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.     

Effect of ultrasonic power on soil organic carbon fractions

Ultrasonic dispersion is a prevalent tool for soil fractionation. It is widely ignored that variation in ultrasonic power might lead to significantly different dispersion. We evaluated the effect of power variation with constant energy on the fine fraction mass, its organic C content and quality. All parameters increased significantly with power. The term “stable aggregates” as used in fractionation schemes cannot be defined by ultrasonic energy alone but power needs to be standardized, too.     

长期免耕对东北地区玉米田土壤有机碳组分的影响

Increasing evidence has shown that conservation tillage is an effective agricultural practice to increase carbon (C) sequestration in soils. In order to understand the mechanisms underlying the responses of soil organic carbon (SOC) to tillage regimes, physical fractionation techniques were employed to evaluate the effect of long-term no-tillage (NT) on soil aggregation and SOC fractions. Results showed that NT increased the concentration of total SOC by 18.1% compared with conventional tillage (CT) under a long-term maize (Zea mays L.) cropping system in Northeast China. The proportion of soil large macroaggregates ( 2000 μm) was higher in NT than that in CT, while small macroaggregates (250-2000 μm) showed an opposite trend. Therefore, the total proportion of macroaggregates ( 2000 and 250-2000 μm) was not affected by tillage management. However, C concentrations of macroaggregates on a whole soil basis were higher under NT relative to CT, indicating that both the amount of aggregation and aggregate turnover affected C stabilization. Carbon concentrations of intra-aggregate particulate organic matter associated with microaggregates (iPOM m) and microaggregates occluded within macroaggregates (iPOM mM) in NT were 1.6 and 1.8 times greater than those in CT, respectively. Carbon proportions of iPOM m and iPOM mM in the total SOC increased from 5.4% and 6.3% in CT to 7.2% and 9.7% in NT, respectively. Furthermore, the difference in the microaggregate protected C (i.e., iPOM m and iPOM mM) between NT and CT could explain 45.4% of the difference in the whole SOC. The above results indicate that NT stimulates C accumulation within microaggregates which then are further acted upon in the soil to form macroaggregates. The shift of SOC within microaggregates is beneficial for long-term C sequestration in soil. We also corroborate that the microaggregate protected C is useful as a pool for assessing the impact of tillage management on SOC storage.     

耕地土壤有机碳组分的季节变化

Carbon fractions in soils apparently vary not only in space, but also over time. A lack of knowledge on the seasonal variability of labile carbon fractions under arable land hampers the reliability and comparability of soil organic carbon(SOC) surveys from different studies. Therefore, we studied the seasonal variability of two SOC fractions, particulate organic matter(POM) and dissolved organic carbon(DOC), under maize cropping: POM was determined as the SOC content in particle-size fractions, and DOC was measured as the water-extractable SOC(WESOC) of air-dried soil. Ammonium, nitrate, and water-extractable nitrogen were measured as potential regulating factors of WESOC formation because carbon and nitrogen cycles in soils are strongly connected. There was a significant annual variation of WESOC(coefficient of variation(CV) = 30%). Temporal variations of SOC in particle-size fractions were smaller than those of WESOC. The stocks of SOC in particle-size fractions decreased with decreasing particle sizes, exhibiting a CV of 20%for the coarse sand-size fraction(250–2 000 μm), of 9% for the fine sand-size fraction(50–250 μm), and of 5% for the silt-size fraction(20–50 μm). The WESOC and SOC in particle-size fractions both peaked in March and reached the minimum in May/June and August, respectively. These results indicate the importance of the time of soil sampling during the course of a year, especially when investigating WESOC.     

土壤有机碳分组方法概述

土壤有机碳与土壤肥力和气候变化密切相关而成为当今土壤学等相关领域的研究热点之一。由于土壤有机碳是具有某一特性的一类化合物的混合物,存在高度异质性,所以选用合理的方法有效区分不同碳组分是深入研究土壤有机碳的关键。首先回顾了土壤有机碳的传统分组方法 (包括物理分组、化学分组和生物分组),进而介绍了Stewart等人近年提出的土壤有机碳物理-化学联合分组方法,最后对土壤有机碳分组方法的未来趋势进行了展望。     

Dissolved organic matter sorption by mineral constituents of subsoil clay fractions

