Pedotransfer functions to predict Atterberg limits for South African soils using measured and morphological properties          下载免费PDF全文

J. J. van Tol  A. R. Dzene  P. A. L. Le Roux  R. Schall 《Soil Use and Management》2016,32(4):635-643

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Predicting soil organic carbon density using auxiliary environmental variables in northern Iran     

Samereh Falahatkar  Shamsollah Ayoubi  Abdolrassoul Salmanmahiny 《Archives of Agronomy and Soil Science》2016,62(3):375-393

In the present study, artificial neural networks (ANNs) were employed to develop models to predict soil organic carbon density (SOCD) at different depths of soil layers. Selected environmental variables such as vegetation indices, soil particle size distribution, land use type, besides primary and secondary terrain attributes were considered as the input variables. According to the results, the ANN models explained 77% and 72% of the variability in SOCD at soil layer depths of 0–20 cm and 20–40 cm, respectively, at the site studied. Sensitivity analyses showed that the most considerable positive contribution of variables for predicting SOCD included the land use type, normalized difference vegetation index (NDVI) > normalized difference water index (NDWI) > silt > clay > elevation in the 0–20 cm soil layer. On the other hand, for the 20–40 cm soil layer, the land use type following NDVI > NDWI > clay > silt were identified as the most powerful predictive factors. In the Deylaman region, in both soil layers, sand had a considerable negative effect on SOCD and most of the terrain attributes had no significant impact on the SOCD prediction. Therefore, these results provide valuable information for sustainable management and decision-making on a landscape scale for governors and other users.  相似文献   

结合统计和数字地形数据的可视化方法预测土壤深度   总被引：2，自引：0，他引：2  

F. M. ZIADAT 《土壤圈》2010,20(3):361-367

Information about the spatial distribution of soil attributes is indispensable for many land resource management applications; however, the ability of soil maps to supply such information for modern modeling tools is questionable. The objectives of this study were to investigate the possibility of predicting soil depth using some terrain attributes derived from digital elevation models (DEMs) with geographic information systems (GIS) and to suggest an approach to predict other soil attributes. Soil depth was determined at 652 field observations over the Al-Muwaqqar Watershed (70 km²) in Jordan. Terrain attributes derived from 30-m resolution DEMs were utilized to predict soil depth. The results indicated that the use of multiple linear regression models within small watershed subdivisions enabled the prediction of soil depth with a difference of 50 cm for 77% of the field observations. The spatial distribution of the predicted soil depth was visually coincided and had good correlations with the spatial distribution of the classes amalgamating three terrain attributes, slope steepness, slope shape, and compound topographic index. These suggested that the modeling of soil-landscape relationships within small watershed subdivisions using the three terrain attributes was a promising approach to predict other soil attributes.  相似文献   

Assessment of soil texture class on agricultural fields using ECa,Amber NDVI,and topographic properties   总被引：1，自引：0，他引：1       下载免费PDF全文

Michał Stępień  Stanisław Samborski  Dariusz Gozdowski  Eike Stefan Dobers  Jarosław Chormański  Jan Szatyłowicz 《植物养料与土壤学杂志》2015,178(3):523-536

Soil texture (ST) is relatively stable over time, although it may change due to erosion, clay eluviation, and other processes. Soil texture affects soil quality, productivity and management. Therefore, indirect, accurate methods for assessing of soil texture classes (STCs) are needed in agricultural practice. A study was performed on four production fields in northern and central Poland to compare the fitting performance of STC models based on apparent electrical conductivity (ECa), topographic properties (elevation, slope gradient and wetness index) and Amber NDVI measurements. One common and accurate indicator of STCs was not found for all study fields. On average, ECa was most accurate in indicating areas of different STCs within the fields, but it tended to overestimate the size of sandy areas on loamy fields and vice versa. The accuracy of STC assessment using ECa measurements may be biased due to imperfect soil drainage, high elevations, which increase evaporation and STC variation with depth. STC assessment using Amber NDVI measurements may be useful, particularly on flat and sandy fields, but the results are affected by the same factors as ECa, and additionally by crop growth stages and by the weather conditions in the period preceding the measurements. Despite the good quantitative results of the STC assessment by elevation (one field) and by the topographic wetness index (another field), both terrain attributes failed to accurately indicate the distribution of some STC areas within each field. Therefore, in landscapes developed from deposits of the last glaciation relevant ST differences might not sufficiently be detected by the analysis of terrain attributes alone. The selection of STC predictors and evaluation of the assessment quality must consider both the quantitative indicators such as correlation and determination coefficients describing relationships between ST and ECa, NDVI and topography and percentage of a field area with accurately indicated STC and the distribution of areas with different STCs within a field. The use of ECa, NDVI values, and topographic properties for STC assessment may be useful in reducing costs of soil sampling and analysis, but cannot replace it.  相似文献   

