bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fall Contour Ripping Increases Water Infiltration into Frozen Soil
Authors: Pikul J. L. , Aase J. K. 
Published: July 2010

AbstractCrop residue management to trap snow and soil management to improve water infiltration into frozen soil might reduce spring runoff and increase soil water storage. We hypothesized that soil macropores created by tillage would improve water infiltration when the soil was frozen. This hypothesis was tested by ripping a Dooley sandy loam (fine‐loamy, mixed Typic Argiboroll) in the fall of the year and then measuring water infiltration when the soil was frozen. A single subsoiling shank was used to rip soil to a depth of 0.3 m at 6‐m contour intervals. Ripping was compared with no ripping using a randomized experimental design having three replications. Studies were conducted during 4 yr near Culbertson, MT, on plots seeded annually to spring wheat (Triticum aestivum L.). Soil water was measured with neutron attenuation and gravimetric methods. We used a constant‐head (100 mm) method to measure water infiltration into frozen soil and a rainfall simulator for unfrozen soil. Final infiltration rate on frozen, ripped soil averaged 16 vs. 2 mm h‐1 without ripping. Final unfrozen infiltration rate in spring was 34 mm h‐1 with ripping vs. 15 mm h‐1 without ripping. Average spring water content of the top 1.2 m of soil, to a distance 1.5 m downslope from a rip, was 32 mm greater with ripping than without ripping at comparable slope positions. There were no wheat yield differences between treatments. Contour ripping can decrease water runoff, and seems best suited where spring runoff and soil erosion caused by heavy winter snows is a problem.
Restoration and Canopy‐Type Effects on Soil Respiration in a Ponderosa Pine‐Bunchgrass Ecosystem
Authors: Kaye Jason P. , Hart Stephen C. 
Published: July 2010

AbstractIn ponderosa pine (Pinus ponderosa Douglas ex P. Lawson & Lawson)‐bunchgrass ecosystems of the western USA, fire exclusion by Euro‐American settlers facilitated pine invasion of grassy openings, increased forest floor detritus, and shifted the disturbance regime toward stand‐replacing fires, motivating ecological restoration through thinning and prescribed burning. We used in situ soil respiration over a 2‐yr period to assess belowground responses to pine invasion and restoration in a ponderosa pine‐bunchgrass ecosystem near Flagstaff, AZ. Replicated restoration treatments were: (i) partial restoration — thinning to presettlement conditions; (ii) complete restoration — removing trees and forest floor material to presettlement conditions, native grass litter addition, and prescribed burning; and (iii) control. Within treatments, we sampled beneath different canopy types to assess the effects of pine invasion into grassy openings on soil respiration. Growing season soil respiration was greater in the complete restoration (346 ± 24 g CO2‐C m‐2) and control (350 ± 8 g CO2‐C m‐2) than the partial restoration (301 ± 5 g CO2‐C m‐2) in 1995. In 1996, the complete (364 ± 17 g CO2‐C m‐2) and partial (328 ± 7 g CO2‐C m‐2) restoration treatments had greater growing season respiration rates than the control (302 ± 13 g CO2‐C m‐2). Results suggest that restoration effects on soil respiration depend on interannual soil water patterns and may not significantly alter regional C cycles. Soil respiration from grassy openings was 15% greater than from soil beneath presettlement or postsettlement pines in 1995 and 1996. A lack of active management will decrease belowground catabolism if pines continue to expand at the expense of grassy openings.
A Simple Spectrophotometric Determination of Nitrate in Water, Resin, and Soil Extracts
Authors: Yang J. E. , Kim J. J. , Skogley E. O. , Schaff B. E. 
Published: July 2010

AbstractNitrate is one of the most important chemicals in agricultural and environmental management. Most methods for NO3 analysis, however, require expensive equipment or complicated procedures. The objective of this study was to develop a simple, rapid, accurate procedure for NO3 analysis that can be conducted in laboratories worldwide, without the need for specialized equipment. We based our studies on a colorimetric method that involves electrophilic aromatic substitution (nitration) between nitronium and salicylate. The simplified procedure was tested for NO3 analysis of water, soil, and resin extracts. Only 1 mL of sample containing 0 to 4 mg NO3‐N L‐1 is required, and a single solution (TRI solution made as a mixture of sodium salicylate [2‐hydroxybenzoic acid monosodium salt], NaCl, and ammonium sulfamate [sulfamic acid monoammonium salt]) is used for color development. The detection limit is 0.1 µg NO3‐N, with linearity up to 4 µg NO3‐N in a final volume of 11 mL. Evaporation of the sample may be done in several ways to remove water from reactants, as long as the temperature for activiation of nitration is attained. Resin extracts from 2 M HCl required neutralization with 2 M NaOH prior to analysis, and soil extracts from 1 M KCl provided more uniform results than from 2 M KCl. Results from all types of solution samples were highly significantly correlated with those by the automated Cd‐reduction method. This simplified sodium salicylate procedure (SSP) for NO3 analysis is simple, reproducible, and it requires only inexpensive equipment.
Forms of Soil Phosphorus in Selected Hydrologic Units of the Florida Everglades
Authors: Reddy K. R. , Wang Y. , DeBusk W. F. , Fisher M. M. , Newman S. 
Published: July 2010

