

Effects of vegetation restoration on soil organic carbon sequestration at multiple scales in semi-arid Loess Plateau,China

Soil organic carbon (SOC) sequestration by vegetation restoration is the theme of much current research. Since 1999, the program of “Grain for Green”has been implemented in the semi-arid Loess Plateau, China. Its scope represents the largest vegetation restoration activity in China. However, it is still unclear for the SOC sequestration effects of vegetation cover change or natural succession promoted by the revegetation efforts at different scales under the semi-arid conditions. In this study, the changes in SOC stocks due to the vegetation restoration in the middle of Loess Plateau were estimated at patch, hill slope transect and small watershed scale from 1998 to 2006. Soil samples were taken from field for the determination of cesium-137 (¹³⁷Cs) and SOC contents. Vegetation cover change from 1998 to 2006 at the small watershed scale was assessed using Geographic Information System. The results showed that cropland transforming to grassland or shrubland significantly increased SOC at patch scale. Immature woodland, however, has no significant effect. When vegetation cover has no transformation for mature woodland (25 years old), SOC has no significant increase implying that SOC has come to a stable level. At hill slope scale, three typical vegetation cover patterns showed different SOC sequestration effects of 8.6%, 24.6%, and 21.4% from 1998 to 2006, and these SOC increases mainly resulted from revegetation. At the small watershed scale, SOC stocks increased by 19% in the surface soil layer at 0–20 cm soil depth from 1998 to 2006, which was equivalent to an average SOC sequestration rate of 19.92 t C y^− 1 km^− 2. Meanwhile, SOC contents showed a significant positive correlation (P < 0.001) with the ¹³⁷Cs inventory at every soil depth interval. This implied significant negative impacts of soil erosion on SOC sequestration. The results have demonstrated general positive effects of vegetation restoration on SOC sequestration at multiple scales. However, soil erosion under rugged topography modified the spatial distribution of the SOC sequestration effects. Therefore, vegetation restoration was proved to be a significant carbon sink, whereas, erosion could be a carbon source in high erosion sensitive regions. This research can contribute to the performance assessment of ecological rehabilitation projects such as “Grain to Green” and the scientific understanding of the impacts of vegetation restoration and soil erosion on soil carbon dynamics in semi-arid environments.     

Changes in soil properties across a chronosequence of vegetation restoration on the Loess Plateau of China

Soil fertility is important for vegetation growth and productivity. The relationship between vegetation and soil fertility is important for both scientific and practical reasons. However, the effects of soil fertility on vegetation development and succession are poorly documented on the Loess Plateau. In this study, we compared soil properties of the Yanhe Watershed in northern Shaanxi across five different land uses (shrubland, farmland, natural grassland, woodland and artificial grassland) and a chronosequence of soils undergoing restoration for 5, 10, 15, 20, 25, 30, 35, 40 and 45 years. We found that revegetation had a positive effect on soil bulk density decrease, total porosity and capillary porosity increase in the surface soil layers but not in the subsurface layer. Additionally, soil organic matter, total nitrogen, available nitrogen and available potassium were greater at shrubland and woodland sites compared with other land uses. Total phosphorus and available phosphorus were greater at farmland sites. Results of the study indicate that revegetation on eroded soil can produce important increases in soil fertility on older plantations and in areas with natural succession.     

Soil organic carbon distribution in relation to land use and its storage in a small watershed of the Loess Plateau, China

Soil organic carbon (SOC) is an important component in agricultural soil, and its stock is a major part of global carbon stocks. Estimating the SOC distribution and storage is important for improving soil quality and SOC sequestration. This study evaluated the SOC distribution different land uses and estimated the SOC storage by classifying the study area by land use in a small watershed on the Loess Plateau. The results showed that the SOC content and density were affected by land use. The SOC content for shrubland and natural grassland was significantly higher than for other land uses, and cropland had the lowest SOC content. The effect of land use on the SOC content was more significant in the 0-10 cm soil layer than in other soil layers. For every type of land use, the SOC content decreased with soil depth. The highest SOC density (0-60 cm) in the study area was found in shrublandII (Hippophae rhamnoides), and the other land uses decreased in the SOC density as follows: natural grassland > shrublandI (Caragana korshinskii) > abandoned cropland > orchard > level ground cropland > terrace cropland > artificial grassland. Shrubland and natural grassland were the most efficient types for SOC sequestration, followed by abandoned cropland. The SOC stock (0-60 cm) in this study was 23,584.77 t with a mean SOC density of 4.64 (0-60 cm).     

