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1.
Carbon 13 nuclear magnetic resonance spectroscopy (13C NMR) is a powerful technique for studying the structure and turnover of soil organic matter, but is time consuming and expensive. It is therefore worth seeking swifter and cheaper methods. Diffuse reflectance FT‐IR spectroscopy (DRIFT), along with partial least squares (PLS) algorithms, provides statistical models to quantify soil properties, such as contents of C, N and clay. I have applied DRIFT?PLS to quantify soil organic C species, as measured by solid state 13C NMR spectroscopy, for several bulk soils and physical soil fractions. Calibration and prediction models for organic C and for particular NMR regions, namely alkyl C, O?alkyl C and carboxyl C, attained R2 values of between 0.94 and 0.98 (calibration) and 0.70–0.93 (cross‐validation). The prediction of unknown soil samples, after pre‐selection by statistical indices, confirmed the applicability of DRIFT?PLS. The prediction of aromatic C failed, probably because of superimposition of aromatic bands by signals from minerals. Results from fractions of particulate organic matter suggest that the chemical homogeneity of the material hampers the quantification of its constituting C species by DRIFT?PLS. For alkyl C, prediction of carbon species by DRIFT?PLS was better than direct peak‐area quantification in the IR spectra, but advantageous in parts only compared with a linear model correlating C species with soil C contents. In conclusion, DRIFT?PLS calibrated with NMR data provides quantitative information on the composition of soil organic matter and can therefore complement structural studies by its application to large numbers of samples. However, it cannot replace the information provided by more specific methods. The actual potential of DRIFT?PLS lies in its capacity to predict unknown samples, which is helpful for classification and identification of environmental outliers or benchmarks.  相似文献   

2.
According to recent conceptual models, the organic carbon (OC) of soils can be divided into OC fractions of increasing stability from labile free OC to resistant OC associated with the soil mineral phase. In this study, we present a method for quantifying two OC fractions based on soil aggregate–size fractionation and the N2 gas–adsorption method. For this purpose, we analyzed soil material of the plow layer of a Haplic Chernozem subjected to different fertilizer treatments (no fertilizer, mineral fertilizer, mineral and organic fertilizer). The total organic‐C concentration (TOC) and the clay content of the different size fractions were determined as well as the specific surface area (SSAmineral) and the sample pore volume after thermal oxidation (OC‐free). The TOC of the different soil‐aggregate fractions was linearly related to SSAmineral. Clay‐associated OC and nonassociated OC fractions of the different soil samples were quantified using two methods based on the OC surface loading at the clay fraction. The application of organic fertilizer increased the amount of nonassociated OC but hardly affected the concentration of clay‐associated OC. This finding agrees with previous studies on C dynamics in soils and indicates a finite capacity of soil materials to sequester OC. Even without any addition of organic fertilizer, the mineral phase of the analyzed soil material appears to be C‐saturated.  相似文献   

3.
We tested the hypothesis whether organic matter in subsoils is a large contributor to organic carbon (OC) in terrestrial ecosystems and if survival of organic matter in subsoils is the result of an association with the soil mineral matrix. We approached this by analyzing two forest soil profiles, a Haplic Podzol and a Dystric Cambisol, for the depth distribution of OC, its distribution among density and particle‐size fractions, and the extractability of OC after destruction of the mineral phase by treatment with hydrofluoric acid (HF). The results were related to indicators of the soil mineralogy and the specific surface area. Finally, scanning electron microscopy combined with energy dispersive X‐ray spectroscopy (SEM‐EDX) was used to visualize the location of OC at mineral surfaces and associations with elements of mineral phases. The subsoils (B and C horizons) contained 40—50% of the soil OC including the organic forest floor layers. With increasing depth of soil profiles (1) the radiocarbon ages increased, and (2) increasing portions of OC were either HF‐soluble, or located in the density fraction d >1.6 g cm—3, or in the clay fraction. The proportions of OC in the density fraction d >1.6 g cm—3 were closely correlated to the contents of oxalate and dithionite‐citrate‐bicarbonate‐extractable Fe (r2 = 0.93 and 0.88, P <0.001). SEM‐EDX analyses suggested associations of OC with aluminum whereas silicon‐enriched regions were poor in OC. The specific surface area and the microporosity of the soil mineral matrix after destruction of organic matter were less closely correlated to OC than the extractable iron fractions. This is possibly due to variable surface loadings, depending on different OC inputs with depth. Our results imply that subsoils are important for the storage of OC in terrestrial ecosystems because of intimate association of organic matter with secondary hydrous aluminum and iron phases leading to stabilization against biological degradation.  相似文献   