Spatial modeling of soil salinity using multiple linear regression,ordinary kriging and artificial neural network methods     

Mahmoud Shahabi  Ali Asghar Jafarzadeh  Mohammad Reza Neyshabouri  Mohammad Ali Ghorbani  Khalil Valizadeh Kamran 《Archives of Agronomy and Soil Science》2017,63(2):151-160

Salinity as an important property of soil plays a major role in reducing the fertility in the world. Accurate information about the spatial change of soil salinity is essential for sustainable soil management and utilization in agriculture lands. For this purpose, 150 soil samples were collected from Dashte-e-Tabriz Iran and tested and soil salinity was estimated by land surface parameters including elevation, aspect, length of slope, wetness index, slope and normalized difference vegetation index as basic parameters. In order to model and predict the salinity, ordinary kriging (OK), artificial neural networks (ANN) and multiple linear regressions (MLR) were used. Accuracy of models was evaluated by the coefficient of determination (R²), root mean square error (RMSE) and mean absolute error (MAE). Based on Pearson correlation, elevation, normalized difference vegetation and wetness indices were selected for soil salinity spatial modeling from six land surface parameters. The results showed that the ANN had the lowest RMSE and highest R2. The values of R2, RMSE and MAE were 0.36, 25.89 and 17.06 for regression and 0.56, 17.70 and 13.05 for OK and 0.69, 16.06 and 11.60 for ANN, respectively, which indicated more accuracy of ANN in comparison with MLR and OK.  相似文献   

Soil Particulate Organic Matter (POM) Prediction in a Mountainous Watershed using Artificial Neural Networks     

《Communications in Soil Science and Plant Analysis》2012,43(8):925-938

Soil organic matter is a very important component of soil that supports the sustainability and quality in all ecosystems, especially in arid and semi-arid regions. A comparison study was carried out to verify when the artificial neural network (ANN) and multiple linear regression (MLR) models are appropriate for the prediction of soil organic matter (SOM) and particulate organic matter (POM). Discussions of advantages and disadvantages are given for both methods. Three different sets of easily available properties (soil properties alone, topographic and vegetation index, a combination of soil and topographic data) were used as inputs and the one affecting the model the most was determined. The smallest prediction errors were obtained by the ANN method; however, the prediction accuracies of the constructed MLR models using different data sets were closed to the ANN models in many cases.  相似文献   

Predicting Cationic Exchange Capacity in Calcareous Soils of East-Azerbaijan Province,Northwest Iran     

Farrokh Asadzadeh  Mahdi Maleki-Kakelar  Farzin Shabani 《Communications in Soil Science and Plant Analysis》2019,50(9):1106-1116

The aim of this research is to study the efficiency of pedotransfer functions (PTFs) and artificial neural networks (ANNs) for cationic exchange capacity (CEC) prediction using readily available soil properties. Here, 417 soil samples were collected from the calcareous soils located in East-Azerbaijan province, northwest Iran and readily available soil properties, such as particle size distribution (PSD), organic matter (OM) and calcium carbonate equivalent (CCE), were measured. The entire 417 soil samples were divided into two groups, a training data set (83 soil samples) and test data set (334 soil samples). The performances of several published and derived PTFs and developed neural network algorithms using multilayer perceptron were compared, using a test data set. Results showed that, based on statistics of RMSE and R², PTFs and ANNs had a similar performance, and there was no significant difference in the accuracy of the model results. The result of the sensitivity analysis showed that the ANN models were very sensitive to the clay variable (due to the high variability of the clay). Finally, the models tested in this study could account for 85% of the variations in cationic exchange capacity (CEC) of soils in the studied area.

