bluuebunny/crossref_metadata_2025_split huggingface dataset:
Release of Fixed Ammonium during Nitrification in Soils
Authors: Green C. J. , Blackmer A. M. , Yang N. C. 
Published: July 2010

AbstractAmmonium added to soils can be fixed by clay minerals and subsequently released. There is, however, uncertainty concerning how rapidly this release occurs. We evaluated the possibility that relatively rapid release of recently fixed NH+4 may accompany nitrification of exchangeable NH+4 in soils. Labeled urea was added to four soils at rates of 0, 100, or 200 mg N/kg, and the soils were incubated anaerobically for 20 d to allow ample time for urea hydrolysis and NH+4 fixation to occur. Recovery of the labeled N as fixed NH+4 at 20 d averaged 1% in a Nicollet (fine‐loamy, mixed, mesic Aquic Hapludoll) soil, 3% in a Bremer (fine, montmorillonitic, mesic Typic Argiaquoll) soil, 10% in a Webster (fine‐loamy, mixed, mesic Typic Haplaquoll) soil, and 23% in a Canisteo (fine‐loamy, mixed [calcareous], mesic Typic Haplaquoll) soil. Air was introduced after 20 d to promote nitrification of NH+4 and release of fixed NH+4. In the two soils with greatest fixation, a mean of 45% of the labeled N present as fixed NH+4 after 20 d was released in the next 15 d. These observations indicate relatively rapid release of fixed NH+4 during nitrification. Failure to recognize the importance of release of fixed NH+4 during nitrification in recently fertilized soils could result in underestimates of the amounts of N available to plants and microorganisms and in overestimates of mineralization‐immobilization turnover of N.
Multivariate Diagnosis of Nutrient Imbalance in Potato Crops
Authors: Parent L. E. , Cambouris A. N. , Muhawenimana A. 
Published: July 2010

AbstractCompositional Nutrient Diagnosis (CND) involves a correction procedure for two constraints inherent to foliar analytical data, i.e., the bounded‐sum constraint to 100% of the components and the redundant information among interactive nutrients, which are addressed only partially by the Diagnosis and Recommendation Integrated System (DRIS) and not at all by the Critical Value Approach (CVA). The objective of this study was to extract the correlation structure among nutrients using principal component analysis, to test for correlation between DRIS and CND nutrient indices, and to diagnose independent samples. Yield and foliar analyses (N, P, K, Ca, and Mg) of late potato were collected in the St‐Lawrence Lowlands for 3 yr. The high‐yielding subpopulation (182 observations) produced >40 Mg ha−1. Three varimax‐rotated principal components (PC) explaining 93.5% of total variation in the high‐yielding subpopulation were designated as (N−P−Ca+), (P−Mg+) and (K+). A euclidian distance d computed from the PCs provided a nutrient imbalance index for the crop. DRIS and CND indices were highly correlated to each other (r = 0.956‐0.989) using 36 independent early potato samples. The CVA diagnosed correctly 66.7% of the cases. The CND classified the crops in two groups assuming χ2 distribution for d2 values (P ≤ 0.10). Nitrogen was the most limiting nutrient in the high‐yielding subgroup and K was extremely limiting in the low‐yielding subgroup. Defining critical CND nutrient indices empirically, CND produced correct diagnoses 87.5% of the time.
Temporal and Spatial Patterns of Episaturation in a Fragixeralf Landscape
Authors: McDaniel P. A. , Falen A. L. 
Published: July 2010

