bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sediment Regimes under Different Slope and Surface Hydrologic Conditions
Authors: Huang Chi‐hua 
Published: July 2010

AbstractDuring rainfall events, many physical processes occur simultaneously. Conceptual frameworks for infiltration, runoff, surface sealing, sediment detachment, transport, and deposition processes have long been recognized. Nevertheless, interactions between hydrologic and sediment regimes and how they are affected by changes in slope steepness, soil erodibility, and rainfall erosivity have not been evaluated. A laboratory study on the Glynwood clay loam (fine, illitic, mesic Aquic Hapludalf) was designed to demonstrate interactions between hydrologic and sediment regimes. Four rainfall intensities, from 30 to 120 mm h−1, and two inflows, equivalent to 30 and 60 mm h−1 rainfall, were applied to create different combinations of rainfall detachment and shallow flow transport. Sediment delivery was quantified from two rainfall events: first on freshly packed soil under free drainage and later on the eroded surface under seepage. During the first rainfall event, average sediment deliveries from 30 to 100 mm h−1 runoff were 1.8, 3.4, and 3.3 kg m−2 h−1 for slopes of 5, 10, and 15%, respectively. The lack of slope effects from 10 to 15% slope indicates the shift from a transport‐limiting sediment regime at low slopes to a detachment‐limiting sediment regime at high slopes. Under the potentially more erodible seepage condition, the second rainfall event produced only 1.3, 1.8, and 1.5 kg m−2 h−1 sediment from the same range of slopes and runoff rates. Reduction in sediment delivery during the second run was caused by removal of the easily erodible fraction during the first run. Increased profile drainage at the 15% slope further limited sediment detachment. These results show interactions between surface hydrologic conditions and erosion processes and the importance of understanding dominant sediment regimes in developing erosion prediction models.
Characterizing Interrill Sediment Size by Partitioning Splash and Wash Processes
Authors: Wan Y. , El‐Swaify S. A. 
Published: July 2010

AbstractSediment transported from interrill areas is generally finer than the in situ soil matrix. We hypothesized that sediment size depends on the processes dominating interrill sediment transport, i.e., splash or wash, which, in turn, are influenced by rainfall intensity and slope gradient. Aggregate size distribution of directional splash and wash sediment from a Rhodic Eutrustox (Wahiawa silty clay) was measured at 4, 9, 18, 27, and 36% slopes under simulated rainfall with 45, 65, 90, and 135 mm h−1 intensities. Mean sediment geometric mean diameter (GMD) was 0.74 mm for downslope splash, 0.67 mm for lateral splash, 0.59 mm for upslope splash, and 0.40 mm for wash. Both splash and wash preferentially transported aggregates <0.063 mm. However, mean enrichment ratios (ER) for this fraction were <2 for splash and ≈12 for wash. Wash sediment GMD significantly increased with increasing rainfall intensity and slope, and was thus positively correlated with the erosion rate of wash (r = 0.95). In contrast, splash sediment GMD was much less influenced by rainfall intensity and slope, and was weakly correlated with the corresponding splash rate (r = −0.17 for total splash). Splash tended to generate sediment with similar size to the in situ soil and the size sorting process was in a matrix‐limited regime. Wash appeared to be in a force‐limited regime and produced sediment that was much finer than the in situ soil.
Modeling Interrill Sediment Delivery
Authors: Zhang X. C. , Nearing M. A. , Norton L. D. , Miller W. P. , West L. T. 
Published: July 2010

