bluuebunny/crossref_metadata_2025_split huggingface dataset:
Triammonium Pyrophosphate as a Source of Phosphorus for Plants
Authors: Hughes J. D. , Hashimoto Isao 
Published: July 2010

AbstractWhen ammonium ortho‐ and pyrophosphates were applied to mixtures of sand and a soil mineral (kaolinite, montmorillonite, or gibbsite), both the uptake of P by plants and the immobilization of the P were affected more by the soil mineral than by any other factor. Pyrophosphate was hydrolyzed to orthophosphate during incubation more rapidly in the presence than in the absence of a soil inoculum. The results tend to support the hypothesis that plants utilize orthophosphate more readily than pyrophosphate. Although the reactions of pyrophosphate with soil minerals differ markedly from those of orthophosphate, the two forms of phosphate were immobilized by the soil minerals to about the same extent, and differences between the two forms disappeared as hydrolysis and immobilization proceeded. The P uptake was in the order control (no mineral) > kaolinite > montmorillonite > gibbsite, in agreement with the extent of reaction of the applied phosphate with these minerals.
A Simple Statistical Procedure for Partitioning Soil Test Correlation Data Into Two Classes
Authors: Cate Robert B. , Nelson Larry A. 
Published: July 2010

AbstractMost soil test laboratories divide soil test results into two or more classes for the purpose of making fertilizer recommendations. This is usually done for the practical reason that it reduces the number of different recommendations necessary. However, the basis for defining the different classes (e.g., Very Low, Low, Medium, etc.) is often subjective or arbitrary. This paper explains a simple, yet statistically sound, method for setting the class limits. The procedure is to split the data into two groups, using successive tentative critical levels to ascertain that particular critical level which will maximize overall predictive ability (R2), with the means of the two groups (classes) as the predictor values. The paper presents an actual example, using data believed typical of this kind of problem. Several continuous correlation models were also fitted to the same data. None gave as high an R2 as a single Low‐High split defined by the suggested procedure. Similar results have been obtained with a majority of 200 sets of soil test correlation data, indicating that the new procedure may be widely applicable.
Steady Infiltration from Point Sources, Cavities, and Basins
Authors: Raats P. A. C. 
Published: July 2010

AbstractSteady infiltration from buried point sources and surface point sources is analyzed. The partial differential equations for the matric flux potential and the Stokes' stream function associated with axially symmetric flows are derived. The discussion is based on the assumption that the hydraulic conductivity is an exponential function of the pressure head. Explicit expressions for the matric flux potential, the Stokes' stream function, the flux, the pressure head, and the total head are obtained. Some features of the solutions for buried point sources, surface point sources, and gravity‐free flows are compared. Related upward flows for which the soil becomes saturated everywhere are discussed briefly.
Nitrate Adsorption: III. Desorption Movement and Distribution in Andepts
Authors: Kinjo T. , Pratt P. F. , Page A. L. 
Published: July 2010

AbstractA peak of NO3‐ accumulation occurred in the 1‐ to 2‐cm depth of an 11‐cm soil column when 0.2 meq of KNO3 was applied in sufficient solution (16 ml) to fill the pore space in a column of air‐dry San Gregorio soil. Practically no NO3‐ was found below the 4‐cm depth. The greater portion of the NO3‐ applied was displaced from the soil column by the addition of 3 pore volumes of water. The anion distribution coefficient obtained from a column of San Gregorio soil was 2.2 ml/g and was similar to that obtained from a batch‐type method when the soil was in equilibrium with the same concentration of NO3‐. The rate of NO3‐ desorption was described by a first‐order reaction equation. The effect of adding SO42‐ and NO3‐ in the same column was to increase the rate of movement of NO3‐. Sulfate movement was much slower than that of NO3‐.
Montmorillonite Equilibria and the Weathering Environment
Authors: Kittrick J. A. 
Published: July 2010