AbstractRelatively low saturated hydraulic conductivities associated with fragipans result in seasonal perched zones of saturation (episaturation). This study was conducted to monitor seasonal episaturation in a Fragixeralf landscape of northern Idaho. Perched zones of saturation above a fragipan in a 1.4‐ha field were monitored during a 2‐yr period using 64 piezometers arranged on a 15‐m grid spacing. During the winter of 1991–1992, relatively mild temperatures and high rainfall resulted in development of perched zones of saturation lasting from early December into May. Average quantities of perched water present within the landscape during the winter and early spring months ranged from 8.4 to 15.4 cm, representing between 34 and 43% of the seasonal precipitation that had been received at the study site. During the 1992–1993 winter, colder temperatures and relatively large quantities of snow delayed development of episaturation. When the snow pack began to melt in early March, an average of >20 cm of water was present in the saturated zone above the fragipan. This water represented 58% of the seasonal precipitation that had been received. Soil morphological characteristics and elevation were correlated with quantities of perched water present on sampling dates when potential evapotranspiration was low. For all sites, quantity of perched water was most strongly correlated with the thickness of the zone above the fragipan exhibiting redoximorphic features; depth to the fragipan was less strongly correlated. Elevation was generally a poor indicator of episaturation. Results of this study indicate that significant periods of episaturation occur in fragipan‐dominated landscapes under xeric moisture regimes.
Comparison of Six Methods To Determine Unsaturated Soil Hydraulic Conductivity
Authors: Stolte J. , Freijer J. I. , Bouten W. , Dirksen C. , Halbertsma J. M. , Van Dam J. C. , Van den Berg J. A. , Veerman G. J. , Wösten J. H. M. 
Published: July 2010

AbstractKnowledge of soil hydraulic properties is required for soil‐water flow models. Although many studies of individual methods exist, comparisons of methods are uncommon. Therefore, we compared application ranges and results for six laboratory methods for determining hydraulic conductivity or diffusivity on eolian sand, eolian silt loam, marine sandy loam, and fluviatile silt loam. The methods, hot air, sorptivity, crust, drip infiltrometer, Wind's evaporation, and one‐step outflow, fall into three groups: (i) those that only yield a conductivity curve; (ii) those that yield a simultaneous estimate of conductivity, diffusivity, water content, and pressure head; and (iii) those that yield a diffusivity curve. Diffusivities were converted to conductivities with a water retention curve. One main difference between the methods was the pressure head‐water content range. Despite the large differences between the methods, the results for the first two groups tended to be similar. The results of the third group did not match well with those of the first two. It proved difficult to compare these methods correctly due to hysteresis.
Gypsum Determination in Soils by Conversion to Water‐Soluble Sodium Sulfate
Authors: Berigari M. S. , Al‐Any F. M. S. 
Published: July 2010

AbstractPrecise and accurate determination of gypsum in soils has been difficult by the wet‐chemical methods, based on its solubility in water. In this work, 2‐g samples of three Typic Gypsiorthids were washed once with 25‐mL portions of 50% (v/v) ethanol to selectively remove nongypsic soluble sulfates. Soil gypsum was subsequently converted to CaCO3(s) and Na2SO4 by ultrasonic dispersion of the samples twice with 25‐mL increments of 0.5 M Na2CO3 solution. The SO2−4 in the supernatant solution was centrifuge separated and analyzed by the standard gravimetric BaSO4 (A) and turbidimetric (B) methods to obtain the gypsum content of the samples. The agreement between the data of Methods A and B was excellent where the best‐fitted regression line coincided with the 1:1 line in a scattergram. Soil gypsum was also extracted with water, then determined by turbidimetric SO2−4 (C) and the Bower‐Huss conductometric (D) methods for comparison. Statistical analyses of the data showed higher values (P = 0.05) of gypsum in soils obtained by the proposed method than by water extraction even when the same method of SO2−4 analysis was applied. The efficiency of the proposed method was 25 to 31 times greater than that achieved by water. The proposed method of gypsum extraction and its determination in soils from turbidimetric SO2−4 analysis was applied. The efficiency of the proposed method was 25 to 31 times greater than that acheived by water. The proposed method of gypsum extraction and its determination in soils from turibidimetric SO2−4 analysis is simple, rapid, and quite accurate for soil taxonomy, land reclamation, and other engineering purposes.
Atrazine Desorption from Smectites
Authors: Barriuso E. , Laird D. A. , Koskinen W. C. , Dowdy R. H. 
Published: July 2010

