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1.
Abstract

A simple and rapid procedure for the determination of organic matter content in mineral soils by loss‐on‐ignition without pretreatment was studied. Attention was given to the possible effect of inorganic compounds abundant in mineral soils on the estimation of organic matter content by this method. Both fast heating (DTA‐TGA type) studies and prolonged heating procedures were employed on natural and “synthetic”; soils. The results were compared to those obtained by the dichromate wet‐oxidation method widely used in soil laboratories for organic matter determination. In a group of 91 soils collected from various mineral soils in Israel, and having OM contents between 0.09 and 13.23%, a correlation coefficient of 0.972 was obtained for the linear regression between organic matter content measured by the proposed method and organic carbon measured by the dichromate wet‐oxidation method.  相似文献   

2.
Abstract

We compared three methods of estimating soil organic carbon (dichromate oxidation with and without external heating and loss‐on‐ignition) with a method for total carbon measured in an automated resistance furnace. In 38 surface (0–150 mm) podzolized sands the concentration of total carbon ranged from 0.39 to 4.57% and was highly correlated with all three methods (r2=0.99, p<0.0001, in each case). Dichromate oxidation with and without external heating recovered 99.1 and 88.8% of total carbon respectively, indicating that all carbon was organically bound, and that the ‘heat of reaction’ was not sufficient for total oxidation of organic carbon. Because the organic carbon content of the organic matter varied from 38% to 55% a mean value of 46% would be more appropriate for these soils than the Van Bemmelen factor of 58% for converting organic matter to organic carbon concentration The loss‐on‐ignition procedure represents a precise technique for the estimation of organic matter and, when calibrated, organic carbon in surface sandy soils.  相似文献   

3.
Abstract

This study compared three dichromate‐oxidation methods adapted for use with 100‐mL digestion tubes and 40‐tube block digester (for controlled heating), the Walkley‐Black method, a loss‐on‐ignition procedure and an automated dry combustion method for the determination of organic carbon in soils of the northwestern Canadian prairie. The Walkley‐Black method required a correction factor of 1.40. The modified Tinsley method and the Mebius procedure, adapted for use with 100‐mL digestion tubes, recovered 95% and 98%, respectively, of soil carbon against the dry combustion procedure. The presence of elemental carbon in some soils probably caused, at least partially, the slightly incomplete recovery; thermal decomposition of dichromate may not have been accurately corrected for. A dichromate‐oxidation procedure with controlled digestion at 135°C gave 100% recovery, but somewhat more variable results. The loss‐on‐ignition procedure, even when allowance was made for clay content of the soils, was the least satisfactory of the methods tested. All procedures produced correlation coefficients of 0.980 or better against the dry combustion method.  相似文献   

4.
运用地统计和多元回归分析方法,探讨大沽河流域土壤阳离子交换量(CEC)的空间变异和影响因子。结果表明,上下层土壤CEC与有机质、黏粒和粉粒含量有着显著的正相关,而与砂粒含量则存在显著的负相关,其中与黏粒含量的相关系数最大,与粉粒含量的相关性最弱;对CEC的贡献能力依次为黏粒有机质砂粒,黏粒的贡献能力平均为有机质的1.5～2.5倍;以黏粒为辅助变量的Cokriging(COK)较之Ordinary Kriging(OK)能提高插值精度,上下层均方根误差RMSE值分别减少了18.94%和41.05%,辅助变量与主变量的相关程度决定了估值的精度;大沽河流域中东、西北部及西南方向中部地区土壤CEC较高,而北部与西南角局部地区土壤CEC保肥能力非常弱,是以后土壤改良的重点地区,可通过增施有机肥以及改土培肥等措施来提高土壤肥力水平。  相似文献   