AbstractThe Florida Everglades wetland ecosystem is subject to changes in hydroperiod and nutrient loading, resulting in soil P enrichment and changes in vegetation communities. The objectives of this study were to: (i) quantify the forms of inorganic and organic P in soils from four hydrologic units of the Everglades, and (ii) develop empirical relationships among various soil P forms. Soil samples from selected hydrologic units, including the Water Conservation Areas (WCAs) and the Holey Land Wildlife Management Area (HWMA), were obtained at various locations along transects perpendicular to each nutrient input source, while selected field sites were sampled in the Everglades Agricultural Area (EAA). Spatial distribution of total P in the surface 0‐ to 10‐cm soil depth showed distinct gradients in the WCAs and HWMA soils, with high total P in soils closer to sources (canals and inflow structures) than in interior, unimpacted areas. Soil ash content and bulk density were also altered as a result of soil subsidence (for EAA soils), hydrology, and nutrient loading (for the WCAs and the HWMA soils). Influence of P loading was primarily confined to the top 30‐cm soil depth, with about one‐third of the P stored in the inorganic pool (primarily as Ca‐ and Mg‐bound P), and the remainder present as organic P. Inorganic P content was higher in surface soils and decreased with depth. Soil P enrichment indicated that for approximately 5 km from the inflow structures or canals, soils have been impacted by nutrient loading. Empirical relationships developed in this study should be useful for estimating soil P forms at the landscape level, using total P data available for a large number of sites throughout the Everglades region.
Measurement of Field Soil Hydraulic and Solute Transport Parameters
Authors: Casey Francis X. M. , Horton Robert , Logsdon Sally D. , Jaynes Dan B. 
Published: July 2010

AbstractAgricultural chemical presence in groundwater has drawn attention toward transport processes occurring in soil. Hydraulic conductivity (K) and water‐holding capacity of a soil have great influence on water flow and solute transport. However, much of the chemical transport to groundwater can occur through preferential flow pathways. The simplified, preferential flow, mobile‐immobile model partitions the water content (θ) into mobile (θm) and immobile (θim) domains, with solute exchange between the domains characterized by the mass‐exchange coefficient (α). In this study a sequential tracer application technique was used and K, θ, θim, and α were estimated for a series of pressure heads (H = 10, −30, −60, and −150 mm). This method uses a tension infiltrometer to measure both hydraulic and solute transport parameters in situ. The study took place in a no‐till corn (Zea mays L.) field mapped as a Harps series soil (fine‐loamy, mixed, mesic Typic Calciaquoll). Unsaturated values of θ and K were distinct from the saturated values. Similarly, though less clear cut, distinctions between saturated and unsaturated values of θim, immobile water fraction (θim/θ), and α were observed. The medians of θ for the sequence of decreasing H values were 0.40, 0.34, 0.34, and 0.33 m3 m‐3. The median K values for the same sequence of H were 108, 1.69, 1.51, and 0.72 µm s‐1. The median θim/θ values for the H sequence were 0.40, 0.28, 0.25, and 0.39. The median values of α for the H sequence were 0.59, 0.015, 0.0028, and 0.0029 h‐1. A strong correlation between α and H suggests a velocity dependence of α.
Sensitivity of Soil Enzyme Activities to Conservation Practices
Authors: Bergstrom D. W. , Monreal C. M. , King D. J. 
Published: July 2010