Abbreviations: ANN: arti?cial neural networks; MLP: multilayer perceptron; MLR: multiple linear regression; PTFs: Pedotransfer Functions; RBF: Radial Basis Function; MAE: mean absolute error; MSE: mean square error; CEC: cationic exchange capacity  相似文献   

Kinetics of Copper Desorption from Highly Calcareous Soils     

《Communications in Soil Science and Plant Analysis》2012,43(5-6):797-809

Abstract

Desorption of copper (Cu) is an important factor in determining Cu availability in calcareous soils. Kinetics of native and added Cu desorption by DTPA (diethylene‐triaminepentaacetic‐acid) from 15 highly calcareous soils of southern Iran were studied in a laboratory experiment. Our results showed that two constant‐rate, Elovich, simple Elovich, and parabolic‐diffusion equations were the best‐fitted equations among eight kinetic models used. The copper desorption pattern based on the parabolic‐diffusion equation revealed that the rate of native Cu desorption was higher in the first 2 h followed by a slower release rate, which suggests that two different mechanisms are involved. The trend may describe why the DTPA soil test has been considerably successful in predicting Cu availability in calcareous soils. Stepwise multiple regression equations indicated that CCE (calcium carbonate equivalent), CEC (cation exchange capacity), and clay content are the most important soil characteristics that predict the rate constants of the kinetic models. Mean extractant recovery percentage (ERP) of the soils was only 20%, which indicated that after 20 days, DTPA extracted only one‐fifth of added Cu. Regression equations indicated that as soil OM (organic matter) content increased, the value of ERP decreased. From results reported herein it seems that CCE, CEC, and clay are the most important factors controlling Cu release from highly calcareous soils of southern Iran. However, the initial soil Cu desorption rate is probably controlled by CEC.  相似文献   

鄂西犟河流域表层土壤有机碳时空变化及其影响因素     

符雅盛  张利华  郑芸蔷  朱志儒  马永明  崔越 《水土保持通报》2020,40(5):189-195

[目的] 研究土壤有机碳（SOC）在小型丘陵山地集水区的分异规律及其影响因素,为土壤资源的可持续利用以及保护南水北调水源地提供科学依据。[方法] 基于数字高程、Landsat 8 OLI影像和2016—2018年实测土壤有机碳等数据,运用相关分析、主成分分析法等研究湖北省十堰市犟河流域表层土壤有机碳含量的时空变化,厘清其影响因子和主导因素。[结果] 犟河流域SOC含量整体呈条带状分布的格局,由东北向西南逐渐增加,呈中等强度变异。夏秋两季SOC处于流失状态,而冬季SOC含量明显增加。不同质地SOC的平均含量：石灰性冲积土 > 简育高活性淋溶土 > 不饱和雏形土。不同覆盖下SOC平均含量：农田 > 园地 > 混交林 > 针叶林 > 灌木。土壤SOC含量呈现随地表曲率绝对值增大而增大,随比值植被指数（RVI）和归一化植被指数（NDVI）增加而增加的趋势。[结论] 地形因子（地表曲率）是影响犟河流域土壤有机碳的主导因子,植被因子（NDVI和RVI）是次要因子。改变局部小地貌、增加林种、改善水肥管理等措施均可以提高流域土壤有机碳含量。  相似文献   

DEM栅格分辨率对丘陵山地区定量土壤-景观模型的影响   总被引：2，自引：2，他引：0  

郭澎涛  武伟  刘洪斌  谢德体  李茂芬 《农业工程学报》2010,26(12):330-336

基于数字高程模型（Digital Elevation Model,DEM）的定量土壤-景观模型的精度依赖于DEM栅格分辨率,而DEM栅格分辨率如何影响土壤-景观模型及其预测精度目前研究较少。以西南丘陵山地区一典型汇水盆地为研究对象,以该区2.5、5、10、20和30 m DEM为基础,利用逐步线性回归方法建立起研究区不同分辨率下的定量土壤-景观模型,并应用这些模型预测研究区内土壤表层碱解氮含量的空间分布,进而比较DEM不同分辨率下土壤-景观模型及其预测精度。结果表明,随着DEM栅格分辨率的降低,比汇水面积、地形湿度指数的均值逐渐增加;平均坡度逐渐降低;曲率变化的范围逐渐减小。地形指数的这一变化规律对土壤-景观模型及其预测结果产生显著影响,模型的校正决定系数、平均绝对误差和均方根误差都以5 m栅格分辨率为转折点,分辨率低于5 m,模型的校正决定系数显著减小,平均绝对误差和均方根误差显著增加。  相似文献   