AbstractIn soils low in organic matter, pesticide adsorption and desorption by clay minerals may strongly influence the fate of pesticides in soil environments. Atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine) adsorption‐desorption was determined on 11 reference smectites (<2‐µm size fraction), and a soil smectite (<0.02‐µm size fraction from the Ap horizon of a fine‐loamy, mixed, mesic Typic Haplaquoll). For each clay sample, adsorption and desorption isotherms were determined using batch equilibration. Atrazine adsorption on the clays decreased with increasing surface change density (SCD) of the smectites. The desorption isotherms indicated that adsorption was generally reversible. This suggests that atrazine is primarily adsorbed on smectite surfaces through relatively weak van der Waals or H bonds. However, a small positive hysteresis was observed with some clays, and the magnitude of the hysteresis, evaluated using the ratio of the Freundlich isotherm coefficients for adsorption and desorption, increased with SCD. This suggests that atrazine is retained by stronger binding mechanisms on smectites with high SCD, in spite of its lower adsorption capacity. On clays with high atrazine adsorption coefficients, the amount of atrazine desorbed was larger than would be predicted from the adsorption isotherms, resulting in a “negative hysteresis” whereby the desorption isotherm slope was greater than the adsorption isotherm slope. “Negative hysteresis” can be explained if atrazine is assumed to be excluded from interlayer or intraquasi‐crystal water, where only external or interquasi‐crystal water would be available during the desorption process.
Spatial and Temporal Variability of Ammonium in Flooded Rice Fields
Authors: Dobermann A. , Gaunt J. L. , Neue H. U. , Grant I. F. , Adviento M. A. , Pampolino M. F. 
Published: July 2010

AbstractMonitoring and modeling the dynamics of N in flooded rice fields require reliable methods for both sampling and analysis. Destructive soil sampling and centrifugation and in situ sampling of soil solution using microporous polymer tubes (rhizon soil solution samplers; RSSS) were used to study the dynamics and variability of NH+4 in two field experiments. Both methods gave similar results in unfertilized treatments, whereas significant differences were measured in treatments with N application. The RSSS were suited for measuring point dynamics or microvariation of nutrients in the root zone, whereas soil‐core sampling was a better method to obtain quantitative N data integrated across a particular depth range. We observed a highly significant linear relationship between the logs of soil exchangeable and solution NH+4 only until panicle initiation (PI). Microvariability accounted for a large proportion of the within‐field variation and was significantly reduced by bulking of soil cores. Coefficients of variation were higher in the fertilized field compared with an unfertilized field and were changing throughout the growth period of rice, with the highest variability between PI and flowering. Sampling to obtain representative mean values at the plot or field scale can be optimized with regard to temporal changes in the spatial distribution patterns of NH+4. Before transplanting (TP) and at the end of the growth period, less samples are needed and can be taken as composite samples of the whole puddled soil layer. Between TP and flowering, more samples are needed and should be taken in several depth ranges.
Effects of Bulldozer and Chain Clearing on Soil Properties and Crop Yields
Authors: Barber R. G. , Romero D. 
Published: July 2010

AbstractThe use of bulldozers and straight blades for clearing subtropical forests in eastern Bolivia is believed to result in serious soil degradation and low crop yields. It was hypothesized that chain felling with a tree pusher and rake windrowing would cause less soil degradation and give higher crop yields. An experiment established on a Typic Haplustalf compared the effects on soil degradation and subsequent crop yields of (i) conventional bulldozer felling and windrowing with a straight blade (land clearing control), (ii) bulldozer felling with a straight blade and tree pusher, and rake windrowing, (iii) chain felling with a tree pusher and straight blade windrowing, (iv) chain felling with a tree pusher and rake windrowing, and (v) undisturbed forest (control). All four methods caused significant soil physical degradation as manifest by 10 to 20% increases in bulk density and a 6.2% loss of total porosity at the 0‐ to 0.20‐m depth, a lowering of the soil surface by about 30 mm due to compaction, and a significantly lower 30‐min cumulative infiltration (4.36 cm) compared with the forest control (15.08 cm). All four land clearing methods gave significant increases in Ca (from 7.7 to 11.6 cmolc kg−1) in the 0‐ to 0.20‐m depth as a result of forest burning. Very few significant differences in soil properties, and no significant differences in subsequent yields of corn (Zea mays L.) or soybean (Glycine max. L.), were found among land clearing methods. Thus, under dry to slightly moist soil conditions and with skilled operators, the clearing of a low‐biomass, subtropical forest by bulldozer clearing with a straight blade was no more degrading to the soils than chain felling with a tree pusher and rake windrowing, and did not result in lower yields of subsequent crops.
Controlled Displacement Technique for Measuring Soil Friability
Authors: Snyder V. A. , Vázquez M. A. , Martínez G. , Ramírez L. , Hadas A. 
Published: July 2010