黄土台塬不同林分结构土壤有机碳质量分数特征

为探讨林分结构对土壤有机碳固定的影响,本文以黄土台塬的油松、 沙棘、 刺槐和侧柏纯林及其混交林为对象,对土壤有机碳、 易氧化态、 轻组、 颗粒态以及可溶性有机碳进行了分析。结果表明, 1）混交林可有效增加土壤不同组分有机碳含量,侧柏混交林与纯林相比增加最为明显,其土壤有机碳增加了123%和160%,易氧化态有机碳增加了161%和304%,轻组有机碳增加了1399%和482%,颗粒态有机碳增加了454%和436%,可溶性碳增加了138%和170%（05 cm土层）; 刺槐-沙棘、 油松-沙棘-刺槐混交林相对改良效果较差。2）各活性有机碳间相比较,混交林对土壤易氧化态碳含量增加效果最显著,而对土壤颗粒有机碳的改善效果不甚明显。3）在0100 cm土层,轻组有机碳敏感性指标分别是总有机碳、 可溶性和易氧化态有机碳的1.00~10.58、 3.83~10.19和1.78~5.10倍。4）有机碳与活性有机碳组分均呈线性极显著正相关关系; 轻组有机碳与颗粒有机碳二者之间的相关性大于其与其他,易氧化态碳与可溶性有机碳二者之间的相关性大于其与其他。     

陇中黄土高原不同耕作措施下土壤磷动态研究

依托陇中黄土高原旱作农田已实施13 a的保护性耕作试验,研究传统耕作、免耕、传统耕作秸秆还田、免耕秸秆覆盖、传统耕作地膜覆盖和免耕地膜覆盖6种耕作措施下土壤全磷及磷组分动态变化特征。结果表明:试验期各处理土壤全磷和总无机磷均逐年增长;两个秸秆还田处理总有机磷逐年增长,免耕地膜覆盖和免耕处理总体增长,传统耕作和传统耕作地膜覆盖处理相对稳定;各无机磷组分均总体增长,其中氢氧化钠提取态无机磷、水溶态无机磷和碳酸氢钠提取态无机磷涨幅较大,平均涨幅分别为253.6%、128.6%和66.9%;保护性耕作可不同程度地提高水溶态无机磷、碳酸氢钠提取态无机磷和氢氧化钠提取态无机磷含量,相同覆盖条件下免耕较传统耕作效果明显,尤其免耕秸秆覆盖处理最明显;耕作方式对浓盐酸提取态无机磷和残留磷的影响不明显;保护性耕作可提高碳酸氢钠提取态有机磷和氢氧化钠提取态有机磷含量,两个秸秆还田处理最明显,两处理也可提高浓盐酸提取态有机磷含量,但免耕、传统耕作地膜覆盖和免耕地膜覆盖处理下该组分含量降低。综上,采取保护性耕作可适当减少磷肥用量,保护性耕作尤其是免耕秸秆覆盖方式值得在该区推广。     

黄土高原撂荒草地土壤碳库对两年增温增雨的响应

阐明暖湿的气候趋势下黄土高原土壤有机碳库不同活性组分和碳库稳定性的变化特征,对脆弱生态区碳库的可持续发展以及评估区域生态效益具有重要意义。以黄土丘陵区自然撂荒草地为研究对象,人工模拟增温和增雨,分析了在增温（W）、增雨（P50%）及其交互作用（WP50%）下植被群落变化特征、土壤有机碳库组分含量、碳库组分的分配比例以及碳库稳定性的变化特征。结果发现：（1）增雨显著增加了植被丰富度指数,而增温和增温增雨显著降低了植被丰富度指数。（2）增雨处理下土壤有机碳、酸解有机碳、易氧化有机碳、溶解性有机碳含量及分配比例在两个取样年均显著高于对照;增温增雨处理则进一步增加了土壤易氧化有机碳和微生物生物量碳含量以及分配比例。相关性分析表明,土壤有机碳与各个活性碳组分之间存在显著相关性。（3）增温增雨处理下土壤碳库活度、碳库活度指数以及碳库管理指数均高于其他处理。酸解有机碳和微生物生物量碳的敏感指数在气候变化处理下相对较高。综上所述,暖湿化的气候背景下黄土丘陵区撂荒草地土壤有机碳、有机碳活性组分含量和分配比例以及碳库稳定性显著提高,有助于碳库良性发展,酸解有机碳和微生物生物量碳可作为未来土壤有机碳变化的重...     