AbstractShallow surface runoff is a primary transport agent for interrill sediment delivery. Runoff, rainfall intensity, and slope interactively affect interrill erosion. We hypothesized that the inclusion of a runoff factor in an interrill erosion model can reduce the dependence of the interrill soil erodibility (Ki) on soil infiltration characteristics as well as improve model predictability. A complete factorial rainfall simulation experiment with two soils (Cecil sandy loam, a clayey, kaolinitic, thermic Typic Kanhapludult, and Dyke clay, a clayey, mixed, mesic Typic Rhodudult), four rainfall intensities, four slopes, and two replicates was conducted under prewetted conditions to measure runoff and sediment delivery rates. Tap water with electrical conductivity <0.2 dS m−1 was used in all the runs. Rainfall intensity I, unit discharge q, slope S, soil type, and their interactions significantly affected sediment delivery per unit area (Di). Sediment delivery had the greatest correlation (r = 0.68) with unit discharge; however, neither discharge nor rainfall alone adequately predicted sediment delivery. The equation Di = KiIq1/2S2/3 was proposed. The linear intensity term (I) represents detachment of soil by raindrop impact and enhancement of transport capacity of sheet flow, while the product of q1/2S2/3 describes sediment transport by sheet flow. Validation with independent data showed that the model predicted soil erodibilities well. The mean r2 for four validation soils was 0.93 when the proposed model was fitted to validation data to predict interrill erodibility (Ki). The better estimation of Ki indicates that interrill erosion processes were adequately described by the model.
Aluminum in Soil Solutions of Forest Soils: Influence of Water Flow and Soil Aluminum Pools
Authors: Matzner E. , Pijpers M. , Holland W. , Manderscheid B. 
Published: July 2010

AbstractThe Al3+ saturation of soil solutions of acid forest soils (defined as pAl3+‐3pH) is highly variable with time and soil depth under field conditions. We hypothesized that the release of Al from soil solids into the soil solution is kinetically restricted. This hypothesis was tested by evaluating soil solution data from a field site and in an experiment with large undisturbed soil columns from two acid forest soils. Soil columns of 40‐cm diameter and 90‐cm height were established in six replicates at 10°C and irrigated in a steady‐state flow with an artificial acid throughfall (pH 3.5 and 2.8) at rates of 1, 4, and 12 mm d−1. Soil solutions from the columns as well as in the field were taken by suction lysimeters from various depths and the Al3+ saturation of the soil solutions was related to the extractable soil Al pools and water flow rates. Under field conditions, undersaturation was related to high water flow rates through the soil profile at both the 20‐ and 90‐cm depths. This was attributed to preferential flow in the soil profile. In contrast with the field results, Al3+ saturation of soil solutions from the column experiments was not affected by flow rate despite a large variation in flow rate, acid input, and ionic background. In the column study, the Al3+ saturation differed between soils, soil horizons, and replicates; increased with soil depth; and was undersaturated with respect to gibbsite in the upper soil profile. The Al3+ saturation of soil solutions was spatially highly variable both in the field and in the column experiment corresponding to the heterogeneity of soil extractable Al pools. The relation of soil extractable Al to the Al3+ saturation was different for the two soils. The modeling of soil solution Al and pH under equilibrium assumptions and without kinetic constraints is rather uncertain when short‐term variations and different soil horizons are considered.
Recovery of Leucaena and Dactyladenia Residue Nitrogen‐15 in Alley Cropping Systems
Authors: Vanlauwe B. , Sanginga N. , Merckx R. 
Published: July 2010

AbstractQuantification of the fate of residue N is essential in low‐input tropical cropping systems for the development of management practices that optimize N‐use efficiency. The recovery of N from 15N‐labeled leucaena [Leucaena leucocephala (Lam.) de Wit] and dactyladenia [Dactyladenia barteri (Hook fex Oliv.) Engl.] leaf residues was followed in the soil, crop, and hedgerow of the respective alley cropping systems during three maize (Zea mays L.) and two cowpea (Vigna unguiculata L. Walp. subsp. unguiculata) seasons. More residue N was recovered in the top 5 cm of soil in the leucaena than in the dactyladenia microplot during the first 471 d after residue application (DAA). The first maize crop recovered 8.6 and 5.2% of the N from leucaena and dactyladenia, respectively, while the two subsequent crops recovered <1%. The cowpea plants in the leucaena and dactyladenia microplots contained 0.5 and 1.1% of the residue N in the first harvest. Sixteen and 9% of the residue N was recovered by the leucaena hedgerow in the first and second pruning following residue application. The dactyladenia hedges recovered maximally 3.1% of the residue N in a single pruning. The total N recovery in the leucaena microplots was ≈90% at 120 and 471 DAA, compared with 56 and 35% in the dactyladenia microplots. At 858 DAA, 62% of the added leucaena N was accounted for, compared with 25% of the dactyladenia N. Residue quality was shown to have a major impact on the dynamics of applied residue N in alley cropping systems and will be an important factor in deciding which residue‐supplying plant species to integrate into similar cropping systems.
Process‐Based Analysis of Aggregate Stability Effects on Sealing, Infiltration, and Interrill Erosion
Authors: Fox D. M. , Le Bissonnais Y. 
Published: July 2010