5.
康倍铭  徐健  吴淑芳    徐晓敏  冯浩 《水土保持研究》2014,21(3):68-72,78
为了充分发挥高分子土壤改良剂和一些天然土壤改良材料改土培肥作用,选取了高分子土壤改良剂聚丙烯酰胺（PAM）,分别与具有改土培肥功能的天然土壤改良材料——油渣、秸秆、蛭石、草炭、页岩、风化煤按不同用量混合施入土壤,利用湿筛法、称重法、重铬酸钾容量法、离心机法,测定对土壤水稳性团聚体、孔隙度、土壤有机质、有效含水量和水分蒸发等土壤理化性质的影响。结果表明:（1）各处理与单施PAM相比,对土壤孔隙度没有明显影响,但对土壤水稳性团聚体含量均有不同程度的提高,其中PAM与0.6%秸秆处理和PAM与0.3%油渣处理对其影响最为显著,较单施PAM提高4.9%和4.6%;（2）通过天然土壤改良剂自身的有机质含量测定以及PAM分别与六种天然土壤改良材料混合施入土壤培养前后有机质含量测定,结果分析得出,随着材料施入量增加,各处理培养前后土壤有机质含量呈现递增趋势;风化煤处理对土壤有机质含量增加显著,培养后其土壤损失有机质百分比较高,幅度约50%,页岩处理培养土壤损失有机质的百分比较少,幅度约为6%;（3）通过各处理在不同水吸力下土壤持水量和蒸发观测得出,PAM与3%的风化煤处理显著提高土壤有效水含量,PAM与1%的秸秆处理和PAM与1%的油渣处理显著提高了土壤抗蒸发能力。总体上,PAM与风化煤、PAM与油渣和PAM与秸秆处理对土壤结构、土壤有机质含量、土壤水分等方面有显著改善作用。这对进一步研制具有多重功能的土壤改良剂提供参考。  相似文献   

6.
基于灰度关联-岭回归的荒漠土壤有机质含量高光谱估算   总被引：13，自引：7，他引：6  
为改善高光谱技术对荒漠土壤有机质的估测效果,该文采集了以色列Seder Boker地区的荒漠土壤,经预处理、理化分析后将土样分为砂质土和黏壤土2类,再通过光谱采集、处理得到6种光谱指标:反射率(reflectivity,REF)、倒数之对数变换(inverse-log reflectance,LR)、去包络线处理(continuum removal,CR)、标准正态变量变换(standard normal variable reflectance,SNV)、一阶微分变换(first order differential reflectance,FDR)和二阶微分变换(second order differential reflectance,SDR)。通过灰度关联(gray correlation,GC)法确定SNV、FDR、SDR为敏感光谱指标,采用偏最小二乘回归(partial least squares regression,PLSR)法和岭回归(ridge regression,RR)法,构建基于敏感光谱指标的土壤有机质高光谱反演模型,并对模型精度进行比较。结果表明:砂质土有机质含量的反演效果要优于黏壤土;基于SNV指标建立的模型决定系数R~2和相对分析误差RPD均为最高、均方根误差RMSE最低,所以SNV是土壤有机质的最佳光谱反演指标;对SNV-PLSR模型和SNV-RR模型综合比较得出,SNV-RR模型仅用全谱4%左右的波段建模,实现了更为理想的反演效果:其中,对砂质土有机质的预测能力极强(R_p~2为0.866,RMSE为0.610 g/kg、RPD为2.72),对黏壤土有机质的预测能力很好(Rp2为0.863,RMSE为0.898 g/kg、RPD为2.37)。荒漠土壤有机质GC-SNV-RR反演模型的建立为高光谱模型的优化、土壤有机质的快速测定提供了一种新的途径。  相似文献   

7.
Abstract

Procedures for determining organic matter indirectly and directly in sludges are described. A good agreement between chromic acid oxidation and dry—combustion elemental analysis methods of determining organic‐C was observed. Sludge organic matter content was determined directly by loss‐on‐ignition by thermal analysis. An average C factor of 1.68 to estimate the organic matter from organic‐C, obtained by chromic acid oxidation method, was calculated for aerobically digested sludges.  相似文献   

8.
Abstract

The determination of soil organic matter by wet digestion techniques is a slow and laborious analysis. Loss‐on‐ignition (LOI) provides a simple alternative technique for the estimation of soil organic carbon in non‐calcareous A horizon soils of the Natal midlands and Zululand forestry regions. Using multiple regressional techniques, the relationships between loss‐on‐ignition, Walkley organic carbon and soil texture for 55 soils were determined over a range of ignition temperatures. The relationships hold best for soil samples with relatively low organic carbon contents (< 5%). The optimum temperature for ignition was found to occur at 450°C and resulted in the relationship: Soil organic carbon = 0.284*LOI percent. No advantage is gained through ignition at higher temperatures due to the loss of clay mineral structural water, even if the soil texture is accurately known.  相似文献   