黄土高原草地土壤有机碳分布及其影响因素

以黄土高原水平方向的4种主要草地类型为研究对象,分析了不同草地类型土壤有机碳(SOC)的分布特征及其影响因素。结果表明:土壤有机碳含量随土壤深度的增加而降低,其中0～20 cm土壤有机碳含量与20～40、40～60、60～80、80～100 cm有机碳含量差异显著。4种草地类型土壤有机碳含量分布规律:0～40 cm为高山草甸草原>典型草原>森林草原>荒漠草原,40～100 cm为高山草甸草原>森林草原>典型草原>荒漠草原;4种草地类型中各土层土壤有机碳含量最高的是高寒草甸,其空间变异最大,最小的是荒漠草原,其变异最小。黄土高原上高寒草甸草原、森林草原、典型草原土壤有机碳均集中分布在浅表层0～40 cm,分别占0～100 cm的71%、50%、46%,而荒漠草原各层分布较均匀;黄土高原土壤有机碳含量与海拔高度呈显著正相关(p<0.01);0～40 cm土壤有机碳含量与土壤含水量呈显著正相关(p<0.01);与全氮有极显著的正相关性,相关系数达0.984 3;与年均温呈极显著负相关(p<0.01),几种草地类型100 cm深土壤有机碳含量与年降水量无明显相关。     

黄土丘陵区不同植被群落土壤团聚体有机碳及其组分的分布

有机碳是形成土壤团聚体的重要物质,植被群落通过有机残体的输入增加土壤有机碳含量,从而通过影响团聚体的形成而影响土壤结构。为探究不同植被群落对土壤结构改良的意义,对黄土丘陵区森林带和草原带的不同植被群落土壤团聚体中有机碳组分进行了研究。结果表明:(1)研究区域森林带土壤有机碳含量大于草原带,森林带植被群落土壤总有机碳含量大小顺序为:辽东栎群落>人工刺槐群落>狼牙刺群落,草原带植被群落土壤总有机碳含量大小顺序为:人工沙棘群落>达乌里胡枝子+茭蒿群落>铁杆蒿+达乌里胡枝子群落;(2)土壤活性有机碳和腐殖质碳占土壤总有机碳的比例在两种植被带之间基本相同,相同植被群落土壤活性有机碳占土壤总有机碳的比例高于腐殖质碳占总有机碳的比例;(3)森林带土壤>0.25 mm团聚体含量显著高于草原带土壤>0.25 mm团聚体含量,各种形态的有机碳随着土壤团聚体粒级的增大有机碳含量呈先增加后减少或者随着团聚体粒级的增大而增大的趋势,2~0.25 mm和<0.25 mm团聚体中有机碳含量最高;(4)草原带每种植被群落土壤活性有机碳含量空间差异性较大,辽东栎群落各种形态土壤有机碳含量的空间差异性都较大,<0.25 mm团聚体腐殖质碳含量大于其他粒径;(5)草原带人工沙棘群落土壤各种形态有机碳在土壤剖面上的含量差异很小,其他各植被群落0~10 cm土层土壤有机碳含量均大于10~20 cm土层。     

黄土丘陵区人工林地土壤肥力质量

以黄土高原北部的陕西省吴起县为例,通过对不同灌木类型和不同生长年限的乔木林地土壤样品的分析测试与数理统计,研究黄土丘陵沟壑区不同人工林植被对土壤肥力质量的影响。结果表明：1）土壤碱解N和速效K,柠条林地是沙棘林地的2倍以上,二者之间达到极显著差异水平;柠条对土壤肥力的提高效果要优于沙棘,仅从对土壤性质的改善来看,建议选择种植柠条。2）乔木林地,从幼年林地到成年林地,土壤全N、碱解N、有机质和阳离子交换量不断增加,土壤速效K、全P和速效P略有增加,土壤有机质和养分的表聚性加强。3）总体上,乔木林地0～100cm土层土壤碱解N、速效K、有机质、阳离子交换量、全N、全P、全K均高于灌木林地,表明乔木林地对土壤的培肥效果优于灌木林地。     

不同植被类型对滨海盐碱土壤有机碳库的影响

对江苏滨海盐碱地5种不同植被类型土壤（0 ~ 40 cm）有机碳（SOC）含量、密度和表层（0 ~ 20 cm）土壤微生物量碳（SMBC）、可溶性有机碳（DOC）含量及其占总有机碳（TOC）的比例进行了分析。结果显示,随土层深度的增加,SOC含量降低,表层SOC密度占整个剖面的54.6% ~ 75.8%。表层SOC含量和密度分别介于2.02 ~ 9.61 g/kg和5.87 ~ 21.54 t/hm2,平均值分别为4.77 g/kg和12.56 t/hm2。随着原生植被群落的演替（光滩→盐蒿→茅草）,SOC、SMBC和DOC含量均依次增加。茅草荒地围垦后,稻-油轮作地和菊芋地表层SOC密度分别比茅草地的增加了55%（5.77 t/hm2）和107%（11.15 t/hm2）;稻-油轮作地的SMBC含量及SMBC/TOC比值下降,而菊芋地的上升;围垦后土壤DOC含量及DOC/TOC比值都明显下降。结果表明,滨海盐碱地SOC主要分布在表层,原生植被群落的顺行演替使SOC库容增加且活性增强,在盐荒地围垦初期（3年）,SOC库容增加但活性有所减弱。经估算,滨海盐碱非耕地具有较大的固碳潜力,但需要合理的耕作管理措施来保证农业生产的可持续发展并实现增汇减排的目标。     