The retention of dissolved organic matter in soils is mainly attributed to interactions with the clay fraction. Yet, it is unclear to which extent certain clay‐sized soil constituents contribute to the sorption of dissolved organic matter. In order to identify the mineral constituents controlling the sorption of dissolved organic matter, we carried out experiments on bulk samples and differently pretreated clay‐size separates (untreated, organic matter oxidation with H₂O₂, and organic matter oxidation with H₂O₂ + extraction of Al and Fe oxides) from subsoil horizons of four Inceptisols and one Alfisol. The untreated clay separates of the subsoils sorbed 85 to 95% of the dissolved organic matter the whole soil sorbed. The sorption of the clay fraction increased when indigenous organic matter was oxidized by H₂O₂. Subsequent extraction of Al and Fe oxides/hydroxides caused a sharp decrease of the sorption of dissolved organic matter. This indicated that these oxides/hydroxides in the clay fraction were the main sorbents of dissolved organic matter of the investigated soils. Moreover, the coverage of these sorbents with organic matter reduced the amount of binding sites available for further sorption. The non‐expandable layer silicates, which dominated the investigated clay fractions, exhibited a weak sorption of dissolved organic matter. Whole soils and untreated clay fractions favored the sorption of ”︁hydrophobic” dissolved organic matter. The removal of oxides/hydroxides reduced the sorption of the lignin‐derived ”︁hydrophobic” dissolved organic matter onto the remaining layer silicates stronger than that of ”︁hydrophilic” dissolved organic matter.     

不同轮作制度下土壤中不稳定有机碳组分的变化

Taking Kenli County in the Yellow River Delta, China, as the study area and using digital satellite remote sensing techniques, cultivated land use changes and their corresponding driving forces were explored in this study. An interactive interpretation and a manual modification procedure were carried out to acquire cultivated land information. An overlay method based on classification results and a visual change detection method which was supported by land use maps were employed to detect the cultivated land changes. Based on the changes that were revealed and a spatial analysis between cultivated land use and related natural and socio-economic factors, the driving forces for cultivated land use changes in the study area were determined. The results showed a decrease in cultivated land in Kenli County of 5321.8 ha from 1987 to 1998, i.e., an average annual decrement of 483.8 ha, which occurred mainly in the central paddy field region and the northeast dry land region. Adverse human activities, soil salinization and water deficiencies were the driving forces that caused these cultivated land use changes.     

耕层厚度对华北高产灌溉农田土壤有机碳储量的影响

针对华北平原长期少免耕可能导致的耕层变浅、变紧的问题,通过人为设置不同耕层厚度试验,采用等质量土壤有机碳库储量和层化比的研究方法,研究了4种耕层厚度（10、20、30、40 cm）水平下0～50 cm土壤有机碳的变化。2 a的田间试验结果表明,不同耕层厚度对土壤有机碳含量有显著差异,与2007年试验开始时相比,土壤有机碳质量分数都不同程度下降,下降幅度为22%～48%。利用等质量计算方法表明20 cm耕层厚度的处理土壤有机碳储量最高。通过层化比的研究表明,随着时间的推移,20 cm的耕层厚度层化比最高,其     

不同有机物料对苏打盐化土有机碳和活性碳组分的影响

【目的】在大同盆地苏打盐化土上,研究不同有机物料对春玉米产量、土壤有机碳及活性碳组分的影响,明确土壤有机碳及活性碳组分与主要盐碱指标的相关关系,为苏打盐化土改良及有机物料资源化利用提供理论支撑。【方法】2016-2017年在山西省北部怀仁县开展田间定位试验,设对照(CK)、风化煤、生物炭、牛粪和秸秆5个处理,各处理有机物料施用量按照每年9000 kg/hm^2等有机碳投入量折算,收获时对春玉米进行测产。2017年春玉米收获后,采集土壤样品测定土壤有机碳总量(SOC)和水溶性有机碳(WSOC)、易氧化有机碳(EOC)、轻组有机碳(LFOC)含量,分析土壤活性碳组分占有机碳的比例、土壤有机碳及活性碳组分与盐碱指标之间的关系。【结果】与CK相比,生物炭和秸秆处理春玉米产量无明显差异,而风化煤和牛粪处理春玉米产量则分别显著提高30.2%和30.3%。添加有机物料促进了0-20 cm土层SOC累积,其中以风化煤和牛粪处理效果最佳,较CK分别提高47.6%和36.1%。在有机碳组分方面,风化煤和牛粪处理提高WSOC、EOC含量的效果显著高于生物炭、秸秆处理;风化煤、牛粪和秸秆处理的LFOC含量显著高于生物炭处理。四类有机物料处理的WSOC占总有机碳的比例差异不显著,牛粪处理的占比显著高于CK。EOC占总有机碳的比例以牛粪处理最高,风化煤次之,且二者均显著高于CK处理;LFOC占总有机碳的比例则表现为秸秆、牛粪>风化煤、生物炭> CK。此外,添加有机物料能有效降低0-20 cm土层土壤pH、电导率(EC)和碱化度(ESP),其中以风化煤和牛粪处理降幅最大。相关分析表明,土壤SOC与pH、EC和ESP呈显著负相关。【结论】通过有机物料改良效果比较,发现牛粪和风化煤处理能促进苏打盐化土有机碳累积,提高可溶性、易氧化态及轻组有机碳组分在总有机碳中的占比,降低土壤pH、EC和ESP,明显提高春玉米产量。因此,风化煤和牛粪是山西北部苏打盐化土良好的改良剂。     

