bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Long‐term Lime and Potassium Applications on Quantity‐Intensity (Q/I) Relationships in Sandy Soil
Authors: Sparks D. L. , Liebhardt W. C.
Published: July 2010

The effects of long‐term lime and K applications on quantity‐intensity (Q/I) relationships were investigated on the Ap and B21t horizons of a Kalmia soil (a fine‐loamy over sandy or sandy‐skeletal, siliceous thermic (Typic Hapludults) from the Delaware Coastal Plain. The predominant mineral suite of the <2µm clay fraction was mica, vermiculite, and chloritized vermiculite. Soil pH and exchangeable bases increased with depth and with lime additions. The equilibrium potassium activity ratio (ARke) decreased with profile depth due to greater K fixation by specific sites for K in the B21t horizon. The ARke decreased in the Ap horizon and increased in the B21t horizon with lime additions. The magnitude of ARke [> 0.01 (moles/liter)½] suggests that K adsorption in the Ap horizon occurred on planar positions while adsorption at specific sites was predominant in the B21t horizon [> 0.006 (moles/liter)½]. The parameter δKo, which measures labile K, became more negative with increased lime and K additions, indicating a greater K release into soil solution. While the quantity of K extracted by NH4OAc compared favorably to δKo in the Ap horizon, it exceeded δKo in the B21t horizon, suggesting K exchange involving specific sites in the B21t horizon. The number of specific sites (Kx) increased with K fertilization and with soil depth. The decreased Kx with increased lime additions could be ascribed to increased neutralization of hydroxyaluminum interlayer material, resulting in an increase in interlayer “islands.” The potential buffer capacity (PBCk) parameter increased with lime additions due to increased pH‐dependent cation exchange capacity (CEC).
Potential for Phosphorus Toxicity in Zinc‐Stressed Corn and Potato
Authors: Christensen N. W. , Jackson T. L.
Published: July 2010

Corn (Zea mays L., ‘Illinois WF 9 × 38‐11’) and potato (Solanum tuberosum L., ‘Russet Burbank’) were grown in dithizone purified nutrient solutions to contrast relationships between dry matter yield, tissue phosphorus (P) concentration, and tissue zinc (Zn) concentration as they influence the development of Zn deficiency and P toxicity. Treatments consisted of Zn at 0, 0.14, and 0.41 µM in factorial combination with P at 0.02, 0.10, 1.0, and 3.0 mM. Yield and tissue concentration of P and Zn were affected by statistically significant P‐Zn treatment interactions in both species. Corn plants developed Zn deficiency symptoms and responded to nutrient solution Zn when plant growth was not limited by inadequate nutrient solution P. Corn plants grown in nutrient solutions containing 0 µM Zn and 3.0 mM P contained 3.39% P in leaf tissue and had significantly lower yields than did plants grown in nutrient solutions containing 1.0 mM P. Even though no visual symptoms were evident, P toxicity probably was responsible for the reduction in yield. Potato plants responded to nutrient solution Zn when growth was not limited by inadequate P but did not exhibit visual symptoms of Zn deficiency. Zinc‐deficient potato plants containing in excess of 2.22% P in leaf tissue exhibited probable P toxicity symptoms characterized by puckering of leaf edges, thickening and upward curling of leaves, and leaf necrosis. Excessive concentration of P in leaf tissue of Zn‐deficient potato was the result of increased mobilization and translocation of P from roots to above‐ground parts, increased total P uptake, and concentration of P resulting from restricted growth. Excessive levels of P in corn leaf tissue were primarily the result of concentration of P due to restricted growth. Zinc concentration in tissue of both species was reduced by growth response dilution, but Zn uptake by plants receiving low levels of Zn was not reduced by increasing nutrient solution P concentrations. Apparent accentuation of Zn deficiency by P application is explained on the basis of accumulation of toxic levels of P in Zn‐deficient plants. Species such as potato which show increased P uptake and increased mobilization and translocation of P to tops when under Zn stress are probably more susceptible to P toxicity.
Long‐Term Tillage Effects on Interrow Runoff and Infiltration
Authors: Lindstrom M. J. , Voorhees W. B. , Randall G. W.
Published: July 2010

Simulated rainfall trials were conducted in wheel‐tracked and nonwheel‐tracked interrows for three continuous corn (Zea mays L.) tillage systems (fall moldboard plow with spring field cultivate, fall chisel with field cultivate, and no till designated as conventional, conservation, and no till, respectively) in the 10th year of the tillage and crop system in south central Minnesota to determine the effect of long‐term tillage systems on interrow runoff and infiltration. Wheeltracked interrow refers to tractor tire tracks from the planting operation. Simulated rainfall was applied with a sprinkling‐type infiltrometer at a rate of 12.7 cm/hour simultaneously to wheel‐tracked and nonwheel‐tracked interrows. Differences were observed in random roughness and soil bulk density of the surface 7.6 cm between wheel‐tracked variables, tillage systems, or both. Energy required to initiate runoff, reported as rainfall kinetic energy (KE), was significantly different among tillage systems for each wheel‐tracked variable. Ranking of the treatments was conservation > conventional > no till for the nonwheel‐tracked interrow, and conservation = conventional > no till for the wheel tracked interrow in relation to KE required to start runoff. The conservation and conventional nonwheel‐tracked interrows had a greater infiltration rate after runoff started than the wheel‐tracked interrows and the no till system. Evidence from this study indicates that the no till system may result in a consolidated soil surface with a low infiltration capacity that is persistent with time and susceptible to high volumes of runoff during severe rainstorm events.
Evaluation of Slow‐Release Nitrogen Sources on Baron Kentucky Bluegrass
Authors: Hummel N. W. , Waddington D. V.
Published: July 2010