AbstractThere is a need to assess changes in soil quality resulting from introduction of conservation practices. This study tested for an effect of tillage practice and crop rotation on activity of six soil enzymes (dehydrogenase, urease, glutaminase, phosphatase, arylsulfatase, and β‐glucosidase). Samples of the Ap horizon were collected from adjacent no‐till and tilled fields. At one site, fields were located on a simple, single slope averaging 4%, and differed in previous cropping history. The second site included coarse‐ and fine‐textured soils at lower and upper slope positions, respectively. Enzyme activities of field‐moist samples were measured during two growing seasons, and maximum reaction velocity (Vmax) values were estimated for three enzymes on a subset of air‐dry samples. At the first site, implementation of no‐till and previous cropping to forages increased activity of all enzymes. At the second site, there was no consistent response of enzyme activities to tillage practice in the coarse‐textured soils, which had relatively large total C content. In the fine‐textured soil, activity of phosphatase and arylsulfatase, and dehydrogenase in the surface (0–8 cm) layer, was greater in the no‐till field. At this location, these enzyme activities were more sensitive than total C (TC) concentration to tillage practice. Slope position and time and depth of sampling influenced enzyme activities and affected management comparisons.
Soil Aggregate and Texture Effects on Suspension Components from Wind Erosion
Authors: Mirzamostafa N. , Stone L. R. , Hagen L. J. , Skidmore E. L. 
Published: July 2010

AbstractMany detrimental impacts are caused by the suspension‐size (<0.10‐mm) dust (SSD) generated during wind erosion. Prediction models of SSD are needed to assess SSD magnitudes and also aid in design of controls. Current models tend to lump together all sources of SSD from the soil surface, and their overall structure is best suited for use on large, uniform source areas. We reviewed equations developed to simulate generation of SSD on a subfield scale from individual structural components of the soil. These sources include direct emission of loose SSD, abrasion of SSD from surface clods by impacting saltating aggregates, and breakdown of saltating soil aggregates to SSD. The main objective of this study was to experimentally determine the effects of aggregate structure and soil texture on the individual SSD sources for a range of Kansas soils. Periodic sampling of 11 soils showed that the fraction of loose SSD in the upper 20 mm available for emission ranged from 0.7 to 80% of soil mass. However, variation in the mean SSD fraction in these soils was directly related to soil texture (r2 = 0.87). Content of SSD in the total mass abraded from clods in a wind tunnel ranged from 14 to 27%. This range was relatively narrow, but related to parent soil clay content (r2 = 0.69). Saltation‐size aggregates were about nine times more stable than target clods of the same soils. However, the production of SSD based on breakage coefficients of saltating aggregates was also related to clay content of the parent soils (r2 = 0.96).
Aggregation and Soil Organic Matter Accumulation in Cultivated and Native Grassland Soils
Authors: Six J. , Elliott E.T. , Paustian K. , Doran J. W. 
Published: July 2010

AbstractTillage intensity affects soil structure and the loss of soil organic C and N. We hypothesized that no‐tillage (NT) and conventional tillage (CT) differentially affect three physically defined particulate organic matter (POM) fractions. A grassland‐derived Haplustoll was separated into aggregates by wet sieving. Free light fraction (LF) and intra‐aggregate POM (iPOM) were isolated. Natural abundance 13C was measured for whole soil C, free LF C, and iPOM C. The mean residence time of soil C under CT (44 yr) was 1.7 times less than in NT (73 yr). The amount of free LF C was 174, 196, and 474 g C m‐2 for CT, NT, and NS, respectively. Total iPOM C amounts in CT, NT, and NS were 193, 337, and 503 g C m‐2, respectively. The level of fine iPOM C (53–250 µm) level in macroaggregates (250–2000 µm) obtained after slaking was five times greater in NT vs. CT and accounted for 47.3% of the difference in total POM C between NT and CT. The amount of coarse iPOM C (250–2000 µm) was only 2.4 times greater and accounted for only 21% of the difference in total POM C. Sequestration of iPOM was observed in NT vs. CT, but free LF was not influenced by differential tillage. We conclude that differences in aggregate turnover largely control the difference in fine iPOM in CT vs. NT and consequently SOM loss is affected by both the amount of aggregation and aggregate turnover.
Residual Effects of Crop Residues on Grain Production and Selected Soil Properties
Authors: Power J. F. , Koerner P. T. , Doran J. W. , Wilhelm W. W. 
Published: July 2010