加拿大西部起伏地貌的地形指数与产量变异性   总被引：1，自引：0，他引：1  

CHI Bao-Liang  BING Cheng-Si  F. WALLEY  T. YATES 《土壤圈》2009,19(3):362-370

Understanding the relationships between topographic indices and crop yield variability is important for soil management and crop production in rolling landscape. Two agricultural fields at Alvena and Hepburn, Saskatchewan, Canada were selected to examine how topographic indices were related to wheat yield under two topographic and weather conditions in the Canadian prairies. The landscapes of the two sites are classified as hummocky and the dominant soil type is an Aridic Ustoll. The relationships among yield, topography, soil, and weather were analyzed using wheat (Triticum aestivumL.) grain yield from Alvena in 2001 (dry year) and 2004 (wet year) and from Hepburn in 1998 (dry year). Topographic/soil indices included relative elevation, wetness index, upslope length, curvature, soil organic matter, and soil moisture storage before seeding. The results indicated that, in the dry years, the correlation coefficients between upslope length and grain yield were 0.79 for the typical rolling landscape (Alvena) in 2001 and 0.73 for shallow gentle rolling landscape (Hepburn) in 1998. In the wet year (2004), the relationships between yield and topographic/soil attributes were not as strong as in dry years. Therefore, upslope length was the best yield indicator for the two landscapes in dry years, whereas no topographic indices were highly correlated to crop yield in wet years. Those topographic indices seemed useful in identifying the yield variability and delineating the proper management zone.  相似文献   

Spatial distribution of soil‐available phosphorus and single‐point phosphorus buffering index in the Khoy region,Iran          下载免费PDF全文

H. R. Momtaz  N. Ghasemi  E. Sepehr  S. M. Mousavifard 《Soil Use and Management》2017,33(1):13-24

Knowledge of the amount of nutrients in soil is required to achieve sustainable management. The objective of this study was to assess the variability of soil‐available and single‐point buffering index of phosphorus (P) in the farmlands of the Khoy region, Iran. Composite soil samples (0–30 cm) were collected at 114 locations on regular grid of 1000 m. Some soil physico‐chemical characteristics such as soil texture, soil organic matter (OM) content, soil pH, electrical conductivity (EC), calcium carbonate equivalent (CCE), available P (P_ava) and single‐point P sorption index (PSI) were measured. Results showed that all variables in this study have spatial distribution in the effective range of 1500–4800 m. Moreover, experimental semivariograms of all studied variables were best‐fit by spherical and exponential models. Most importantly, kriged maps revealed that a major part of the study area contains high P_ava, which is seemingly due to the frequent application of phosphate fertilizers along with poultry manure. Some soils in the western part showed low PSI index; they therefore need more P fertilizer application. In addition, due to the lower PSI value in the eastern half of the study region, applying less fertilizer at more frequent intervals seems to be more beneficial than larger single applications. Eventually, to reduce environmental risks and prevent the loss of natural resources, the method of applying P fertilizer needs to be mainly based on the created PSI distribution map.  相似文献   

Plasticity,Mineralogy, and WRB Classification of Some Typical Clay Soils along the Two Major Rivers in Croatia     

Rubinić  V.  Ilijanić  N.  Magdić  I.  Bensa  A.  Husnjak  S.  Krklec  K. 《Eurasian Soil Science》2020,53(7):922-940

Eurasian Soil Science - Quantification of soil plasticity is usually based on Atterberg limits or indices, which are then used for engineering and agricultural purposes on clay soils. Because these...  相似文献   

流域地貌分形特征与侵蚀产沙定量耦合关系试验研究   总被引：5，自引：1，他引：5  

崔灵周  李占斌  朱永清  郭彦彪  肖学年 《水土保持学报》2006,20(2):1-4,9

流域地貌形态科学、准确和综合量化成为建立具有广泛适用性的流域土壤侵蚀预报模型的关键科学问题之一。分形理论的提出为流域地貌形态定量研究开辟了新的思路。本文依据分形理论，在建立小流域概化模型基础上，采用模拟降雨试验、高精度摄影测量和GIS技术，对流域模型地貌形态分形特征与侵蚀产沙定量耦合关系进行了研究。结果表明，基于消除了降雨特征影响的相对输沙率，可将流域模型侵蚀产沙过程划分为初期、活跃期和稳定期3个阶段；在不同侵蚀产沙时段，流域模型地貌形态分形信息维数Di呈现与相对输沙率Sr基本类似的变化趋势，即先增大再减小、最后趋于平稳；流域模型相对输沙率Sr与地貌形态分形信息维数Dr以乘幂形式呈显著正相关，相关指数r^2为0．7423；地貌形态分形信息维数Dr较好反映了地貌形态特征对流域模型侵蚀产沙过程的影响，可以作为流域模型侵蚀产沙过程预报地貌形态特征综合量化指标。  相似文献   