AbstractStability equations were derived for Belle Fourche and Aberdeen montmorillonites. Both the composition of structural ions and the cation exchange capacity (CEC) were considered to be essential features of montmorillonite stability. However, montmorillonite stability was considered to be independent of the solution activity of exchangeable ions.Simultaneous solution of the stability equations for Belle Fourche and Aberdeen montmorillonites indicated the two minerals could be at equilibrium with one another, but only under solution conditions quite different from those of their original stability determinations. The two montmorillonites (with hematite to control pH — 1/3pFe3+, kaolinite to control H4SiO4 activity, and a constant high Mg2+ activity) were then equilibrated from both low pH (undersaturation) and from high pH (supersaturation). The agreement between experimental and predicted equilibria was well within the experimental error of the original montmorillonite stability determinations. The good agreement between calculated and experimental equilibria under solution conditions far different from those employed for the original stability determinations (about 4 pH units higher, for example) confirms the accuracy of the original stability determinations.Agreement between predicted and experimental equilibria also supports the view that structural ions such as Mg2+, Fe3+, Al3+, and Si4+, as well as the CEC, are essential features of the montmorillonite structure. The relationship between montmorillonite stability and the activities of constituent ions in solution permits the construction of several diagrams showing the variation in stability of Belle Fourche and Aberdeen montmorillonites with change in composition of the soil solution. From these diagrams, it is concluded that the various montmorillonite compositions encountered in nature are primarily a reflection of diverse solution environments rather than a chance incorporation of ions during the crystal growth process.
Capacity of Desert Algal Crusts to Fix Atmospheric Nitrogen
Authors: Macgregor A. N. , Johnson D. E. 
Published: July 2010

AbstractApproximately 4% of the soil surface of an area of desert grassland in the Sonoran Desert of southern Arizona possessed algal‐crust formations. Samples of dry intact algal crusts were examined for nitrogen fixation by the acetylene‐ethylene method. Three hours after being moistened, algal crusts produced detectable levels of ethylene. Premoistened algal crusts were capable of producing ethylene equivalent to 0.7 µg of N/cm2 of algal crust per hour. On the basis of these findings, 1 ha of desert grassland may receive a nitrogen input of 3 to 4 g of N/hour (0.3 mg to 0.4 mg N/m2 per hr) following a rainfall.
Water and Solute Movement in Svea Loam for Two Water Management Regimes
Authors: Cassel D. K. 
Published: July 2010

AbstractSoil water and soil solute movement were investigated in a sub‐humid environment over a 3‐month period for two water regimes. Ammonium nitrate and KCl were broadcast on duplicate 3.7‐m square plots. Each plot was irrigated with 6 to 10 cm of water at 7‐ to 14‐day intervals. One plot was covered to prevent exchange of water at the soil surface (covered plot) while the second remained bare and was thus subjected to the prevailing environmental conditions. Soil water flux and unsaturated hydraulic conductivity values were calculated using soil water pressure and water content data from the covered plot. Analyses of soil solution collected from 30‐, 61‐, 91‐, 122‐, and 152‐cm depths for NO3‐N and Cl revealed that, for the environmental conditions encountered (35 cm pan evaporation and 15 cm rainfall), downward movement of ions was nearly 1.5 times greater for the covered compared with the bare plot. The solute did not move with the soil water in a one to one relationship for either plot.
General Theorem on Steady Infiltration from Surface Sources, With Application to Point and Line Sources
Authors: Philip J. R. 
Published: July 2010

AbstractA general theorem is established that enables the solution of the quasilinearized steady infiltration equation for any distribution of surface sources to be found immediately from the corresponding (mathematically simpler) solution for buried sources. It is introduced through the special cases of the surface line and point sources. The first of these solutions is new and the present derivation of the second is much simpler and more direct than that available hitherto. These solutions hold also for steady infiltration from suitably‐shaped furrows and basins. Corollary to the general theorem, relations of the same type hold between the horizontal flux density components. Both the theorems and the special results apply also to processes such as diffusion in a uniform convective flow and sedimentation under gravity and Brownian motion.
Influence of Soil Treatment on Persistence of Six Chlorinated Hydrocarbon Insecticides in the Field
Authors: Guenzi W. D. , Beard W. E. , Viets F. G. 
Published: July 2010