AbstractAn important physical property of agricultural soils is their friability or tendency to fracture into small fragments when tilled. Because friability varies greatly with soil water content, simple tests to determine the point of maximum friability are needed. Previous tests have failed to simulate a set of conditions that are necessary to achieve effective soil fragmentation in tillage. The most important of these conditions is a loading path that imposes a compression/shear ratio conducive to fracture and that also provides continuous energy for crack propagation after fracture initiation. Also, many tests do not directly measure the amount of soil fragmentation. The latter is a primary variable of interest when considering soil reaction to tillage. A new procedure is described that provides the necessary fracture conditions and gives a direct measure of the amount of soil fragmentation under any desired compression/shear ratio. Forces, displacements, and energy expenditures during the soil fragmentation process can be measured. The amount of soil fragmentation determined by the method was found to be very sensitive to compression/shear ratio, particularly in highly plastic soils. However, different soils always ranked the same for all ratios. Friability indices were measured with the technique on a set of soil cores sampled in the field at different soil water matric pressures. The matric pressure at which these indices indicated maximum soil friability agreed well with the point of maximum friability determined by tillage of the same soil.
Field and Undisturbed‐Column Measurements for Predicting Transport in Unsaturated Layered Soil
Authors: Ward A. L. , Kachanoski R. G. , von Bertoldi A. P. , Elrick D. E. 
Published: July 2010

AbstractTransport properties vary considerably over small distances in most soils. The stochastic streamtube model offers one approach to incorporating heterogeneity into transport predictions. This study tested the ability of the streamtube concept to predict transport in heterogeneous fields using measurements from undisturbed columns. Fifty undisturbed columns (0.15‐m diam. by 1.5 m deep) were taken every 0.4 m from a 20‐m‐long transect in a loamy sand soil with variable horizon thickness. Each core was instrumented at 0.1‐m intervals with time domain reflectometry probes to measure resident fluid concentrations of a conservative (Cl−) tracer under steady flow conditions. Large‐scale concentration curves of Cl− from solution samplers and coring were obtained from field experiments conducted on the same soil under similar boundary conditions. Differences were observed in the solute spread and mass recovery, but not in the centers of mass. Horizontal scale dependence of transport was observed in the field but not in the columns. This suggests that a higher dimensionality of transport, probably along the horizon interfaces, may be responsible for the observed scale dependence in the field. Although the stochastic streamtube model gave good predictions of the center of mass, it does not appear to be a realistic physical analogue for describing solute dispersion in soils with spatially variable layer thickness.
Comparison of Diagnosis and Recommendation Integrated System and Nutrient Sufficiency Range for Corn
Authors: Soltanpour P. N. , Malakouti M. J. , Ronaghi A. 
Published: July 2010

AbstractThe diagnosis and recommendation integrated system (DRIS) is a potential method for interpreting plant foliar nutrient composition. The objective of our study was to compare DRIS with the nutrient sufficiency range (NSR) for corn (Zea mays L.). We used published standard DRIS norms and Colorado DRIS norms calculated from ear leaf composition at tasseling to silking of corn yielding 11 Mg grain ha−1 or higher. Our NSR values are based on the minimum and maximum nutrient concentration values found in the literature. We changed the minimum value of 21 g kg−1 for N to 26 g kg−1. For identifying nutrient needs of corn, the NSR was superior to DRIS regardless of the DRIS norms used. Identified flaws of DRIS are: (i) very high levels of one nutrient can cause false relative deficiency (imbalance) diagnosis of other nutrients, and (ii) an optimal ratio between two nutrients produces maximum yields only when both nutrients are in their respective sufficiency ranges. We recommend use of the NSR technique in combination with a soil test to avoid the misdiagnosis of Zn and Cu deficiencies in corn when N is extremely deficient.
Freeze‐Drying Effects on Wet and Dry Soil Aggregate Stability
Authors: Staricka J. A. , Benoit G. R. 
Published: July 2010