As new nitrogen (N) sources are introduced, it is important that they be evaluated and their release characteristics determined in order to provide us with a basis on which to make fertilizer recommendations. In this study, several N sources were evaluated for maintenance fertilization of Kentucky bluegrass (Poa pratensis L.) turf. Treatments included isobutylidene diurea (IBDU) materials of two particle‐size ranges, sulfur‐coated ureas (SCU) in two size ranges from Canadian Industries Limited (CIL), SCU from the Tennessee Valley Authority (TVA), ureaformaldehyde (UF), activated sewage sludges, Organiform, soluble N sources, and combinations of slow‐release and soluble N. All N sources were applied at a rate of 197 kg N·ha−1·yr−1, divided into equal fall and spring applications for 3 consecutive years. Weekly clipping yields, color ratings, and annual N recovery were the response criteria.

Sulfur‐coated urea produced a more uniform growth and had higher N recovery than IBDU, which was characterized by a delayed response following fertilization. Turfgrass response to the CIL and TVA SCU materials applied alone was similar. Particle‐size effects with CIL SCU were slight; however, N release was quicker from fine IBDU than coarse IBDU. Slow‐release characteristics were also observed for ureaform, Organiform, and the sludges, but turf quality was generally poor for these treatments. Substituting soluble N for a portion of the SCU N gave inferior turfgrass response as compared to SCU applied alone. When soluble N was used in conjunction with ureaform, Organiform LT, and IBDU, turfgrass response was improved over that obtained when these N sources were used alone. Recovery of N in the clippings was greatest for soluble N sources and SCU treatments (48 to 52%), while lowest values (15 to 29%) were associated with ureaform, Organiform, and sludges.
The Manufacture and Agronomic Efficiency of a Partially Acidulated Phosphate Rock Fertilizer
Authors: Garbouchev I. P.
Published: July 2010

North Africa phosphate rock, Gafsa type (PR), and different PR/H3PO4 ratios were investigated to find an efficient, partially acidulated PR fertilizer (PAPR). A monocalcium phosphate (MCP)/PR ratio of approximately 60/40, produced by 26 to 30% acidulation of PR by H3PO4, was the most efficient PAPR product; it requires 68 to 70% less H3PO4 than the amount required for manufacture of triple superphosphate (TSP).

PAPR products made in pilot plants by the “Door‐Oliver” process were more efficient than those produced by the “Batch” process. Field experiments with PAPR fertilizer were carried out from 1970 to 1978. Agronomic results showed that the above product was generally equal or slightly superior to TSP in terms of P availability as detected by routine soil test methods. Models on control of the P status in several soils were established on the basis of greenhouse experiments with increasing P rates for ryegrass (Lolium perenne L).

Commercial factory production of PAPR by the “Door Oliver” process costs 30 to 35% less than that of TSP because of lower total energy and less H3PO4 used. An additional advantage appears to be a 50 to 65% increase in fertilizer output in factory‐scale installation. In practice, higher available soil P was maintained, and at least equal crop yields were obtained with a higher rate, less frequently applied, than with the same total P rate applied more often in fractional applications. This was especially true for PAPR.
A Comparison of Three Extractants for Soil Zinc
Authors: Kennedy A. C. , Brown J. R.
Published: July 2010

An HEDTA (hydroxyethylenediaminetriacetic acid) soil zinc (Zn) extractant was compared to 0.1M HCL (1) and DTPA [diethylenetri‐aminepentacetic acid; (4)] for their value in detecting zinc deficient sites. Published formation constants suggested that HEDTA should be an effective chelator of soil zinc below pH 7.0. Calculations based upon these formation constants were the impetus for further investigation of HEDTA as a zinc extractant. The extractant consisted of 0.005M HEDTA in a 0.1M calcium acetate buffer adjusted to pH 6.0. Ten grams of air‐dried soil were shaken with 20 ml of extractant for 30 min. After filtration the concentration of zinc in the filtrate was determined.

Three extractants, HCI, DTPA, and HEDTA, were compared for their ability to extract zinc from soils at 11 sites in Missouri. The three tests were equally successful at separating deficient from nondeficient soils. Zinc extracted by HEDTA varied less within each site than did that extracted by HCI to DTPA.
Spatial Variability of Field‐Measured Infiltration Rate
Authors: Vieira S. R. , Nielsen D. R. , Biggar J. W.
Published: July 2010

Spatial variability of 1,280 field‐measured infiltration rates on Yolo loam (fine‐silty, mixed, nonacid, thermic Typic Xerorthents) was studied using geostatistical concepts. The measurements were made at the nodes of an irregular grid consisting of 160 rows and eight columns. Sample spacing within columns was 1 m. Columns were spaced irregularly at 1, 5, 15, and 19 m.

A variogram for the 1,280 measurements was used to krige 800 additional values within five more columns and to draw a contour map of the area.