AbstractAn experiment was designed to compare the rate of disappearance of dieldrin, endrin, heptachlor, lindane, DDD, and DDT from flooded and nonflooded soils. Chopped alfalfa (Medicago sativa L.) (0.25% in the top 10 cm of soil) was added to half of the plots. The nonflooded treatment was subdivided into a soil mixing treatment (surface 8 cm of soil mixed every 2 weeks) and a nonmixing treatment. Holes were dug in the field and plastic containers (43 cm in diameter and 53 cm in depth) were placed in the holes and filled with soil to a depth of 48 cm so that the soil surface inside the container was level with the surrounding soil. Pesticides were incorporated into the surface 10 cm of soil. In the nonflooded soil, neither soil mixing nor added alfalfa enhanced the loss of dieldrin, endrin, DDD, or DDT from the top 8 cm of soil during a 22‐week period. Under the same conditions, the concentrations of lindane and heptachlor decreased with time, and more pesticide was lost from the soil receiving the mixing treatment than from the nonmixed soil. Lindane, heptachlor, endrin, and DDT were susceptible to degradation in the flooded soils. The order of degradation for the degradable insecticides was heptachlor > DDT > lindane > endrin.
The Chemistry and Phytotoxicity of Arsenic in Soils: I. Contaminated Field Soils
Authors: Woolson E. A. , Axley J. H. , Kearney P. C. 
Published: July 2010

AbstractArsenic (As) residues on 58 surface soil samples taken from soils with a history of As application averaged 165 ppm As, while nearby soils not treated averaged 13 ppm As. Most of the residual As was found as Fe‐As (0.1N NaOH extractable) by a modified soil P procedure. Water‐soluble As (1N NH4Cl extractable) was detected in soils from two states. Other forms, Al‐ and Ca‐As (0.5N NH4F and 0.5N H2SO4 extractable As, respectively), may predominate if the amount of “reactive” Al or Ca is high and reactive Fe is low. Bioassay of the contaminated and uncontaminated soils showed a correlation of 0.74 between growth reduction and total As and 0.82 with a summation of As fractions. Plants were tolerant to large As applications (670 ppm As) to soils which were high in reactive (1N NaOH extractable) Al.
Calcium Fluoride Formation During Extraction of Calcareous Soils with Fluoride: I. Implications to Inorganic P Fractionation Schemes
Authors: Syers J. K. , Smillie G. W. , Williams J. D. H. 
Published: July 2010

AbstractAdded inorganic P sorbed during 0.5M NH4F extraction of calcite or aragonite was recovered in subsequent citrate‐dithionite‐bicarbonate (CDB) and HCl extractions of the Williams et al. (1967) inorganic P fractionation scheme. The sorbed P was shown to be associated with CaF2 formed by the replacement of CaCO3 during the NH4F extraction. Similar results were obtained for soils which contained calcite but no P fertilizer reaction products. Thus, the amounts of non‐occluded Al‐ and Fe‐bound P (NH4F‐ and NaOH‐extractable) were underestimated whereas reductant‐soluble P (CDB‐extractable) was overestimated and acid‐extractable Ca‐P frequently overestimated. In contrast, magnesite, dolomite, and a dolomitic soil sorbed only a low proportion of added P during NH4F extraction. A modified fractionation procedure, developed for calcareous soils, omitted the NH4F extraction and involved sequential extraction with (i) NaOH to remove nonoccluded Fe‐ plus Al‐bound P, (ii) NaCl and citratebicarbonate (CB) to remove P sorbed by carbonates during the preceding NaOH extraction, (iii) CDB to remove occluded P (reductant‐soluble P), and (iv) HCl to remove Ca‐bound P. Phosphorus added with the NaOH reagent to carbonate minerals and calcareous soils was recovered during the NaOH, NaCl, and CB extractions, enabling differentiation of nonoccluded Fe‐ plus Al‐bound P from occluded P. The procedure also permitted a more meaningful separation of nonoccluded Fe‐ plus Al‐bound P and Ca‐bound P, particularly in calcareous soils which contained P fertilizer reaction products.
Adsorption of Ametryne and Atrazine on an Oxisol, Montmorillonite, and Charcoal in Relation to pH and Solubility Effects
Authors: Yamane V. K. , Green R. E. 
Published: July 2010