Critical-state soil mechanics parameters and their variation for Vertisols in eastern Australia   总被引：3，自引：0，他引：3  

J. M. KIRBY 《European Journal of Soil Science》1991,42(3):487-499

Compression and shear tests were conducted on undisturbed samples from a range of Vertisols to determine the critical-state parameters, their variation, and the relationships between these parameters and the moisture content and density of the soil. The soils varied considerably in their characteristics, with the liquid limit ranging from 0.39 to 0.88, and were tested over a wide range of moisture contents, densities and saturations. The critical-state parameters describing compressional and shear properties varied with the moisture content, Atterberg limits and density of the soil, in contrast to saturated soils where these parameters are considered to be constants. It was found that the liquidity index (moisture content expressed as fractional distance between the liquid and plastic limits) explained the data significantly better than moisture content and also significantly better than did the suction. These data, therefore, supported suggestions that the Atterberg limits may serve as a useful basis for practical soil management guidelines. The measured parameters displayed considerable variation, demonstrating that any such guidelines need to be cast in terms of probabilities. The soil expanded when sheared if the normal stress during shear was less than about half the pre-consolidation stress and compressed when sheared if the normal stress during shear was more than about half the pre-consolidation stress. This behaviour was repeatable.  相似文献   

Guidelines for safe trafficking and cultivation, and resistance–density–moisture relations of three disturbed soils from Alberta     

E. Mapfumo  D. S. Chanasyk 《Soil & Tillage Research》1998,46(3-4):193-202

The Atterberg limits and the Proctor compaction test are used by engineers for classifying soils and for predicting stability of building foundations. Field capacity and wilting point (agronomic limits) are used to indicate available water for plant uptake. Few studies have related the engineering criteria to the agronomic ones with regard to compaction hazard for soils. This study investigated the relationships between Atterberg limits, agronomic limits and the critical moisture content (moisture content at Proctor maximum density) for three disturbed soils (sandy loam and clay loam soils from a reclaimed Highvale mine site, and a silt loam soil from a grazing site at Lacombe) of different textures. Relationships between bulk density, moisture content and penetration resistance for these soils were also investigated. For the sandy loam and loam soils, the field capacity was close to the critical moisture content but lower than the plastic limit. Therefore, cultivation of these two soils at moisture contents close to field capacity should be avoided since maximum densification occurs at these moisture contents. Overall, the critical moisture content or field capacity would be a better guide for trafficking of sandy loam and loam textured soils than the Atterberg limits. For the clay loam, field capacity was within the plastic range. Thus trafficking this soil at field capacity would cause severe compaction. In conclusion, either field capacity or plastic limit, whichever is less, can be used as a guide to avoid trafficking at this moisture content and beyond. For the sandy loam and loam soils penetration resistance significantly increased only with increased bulk density (P≤0.05). For the clay loam soil, penetration resistance was positively related to bulk density and negatively related to moisture content.  相似文献   

Topographic variation of soil nitrogen mineralization and microbial biomass in Japanese cedar (Cryptomeria japonica D. Don) stands at Myougodani watershed,Toyama, Japan     

Kotaro Zushi 《Soil Science and Plant Nutrition》2013,59(6):843-851

The spatial variability of nitrogen (N) mineralization, nitrification, and microbial biomass was investigated using surface soils from various topographic positions at a relatively small watershed with Japanese cedar (Crgptomeria japonica D. Don) plantations. The watershed topography was characterized using a topographic index derived from GIS analysis. The topographic index reasonably reflected the spatial variability of the soil water conditions, total soil carbon (C) and N contents, and exchangeable base concentrations. However, this index was not significantly correlated with the spatial variability of net N mineralization and microbial biomass. Topographic index and soil properties (total soil C and N contents, C / N ratio, exchangeable base concentrations, and clay content) were subjected to principal component analysis to eliminate multiple-collinearity among the variables, and express the variables as new orthogonal variables. Principal component analysis showed that the soil properties could be divided into two groups: PC1 (soil nutrient pools) and PC2 (soil clay content). The topographic index was closely correlated with PC1 and not significantly correlated with PC2. Regression of PC scores on net N mineralization and microbial biomass indicated the relatively high contribution of PC2 to the variability in N mineralization and microbial biomass. This result suggested that not only topographic factors but also the clay content exerted an important influence on the spatial pattern of N mineralization and microbial biomass within a watershed with single species forests.  相似文献   