AbstractReturning crop residue improves water conservation and storage, nutrient availability, and crop yields. We have little knowledge, however, of the residual impacts of crop residues on soil properties and crop production. We hypothesized that residual impacts of crop residues vary with the amount of residues used. A 10‐yr study near Lincoln, NE, evaluated the residual effects of an earlier 8‐yr study of various crop residue amounts on crop growth and selected soil properties. From 1978 through 1985, crop residues were returned at 0, 50, 100, and 150% of the quantity produced by the previous crop (averaging 0 to ≈6 Mg ha‐1 yr‐1). Continuous corn (Zea mays L.) was produced 1986 through 1995 on these plots, except sorghum [Sorghum bicolor (L.) Moench] was substituted in several years. To study management effects on residual responses, plots were subdivided with or without tillage, N fertilizer (60 kg N ha‐1), and hairy vetch (Vicia villosa L.) cover crop. Residual effects of the 150% residue amount increased grain production 16% compared with the 0% amount (4900 vs. 4250 kg ha‐1, respectively), and were not affected by time or other management practices. Increasing previous residue amount did enhance soil N availability (from 73.0 to 82.3 kg autoclave‐mineralizable N ha‐1) and Bray soil P (16.7 to 20.3 kg ka‐1). These results are among the first to show that residual effects of crop residue are prolonged (half‐life of ≈10 yr) and probably result from changes in soil properties that enhance soil nutrient availability.
Temporal Pattern of Oxygen Concentration in a Hydromorphic Soil
Authors: Sierra J. , Renault P. 
Published: July 2010

AbstractOxygen deficiency negatively affects crop yield and has a major impact on soil biological activity. This work was performed to ascertain the factors affecting the O2 concentration in a soil profile, and to analyze the hypothesis used in O2 transport models. Oxygen concentration was measured using platinum microelectrodes. Soil porosity, water content, temperature, groundwater depth, and microbial respiration were analyzed as the driving variables affecting O2 concentration. Soil respiration was well described by a Michaelis kinetics; the maximal rate of respiration for the 0‐ to 0.1‐m layer (2.5 × 10‐5 mol m‐3 s‐1) was five times higher than for the 0.3‐ to 0.5‐m layer. This implies that the simplification of vertical homogeneity and zero‐order kinetics for O2 consumption are invalid to estimate O2 transport. In the topsoil, the amplitude of the changes in O2 concentration after rainfall decreased in the order autumn > winter > summer. At 0.2 m for rainfall of ≈40 mm, the O2 concentration decreased 0.09 m3 m‐3 within 3 d after rainfall in autumn, and 0.05 m3 m‐3 within 6 d in winter. The fluctuations observed in O2 concentration after rainfall indicated that the steady‐state approximation used in models is too restrictive to describe O2 transport in soil. In the subsoil, O2 concentration varied slightly due to low O2 consumption (≈10‐7 mol m‐3 s‐1). Oxygen concentration in the topsoil was negatively associated with the water‐filled pore space, except for measurements taken immediately after rainfall >30 mm d‐1, which indicated the presence of entrapped air. This suggests that the hypothesis of instantaneous equilibrium between water content and soil O2 concentration is a reasonable simplification except for the 12‐ to 24‐h following high‐intensity rainfall.
Irrigation of Peppermint for Optimal Yield
Authors: Mitchell A. R. , Yang C. L. 
Published: July 2010

AbstractLittle field research has documented the water use of peppermint (Mentha piperita L.), an important irrigated crop of the Pacific Northwest grown for oil and tea leaves. Our objective was to determine a peppermint yield—water use function and to develop a crop coefficient (Kc) to relate crop evapotranspiration (ET) to potential ET. Trials were conducted from 1992 to 1994 at Madras, OR on a Madras loam mesic Aridic Argixeroll (fine‐loamy, mixed, mesic Xerollic Duriargid). A line‐source sprinkler irrigation system was used to impose five irrigation treatments ranging from 30 to 120% of the ET required for maximum yield. Evapotranspiration was measured by monitoring the water balance components of irrigation, precipitation, drainage, and soil water storage. Peppermint yield was sensitive to irrigation, with both deficit and excess irrigation lowering oil yields compared with the optimum treatment, which was 324, 388, 364, and 487 mm season‐1 for the four trials. Peppermint ET‐yield functions exhibited a greater transpiration component (89%) than other crops due to its thick canopy that reduces soil evaporation. The highest yielding irrigation treatment kept the soil water pressure between −18 and −50 kPa in the top 0.3 m. The Kc followed the general three‐lines model with an initial value of 0.3 that increased to 0.85 at mid‐season and declined to 0.5 at harvest. Thermal units were used to normalize the inflection points for the Kc curve for 2 yr of the trial (1993 and 1994). Late winter tillage in 1992 delayed peppermint growth and shifted the Kc curve.
Development and Evaluation of ENVIRO‐GRO, an Integrated Water, Salinity, and Nitrogen Model
Authors: Pang X. P. , Letey J. 
Published: July 2010