The large number of measured values made it possible to calculate the minimum number of samples necessary to reproduce the infiltration rate measurements with a fairly large approximation. As a result, it could be concluded that a minimum of 128 samples was enough to obtain nearly the same information as with 1,280 samples. A suggestion on how to use autocorrelograms in sampling schemes is presented.
Aromaticity of Humic Substances in Soils
Authors: Hatcher Patrick G. , Schnitzer Morris , Dennis Larry W. , Maciel Gary E.
Published: July 2010

Humic acids from different climatic zones and a fulvic acid from an Armadale soil, Prince Edward Island, Canada, have been examined by cross polarization, magic‐angle spinning 13C nuclear magnetic resonance (NMR). Aromaticities calculated from the NMR spectral data are generally high, ranging from 35 to 92%, in general agreement with values obtained from the results of chemical oxidation/gas chromatographic mass spectrometric studies. Most NMR spectra, however, indicate the presence of significant aliphatic structures that generally were not observed by chemical oxidation studies. Chemical techniques have overestimated the degree of aromaticity of humic substances. Phenolic carbons that have always been considered to be major “building blocks” of humic substances are not observed as intense signals by NMR; this fact suggests that these carbons may be minor rather than major components. Carboxyl contents calculated from NMR spectra are greater than those calculated by chemical techniques and approximate the concentrations of total acidic groups.
Incorporation of a Wide Variety of Organic Substrate Carbons into Soil Biomass as Estimated by the Fumigation Procedure
Authors: Kassim G. , Martin J. P. , Haider K.
Published: July 2010

Biodegradation of the carbon or specific carbons of a large variety of 14C‐labeled organic substrates were followed in a closed, constantly aerated system in Steinbeck loam (pH 5.0) and Greenfield sandy loam (pH 7.0) over various periods of incubation at 22°C. Incorporation into biomass and stabilization in humus were estimated after 12 weeks of incubation. The labeled carbons in biomass were estimated using a slight modification of Jenkinson's fumigation method. Readily available substrates such as glucose, acetate, pyruvate, uracil, uridine, amino acids, and some polysaccharides were rapidly metabolized by the soil population, and after 8 to 12 weeks, about 80% or more of the substrate carbons had evolved as CO2. After 12 weeks, about 20 to 40% of the residual carbons of these substrates were present as hiomass, and 60 to 80% was present as new humus. Glucosamine, cysteine, cellulose, protein, and some microbial and plant polysaccharides were degraded to a somewhat smaller extend, 60 to 70%, indicating some stabilization of the intact molecules or partial degradation products by incorporation into humus or by complexing with soil colloids or metals. About 10 to 30% of the residual carbons were associated with the biomass after 12 weeks. Most microbial cells and plant residues such as straw were utilized to a still lesser extent, with about 50 to 60% loss of applied C in 12 weeks and an incorporation of about 5 to 13% of the residual 14C into biomass. A fungal humic acid‐type melanin was still more resistant, and less of the residual C, 0.2 to 1.3%, was present in biomass at 12 weeks.
Comparison of Effects of Nitrate, Nitrite, and Nitric Oxide on Reduction of Nitrous Oxide to Dinitrogen by Soil Microorganisms
Authors: Gaskell J. F. , Blackmer A. M. , Bremner J. M.
Published: July 2010

Recent work has shown that nitrate inhibits reduction of nitrous oxide (N2O) to dinitrogen (N2) by soil microorganisms under anaerobic conditions. Studies to investigate the possibility that this inhibition is caused by nitrite or nitric oxide (NO) formed through microbial reduction of nitrate showed that both NO and nitrite inhibit reduction of N2O to N2 by soil microorganisms under anaerobic conditions (helium atmosphere) but that the inhibitory effect of NO on N2O reduction is much smaller than the effects of nitrate or nitrite. Comparison of the effects of nitrate, nitrite, and mixtures of nitrate and nitrite on reduction of N2O to N2 by soils incubated under He showed that nitrate per se inhibits N2O reduction and did not confirm a recent suggestion that the inhibitory effect of nitrate on N2O reduction is due to nitrite formed through microbial reduction of nitrate.
Soil Properties Influencing Penetration Resistance of Canfield and Geeburg Soils
Authors: McCormack D. E. , Wilding L. P.
Published: July 2010

Penetration resistance was measured in situ by the procedures of the ASTM standard penetration test. Selected horizons were tested at five sites of each of two soil series. Presumptive bearing value is shown to be influenced most strongly by soil moisture content, bulk density, and clay content. These variables explain 78% of the variation in presumptive bearing value.

Soil strength as determined by this test and the vane shear tests were compared and found to be very similar; however, the penetration test is less sensitive to differences in soil moisture content. Determination of presumptive bearing value using the penetration test provides information useful to understanding the behavior of specific horizons of soil series.
Agricultural Erosion Indicated by 137Cs Redistribution: I. Levels and Distribution of 137Cs Activity in Soils
Authors: Brown R. B. , Cutshall N. H. , Kling G. F.
Published: July 2010

Modern agricultural erosion was studied using 137Cs fallout as an indicator of erosion and sedimentation in the hilly margin of the Willamette Valley, Ore. Objectives of this phase of the study were (i) to identify areas most severely eroded over the period of fallout (since early 1954), and (ii) to identify areas that had been subject to net deposition over the same period.

Along each of eight transects, sampling sites were selected in ridgetop, steep sideslope, and concave footslope positions. Also sampled were a single convex ridge shoulder, a high ridgetop, two alluvial fans, two floodplain sites, and two sites in an 8‐year‐old pond. Soil cores were collected at each site and analyzed by depth increment for 137Cs activity.