4.
ABSTRACT

Many factors could influence simultaneously soil spectra. We aimed to study the single effect of organic carbon and total iron in soil visible and short-wave near-infrared spectra and to quantify their contents. Two datasets of soil mixture samples were prepared by mixing, in various fractions, an organic carbon-rich material with a total iron-rich material and then with a total iron-poor material. For these two datasets, contents in organic carbon are quite similar but contents in total iron are significantly different. Results show that samples of the same dataset have the same overall spectral shape. Organic carbon has a decreasing effect that affects the whole spectral range without showing any specific absorption peaks. By contrast, total iron has specific absorption peaks. Spectra of the second dataset characterized by soil mixtures with higher total iron contents were more compact within the spectral bands 400–440 and 920–950 nm. Besides, continuum removal enables to exaggerate absorption peaks of wavelengths linked to total iron content. Partial Least Squares Regression (PLS R) models of both total organic carbon and total iron assign high coefficients to the wavelengths that are considered relevant and conversely low coefficients to those that are considered irrelevant. Both organic carbon content and total iron content were well predicted. For these models, coefficients of determination were superior to 0.9 and RMSE was closed to zero. The global models calibrated on all the samples demonstrated that PLS R was able to integrate sample heterogeneity.  相似文献   

5.
This study explored the potential of mid-infrared spectroscopy (MIR) with partial least-squares (PLS) analysis to predict sorption coefficients (Kd) of pesticides in soil. The MIR technique has the advantage of being sensitive to both the content and the chemistry of soil organic matter and mineralogy, the important factors in the sorption of nonionic pesticides. MIR spectra and batch Kd values of atrazine were determined on a set of 31 soil samples as reference data for PLS calibration. The samples, with high variability in soil organic carbon content (SOC), were chosen from 10 southern Australian soil profiles (A1, A2, B, and C in one case). PLS calibrations, developed for the prediction of Kd from the MIR spectra and reference Kd data, were compared with predictions from Koc-based indirect estimation using SOC content. The reference Kd data for the 31 samples ranged from 0.31 to 5.48 L/kg, whereas Koc ranged from 30 to 680 L/kg. Both coefficients generally increased with total SOC content but showed a relatively poor coefficient of determination (R2 = 0.53; P > 0.0001) and a high standard error of prediction (SEP =1.22) for the prediction of Kd from Koc. This poor prediction suggested that total SOC content alone could explain only half of the variation in Kd. In contrast, the regression plot of PLS predicted versus measured Kd resulted in an improved correlation, with R2 = 0.72 ( P > 0.0001) and standard error of cross-validation (SECV) = 0.63 for three PLS factors. With the advantages of MIR-PLS in mind, (i) more accurate prediction of Kd, (ii) an ability to reflect the nature and content of SOC as well as mineralogy, and (iii) high repeatability and throughput, it is proposed that MIR-PLS has the potential for an improved and rapid assessment of pesticide sorption in soils.  相似文献   