Changes in particulate and mineral-associated organic carbon with land use in contrasting soils

Soil organic carbon(SOC) is the largest terrestrial carbon(C) stock, and the capacity of soils to preserve organic C(OC) varies with many factors,including land use, soil type, and soil depth. We investigated the effect of land use change on soil particulate organic matter(POM) and mineral-associated organic matter(MOM). Surface(0–10 cm) and subsurface(60–70 cm) samples were collected from paired sites(native and cropped) of four contrasting soils.Bulk soils were separated into POM and MOM fract...     

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.     

Storage and stability of organic matter and fossil carbon in a Luvisol and Phaeozem with continuous maize cropping: A synthesis

Quantitative information about the amount and stability of organic carbon (OC) in different soil organic‐matter (OM) fractions and in specific organic compounds and compound‐classes is needed to improve our understanding of organic‐matter sequestration in soils. In the present paper, we summarize and integrate results performed on two different arable soils with continuous maize cropping (a) Stagnic Luvisol with maize cropping for 24 y, b) Luvic Phaeozem with maize cropping for 39 y) to identify (1) the storage of OC in different soil organic‐matter fractions, (2) the function of these fractions with respect to soil‐OC stabilization, (3) the importance and partitioning of fossil‐C deposits, and (4) the rates of soil‐OC stabilization as assessed by compound‐specific isotope analyses. The fractionation procedures included particle‐size fractionation, density fractionation, aggregate fractionation, acid hydrolysis, different oxidation procedures, isolation of extractable lipids and phospholipid fatty acids, pyrolysis, and the determination of black C. Stability of OC was determined by ¹³C and ¹⁴C analyses. The main inputs of OC were plant litter (both sites) and deposition of fossil C likely from coal combustion and lignite dust (only Phaeozem).     

The quality of exogenous organic matter: short-term effects on soil physical properties and soil organic matter fractions

We examined the short-term effect of five organic amendments and compared them to plots fertilized with inorganic fertilizer and unfertilized plots on aggregate stability and hydraulic conductivity, and on the OC and ON distribution in physically separated SOM fractions. After less than 1 year, the addition of organic amendments significantly increased ( P  <   0.01) the aggregate stability and hydraulic conductivity. The stability index ranged between 0.97 and 1.76 and the hydraulic conductivity between 1.23 and 2.80 × 10⁻³ m/s for the plots receiving organic amendments, compared with 0.34–0.43, and 0.42–0.64 × 10⁻³ m/s, respectively, for the unamended plots. There were significant differences between the organic amendments (P <  0.01), although these results were not unequivocal for both soil physical parameters. The total OC and ON content were significantly increased ( P  <   0.05) by only two applications of organic fertilizers: between 1.10 and 1.51% OC for the amended plots versus 0.98–1.08% for the unamended and between 0.092 and 0.131% ON versus 0.092–0.098% respectively. The amount of OC and ON in the free particulate organic matter fraction was also significantly increased ( P  <   0.05), but there were no significant differences ( P  <   0.05) in the OC and ON content in the POM occluded in micro-aggregates and in the silt + clay-sized organic matter fraction. The results showed that even in less than 1 year pronounced effects on soil physical properties and on the distribution of OC and ON in the SOM fractions occurred.     