Depth distribution patterns of 137Cs activity suggested that fallout 137Cs was retained in surface soils and was, therefore, a good tracer in erosion/sediment studies. Depositional sites tended to have overthickened 137Cs profiles and high total contents of 137Cs. Average total 137Cs activity in depositional sites was about 12 pCi/cm2.

Sideslopes and ridgetops, with average total 137Cs activities of about 8 pCi/cm2, were indistinguishahle from each other. Failure to distinguish sideslopes from ridgetops based on 137Cs signature was attributed to (i) widespread runoff from these lands, (ii) damping effects of plowing and continuing input of fallout 137Cs, and (iii) an apparent lack of erosion severe enough to have depleted preferentially the 137Cs‐rich surface soils of sideslopes.
Persistence of Potassium in Forest Systems: Further Studies with the Rubidium/Potassium Technique
Authors: Stone Earl L.
Published: July 2010

Foliar samples from comparable potassium (K)‐fertilized and unfertilized plots of nine forest fertilization trials were analyzed for rubidium (Rb) and K. The trials represented different combinations of soils, species, age classes, and rates. Application of the Hafez and Stout Rb/K “reverse tracer” procedure demonstrated that in seven of the nine experiments, fertilizer K still made up 25 to 45% of total foliage K 4 to 12 years after application. Inconclusive results from the remaining trials were probably due to inappropriate sampling in one instance but are unexplained in the other.

Overall results, in conjunction with previous reports, suggest that the Rb/K technique may be widely useful in studies of K retention and circulation in forest systems.
Analysis of Chamber Methods Used for Measuring Nitrous Oxide Production in the Field
Authors: Jury W. A. , Letey J. , Collins Tim
Published: July 2010

Two current procedures for measuring nitrous oxide (N2O) production in the field are studied using a two‐dimensional model of gas production and diffusion through soil. These procedures consist of trapping the gas as it leaves the soil surface, either by allowing the gas to build up in a closed chamber (closed cover), or by removing and measuring the gas as it leaves the soil (open cover). The model calculations suggest that in many cases, neither measurement relates well to the N2O production rate because the gas concentration is still building up in the soil. There are also expected differences between the two methods, with the closed cover measurement underestimating the flux from the soil when air contents are relatively high while production is occurring, if gas is allowed to build up in the chamber for more than a few hours.

The calculations suggest that, due to the large phase lag caused by gaseous diffusion, the only way to obtain accurate information about the extent of N2O release to the atmosphere from the soil from a denitrification‐reduction event is to trap all gas which is produced by the process. This may require monitoring for up to several weeks after production ceases if soil water content remains high.
Modification of Buried Soils by Postburial Pedogenesis, Southern Indiana
Authors: Mausbach M. J. , Wingard Robert C. , Gamble E. E.
Published: July 2010

The integration of buried soils with overlying soils was evaluated by examining base saturation, clay illuviation, and the clay weathering products of soil formation. Base saturation is considered as a rapidly changing characteristic, clay illuviation as slow to change, and clay minerals as most resistant to alteration. The soils studied have loamy or clayey buried B horizons that overlie clastic or limestone rock of Mississippian age. Pedisediment or a zone of mixed loess and pedisediment separates a surficial loess from the buried Sangamon B horizon. Base saturation and fine clay distributions above clayey and loamy Sangamon B horizons show little change through the loess and pedisediment. This distribution of base saturation and fine clay indicates that the pedisediment is integrated with the ground soil.

However, where the Sangamon B is clayey, trends in base saturation and fine clay distributions break abruptly at the buried B. Integration of the ground soil with the clayey Sangamon B is not indicated by these properties. When the buried horizons are loamy, there has been post‐loess leaching of bases and illuviation of clay. Apparently, clayey buried Bt horizons retard downward movement of solutes which effectively inhibits post‐loess alteration of the clayey Sangamon B horizon. Amounts and kinds of clay minerals are about the same in the pedisediment and Sangamon B, which indicates that post‐loess integration of the pedisediment has not proceeded to the extent of altering clay mineral suites.
Predicting Temperatures of Bare‐ and Residue‐covered Soils from Daily Maximum and Minimum Air Temperatures
Authors: Gupta S. C. , Radke J. K. , Larson W. E. , Shaffer M. J.
Published: July 2010

The manuscript describes a model for prediction of soil temperature of bare and various residue‐covered soils with and without a corn crop where the needed inputs are (i) daily maximum and minimum air temperatures at the 2‐m height, (ii) initial soil temperature, and (iii) thermal diffusivity profiles. This is a simplification of our earlier model and involves the replacement of measured hourly air temperature by an estimate.

Predictions of root zone temperature from the current model are tested against the measured values for six treatments representing various degrees of cover resulting from either the residue or shading by growing plants. Ninety‐five percent of the daily predicted temperatures at the 5‐cm depth are within −5.3 to 7.1°C and −2.0 to 3.1°C of the measured values for bare soil and corn plus 50% residue‐covered soil, respectively. Differences between the predicted and measured root zone temperatures decreased with an increase in plant or residue cover at the surface and soil depth.