6.
Physical protection is one of the most important ways for stabilization of organic carbon (OC) in soils, and in order to properly manage soils as a sink for carbon, it is necessary to know how much OC a given soil could protect. To this end, we studied individual horizons taken from 16 soil profiles under Quercus rotundifolia stands, all over calcareous parent materials. Horizons were subjected to a sequential extraction using solutions of sodium polytungstate (NaPT) of increasing density: (i) NaPT d=1.6, using slight hand agitation, to obtain the free light fraction (FL); (ii) NaPT d=1.6 and ultrasonic dispersion, to obtain the Occluded Fraction I (Ocl I); (iii) NaPT d=1.8, to obtain the Occluded Fraction II (Ocl II); and (iv) NaPT d=2.0, to obtain the Occluded Fraction III (Ocl III). The fraction of density>2.0 are taken as dense fraction (DF). The free organic matter was further divided into FL>50 (retained by a 50 μm mesh: coarse organic fragments) and FL<50 (non-retained: fine organic fragments). The fractions FL>50 and FL<50 were taken together as free organic matter. The rest of the fractions are taken together as protected organic matter. The obtained fractions were analyzed for total OC, total N, and carbohydrate content. The percentage of non-hydrolyzable OC and N in each fraction was taken as an indicator of OC and N recalcitrance, respectively.For both OC and N, the fractions FL>50 and DF are dominant; the rest of the fractions are of much lower quantitative importance. In H horizons and in most A horizons, most of the OC and N are free, whereas in B horizons both OC and N are mostly protected. Overall, the percentages of free OC and N are very high and are currently amongst the highest ever recorded.Organic matter recalcitrance is lowest in the two most protected fractions (Ocl III and especially DF), and highest in the first occluded fractions (Ocl II and especially Ocl I). The free organic matter (FL>50 fraction) has an intermediate quality: it includes recognizable plant fragments, but the indicators tested (recalcitrance, carbohydrate content, cellulose to total carbohydrates ratio) suggest that it is not always the most fresh and non-decomposed fraction.There are clear maxima for both protected OC and N, which can be approached by curve fitting. By exponential fit, the obtained maxima are 84.1 g of OC and 7.7 g of N kg−1 of mineral particles <20 μm. These maxima are much higher than the upper limits obtained by other authors. Differences in the sampling approach are suggested as the reason for such discrepancies.  相似文献   

7.
To quantify the relationship between the soil organic matter and color parameters using the CIE-Lab system, 62 soil samples (0–10 cm, Ferralic Acrisols) from tea plantations were collected from southern China. After air-drying and sieving, numerical color information and reflectance spectra of soil samples were measured under laboratory conditions using an UltraScan VIS (HunterLab) spectrophotometer equipped with CIE-Lab color models. We found that soil total organic carbon (TOC) and nitrogen (TN) contents were negatively correlated with the L* value (lightness) (r = –0.84 and –0.80, respectively), a* value (correlation coefficient r = –0.51 and –0.46, respectively) and b* value (r = –0.76 and –0.70, respectively). There were also linear regressions between TOC and TN contents with the L* value and b* value. Results showed that color parameters from a spectrophotometer equipped with CIE-Lab color models can predict TOC contents well for soils in tea plantations. The linear regression model between color values and soil organic carbon contents showed it can be used as a rapid, cost-effective method to evaluate content of soil organic matter in Chinese tea plantations.  相似文献   

8.
施肥措施对复垦土壤团聚体碳氮含量和作物产量的影响   总被引：4，自引：1，他引：3  
研究复垦后不同施肥措施下有机碳（OC）和全氮（TN）在水稳性团聚体及粉黏粒组分中的分布特征,以期深入理解不同施肥措施下土壤有机碳的固持机制。以生土和连续6年不同施肥措施的复垦土壤为研究对象,采集0～20 cm耕层土壤样品,利用湿筛法进行土壤粒径分组,分析大粒径大团聚体（> 2 mm）、小粒径大团聚体（0.25～2 mm）、微团聚体（0.053～0.25 mm）和粉黏粒组分（< 0.053 mm）中OC和TN含量,判断各粒径团聚体及粉黏粒组分中有机碳储量的驱动因素,探究团聚体及粉黏粒组分中有机碳含量与作物产量之间的关系。试验设不施肥（CK）、施氮磷钾化肥（NPK）、单施有机肥（M）和有机无机肥配施（MNPK）4个处理。结果表明：1）整个试验周期（2008-2013年）,同CK相比, NPK、M以及MNPK处理均显著提高了玉米籽粒产量,且以MNPK处理的效果最显著,分别提高了79.49%、116.07%和113.85%。  相似文献   