AbstractAggregate stability indices are correlated with soil erosion rates. Although aggregate stability influences soil erodibility and aggregate breakdown product size distributions, these indices are usually unsatisfactory because of interacting physicochemical considerations affecting infiltration and erosion. We examined the spatial variability in structural and depositional seal composition, and the influence of breakdown fragment size distribution on seal hydraulic resistance and interrill erosion. Two Alfisols, Villamblain clay loam and Blosseville silt loam, were sieved to retain <2.0‐cm aggregates and packed in 0.25‐m2 soil trays. Soil trays were rained upon for 4 h at 23 mm h−1. Infiltration, runoff, and subseal pressure head were measured throughout the experiment, and surface roughness and depositional seal area were measured at selected times during the event. Aggregate stability, hydraulic resistance, and fragment size distribution of the seal matrix were also determined. Mean weight diameter (MWD) of aggregates after mechanical breakdown by stirring was greater for Villamblain (1.70 mm) than for Blosseville (0.92 mm) (r2 = 0.94, P < 0.001). Blosseville seals had finer fragments than those of Villamblain (r2 = 0.82, P < 0.001): fewer than 28% of fragments >1 mm and more than 40% <0.1 mm, compared with 60 and 15% for Villamblain. Depositional seals had finer fragments than structural seals for both soils. For the same runoff rate (15 mm h−1), soil loss was greater for Blosseville (2 g m2 min−1) than for Villamblain (0.4 g m2 min−1) since breakdown products were finer and more transportable. Seal hydraulic resistance was correlated (r2 = 0.53, P < 0.01) with MWD of seal fragments.
Bulk Densities of Brazilian Amazon Soils Related to Other Soil Properties
Authors: Bernoux Martial , Cerri Carlos , Arrouays Dominique , Jolivet Claudy , Volkoff Boris 
Published: July 2010

AbstractThe results of this study provide the first baseline for predicting Db from soil properties for soils across the Amazon basin. Bulk density values are needed to convert nutrient content and organic carbon (OC) content to weight of nutrient and OC per unit area; unfortunately, common field methods to measure Db are limited with regard to reliable, complete, and uniform soil data. Much effort has been made in finding alternative solutions to predict Db from soil properties. We hypothesized that Db could be reliably estimated by multiple regression of OC, soil textural properties, and some chemical properties. Using the data of 323 soil horizons from the Brazilian Amazon basin, a stepwise multiple regression (SMR) procedure was developed to predict Db from other soil properties. Multiple regression relationships were obtained for all the data, which were also partitioned by layer and then by main soil order: Latossolos (Oxisols, 62 horizons) and Podzólicos (Alfisols and Ultisols, 212 horizons). The SMR on all the data showed that clay content is the best predictor of Db, accounting for 37% of the variation. Adding OC content increased the explained variance up to nearly 50%. Predictions of the models were improved when the data were partitioned by order and by horizon type. In the case of Latossolos (Oxisols), the use of OC and clay content as predictors increased the percentage of explained variation, reaching 71% using all layers and 79% for A horizons. The results of this study will provide a basis for estimating OC stocks in the Amazon basin.
Statistical Distributions of Soil Loss from Runoff Plots and WEPP Model Simulations
Authors: Baffaut Claire , Nearing M. A. , Govers Gerard 
Published: July 2010

AbstractSoil conservation measures may be better designed with the knowledge of daily distributions of erosion. Collecting reliable data to determine daily erosion distributions is costly; however, new process‐based soil erosion models have the potential to simulate extended records. The objectives of this study were to analyze frequency distributions of measured daily soil loss values and to determine if the Water Erosion Prediction Project (WEPP) model accurately reproduced statistical distributions of the measured daily erosion series. A Log‐Pearson Type III (LP III) distribution was fitted to measured and WEPP‐predicted soil loss values from six sites for periods ranging from 6 to 10 yr. Cumulative soil loss as a function of storm recurrence interval was used to show the relative contributions of large and small storms to total soil loss at each site. Results showed that both measured and predicted frequency curves fell within the 95% confidence range of the LP III distributions. This was true both using weather data from the site for the period of monitoring as well as when using synthetic weather series generated with the CLIGEN model. Thus the results were encouraging in terms of using WEPP in conjunction with CLIGEN to generate long‐term daily soil loss frequency distributions, which can contribute toward alleviating the problem of having only a short monitoring period for measured erosion. Cumulative soil loss results indicated that large storms contributed a major portion of the erosion under conditions where cover was high, but not necessarily under conditions of low cover.
Spatial and Temporal Variability of Corn Grain Yield on a Hillslope
Authors: Timlin D. J. , Pachepsky Ya. , Snyder V. A. , Bryant R. B. 
Published: July 2010