9.
利用烧失量方法精确测定土壤有机质   总被引：3，自引：0，他引：3  
Wet oxidation procedure,i.e.,Walkley-Black (WB) method,is a routine,relatively accurate,and popular method for the determination of soil organic matter (SOM) but it is time-consuming,costly and also has a high potential to cause environmental pollution because of disposal of chromium and strong acids used in this analysis.Therefore,loss-on-ignition (LOI) procedure,a simple and cheap method for SOM estimation,which also avoids chromic acid wastes,deserves more attention.The aims of this research were to study the statistical relationships between SOM determined with the LOI (SOMLOI) and WB (SOMWB) methods to compare the spatial variability of SOM in two major plains,Shahrekord and Koohrang plains,of Chaharmahal-va-Bakhtiari Province,Iran.Fifty surface soil samples (0-25 cm) were randomly collected in each plain to determine SOM using the WB method and the LOI procedure at 300,360,400,500 and 550 ℃ for 2 h.The samples covered wide ranges of soil texture and calcium carbonate equivalent (CCE).The general linear form of the regression equation was calculated to estimate SOM LOI from SOM obtained by the WB method for both overall samples and individual plains.Forty soil samples were also randomly selected to compare the SOM and CCE before and after ignition at each temperature.Overall accuracy of the continuous maps generated for the LOI and WB methods was considered to determine the accordance of two procedures.Results showed a significant positive linear relationship between SOM LOI and SOM WB.Coefficients of determination (R2) of the equations for individual plains were higher than that of the overall equation.Coefficients of determination and line slopes decreased and root mean square error (RMSE) increased with increasing ignition temperature,which may be due to the mineral structural water loss and destruction of carbonates at higher temperatures.A temperature around 360 ℃ was identified as optimum as it burnt most organic carbon,destroyed less inorganic carbon,caused less clay structural water loss,and used less electrical energy.Although the trends of SOM in the kriged maps by the two procedures accorded well,low overall accuracy was observed for the maps obtained by the two methods.While not suitable for determination where high accuracy is required,determination of organic carbon through LOI is likely suitable for exploratory soil surveys where rough estimation of organic matter is required.  相似文献   

10.
[目的]通过光谱识别太湖流域农用地面源磷流失的土壤主控因子,为简化面源磷流失强度估算提供依据。[方法]通过分析梅梁湾流域耕地和园地中不同面源磷流失强度下的土壤光谱特征,确定影响面源磷流失强度的主要土壤理化性质。[结果]耕地面源磷流失强度的特征波段为650~670nm,1 475nm和1 680~1 695nm,土壤主控因子是有机质,二者之间呈正相关;园地面源磷流失强度的特征波段为685~690nm,710~720nm,1 110~1 115nm,1 150~1 155nm和2 170nm,主控因子是有机质、水分和Fe2+,分别和面源磷流失强度呈负相关、正相关和负相关;有机质对耕地的面源磷流失强度的影响更加显著:耕地面源磷流失强度与光谱指数间的相关系数在1 685nm处达到0.74,而园地条件下相关系数最高值在715nm处仅为0.48。[结论]耕地面源磷流失主控因子为有机质,园地的主控因子为有机质、水分和Fe2+。  相似文献   

11.

The performance of different methods for making soil maps from a small dataset was assessed. Soil samples obtained at five different depths were taken from 39 locations within an arable field in Sweden and analysed for clay content, soil organic matter content, pH (H2O), K-HCl, P-AL, K-AL and Mg-AL. Detailed and densely sampled soil electrical conductivity (EC) data with a distinct border between two different regions was used for dividing the field into two zones. Averages from these zones gave better prediction for most variables than interpolation without respect to the border. With the border taken into account, cokriging with EC as a covariable improved the prediction, whereas the improvement with ordinary kriging and inverse distance weighting (IDW) was insignificant. Direct interpretation of EC by a simple linear regression model gave reasonable predictions for clay content. In general, even the simplest interpolation method improved the prediction compared to field average.  相似文献   