9.
The long-term storage of soil organic matter (SOM) in forest soils is still poorly understood. In this study, particle size fractionation in combination with accelerator mass spectroscopy (AMS) and solid state 13C nuclear magnetic resonance (NMR) spectroscopy was applied to investigate organic carbon (OC) stabilisation in Cambisol and Luvisol profiles under spruce (Picea abies) and beech (Fagus sylvatica L.) forests. In most samples, OC was preferentially associated with <2 μm fractions. Throughout soil profiles the contribution of OC in the clay fraction to the total OC increased from 27%-53% in A horizons to 44-86% in E, B and EB horizons. The 200-2000 μm fractions from all sites and all depths showed a percentage of modern C (pmC)>100. They were enriched in 14C owing to high inputs of recent material from leaves and roots. Clearly less active material was associated with <2 and 2-20 μm fractions. This demonstrated that the particle size fractionation procedure applied to our study was capable to isolate a young OC fraction in all samples. The pmC values were strongly decreasing with depth but the decrease was much more pronounced in the fine fractions. The <2 and 2-20 μm fractions of B, E and EB horizons revealed radiocarbon ages between 512 and 4745 years before present which indicated that the SOM in those horizons was little affected by the recent vegetation. The major components of labile and stable SOM pools in topsoils and subsoils were always O/N-alkyl C (28-53%) and alkyl C (14-48%) compounds. NMR spectra of bulk soils and particle size fractions indicated that high alkyl C and O/N-alkyl C proportions throughout the soil profile are typical of Cambisols and Luvisols which were not subjected to regular burning. A relation between radiocarbon age and chemical composition throughout soil profiles was not observed. This suggests that the long-term stabilisation of SOM is mainly controlled by the existence of various mechanisms of protection offered by the soil matrix and soil minerals but not by the chemical structure of SOM itself.  相似文献   

10.
The feasibility of near infrared (NIR) spectroscopy for quantifying labile organic matter (OM) in arable soils and for predicting soil refractory OM fractions was tested on 37 soils varying in texture and soil carbon (C) content. Three sets of arable soils (0-20 cm depth) were sampled from 1) long-term field experiments with different OM inputs, 2) individual sites with inherent with-in field gradients in soil texture and/or C content, and 3) from a range of different sites covering variations in management and geological origin. The labile OM fraction was defined by the CO2 evolved from the soils incubated for 34 weeks while refractory OM was obtained by NaOCl oxidation.The labile fraction of the soil C accounted for 2-12% of the total soil C content. No systematic relationship between labile C content and total soil C or clay was found, but NIR spectra could be correlated well with the labile C fraction. A distinct, close linear relationship was found for C in soil before and after the NaOCl oxidation, indicating that this method was unable to reveal any additional information not contained in the total soil C measurement. NIR was also correlated with the NaOCl resistant C fraction, but this was considered to relate to the ability of NIR to predict total soil C contents. Thus NIR seemed to have the potential to estimate labile OM determined under laboratory incubations, while it still remains open how to identify and quantify refractory pools of soil OM.  相似文献   

11.
We studied the quantitative and qualitative changes of soil organic matter (SOM) due to different land uses (arable versus grassland) and treatments (organic manure and mineral fertilizer) within an agricultural crop rotation in a long‐term field experiment, conducted since 1956 at Ultuna, Sweden, on a Eutric Cambisol. The organic carbon (OC) content of the grassland plot was 1.8 times greater than that of the similarly fertilized Ca(NO3)2 treated cropped plots. The comparison of two dispersion techniques (a low‐energy sonication and a chemical dispersion which yield inherent soil aggregates) showed that increasing OC contents of the silt‐sized fractions were not matched by a linear increase of silt‐sized aggregates. This indicated saturation of the aggregates with OC and a limited capacity of particles to protect OC physically. Thermogravimetric analyses suggested an increase of free organic matter with increasing OC contents. Transmission FT‐IR spectroscopy showed relative enrichment of carboxylic, aromatic, CH and NH groups in plots with increasing OC contents. The silt‐sized fractions contained the largest SOM pool and, as revealed by 13C NMR spectroscopy, were qualitatively more influenced by the plant residue versus manure input than the clay fractions. Alkyl and O‐alkyl C in the silt‐sized fractions amounted to 57.4% of organic carbon in the animal manure treated plots and 50–53% in the other treatments.  相似文献   