Land‐use change in subalpine grassland soils: Effect on particulate organic carbon fractions and aggregation

Abandonment of mountain grassland often changes vegetation composition and litter quantity and quality, but related effects on labile soil organic matter (SOM) are largely unknown. The aim of this study was to investigate the impacts of grassland management and abandonment on soil carbon distribution in light (< 1.6 g cm^–3) particulate organic matter (POM) and aggregation along a gradient of management intensity including hay meadows, pastures, and abandoned grasslands. The reduction of management intensity is an interregional phenomenon throughout the European Alps. We therefore selected sites from two typical climate regions, namely at Stubai Valley, Austria (MAT: 3°C, MAP: 1097 mm) and Matsch Valley, Italy (MAT: 6.6°C, MAP: 527 mm), to evaluate effects of land‐use change in relation to climate. Free water‐floatable and free POM (wPOM, fPOM), and an occluded POM fraction (oPOM), were isolated from three water‐stable aggregate size classes (2–6.3 mm, 0.25–2 mm, < 0.25 mm) using density fractionation. Aggregate mean weight diameter slightly decreased with decreasing management intensity. In contrast to absolute POM‐C, fPOM‐C increased in aggregates at both sites with abandonment. Because the oPOM‐C was less affected by abandonment, the ratio of oPOM‐C : fPOM‐C shifted from > 1 to < 1 from meadow to abandoned grassland in aggregates at both sites and thus independent of climate. This suggests that in differently managed mountain grasslands free and occluded POM are functionally different SOM fractions. In bulk soil, the oPOM‐C : fPOM‐C ratio is better suited as an indicator for the response of SOM to management reduction in subalpine grasslands than the total soil C, absolute or relative POM‐C content.     

不同封育年限草地土壤有机质组分及其碳库管理指数

土壤有机质对草地封育的生态效应具有重要指示作用,本文结合野外调查和室内分析,研究了半干旱区不同封育年限草地土壤有机质组分及其碳库管理指数变化,以分析土壤有机质对草地封育的响应特征,从而为该区土壤质量的改善和植被建设的生态效应评价提供依据。研究结果表明,土壤有机质及不同活性有机质含量均随土层加深而降低,且在各土层基本表现出封育18年、封育23年封育13年未封育封育3年的趋势。除封育3年土壤的3种活性有机质碳库管理指数在090cm土壤剖面均低于100外,封育13年草地060cm土层、封育18和23年草地090cm土层的3种活性有机质碳库管理指数均高于100,表明随年限的延长,封育对土壤有机质的改善深度也在加深。土壤3种活性有机质与有机质及多数土壤性质呈极显著正相关,能更为灵敏和直观地表征土壤管理的长期效应和土壤质量变化。     

Precipitation of enzymes and organic matter by aluminum—Impacts on carbon mineralization

The precipitation of dissolved organic matter (DOM) by aluminum (Al) results in a stable soil organic matter (OM) fraction. Extracellular enzymes can also be removed from soil solution by sorption or precipitation, but whether this affects their activity and their importance for carbon (C) mineralization is largely unknown. We studied the activity of eight extracellular enzymes, precipitated by Al together with DOM, in relation to C mineralization of the precipitated OM. Dissolved OM was obtained from the Oi and Oa horizon of two forest soils and precipitated at different Al : C ratios and pH values to achieve a large variation in composition and C mineralization of precipitated OM. All eight enzymes were present in a functional state in precipitated OM. On average 53% of DOM was precipitated, containing on average 17%–41% of the enzyme activity (EA) involved in C degradation (chitinase, cellobiohydrolase, β‐glucosidase, glucuronidase, lacasse, and xylosidase) previously present in soil solution. In contrast, on average only 4%–7% of leucine‐aminopeptidase and acid‐phosphatase activity was found in precipitated OM. The EA found in precipitates significantly increased the percentage of C mineralized of precipitated OM, with a stronger influence of C‐degrading enzymes than enzymes involved in N and P cycling. However, after 8 weeks of incubation the correlations between EA and C mineralization disappeared, despite substantial EA being still present and only 0.5%–7.7% of C mineralized. Thus, degradation of precipitated OM seems to be governed by EA during the first degradation phase, but the long‐term stability of precipitated OM is probably related to its chemical properties.     