12.
Soil organic matter (SOM) plays a key role in soil, and is used to determine soil quality. Conventional soil property analysis is relatively slow, expensive and laborious. Although using a spectrometer can quickly assess a large amount of organic matter content, it is an expensive, complex and undefined process. This article presents a potential simple method for estimating black-SOM that uses a digital camera that is cheaper and easier to operate than a spectrometer. RGB (red, green and blue) image-intensity values of the soil from a digital camera were measured, to research the relationship between black-SOM and RGB. The results show the red image-intensity values provide the greatest correlation with SOM, with a correlation coefficient (r) reaching 0.73. A comparison with spectrometer results for SOM predictions shows that the best prediction result for the digital camera (R2 = 0.72, root-mean-square error [RMSE] = 0.40) is slightly better than the spectrometer (R2 = 0.65, RMSE = 0.45) at certain band points. Thus, a low-cost digital camera that is easy to operate can be used as an alternative tool for the rapid and accurate estimation of black-SOM content.  相似文献   

13.
Reliable measurement of soil organic matter (SOM) contents is crucial to assessment of soil health, productive longevity and the effects of climate change. In this study, the loss‐on‐ignition (LOI) method has been used to determine the SOM of dried soil samples with a wide range of clay, sand and silt contents from the Agricultural Laboratory Proficiency (ALP) program. Regressions of ALP participant data against LOI measurements at 350–650°C indicate that the extent of SOM oxidation depends more on the ignition temperature and time than on the sample compositions. Thus, LOI data from ignition at 350–550°C for 12 h relative to ignition at 650°C for 12 h converge at 650°C and the average coefficient of variance decreases to ≈ 4% at 650°C. Also examined are regressions of soil organic C from direct dry combustion as standards with LOI measured at 360°C for 2 h, LOI measured at 650°C for 12 h and with the Walkley‐Black procedure used in the ALP program.  相似文献   

14.
Abstract

A simple procedure is described for the rapid determination of organic carbon content in a large number of soil samples using an automated segmented flow analyser. The method is a modification of the wet oxidation/ digestion methods based on potassium dichromate combined with a colorimetric method for determination of chromic oxide (Stevenson and Clare, 1962). Using a segmented flow analyser for the colorimetry, the procedure is capable of automated routine analyses of large numbers of samples and was shown to give high and repeatable recoveries of organic carbon from a range of compounds. Organic carbon values for a range of soils analysed by the reported method and by the dry combustion technique showed a high correlation.  相似文献   

15.
Abstract

The conventional dichromate (Walkley and Black), carbon analyzer, and weight loss‐on‐ignition (WLOI) methods are compared for determination of organic matter contents in composts and organic mulches. The objective of this study was to evaluate these three methods for their reliability in determining the organic matter contents of composts and organic mulches that also contain inorganic carbon. The carbon analyzer method overestimated organic matter contents for samples containing inorganic carbon (C) as carbonate or charcoal C. The removal of inorganic C improved the correlation coefficients (r) of results obtained by the carbon analyzer method and the Walkley and Black method (0.95 vs. 0.89). The WLOI method produced results more similar to those obtained with the Walkley and Black method than with a carbon analyzer. Oven drying samples for 16–24 h at 105°C as a basal temperature for WLOI improved results compared with a basal temperature at 70°C, which is commonly used. A heating temperature of 500°C for 12 h resulted in organic matter determinations by the WLOI method in the closest agreement with those obtained by the Walkley and Black method.  相似文献   

16.
[目的]研究丹江口水库水源区不同降雨强度和土地利用方式对土壤中有机质流失的影响,为该区域的面源污染和水土流失防治提供依据。[方法]通过人工模拟降雨试验,以豫西南山区5种常见土地类型的表层土壤为研究对象,应用双因素方差分析,研究雨强和土地利用方式对土壤中有机质的影响。[结果]雨强对径流中有机质的流失影响显著,雨强越大流失量也越大,而土地类型对其影响不大;泥沙中的有机质流失量受雨强和土地类型的影响均显著,随雨强增加而增大;农用地(梯田和坡耕地)中随泥沙流失的有机质含量较高,林草地则低;分别对径流和流失泥沙中的有机质含量与雨强作回归分析,均显示出多项式拟合效果最好(除灌草地的泥沙拟合外)。[结论]梯田作为一种水保措施,能够保持养分和水土流失,因此其土壤中富集的养分也最多;林草地土壤结构较好,能够减缓土壤侵蚀,因而流失的养分也较少。  相似文献   