12.
Land use changes profoundly affect the equilibrium of soil organic carbon (SOC) sequestration and greenhouse gas emissions. With the current global climatic changes, it is vital to understand the influence of ecological restoration and conservation management on the dynamics of SOC under different land uses, especially in erosion-endangered Loess soils. Therefore, we investigated changes in SOC through a suit of labile fractions, namely: light fraction organic C (LFOC), heavy fraction organic C (HFOC), coarse particulate organic C (CPOC), fine particulate organic C (FPOC), and dissolved organic C (DOC), from two forests i.e., Robinia pseudoacacia (RP) and Platycladus orientalis (PO), with different ages, in comparison with farmland (FL). The SOC and STN contents significantly increased over 42 years in the RP forest where the contents of CPOC and FPOC were significantly higher than in the FL. Moreover, total SOC and its labile fractions, in the studied land use types, significantly correlated with soil CaCO3, pH, and STN contents, indicating their key roles in SOC sequestration. The results reported here from different vegetation with different ages provide a better understanding of SOC and STN alterations at different stages of vegetation restoration. Our findings suggest that long-term natural vegetation restoration could be an effective approach for SOC sequestration and soil conservation on the Loess soil.  相似文献   

13.
The association of organic carbon with secondary particles (aggregates) results in its storage and retention in soil. A study was carried out at a catchment covering about 92 km2 to predict spatial variability of soil water-stable aggregates (WSA), mean weight diameter (MWD) of aggregates and organic carbon (OC) content in macro- (> 2 mm), meso- (1-2 mm), and micro-aggregate (< 1 mm) fractions, using geostatistical methods. One hundred and eleven soil samples were collected at the 0-10 cm depth and fractionated into macro-, meso-, and micro-aggregates by wet sieving. The OC content was determined for each fraction. A greater percentage of water-stable aggregates was found for micro-aggregates, followed by meso-aggregates. Aggregate OC content was greatest in meso-aggregates (9 g kg?1), followed by micro-aggregates (7 g kg?1), while the least OC content was found in macro-aggregates (3 g kg?1). Although a significant e?ect (P = 0.000) of aggregate size on aggregate OC content was found, however, our findings did not support the model of aggregate hierarchy. Land use had a significant e?ect (P = 0.073) on aggregate OC content. The coe?cients of variation (CVs) for OC contents associated with each aggregate fraction indicated macro-aggregates as the most variable (CV = 71%). Among the aggregate fractions, the micro-aggregate fraction had a lower CV value of 27%. The mean content of WSA ranged from 15% for macro-aggregates to 84% for micro-aggregates. Geostatistical analysis showed that the measured soil variables exhibited di?erences in their spatial patterns in both magnitude and space at each aggregate size fraction. The relative nugget variance for most aggregate-associated properties was lower than 45%. The range value for the variogram of water-stable aggregates was almost similar (about 3 km) for the three studied aggregate size classes. The range value for the variogram of aggregate-associated OC contents ranged from about 3 km for macro-aggregates to about 6.5 km for meso-aggregates. Kriged maps of predicted WSA, OC and MWD for the three studied aggregate size fractions showed clear spatial patterns. However, a close spatial similarity (co-regionalization) was observed between WSA and MWD.  相似文献   