连续五年生物垃圾堆肥施用后地中海蔬菜种植系统中土壤有机碳的变化

Biowaste compost can influence soil organic matter accumulation directly or indirectly. A 5-year experiment was conducted to assess the influence of biowaste compost on the process of soil aggregation and soil organic carbon(SOC) accumulation in a Mediterranean vegetable cropping system. The study involved four treatments: biowaste compost(COM), mineral NPK fertilizers(MIN), biowaste compost with half-dose N fertilizer(COMN), and unfertilized control(CK). The SOC stocks were increased in COM, COMN, and MIN by 20.2, 14.9, and 2.4 Mg ha~(-1)over CK, respectively. The SOC concentration was significantly related to mean weight diameter of aggregates(MWD)(P 0.05, R~2= 0.798 4) when CK was excluded from regression analysis. Compared to CK, COM and COMN increased the SOC amount in macroaggregates( 250 μm) by 2.7 and 0.6 g kg~(-1)soil, respectively, while MIN showed a loss of 0.4g kg~(-1)soil. The SOC amount in free microaggregates(53–250 μm) increased by 0.9, 1.6, and 1.0 g kg~(-1)soil for COM, COMN, and MIN, respectively, while those in the free silt plus clay aggregates( 53 μm) did not vary significantly. However, when separating SOC in particle-size fractions, we found that more stable organic carbon associated with mineral fraction 53 μm(MOM-C) increased significantly by 3.4, 2.2, and 0.7 g kg~(-1)soil for COM, COMN, and MIN, respectively, over CK, while SOC amount in fine particulate organic matter(POM) fraction(53–250 μm) increased only by 0.3 g kg~(-1)soil for both COM and COMN, with no difference in coarse POM 250 μm. Therefore, we consider that biowaste compost could be effective in improving soil structure and long-term C sequestration as more stable MOM-C.     

Soil organic carbon and fractions of a Rhodic Ferralsol under the influence of tillage and crop rotation systems in southern Brazil

Soil organic matter (SOM) and its different pools have key importance in optimizing crop production, minimizing negative environmental impacts, and thus improving soil quality. The objective of this study was to evaluate the soil C and N contents in bulk soil and in different SOM pools (light and heavy fractions) of a clayey Rhodic Ferralsol after 13 years of different tillage and crop rotations in Passo Fundo, State of Rio Grande do Sul, Brazil. Soil samples were collected from no-tillage (no soil disturbance except for sowing; NT) and conventional tillage (disc plough followed by light disc harrowings; CT) applied to wheat/soybean (W/S) and wheat/soybean–vetch/maize (W/S–V/M) rotations. As reference, soil was sampled from a non-cultivated area adjacent to the field experiment. The greatest soil C and N contents were found in non-cultivated soils in the 0–5 cm depth (45 g C kg⁻¹ soil and 3.6 g N kg⁻¹ soil). Crop cultivation led to a decrease in SOM content which was higher for CT soils (approx. 60% decrease in C and N contents) than NT soils (approx. 43% decrease in C and N contents) at 0–5 cm. Tillage had the greatest impact on soil C and N storage. Soils under NT did not contain higher C and N storage than CT soils below 5 cm depth. Significantly, higher amounts of organic carbon of FLF in CT (0.5–0.7 g C kg⁻¹ soil) than in NT soils (0.2 g C kg⁻¹ soil) at 10–20 cm depth were also observed and the differences in C and N storage between CT and NT soils in the 0–30 cm layer were not significant. Silt and clay fractions contained the largest amount of organic carbon (60–95% of total organic carbon), and free light fraction was the most sensitive pool of organic carbon to detect changes in SOM due to soil tillage and crop rotations.     

长期不同施肥下黑土与灰漠土有机碳储量的变化

采用长期试验,研究了20年不同施肥下1 m深黑土与灰漠土有机碳含量与碳储量的剖面变化。结果表明,单施化肥和不施肥对黑土1 m土层有机碳储量没有显著影响,但灰漠土略有降低。有机肥配施化肥能显著提高土壤有机碳含量和储量。高量有机肥配施化肥（NPKM2）能提高020 cm和2040 cm土层土壤有机碳含量,黑土分别提高56.6%和49.6%、灰漠土提高143.1%和46.9%;常量有机无机配施（NPKM）效果较差,增幅分别为黑土35.1%和35.3%,灰漠土80.2%和4.1%。两种土壤1 m土体的有机碳储量,NPKM2处理分别提高了C 30.7 t/hm2与C 40.6 t/hm2。显然,有机无机肥配施可以显著提高1 m深土体中有机碳储量,主要是由于提高了040 cm土层土壤有机碳含量。