Soil erosion risk assessment using GIS and CORINE model: a case study from western Shiraz,Iran     

Mohboobeh Tayebi  Mohammad H. Tayebi  Abdolmajid Sameni 《Archives of Agronomy and Soil Science》2017,63(8):1163-1175

This study employs the Coordination of Information on the Environment (CORINE) model with geographic information system to assess soil erosion risk for restoring and protecting areas within the Bonrod Zangane watershed, western Shiraz, Iran. Actual soil erosion risk was determined by combining two main parameters including potential soil erosion risk and vegetation cover. The potential soil erosion risk was generated by integrating soil erodibility, erosivity and slope parameters. Soil texture, depth and stoniness layers were overlaid to form a soil erodibility map. Modified Fournier index and Bagnouls–Gaussen aridity index were integrated to generate the erosivity layer. The slope classes also were generated from digital elevation model. In order to estimate vegetative land cover, the normalized difference vegetation index (NDVI) was used. The raster-based layers were then integrated to produce erosion risk map. The results showed that 34.7% of the study area has high and only 31.4% of the study area has low soil erosion risk. It is concluded that CORINE model can be used to delineate the soil erosion risk and also to discriminate the potential soil erosion risk areas.  相似文献   

Delineation of Management Zones for Southern Root-Knot Nematode using Fuzzy Clustering of Terrain and Edaphic Field Characteristics     

《Communications in Soil Science and Plant Analysis》2012,43(16):1972-1994

Management zones (MZs) for southern root-knot nematode (RKN) from the integration of terrain (TR) and edaphic (ED) field features might facilitate variable rate nematicide applications. This study was conducted on 11 coastal plain fields in the USA. The relationships between RKN populations and five soil ED and TR attributes (apparent soil electrical conductivity [shallow (EC_a-s) and deep (EC_a-d)], elevation (EL), slope (SL), and changes in bare soil reflectance) were analyzed using canonical correlation. Using two ED and TR data sets, canonical predictors were used for zone delineation. Although the results showed that the zones with RKN population above the RKN field average were associated with the lowest values of EC_a-s, EC_a-d, normalized difference vegetation index (NDVI), and SL with respect to field average values, zone segregation was enough using EC_a-s and EC_a-d data. The results suggest the potential for using soil properties to identify RKN risk zones.  相似文献   

Field-scale spatial variability of soil calcium in a semi-arid region: Implications for soil erosion and site-specific management     

Yazhou SUN  Wenxuan GUO  David C. WEINDORF  Fujun SUN  Sanjit DEB  Guofeng CAO  Jasmine NEUPANE  Zhe LIN  Abir RAIHAN 《土壤圈》2021,31(5):705-714

Excess calcium(Ca) in soils of semi-arid and arid regions has negative effects on soil structure and chemical properties, which limits the crop root growth as well as the availability of soil water and nutrients. Quantifying the spatial variability of soil Ca contents may reveal factors influencing soil erosion and provide a basis for site-specific soil and crop management in semi-arid regions. This study sought to assess the spatial variability of soil Ca in relation to topography, hydraulic attributes, and soil types for precision soil and crop management in a 194-ha production field in the Southern High Plains of Texas,USA. Soils at four depth increments(0–2, 0–15, 15–30, and 30–60 cm) were sampled at 232 points in the spring of 2017. The Ca content of each sample was determined with a DP-6000 Delta Premium portable X-ray fluorescence(PXRF) spectrometer. Elevation data was obtained using a real-time kinematic GPS receiver with centimeter-level accuracy. A digital elevation model(DEM) was derived from the elevation data, and topographic and hydraulic attributes were generated from this DEM. A generalized least-squares model was then developed to assess the relationship between soil Ca contents of the four layers and the topographic and hydraulic attributes. Results showed that topographic attributes, especially slope and elevation, had a significant effect on soil Ca content at different depths(P 0.01). In addition, hydraulic attributes, especially flow length and sediment transport index(STI), had a significant effect on the spatial distribution of soil Ca. Spatial variability of soil Ca and its relationships with topographic and hydraulic attributes and soil types indicated that surface soil loss may occur due to water or wind erosion, especially on susceptible soils with high slopes. Therefore, this study suggests that the application of PXRF in assessing soil Ca content can potentially facilitate a new method for soil erosion evaluation in semi-arid lands. The results of this study provide valuable information for site-specific soil conservation and crop management.  相似文献