Replacement of measured hourly air temperature by an estimate in the soil temperature model drastically reduces the amount of input data needed to predict root zone temperatures. The predicted temperatures are valuable as inputs for crop growth and nitrogen transformation modeling and in forecasting spring root zone temperatures for various plant or residue covers based upon forecasts of the daily maximum and minimum air temperatures. These predicted values of root zone temperatures can be useful in deciding the planting dates for the Northern Corn Belt States.
Soil Physical Properties as Affected by Soybean and Other Cropping Sequences
Authors: Fahad A. A. , Mielke L. N. , Flowerday A. D. , Swartzendruber D.
Published: July 2010

Infiltration, water stability of soil aggregates, and water retention characteristics were measured on a Sharpsburg silty clay loam (Typic Argiudolls) in a 4‐year cropping sequence. The cropping systems include soybean (Glycine max L. Merr.), sorghum (Sorghum bicolor L. Moench), corn (Zea mays L.), and fallow, in various sequential cropping combinations.

The influence of cropping systems on size distribution of water‐stable aggregates is indicated by the values of geometric mean diameter (GMD). The rank order of GMD for the soybean sequences was: soybean after fallow > soybean after sorghum > soybean after corn > continuous soybean. The low GMD of continuous soybean reflected the negative effect of soybean roots in building a stable soil structure. Cumulative infiltration after 4 hours of water application was 6, 13, 29, and 41 cm for continuous soybean, sorghum after soybean, fallow after soybean, and corn after sorghum, respectively. The low infiltration was associated with low macroporosity and decreased aggregate stability. Both Kostiakov's and Philip's equations fitted the infiltration data reasonably well statistically, but Kostiakov's equation was a better fit for the early and late stages of infiltration.
Dry Soil Aggregation as Influenced by Crop and Tillage
Authors: Armbrust D. V. , Dickerson J. D. , Skidmore E. L. , Russ O. G.
Published: July 2010

Soil loss by wind erosion is greater in the spring due to higher wind velocities, loss of protective crop residues by tillage and decomposition, and overwinter changes in nonerodible soil aggregates. This study was conducted to determine the effect of crop species and tillage on soil aggregation. Plots of continuous winter wheat (Triticum aestivum L.), grain sorghum (Sorghum bicolor L. Moench), and soybean (Glycine max L. Merr.) with tillage treatments of mechanical, chemical, and combination of mechanical and chemical weed control were sampled for aggregate distribution, stability, and overwinter breakdown.

Winter wheat plots contained more nonerodible aggregates (> 0.84 mm), and the aggregates were more aggregates from sorghum or soybean plots. Soybean plots were lowest in all three variables measured. Tillage‐treatment effects varied, with the chemical‐treated plots containing the most nonerodible aggregates and the mechanical‐treated plots having the most stable aggregates.
Soil Bulk Density Analysis in Three Dimensions by Computed Tomographic Scanning
Authors: Petrovic A. M. , Siebert J. E. , Rieke P. E.
Published: July 2010

Current soil bulk densitometric techniques lack the precision to detect three‐dimensional changes in density in a nondestructive manner. The x‐ray transmission computed tomography (CT) scanner was evaluated as a tool to determine soil bulk density. This scanner is an advanced tool in diagnostic radiology used to obtain a nondestructive cross‐sectional representation of the human body. Typical accuracy and precision for CT scanners are known for materials like human tissue with a linear attenuation coefficient near water. Machine response was evaluated near the upper limit of the measurement range where denser materials, such as soil, are located.

Scanner analyses of soil and glass bead‐air filled sphere samples that varied in bulk density from 0.14 to 1.64 g/cm3 revealed that a positive linear response occurred with increasing density. For the Metea sandy loam soil (Arenic Hapludalfs), this CT scanner was found to have precision in the order of 19 mg/cm3. Spatial resolution or the ability to distinguish between two objects in the scanning plane was found to range from 1.25 by 1.25 by 2 mm3 to 6.4 mm in diameter by 2 mm. The greater resolution was obtained when density within the sample varied greatly. Errors in data can occur as a result of certain machine artifacts; however, many of these can be avoided by relatively simple methods.

It was concluded that the CT scanner can be used to determine soil bulk density with good three‐dimensional spatial resolution. This is a potentially promising tool for research in the areas of compaction, soil management, and cultivation.
Temperature Dependence of Unsaturated Hydraulic Conductivity of Two Soils
Authors: Constantz Jim
Published: July 2010

Packed columns of Oakley sand (mixed, mesic Typic Paleudalfs) and Hanford sandy loam (mixed, nonacid, thermic Typic Xerorthents) were used to develop isothermal steady‐state fluxes. Soil matric potentials were measured and unsaturated hydraulic conductivities were calculated over a range of matric potentials at 2°, 25°, and 45° ± 0.5°C. In addition, water retention characteristics (to −100 kPa) were measured at these same temperatures for both soils. In this paper, the calculated results are compared to an equation that relates unsaturated conductivity to the intrinsic permeability, the relative permeability, and the viscosity of water. The equation considers viscosity to be the only parameter that changes with temperature. The results show a much greater temperature dependence in the unsaturated conductivity than would be predicted by this equation. The results indicate that the relative permeability may be a function of temperature. The temperature dependence of the soil water matric potential, surface tension, and diffuse double‐layer thickness are discussed in terms of their possible interaction with the unsaturated conductivity values obtained. A case is presented for further study to isolate these temperature‐sensitive parameters as well as additional parameters related to fluid flow path changes with temperature.
The Effect of Turfgrass Thatch on Water Infiltration Rates
Authors: Taylor D. H. , Blake G. R.
Published: July 2010

A high water infiltration rate is important for high quality sports turfgrass areas. An understanding of the effect of thatch and grass plants on water infiltration is needed in order to improve the management practices used to maintain high rates. The objective of this study was to determine if a layer of thatch acts as a limiting layer to water infiltration on coarse‐textured sports turfgrass soils.