17.
An attempt to predict engineering qualities which are needed in soil evaluation and to enhance nonagricultural use of soil survey data was made. Data from a variety of soils were subjected to simple correlation and multiple regression analyses to relate three pedologic characteristics: clay content, cation-exchange capacity (CEC), and organic matter content to two engineering qualitites: plasticity index, and optimum moisture. Simple correlation coefficients showed that clay content and CEC correlated significantly with the engineering determinations. The relationship between organic matter content and these engineering determinations was weaker. Multiple regression analyses showed that the three pedologic characteristics accounted for most of the variation in each of the engineering qualities, and that prediction was feasible.  相似文献   

18.
A dry combustion (Dumas) reference method for measuring total organic C (T), is compared with two other methods: the wet acidified dichromate oxidation, Walkley-Black procedure (an estimator of organic C) and loss on ignition (L) (an estimator of organic matter) for 40 samples from various depths from five New Zealand mineral soils, spanning a range of textures and cultivation treatments. Regression analyses reveal the following: (1) an excellent linear relation exists for all samples between Walkley-Black procedure and reference method results, with a mean conversion factor 1.25, which compares with the original value 1.32 recommended by Walkley & Black (1934). (2) L and T are less well-related by an equation of the form L=a+bT. In contrast to the traditional assumption that b? 1.72 and a? 0, a strong ‘intercept effect’ (a > 0) is revealed, reflecting removal on ignition of non-organic soil constituents. An improved regression of the form L=a+bT+cC, where C= percentage of clay, obtained by inclusion of the clay as an independent variable, points to the role of clay in releasing these constituents, chiefly adsorbed water.  相似文献   

19.
Abstract

Renewed interest in temporal soil organic carbon (SOC) stock changes has stressed the importance of reliable methods for quantitative assessment of organic compound (OC) content. Particularly with the establishment of modern dry‐combustion analyzers, which are replacing the traditional wet‐oxidation methods, the need for correct relationships between both is of crucial importance for comparison of past and current SOC data in long‐term SOC stock change studies. Dry combustion with a Variomax CNS‐analyzer was the standard to evaluate three other methods for Belgian agricultural soils. Excellent linear relationships were found with the Walkey and Black method and the Springer and Klee method, whereas a Shimadzu TOC‐analyzer slightly underestimated the OC content. Precision of the investigated methods was comparable and tended to be dependent on the sample size used for measurement. The OC oxidation efficiency of the most widely applied method of Walkey and Black for the soils in this study was very close to the generally accepted 75%. Mass loss on ignition at 800°C could be very well related to the soil OC content and the clay content. The traditional factor of 1.724 used to convert OC measurements to organic matter percentages is not valid for the investigated soils, which demonstrates that rather regional‐specific factors (in this study 1.911) should be determined and adopted.  相似文献   

20.
荒漠土壤有机质含量高光谱估算模型   总被引：17，自引：6，他引：11  
为解决荒漠土壤有机质含量高光谱估算存在的困难,提高土壤有机质含量估算的精准性,该文对准噶尔盆地东部荒漠土壤进行采样、化验分析和光谱测量、处理,分析土壤光谱与有机质含量的相关性,确定敏感光谱波段,建立荒漠土壤有机质含量多种高光谱估算模型,旨在通过模型精度的比较,确定最优模型。结果表明：反射率、倒数对数光谱与荒漠土壤有机质含量相关性低,而经过一阶微分、二阶微分变换后,相关系数有所提高,部分波段的相关系数通过0.01显著水平的检验,可以用来荒漠土壤有机质含量的估算;一元线性回归建立的估算模型的精度低,不适用荒漠土壤有机质含量高光谱的估算。荒漠土壤有机质多元逐步回归模型的二阶微分、倒数对数二阶微分修正决定系数得到了较大提高,分别提高了0.22和0.31,均方根误差下降了0.66和0.80,建模精度高于一元线性回归模型。荒漠土壤有机质一阶微分、二阶微分光谱的最小偏二乘回归模型的决定系数比其多元逐步回归模型提高了0.07、0.04,一阶微分、二阶微分均方根误差都下降了0.11,二阶微分偏最小二乘法回归模型是该研究所建12个模型的最优估算模型。在多元逐步、偏最小二乘回归模型中,最优估算模型是二阶微分模型,因而用偏最小二乘法回归估算荒漠土壤有机质含量是个可行的方法。该研究的成果为荒漠土壤有机质高光谱遥感分析提供了支撑,实现荒漠土壤有机质监测的时效性、准确性,为区域生态环境的修复提供依据。  相似文献   

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