14.
Soil organic carbon (SOC) content depends significantly upon changes in land use and vegetation cover. This study aimed to examine the redistribution of whole soil OC, water-soluble OC (WSOC), and different density-separated OC fractions in soil profiles of 0–100 cm under different land uses and to elaborate the mechanism of C sequestration in response to the land use change. The land use types include maize plots with or without chemical fertilizer application (i.e., Maize-nitrogen, phosphorus, and potassium (NPK) and Maize-NF plots), plots with vegetation removed (No Vegetation), plots with grass (Grass), and alfalfa plant (Alfalfa). These plots used to be maize cropping system with NPK fertilizer for many years before 2003. Significant difference in SOC content generally occurred in soil layers of 0–40 cm among the different plots after 11 years of land-use change. Long-term continuous maize planting decreased SOC content; the significant SOC decrease occurred in Maize plot in the range of 9.3–23.4% for different soil layers compared with the initial soil sampled in 2003. In addition, SOC in Maize plot decreased by 3.6% and 8.5% at top two soil layers, respectively, in comparison with No Vegetation plot. The similar reduction of OC was observed in heavy OC fractions. The calculated sensitivity index for OC decreased in the order of light fraction > water-soluble fraction > the whole soil > heavy fraction. Therefore, the young and labile carbon fractions are much sensitive to land use change relative to the old and recalcitrant carbon fractions. This study indicated that land use changes led to a redistribution of SOC in soil profile, particularly at top soil layers, and conversion from arable land to natural grass cover or nitrogen-fixation plant cultivation such as alfalfa led to the enrichment of SOC at different depths of soil profile.  相似文献   

15.
Applicability of near infrared reflectance (NIR) and fluorescence spectroscopic techniques was tested on highly organic arctic soil. Soil samples were obtained at a long-term climate change manipulation experiment at a subarctic fell heath in Abisko, northern Sweden. The ecosystem had been exposed to treatments simulating increasing temperature (open-top greenhouses), higher nutrient availability (NPK fertilization) and increasing cloudiness (shading cloths) for 15 years prior to the sampling. For each of the 72 samples from the 0 to 5 cm soil depth and 36 samples from the 5 to 10 cm depth, the wavelength range of 400-2500 nm (visible and near infrared spectrum) was scanned with a NIR spectrophotometer and fluorescence excitation-emission matrices (EEMs) were recorded with a spectrofluorometer.Principal component analyses of the visible, NIR and fluorescence spectra clearly separated the treatments, which indicates that the chemical composition of the soil and its spectral properties had changed during the climate change simulation. Similarly to the results from the conventional analyses of soil chemical and microbiological properties, fertilization treatment posed strongest effects on the spectra. Partial least-squares (PLS) regression methods with cross-validation were used to analyse relationships between the spectroscopic data and the chemical and microbiological data derived from the conventional analyses. The fluorescence EEMs of the dried solid soil samples were moderately related to soil ergosterol content (correlation coefficient r=0.84), bacterial activity analysed by leucine incorporation technique (r=0.78) and total phospholipid fatty acid (PLFA) content (r=0.74), but in general fluorescence provided inferior predictions of the chemical and microbiological variables to NIR. NIR was highly related to soil organic matter content (r>0.9) and showed promising predictions of soil ergosterol content (r>0.9), microbial biomass C, microbial biomass P, and total PLFA contents (r=0.78-0.79).These results suggest that especially NIR could be used to predict soil organic matter and fungal biomass. Since it is rapid and inexpensive, and requires little sample mass, it could be used as a ‘quick and dirty’ technique to estimate progression of the treatment responses in long-term ecosystem experiments, where extensive soil sampling is to be avoided.  相似文献   