AbstractDevelopment of a multicomponent model for crop yield and potential groundwater degradation applicable for irrigated agriculture is important. The ENVIRO‐GRO model was developed to simulate (i) water, salt, and N movement through soil with a growing plant; (ii) plant response to matric potential, salinity, and N stresses; (iii) drainage and salt and N leaching; and (iv) cumulatively relative transpiration and relative N uptake, and consequent crop relative yield. This model does not account for denitrification. The utility of the model was illustrated by simulating the effects of irrigation amount, irrigation salinity, and N application on yield and N leaching. The results demonstrated the effects of complex interactions and feedback mechanisms in the plant‐soil‐water‐salinity‐N system. Factors leading to reduced plant growth caused lower transpiration, which created more leaching of salts and N. The simulated interactions are consistent with observed behaviors. Evaluation was done by comparing simulated results with published results of an experiment that had N application rates of 0, 90, 180, and 360 kg N ha‐1 and water application rates of 21, 63, and 105 cm. Agreement between simulated and observed corn (Zea mays L.) relative yield and total N uptake was generally good. The difference between mean observed and predicted values was <0.06 for corn relative yield and 1.34 kg N ha‐1 for total N uptake. Linear regression analyses revealed excellent agreement results for the 63‐cm irrigation and a tendency for the model to overpredict results for the 21‐cm irrigation and underpredict results for the 105‐cm treatment.
Three Decades of Observed Soil Acidification in the Calhoun Experimental Forest: Has Acid Rain Made a Difference?
Authors: Markewitz Daniel , Richter Daniel D. , Allen H. Lee , Urrego J. Byron 
Published: July 2010

AbstractThree decades of repeated soil sampling from eight permanent plots at the Calhoun Experimental Forest in South Carolina allowed us to estimate the rate of soil acidification, the chemical changes in the soil exchange complex, and the natural and anthropogenic sources of acidity contributing to these processes. During the first 34 yr of loblolly pine (Pinus taeda L.) forest growth, soil pH, (pH in 0.01 M CaCl2) decreased by 1 unit in the upper 0‐ to 15‐cm of soils and by 0.4 and 0.3 units in the 15‐ to 35‐ and 35‐ to 60‐cm layers, respectively. Throughout the 0‐ to 60‐cm horizon, base cation depletion averaged 1.57 kmolc ha‐1 yr‐1 and effective and total acidity increased by 1.26 and 3.28 kmolc ha‐1 yr‐1, respectively. A forest H+ budget estimated for these decades indicated that 38% of soil acidification was due to acid deposition, while 62% of soil acidification was attributed to the internal functioning of the ecosystem. Soil samples archived during the three‐decade experiment also document decreases in soil‐adsorbed SO2‐4, presumably in response to decreasing atmospheric inputs in recent years.
Formation and Stability of Hydroxy Aluminum‐Iron‐Montmorillonite Complexes: Influence of Ferrous Iron
Authors: Violante A. , Krishnamurti G. S. R. , Huang P. M. 
Published: July 2010

AbstractSynthetic hydroxy Al‐Fe gels were prepared at pH 6.0 by mixing different amounts of Fe(ClO4)2 to a solution of Al(ClO4)3 (5 mol Al kg‐1 clay) to result in an initial Fe(II)/Al molar ratio (R) of 0, 0.1, 0.3, 0.5, 1.0, and ∞, both in the absence and presence of Na‐saturated montmorillonite. The suspensions were aged up to 100 d at 25°C or 30 d at 70°C. Gibbsite was formed in all the samples (R = 0–1.0) after 30 d of aging at 25°C or 1 d at 70°C, except in the sample formed at R = 1.0, where gibbsite was detected only after >2 mo of aging at 25°C or after aging for 6 d at 70°C. At R = ∞, lepidocrocite, goethite, and ferrihydrite were the Fe oxides/oxyhydroxides formed in the absence of montmorillonite. No crystalline Fe oxides were observed in the presence of montmorillonite. After aging, the degree of interlayering in the montmorillonite was observed to be always greater in the samples where Al and Fe were coprecipitated than in the samples formed at R = 0 or ∞. After prolonged aging up to 100 d at 25°C or 30 d at 70°C, the interlayering was stabilized in the samples formed at R = 0.1 to 1.0, with d‐spacings ranging from 1.48 to 1.85 nm or from 1.55 to 1.74 nm, respectively. All the samples aged for 100 d at 25°C or 30 d at 70°C were treated using acid ammonium oxalate. The oxalate‐extractable Fe/Al molar ratios of the acid ammonium oxalate extractable mixed hydroxy Al‐Fe complexes were much higher than the initial solution Fe/Al molar ratios. The stabilized short‐range ordered materials present in the interlayers of montmorillonite in the samples that formed at R values ranging from 0.1 to 1.0 were apparently Al‐substituted Fe oxides.