The effect of a thatch layer on water infiltration rate was determined using laboratory packed sand columns and field turfgrass areas constructed using soil mixtures with high sand content. Data from both laboratory and field experiments demonstrated that after infiltration reaches a constant rate, a layer of thatch did not reduce the water infiltration rate. Initial infiltration rate for thatch‐covered sand, however, was lower than the sustained infiltration rate, while the initial infiltration rate into sand without thatch was much higher than the sustained infiltration rate. Initial infiltration rate was very low when sand was covered with a layer of dry thatch, but it increased to near the sustained rate within 10 minutes.
Evaporite Mineral Species in Mancos Shale and Salt Efflorescence, Upper Colorado River Basin
Authors: Whittig L. D. , Deyo A. E. , Tanji K. K.
Published: July 2010

Evaporite mineral species associated with Late Cretaceous marine sedimentary formations in a selected region of the Upper Colorado River Basin were identified by x‐ray diffraction analysis. Mancos Shale, a major contributor of dissolved mineral salts to the Colorado River and several of its tributaries in the Upper Basin, contains abundant gypsum as the only detectable evaporite mineral. Salt efflorescence associated with the Mancos Shale, however, contains variable quantities of Ca, Na, and Mg sulfate evaporite species, including gypsum (CaSO4 · 2H2O), epsomite (Mg2SO4 · 10H2O), hexahydrite (MgSO4 · 6H2O), pentahydrite (MgSO4 · 5H2O), starkeyite (leonhardtite) (MgSO4 · 4H2O), kieserite (MgSO4 · H2O), loewite [Na4Mg2(SO4)4 · 5H2O], bloedite [Na2Mg(SO4)2 · 4H2O],mirabilite (NaSO4 · 10H2O), and thenardite [Na2SO4). The hydrated sulfates of Na and Mg, as very labile salts, are subject to change in response to relatively minor changes in temperature and moisture status. Dominant evaporite mineral species associated with a few localized seeps and springs emanating from the Late Cretaceous Mount Garfield formation of the Mesaverde group, overlying the Mancos Shale, include soda (Na2CO3 · 10H2O), trona (Na2CO3 · NaHCO3 · 2H2O), nahcolite (NaHCO3), and halite (NaCl). Origin of the evaporite mineral species and their significance in relation to salt loading of the Colorado River are discussed.
Hydrodynamic Dispersion Involving Cationic Adsorption During Unsaturated, Transient Water Flow in Soil
Authors: Laryea K. B. , Elrick D. E. , Robin M. J. L.
Published: July 2010

The analysis of hydrodynamic dispersion of solutes during one‐dimensional absorption (horizontal flow) of solution into soil columns is extended to solutes which interact with the soil particle surfaces. The exchange process involved is assumed to be instantaneous and is described by a nonlinear adsorption isotherm. The relevant equations are solved for the apparent longitudinal dispersion coefficient using a computer program written in system/360 CSMP.

Experiments with a clay loam soil indicated that when a concentrated solution of potassium chloride (KCl) (1N) infiltrates into a Ca2+‐saturated soil, the apparent longitudinal dispersion coefficient is effectively velocity independent. This calculated coefficient reflects the possible combined effects of an immobile water fraction and salt exclusion.
A “Micro‐Lysimeter” Method for Determining Evaporation from Bare Soil: Description and Laboratory Evaluation
Authors: Boast C. W. , Robertson T. M.
Published: July 2010

A new (“micro‐lysimeter”) method for estimating evaporation from soil consists of pushing a thin‐walled cylinder 76 mm in diameter into field soil, removing the soil‐filled cylinder from the field, closing the bottom to make it water‐tight, determining the mass of the micro‐lysimeter, replacing it in the field with its top surface even with the surrounding soil, leaving it exposed to environmental conditions for a period of time (typically 1 d), and redetermining its mass. Evaporation loss from the micro‐lysimeter is the difference between the two masses.

The objective of this study is to quantify the systematic deviations of such micro‐lysimeters from reality in order (i) to determine how long a given micro‐lysimeter can be used before its soil must be discarded (and a new sample taken if further readings are desired), and (ii) to correct for systematic deviations. The deviations are quantified by comparing short micro‐lysimeters with effectively “infinitely long” ones. The deviation is influenced by the time that the micro‐lysimeter is exposed to environmental conditions and by the length of the soil sample. For a silty clay loam soil under evaporativity conditions ranging from 2 to 9 mm/d, the measurement error for micro‐lysimeters 70 mm in length is found to be < 0.5 mm for 1 or 2 d, depending on whether the initial soil condition is “wet” or “dry,” respectively (0.26 or 0.13 g of H2O per gram of dry soil in the top 20 mm).