AbstractThe purpose of this study was to relate the temporal and spatial variability of corn (Zea mays L.) grain yield on a Typic Fragiochrept soil on a hillslope to soil properties and topographic features. Corn grain yields were sampled from a field that measured 280 by 150 m using a grid and five transects. One‐hundred forty yield measurements were taken on the grid (1983–1985) and 190 measurements on the transects (1984 and 1985) from plots 5.3 m long and two corn rows wide. Measurements of soil surface elevation, soil organic matter (OM), P, and K contents were also taken at the grid plot locations. These data were analyzed using the methods of spectral analysis. Yield spatial and temporal variability was strongly related to surface undulations and the value of surface curvature was found to be a useful parameter to quantify variations in topography. The intra‐annual differences in weather had the largest effect on grain yield at locations where the magnitude of curvature was large. Where the magnitude of curvature was small, the correlations of yield for the wet (1984) and dry (1985) years were highly significant. Yields correlated with soil P, K, and OM only in the dry year, 1985. Yields in the relatively dry years (1983 and 1985) correlated with depth to fragipan. Elevation data helped us interpret the spatial and temporal variability of grain yield by separation of areas with convex curvature from areas with concave curvature.
Regional Soil Organic Carbon Storage Estimates for Western Oregon by Multiple Approaches
Authors: Homann P. S. , Sollins P. , Fiorella M. , Thorson T. , Kern J. S. 
Published: July 2010

AbstractSoil is an important factor in regional and global C budgets because it serves as a reservoir of large amounts of organic C. In our study, we compared six approaches of estimating soil organic C (kg C m−2, not including the surface organic horizon, hereafter called soil C) and its spatial pattern in the mountainous, largely forested western Oregon region. The approaches were (i) USDA NRCS pedons, (ii) other pedons, (iii) the State Soil Geographic Data Base (STATSGO), (iv) the United Nations Soil Map of the World, (v) the National Soil Geographic Data Base (NATSGO), and (vi) an ecosystem‐complex map. Agreement between approaches varied with scale. For the entire region (105 km2), estimates of average soil C varied from 4.3 to 6.8 kg C m−2 for the 0‐ to 20‐cm depth and from 12.1 to 16.9 kg C m−2 for the 0‐ to 100‐cm depth. At the subregional scale (≈104 km2), all approaches indicated higher soil C in the coastal area than in the inland southern area, but relative amounts in other subregions varied among the approaches. At the subsubregional scale (≈103 km2), soil C was consistent between individual STATSGO map units and NRCS pedons within those map units, but there was less agreement with other pedons. Rigorous testing of soil‐C maps requires data from pedons that are located by objective criteria, in contrast to the subjectively located pedons now available. The uncertainty associated with regional soil‐C amounts and spatial patterns should be considered when soil‐C maps are integrated into regional or global assessments of physical and biotic processes because simulation‐model outputs may be sensitive to soil C.
Neural Network Analysis for Hierarchical Prediction of Soil Hydraulic Properties
Authors: Schaap Marcel G. , Leij Feike J. , van Genuchten Martinus Th. 
Published: July 2010