16.
Termite activities are known to significantly influence small-scale soil properties in tropical savannas. The lateral and vertical extent of the alterations to the nest's surrounding, and particularly resulting impacts on diagnostic soil horizons remain largely unresolved until today. We examined the effects of mound-building termites on soil genesis and constitutive chemical soil properties in and below their nests. Two transects to a soil depth of 100 cm were dug below three younger mounds of Cornitermes silvestrii (the primary nest builder), three older mounds in which C. silvestrii had died out and which were secondarily colonized mainly by Nasutitermes kemneri, and three reference sites in the Brazilian Cerrado. The samples were characterized by standard procedures for soil classification; in addition, phosphorus extractions were conducted on selected samples using NaHCO3 for labile P forms, and concentrated HCl for stable P forms. This data set was then used to build calibration models for the prediction of labile and stable inorganic (Pi) and organic (Po) P forms, as well as for contents of organic carbon (OC), for the remaining samples applying mid-infrared spectroscopy in combination with partial least squares regression (MIRS-PLSR). We can show that the termite influence on the soil was sufficiently large to change diagnostic characteristics of the soils under termite mounds. The MIRS-PLSR predictions were suitable for quantifying organic carbon and most of the labile and stable phosphorus fractions. They showed an enrichment of OC, NaHCO3-Po and NaHCO3-Pi contents in nests inhabited by primary and secondary termites by factors of 1.6–2.0 and 1.4–1.5, respectively. The soils surrounding the nests had higher contents of OC and NaHCO3-P under both nest types vertically down to 30 cm below the lower nest border, and OC and NaHCO3-Pi contents were elevated at minimum to a lateral distance of 60 cm away from the nest border. As the pattern of HClconc-Pi, which comprised 95% of total P, showed no variations, we conclude that the higher NaHCO3-Pi amount was formed in termite nests by changing the availability of the more stable HClconc-Pi. In contrast to the contents, the OC and NaHCO3-P stocks below the mounds inhabited by primary termites were comparable to those inhabited by secondary ones, because the bulk density of the secondarily inhabited nests was elevated. This was due to a transport of clay-rich material from the subsurface argic horizons into the nests. Here, the secondary termites even reverted the lessivation observed in the reference soils and under mounds inhabited by primary termites, thus causing the soil types to change from Alisols and Acrisols to the properties of Umbrisols.  相似文献   

17.
长期不同施肥对塿土大团聚体中有机碳组分特征的影响   总被引：1，自引：0，他引：1  
【目的】研究长期施肥对土大团聚体中有机碳组分特征的影响,揭示不同施肥方式下土壤有机碳的固持机制,为合理施肥提供理论依据。【方法】采集土35年长期肥料定位试验不同施肥处理0—10 cm和10—20 cm土样,分析其大团聚体中各组分有机碳含量的变化。试验处理为:不施肥(CK)、单施化肥(NP)、单施有机肥(M)和有机肥配施化肥(MNP)。【结果】与CK相比,长期NP处理对大团聚体中粗颗粒有机碳(cPOC)、细颗粒有机碳(fPOC)、大团聚体中微团聚体内颗粒有机碳(iPOC)以及矿质结合态有机碳(MOC)组分的有机碳(OC)含量均无显著影响;而M处理以及MNP处理可显著提高两土层cPOC和iPOC组分的OC含量以及0—10 cm土层MOC组分的OC含量,其中,cPOC含量增幅分别为174%~338%和215%~245%,iPOC含量增幅分别为127%~241%和106%~130%,MOC含量增幅达28.9%~34.6%。MNP处理显著提高了0—10 cm土层fPOC组分的OC含量,增幅达482.1%。累积碳投入量与大团聚体中各组分的OC含量呈显著线性相关,尤其是iPOC含量,表明长期施肥过程中土有机碳在大团聚体中固存的差异主要受物理保护的颗粒有机碳组分的影响。【结论】关中地区土长期施化肥对大团聚体中各组分OC含量没有显著影响,而长期单施有机肥能进一步增加大团聚体中各组分OC含量,有机肥配施化肥能显著增加团聚体中各组分OC含量,特别是大团聚体中微团聚体内颗粒有机碳组分的含量,进而增加土的有机碳固持。因此,有机肥配施化肥是提高土有机碳含量的有效措施。  相似文献   