Hence, for many applications the method is valid for 1 or 2 d. Correction equations for deviations of up to 0.5 mm are given. The method requires little equipment and makes possible evaporation measurement under some conditions (for example, at large numbers of sites or in areas of partial crop shading) where micrometeorological, water balance, and traditional lysimetric methods are unpractical or impossible.
Nutrient Transport Inside and Outside the Root Rhizosphere: Theory
Authors: Cushman John H.
Published: July 2010

The root surface as an absorption mechanism is briefly reviewed and various absorption models are discussed, e.g., the Koshland kinetic and Michaelis‐Menten models.

Differences in nutrient availability and transport between the root rhizosphere and bulk soil matrix are examined. The differences manifest themselves in the diffusion coefficients, buffering powers, soil mechanical structure, and nutrient solubility and production. The differences in nutrient transport properties between the rhizosphere and bulk soil matrix are shown to give rise to two coupled partial differential equations. These equations are analytically solved for four sets of boundary conditions. The solutions are used to compute total nutrient uptake by a growing root.
Predicting Mycorrhizal Dependency of Troyer Citrange on Glomus fasciculatus in California Citrus Soils and Nursery Mixes
Authors: Menge J. A. , Jarrell W. M. , Labanauskas C. K. , Ojala J. C. , Huszar C. , Johnson E. L. V. , Sibert D.
Published: July 2010

In a greenhouse experiment the mycorrhizal fungus, Glomus fasciculatus, significantly increased growth of Troyer citrange (Poncirus trifoliata L.) (TC) seedlings in 20 of 26 methylbromide‐fumigated citrus soils from southern California. Of the six soils in which G. fasciculatus provided no growth increase, two were greenhouse soils, three were nursery soils, and only one was a field soil. Glomus fasciculatus increased foliar P, K, and Cu concentrations and decreased foliar Mg and Na concentrations of TC grown in the majority of the 26 citrus soils. Foliar concentrations of P, K, Ca, Na, Zn, Mn, Cu, and Fe from either mycorrhizal or nonmycorrhizal TC could not be significantly correlated with the mycorrhizal dependency of TC in the soils studied. A positive correlation was observed between foliage concentrations of Mg in nonmycorrhizal TC and mycorrhizal dependency. Mycorrhizal dependency of TC was also positively correlated with soil pH and inversely correlated with extractable soil P (bicarbonate), Zn, Mn, Cu, percent organic matter, and cation exchange capacity. In the fumigated soils studied, it was highly probable that inoculations with G. fasciculatus would induce significant growth response in TC provided the soils had <34 ppm extractable P, 27 ppm extractable Mn, 12 ppm extractable Zn, or 3% organic matter. The magnitude of the mycorrhizal dependencies of TC on G. fasciculatus in the 26 citrus soils were accurately predicted with equations which used soil P, Mn, Zn, and also Cu and pH as independent variables.
The Role of the Western Harvester Ant (Pogonomyrmex occidentalis) in Soil Formation
Authors: Mandel Rolfe D. , Sorenson Curtis J.
Published: July 2010

The effects of harvester ants (Pogonomyrmex occidentalis) on the physical and chemical properties of soils were determined for 20 ant mounds in the semiarid subalpine region of south‐central Colorado. Comparisons of soil materials in mounds of active colonies with surrounding unaffected soils showed significant differences in particlesize distribution and concentrations of CaCO3, exchangeable K, Na, Mg, and total N. The activity of ants in the study area appears to affect less ground surface area than in more humid regions (1 to 10% of respective land areas by regional comparison). The ants also tend to rearrange particles preferentially in the sand fraction instead of in the finer fractions as recorded for more humid regions. However, their role in nutrient enrichment of mound soils is similar to that of different ant species in other regions. The soil alterations induced by P. occidentialis are favorable for plant growth, and the ant mounds may aid revegetation in disturbed areas.
Perched Water Tables on Hillsides in Western Oregon: I. Some Factors Affecting Their Development and Longevity
Authors: Hammermeister D. P. , Kling G. F. , Vomocil J. A.
Published: July 2010

Perched water tables on hillsides located on the western border of the Willamette Valley in Oregon in some cases have the potential to transport pollutants from either domestic or agricultural sources downslope to streams, ponds, or reservoirs, resulting in the deterioration of the quality of these waters. In this paper, some factors responsible for the development and longevity of these potentially problem‐causing perched water tables on three hillsides were examined. Analyses of hydraulic conductivity data and the relationships between rainfall, soil water pressure potential, and time suggest that permeable rock below 110 cm rather than clayey B horizons is mainly responsible for the development of perched water tables on upper convex slope positions on two of these hillsides. The data also suggest that subsurface flow from the upper convex regions contributed significant amounts of water to the lower convex slope positions. Further, perched water tables developed more rapidly, to a greater extent, and lasted longer in upper horizons of a lower concave region of slope where a shallow perched water table was already present at the onset of rainfall. Finally, perched water tables did not develop in the upper horizons on a third hillside that had no impermeable regions in the soil or upper rock mantle.
Internal Energy Balance and the Richards Equation
Authors: Sposito Garrison , Chu Shu‐Yuan
Published: July 2010

The energy concept of soil water introduced by Buckingham and developed by Richards is employed to derive a differential balance equation for the partial specific internal energy of water in an unsaturated soil. This equation is shown to comprise both heat flux and chemical work terms, in correspondence with the first law of thermodynamics. For the case of isothermal water flow through a rigid, homogeneous soil, the balance law for internal energy reduces to the Richards Equation with the soil water matric potential as the dependent variable. This result, which does not require the conventional direct appeal to the law of mass balance, demonstrates that the energy concept of soil water provides a self‐consistent method for obtaining the Richards Equation. Either the energy balance concept or the traditional mass‐balance approach can be used to establish the macroscopic physical foundations of the Richards equation.
Nutrient Availability Under Trickle Irrigation: II. Mineral Nitrogen
Authors: Bacon P. E. , Davey B. G.
Published: July 2010