AbstractFreeze‐drying of soil aggregates may reduce aggregate size and increase erosion potential. We investigated whether freeze‐thaw frequency, water content, and initial aggregate size influences the freeze‐drying disruption of soil aggregates, as measured by dry and water‐drop‐impacted wet sieving. Aggregates of two western Minnesota soils, Barnes loam (a fine‐loamy, mixed Udic Haploboroll) and Hamerly clay loam (a fine‐loamy, mixed, frigid Aeric Calciaquoll) were tested. Vulnerability to wet sieving was increased much more by freeze‐drying than was vulnerability to dry sieving. Freeze‐drying decreased wet aggregate stability in 85 of 96 cases and dry aggregate stability in 56 of 96 cases. Initial water content largely determined whether freeze‐drying decreased aggregate stability. For water contents of 0.05, 0.15, 0.25, and 0.35 kg kg−1, the mean weight diameters (water‐drop‐impacted wet sieving method) of freeze‐dried aggregates were 93, 64, 48, and 46%, respectively, of their non‐freeze‐dried values. For dry sieving, values for the same four water contents were 100, 103, 90, and 88%, respectively. The detrimental effects also generally increased as aggregate size increased. Freeze‐thaw frequency and soil type had less effect on freeze‐drying disruption than did water content and initial aggregate size. Thus soil surface resistance to breakdown by freeze‐drying and raindrop impact would be expected to decline as initial aggregate size and soil water content increases.
Multidimensional Infiltration: Points, Furrows, Basins, Wells, and Disks
Authors: Clothier Brent E. , Green Steven R. , Katou Hidetaka 
Published: July 2010

AbstractMultidimensional infiltration theory continues to be an area of soil physics research dominated by the works of J.R. Philip. The point source of these endeavors was his landmark paper in 1966. Here in our contribution honoring John Philip, we first discuss the multidimensional, similarity‐solution antecedents that were queried by him nearly 30 yr ago. We then list the new theoretical developments contained in this comprehensive treatise on multidimensional flow into unsaturated soil. Next we comment on the three steady‐state sequels derived by J.R. Philip, P.A.C. Raats, and R.A. Wooding, especially in relation to the experimental studies they spawned. Experiments initially began with attempts to verify directly the various multidimensional flow theories. But experimental procedures soon came to use, in an inverse sense, these theories to permit measurements of the hydraulic properties of field soil. The disk permeameter, currently a widely used device, employs multidimensional theory. In a variety of ways, disks are used to infer the hydraulic properties of field soil in the pressure potential range close to saturation. However, here we propose a method by which the disk permeameter can be used to deduce in situ the nonlinear adsorption isotherm that holds for the transport of reactive chemicals through soil. We demonstrate this proposal by using in the inverse sense of parameter identification, not an analytical description, but rather a two‐dimensional numerical simulation of the flow of water and transport of solute away from a surface disk maintained at a given pressure potential, and some fixed concentration of reactive solute.
Desperately Seeking Darcy in Dijon
Authors: Philip J. R. 
Published: July 2010

AbstractHenry Darcy (born 1803, died 1858) is known to soil physicists as the founding father of the science of fluid flow in soils. This illustrated account of a short visit to Dijon, his native town, reveals little‐known aspects of Darcy's character, life, and work. The central square and town gardens are named after Darcy, as are numerous commercial and public undertakings: a cinema, bus stop, a garage, a multistory car park, a pharmacy, and a shopping arcade. Inquiry revealed that Henry Darcy himself has been forgotten by the citizens of Dijon, and that his name persists only as a ubiquitous geographical label. It was not always thus. Darcy, with great vision and skill, designed and built a pure water supply system for Dijon, in place of previous squalor and filth. Dijon became a model for the rest of Europe. Darcy selflessly waived fees due to him from the town, corresponding to about $1.5 million today. Medals were struck recognizing his skill and selflessness; and a monument celebrates his great work. Dijon gave him a public funeral, the whole population lining the streets, and the council renamed the central square in his honor. His simple tomb is in good condition in Dijon cemetery. His letters to Henri‐Emile Bazin reveal him as intelligent, witty, and sceptical, and quite devoid of pretension.