18.
This study investigated the suitability of mid‐infrared diffuse reflectance Fourier transform (MIR‐DRIFT) spectroscopy, with partial least squares (PLS) regression, for the determination of variations in soil properties typical of Italian Mediterranean off‐shore environments. Pianosa, Elba and Sardinia are typical of islands from this environment, but developed on different geological substrates. Principal components analysis (PCA) showed that spectra could be grouped according to the soil composition of the islands. PLS full cross‐validation of soil property predictions was assessed by the coefficient of determination (R2), the root mean square error of cross‐validation and prediction (RMSECV and RMSEP), the standard error (SECV for cross‐validation and SEP for prediction), and the residual predictive deviation (RPD). Although full cross‐validation appeared to be the most accurate (R2 = 0.95 for organic carbon (OC), 0.96 for inorganic carbon (IC), 0.87 for CEC, 0.72 for pH and 0.74 for clay; RPD = 4.4, 6.0, 2.7, 1.9 and 2.0, respectively), the prediction errors were considered to be optimistic and so alternative calibrations considered to be more similar to ‘true’ predictions were tested. Predictions using individual calibrations from each island were the least efficient, while predictions using calibration selection based on a Euclidian distance ranking method, using as few as 10 samples selected from each island, were almost as accurate as full cross‐validation for OC and IC (R2 = 0.93 for OC and 0.96 for IC; RPD = 3.9 and 4.7, respectively). Prediction accuracy for CEC, pH and clay was less accurate than expected, especially for clay (R2 = 0.73 for CEC, 0.50 for pH and 0.41 for clay; RPD = 1.8, 1.5 and 1.4, respectively). This study confirmed that the DRIFT PLS method was suitable for characterizing important properties for soils typical of islands in a Mediterranean environment and capable of discriminating between the variations in soil properties from different parent materials.  相似文献   

19.
三峡库区消落带湿地土壤有机碳及其组分特征   总被引：2，自引：1，他引：2  
贾国梅  席颖  牛俊涛 《土壤》2015,47(5):926-931
湿地生态系统土壤有机碳库的组分变化对于全球碳平衡起着极其重要的作用。本研究选取三峡库区消落带湿地3个海拔梯度的土壤,以从未淹没的样地作为对照,研究消落带湿地不同海拔梯度土壤有机碳组分的特征。结果表明:土壤有机碳、易氧化有机碳、水溶性碳水化合物有机碳和和微生物生物量碳均以消落带小于未淹没样地。在消落带,海拔最低、淹没持续时间较长且正处于水位波动期的样地土壤有机碳、易氧化碳和微生物生物量碳显著低于其他样地,而土壤矿化碳显著高于其他样地。相关性分析表明,土壤有机碳与微生物生物量碳(R~2=0.94)的正相关性显著高于与易氧化有机碳(R~2=0.88)、水溶性有机碳(R~2=0.73)及其水溶性碳水化合物(R~2=0.70)之间的正相关性,但是与矿化碳之间无显著的相关性。因此,土壤微生物生物量碳是消落带湿地土壤有机碳随不同海拔梯度变化的最敏感的组分。  相似文献   

20.
Abstract

Rice farmers apply organic matter and phosphatic fertilizer before or at the time of puddling (an operation involving tilling of puddled soil before transplanting of rice seedlings) as a part of their soil management program for growing wet land rice. This brings about changes in chemical environment which modifies micronutrient redistribution among soil fractions and thus, their availability to rice crops. An experiment was conducted to understand the effect of organic matter and phosphorus (P) on transformation of copper (Cu) in Alfisols under submergence. Soils were incubated for 75 days in the laboratory under submerged condition and were analyzed for different fractions of Cu content at periodic intervals. Copper was mobilized from water soluble plus exchangeable (WSEX), organically complexed (OC), and crystalline iron (Fe) oxides (CRYOX) bound fractions to amorphous iron oxides (AMOX) and residual (RESID) fractions, the rate of mobilization being maximum from CRYOX and to RESID fraction during initial 15‐day period. Organic matter application retarded Cu transformation from OC and into RESID fraction and increased its content in AMOX fractions. It also decreased WSEX Cu markedly. Copper transformation was not significantly influenced by P application.  相似文献   

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