The effects of irrigation and fertilizer application on nitrate, nitrite, and ammonium concentration in a Chromic Luvisol were studied in an orchard that had been trickle irrigated for 5 years. Immediately before the first irrigation of the season, mean plot nitrate‐N was 5 ppm; 8 h of irrigation reduced this to 0.5 ppm. Nitrite concentration fell from 0.8 to 0.4 ppm in the same period. During irrigation ammonium concentration rose from 7.1 to 13.5 ppm (the average rate of increase being 0.8 ppm/h) in the surface 6‐cm depth of soil extending up to a distance varying from 30 to 65 cm from the outlet. There was no evidence that nitrate or nitrite accumulated at the A/B horizon boundary and it is likely that the loss was due to denitrification.

Ammonium concentration decreased rapidly as the soil dried out and 8 h after the end of irrigation it had fallen from 13.5 to 8.5 ppm. As there was no change in the nitrate concentration in this region during the same 8‐h period the ammonium was being immobilized rather than nitrified. The only place where nitrification took place during the first 3‐d cycle was immediately below the fertilizer band at site D where nitrate concentration rose from 0 to 15 ppm in 3 d. Mean plot nitrate‐N at the end of the first cycle was 2.6 ppm. Some 32 cycles later at the beginning of the midseason 3‐d cycle nitrate‐N had fallen to 0.6 ppm. Neither nitrate nor nitrite varied with time during the midseason 3‐d cycle. Ammonium concentration rose significantly over the region extending from at least 12 cm below the surface under the outlet to the 3‐ to 6‐cm depth 65 cm away from the outlet. Over this volume of soil ammonium‐N increased from 3.9 to 19.4 ppm during irrigation. In the 4 h after the end of irrigation the ammonium concentration decreased and there was no significant difference between the pre‐ and post‐irrigation ammonium concentrations within the volume defined above. Apparently all the ammonium released during irrigation and not taken up by plants was immobilized by the soil microbial population. The amount of ammonium released was greater in the midseason (15.5 ppm) than in the first 3‐d cycle (6.4 ppm). Ammonium release rate during the midseason irrigation was 1.3 ppm N · h−1. There were no significant changes in nitrate, nitrite, or ammonium during the midseason 1‐d cycle.

The results obtained for five 3‐d irrigation cycles in early summer again demonstrated that the decrease in nitrate during the irrigation cycle was accompanied by an increase in ammonium. The phenomena was part of a continuous cycle which increased the mineral nitrogen availability during the wet portion of every 3‐d cycle.
Characterization of Nutrient Transport Coefficients in Field‐grown Soybeans
Authors: Scott H. D. , Brewer D. W.
Published: July 2010

A knowledge of nutrient translocation in plants is basic to an understanding of plant nutrition. Thus, a mathematical model was developed to describe nutrient translocation in a four‐compartment soil‐soybean system. Mass balance equations were used to describe the instantaneous rate of change in the amount of a given nutrient in the compartments assuming that the nutrients move at a rate that is proportional to the concentration of the compartment from which it flows. Dry weights and accumulations of N, K, Ca, and Mg in stems, leaves, and pods of ‘Lee 74’ soybeans (Glycine max. L. Merr.) grown on two soils and under two moisture regimes were used as inputs into the model.

Two methods were formulated to describe dry weights and nutrient accumulations in the stems, leaves, and pods. The first method was based on linear vegetative growth of the stems and constant stem and leaf weights during reproductive growth. The second method was based on a statistical fit of the seasonal nutrient concentration in the stems and leaves. The experimental data were used to calculate nutrient uptake rates and transport coefficients during several intervals according to both methods.

Nutrient uptake rates, crop growth rates, the stem‐to‐leaf transport coefficient (Ksl), and the stem‐to‐pod transport coefficient (Ksp) varied considerably during the season and were higher in those soybeans that were irrigated and grown on the clay soil. Of the nutrients studied N had the greatest uptake rate, Ksl, and Ksp.
Long‐term Effects of Manure on Soil Nitrogen, Phosphorus, Potassium, Sodium, Organic Matter, and Water Infiltration Rate
Authors: Meek Burl , Graham Lucy , Donovan Terry
Published: July 2010

High rates of manure were added to field plots of a Holtville silty clay (Typic Torrifluvents) soil in an irrigated desert region, and their effects on the soils' chemical and physical properties were measured for 9 years.

Manure applications resulted in large losses of nitrogen (N), increased potassium (K) levels, increased phosphorus (P) availability, increased water intake rates during the growing season, and an N mineralization rate of about 5% after the first year. At high rates of manure application only 42% of the N applied could be accounted for. One application of 180 t/ha of manure in 1971 doubled the NaHCO3‐extractable P levels in the soil in 1979 compared with that of plots that did not receive manure. The application of manure had only a small or no effect on the water intake rate when it was measured between cropping periods on plots that had been recently tilled, but differences were large when water intake rates were measured while the crop was growing. The increased water infiltration rates during the growing season would be important because of increased crop yields in areas affected by salinity.