AbstractThe solution of many field‐scale flow and transport problems requires estimates of unsaturated soil hydraulic properties. The objective of this study was to calibrate neural network models for prediction of water retention parameters and saturated hydraulic conductivity, Ks, from basic soil properties. Twelve neural network models were developed to predict water retention parameters using a data set of 1209 samples containing sand, silt, and clay contents, bulk density, porosity, gravel content, and soil horizon as well as water retention data. A subset of 620 samples was used to develop 19 neural network models to predict Ks. Prediction of water retention parameters and Ks generally improved if more input data were used. In a more detailed investigation, four models with the following levels of input data were selected: (i) soil textural class, (ii) sand, silt, and clay contents, (iii) sand, silt, and clay contents and bulk density, and (iv) the previous variables and water content at a pressure head of 33 kPa. For water retention, the root mean square residuals decreased from 0.107 for the first to 0.060 m3 m‐3 for the fourth model while the root mean square residual Ks decreased from 0.627 to 0.451 log(cm d‐1). The neural network models performed better on our data set than four published pedotransfer functions for water retention (by ≈0.01–0.05 m3 m‐3) and better than six published functions for Ks (by ≈0.1–0.9 order of magnitude). Use of the developed hierarchical neural network models is attractive because of improved accuracy and because it permits a considerable degree of flexibility toward available input data.
Retention of Phosphate by Hydroxyaluminosilicate‐ and Hydroxyaluminum‐Montmorillonite Complexes
Authors: Saha U.K. , Inoue K. , Hiradate S. 
Published: July 2010

AbstractHydroxyaluminosilicate (HAS) ions were prepared from solutions containing hydroxyaluminum (HyA) ions and orthosilicic acids at an Al concentration of ≈4 mM; Si/Al molar ratios of 0, 0.25, 0.5, and 1.0; and NaOH/Al molar ratios of 1.0, 2.0, and 2.5. Phosphate retention behavior of montmorillonite (Mt) carrying nonexchangeably adsorbed HyA, HAS ions, or both (HyA/HAS‐Mt complexes) was studied at equilibrating solution pH of ≈5.0. The HyA/HAS‐Mt complexes showed larger phosphate retention capacities than untreated Mt. Retention of phosphate by these complexes at 0.5 to 50 mM initial P concentrations decreased with increasing NaOH/Al and Si/Al ratios of the hydroxy materials adsorbed on Mt. Phosphate, probably retained initially through surface complexation and ligand exchange reactions principally with OH or OH2 groups, coordinated with Al atoms at the broken edges of HyA or HAS polymers adsorbed on the external planar surfaces and in the interlayer spaces of Mt. This was followed by expulsion of the phosphated hydroxy materials from the Mt interlayers to the ambient solution, and finally, precipitation as amorphous Al‐phosphate solid phases. Results of this study thus merit attention in P‐fertility management as well as indicate a probable P‐induced weathering process in acidic nonallophanic Andisols and in Red‐Yellow soils (Hapludalfs and Hapludults) with a predominance of hydroxy‐interlayered minerals.
Carbon and Nitrogen Mineralization in Tallgrass Prairie and Agricultural Soil Profiles
Authors: Ajwa H. A. , Rice C. W. , Sotomayor D. 
Published: July 2010

AbstractIn situ mineralization of N may contribute significantly to total inorganic‐N pools deep in the soil profile. We conducted long‐term laboratory incubation experiments to evaluate the net C and N mineralization in soils collected from various depths in tallgrass prairie and agricultural fields of the same geological materials and soil type. Samples were packed to a bulk density of 1.4 g cm‐3 in 5‐cm‐diameter by 10‐cm‐long cores. The cores were incubated at 35°C for 40 wk in sealed containers. Net C mineralization was measured by evolved CO2, and N mineralized was measured by periodic leaching with NH+4 and NO‐3 measured in the leachate. Carbon and N mineralization in the surface horizon were greater in the tallgrass prairie than in the agricultural soil. In both the tallgrass prairie and agricultural soil profiles, C mineralization was least at the water‐table depth. Carbon mineralization was described by a first‐order kinetic model, but N mineralization was described better by a consecutive (sigmoidal) reaction model. At most depths, the ratios of potentially mineralizable organic C (C0) to total organic C (C0/TOC) and potentially mineralizable organic N (N0) to total N (N0/TN) were greater in the agricultural soil profile than in the tallgrass prairie soil profile. The C0 and N0 in the surface soil (0–0.2 m) represented 11.6 and 12.2% of the total organic C and N pools for the tallgrass prairie soil profile, respectively, and 21.0 and 10.2% of the total organic C and N pools for the agricultural soil profile. Management practices affected the mineralization potentials and rates of both the surface and subsurface soils.