黄土高原坝地深层土壤有机碳稳定性研究

淤地坝作为黄土高原重要的碳储库,其深层土壤有机碳稳定性在很大程度上影响坝地土壤储碳能力和碳排放。以黄土丘陵区不同利用年限的坝地为对象,从坝地剖面土壤有机碳含量及其组分入手,研究不同利用年限、不同沉积深度下,土壤有机碳含量及其稳定性的变化特征和影响因素。结果表明：（1）坝地深层土壤有机碳（SOC）含量低于该区坡耕地表层土壤有机碳含量,并未呈现明显的有机碳富集现象。随利用年限增加,坝地SOC含量呈增加趋势。（2）不同利用年限坝地的SOC、易氧化碳（EOC）、微生物量碳（MBC）、水溶性碳（DOC）含量呈现出明显的表聚现象。MBC、DOC和EOC含量在土壤0—60 cm内较高。（3）相较于坝地浅层土壤而言,坝地深层土壤有机碳具有较高的稳定性,长期耕作会降低坝地深层土壤有机碳稳定性。（4）坝地浅层和深层土壤有机碳稳定性变化的主导因素不同。浅层土壤有机碳稳定性主要受土层深度、有机碳含量和黏粒含量的影响,分别能解释其变异的50.4%,19.6%和11.8%;深层土壤有机碳稳定性主要受有机碳含量、土壤含水量和利用年限的影响,分别能解释其变异的38.9%,33.9%和11.8%。     

不同保护性耕作措施对麦-豆轮作土壤有机碳库的影响

通过设置在甘肃省定西市李家堡镇的不同保护性耕作试验,对春小麦、豌豆两种轮作次序下的土壤总有机碳、活性有机碳、微生物量碳含量进行了测定,并计算了各处理土壤碳库管理指数.结果表明:经过5年的轮作后,与传统耕作相比,两种轮作次序下免耕秸秆覆盖和传统耕作结合秸秆还田处理均能不同程度地提高土壤总有机碳、活性有机碳、微生物量碳含量及土壤碳库管理指数,而免耕不覆盖处理除在0～5 cm提高了土壤有机碳库管理指数外,其他各层次均降低了土壤有机碳库管理指数,说明仅依靠免耕而不结合秸秆覆盖或还田对于土壤有机碳库的管理来讲是不可持续的.     

耕作措施对旱作农田土壤颗粒态有机碳的影响

为了探明耕作措施对陇中黄土高原旱作农田土壤有机碳的影响,以连续进行17年的不同耕作措施长期定位试验为研究对象,利用碘化钠重液分组法,探索了传统耕作(T)、传统耕作+秸秆还田(TS)、免耕(NT)、免耕+秸秆覆盖(NTS)4种耕作措施对陇中黄土高原旱作农田土壤游离态颗粒有机碳、闭蓄态颗粒有机碳、颗粒态有机碳和矿质结合态有机碳的影响。结果表明:土壤总有机碳含量随土层加深而降低,游离态颗粒有机碳、闭蓄态颗粒有机碳、颗粒态有机碳的含量和占土壤总有机碳的比例均随土层加深而降低,而矿质结合态有机碳含量和占土壤总有机碳比例则随土层加深而增加。在0~40 cm各土层,各处理土壤颗粒态有机碳占总有机碳的比例(54.02%~76.78%)均高于矿质结合态有机碳占总有机碳的比例(31.78%~46.11%)。较之T处理,TS和NTS处理均不同程度提升土壤游离态颗粒有机碳、闭蓄态颗粒有机碳、颗粒态有机碳的含量和占土壤总有机碳的比例,其中NTS处理的提升效果最显著,TS处理次之。虽然NT、TS、NTS处理可提升土壤矿质结合态有机碳含量,但T处理下的矿质结合态有机碳占总有机碳的比例高于NT、TS和NTS处理。耕作模式和秸秆添加模式均对土壤总有机碳、游离态颗粒有机碳、闭蓄态颗粒有机碳、颗粒态有机碳和矿质结合态有机碳的提升具有显著效应,但秸秆添加模式的效应高于耕作模式。同时,免耕模式仅对0~10 cm各土层土壤总有机碳的提升效应达到显著水平,对0~20 cm各土层土壤碳组分的提升效应均达显著水平,而添加秸秆对0~40 cm各土层土壤总有机碳和各组分均发挥着显著提升效应。综合来看,免耕配合秸秆还田可以提升土壤活力,促进土壤固碳,有利于该区构建环境友好型和可持续发展型农业生产模式。