AbstractAdsorption of ametryne exceeded that of atrazine on soil and montmorillonite at both low and high pH. Ametryne (pKa ≅ 4.0) showed a greater increase in adsorption with decrease in pH than atrazine (pKa = 1.68). Addition of charcoal to soil masked the effect of soil pH on ametryne adsorption. Adsorption of ametryne on charcoal decreased at the low pH values conducive to ametryne protonation, demonstrating the effect of pH on triazine‐water affinity in the absence of specific triazine‐adsorbent interactions which are responsive to triazine protonation. Adsorption isotherms were adjusted by use of “relative solution concentrations” to examine the influence of pH and temperature on the relative affinities of water and adsorbent for triazine herbicides. A wetting agent used in the commercial ametryne product had no effect on the adsorption of ametryne.
Ecology of Nematodes in Clarion‐Webster Toposequences Associated With Glycine Max (L.) Merrill
Authors: Nyhan J. W. , Frederick L. R. , Norton D. C. 
Published: July 2010

AbstractToposequence variations in soil and plant properties were characterized and related to nematode populations associated with soybeans. The smallest populations of Aphelenchus avenae, Helicotylenchus pseudo‐robustus, Tylenchorhynchus nudus, Tylenchus spp., and non‐stylet‐bearing nematodes occurred at the toeslope position within the toposequences. Increases in soil pH, soluble salts, percentages of the soil pores filled with water, soil moisture relative to field capacity, silt plus clay, and soil organic matter within the toposequences were associated with decreases in nematode populations, plant top weight, and the concentrations of nitrogen, potassium, and barium in the plant tops. Factor analysis of the data revealed that 67–73% of the total site‐sampling period variance could be accounted for by soil structure, root activity, soil fertility, dry matter production, and nematode factors. However, nematode populations were more closely correlated with plant variables than with soil variables at each toposequence.
Recovery of 15N‐Labeled Fertilizers in Field Experiments
Authors: Westerman R. L. , Kurtz L. T. , Hauck R. D. 
Published: July 2010

AbstractUrea and oxamide, each labeled with 15N, were compared as fertilizers in two field experiments in adjacent locations in successive years with ‘Sudax SX11’ Sorghum‐sudan hybrid (Sorghum sudanense) as the test crop. Four cuttings were harvested during the first experiment and three during the second. Patterns of uptake of fertilizer N were in accord with the characteristics of the two carriers. In the first harvests in both experiments the amounts of N taken up from urea were markedly greater than from oxamide; but by the third harvests, yield responses and N uptake from oxamide were greater than from urea. Total recoveries of fertilizer N from the two carriers during the entire growing season were similar as greater recoveries of urea‐N in the early summer were compensated for by greater recoveries of oxamide‐N in the late summer.Of the N added in urea in the first experiment, 51% was recovered in the crops and 28% was still in the soil (0–25cm) at the end of the growing season. Corresponding figures for oxamide were 52% in the crops and 31% in the soil. In the second experiment, when fertilizer applications and planting operations were delayed until more favorable growing weather, 93% and 99% of the urea‐ and oxamide‐N, respectively, were estimated as recovered in the crops, and measurements of the amounts of fertilizer remaining in the soil were not attempted.
Residual Effects of 15N‐Labeled Fertilizers in a Field Study
Authors: Westerman R. L. , Kurtz L. T. 
Published: July 2010

AbstractResidual effects of two 15N‐labeled N fertilizers, urea and oxamide, were compared during the second cropping season after they had been applied at rates of 0, 56, 112, and 168 kg N/ha. ‘Sudax SX11’ sorghum‐sudan grass hybrid (Sorghum sudanense) was grown and harvested three times during this second cropping season while the residual effects were being measured.Fertilizer N removed in plant tops during this second year of cropping contained 13–18% of the residual fertilizer N in the soil at the end of the first season and was equal to 4–6% of that applied originally in the fertilizers. At the end of the second cropping season, 22 and 26% of the initial applications of N in urea and oxamide, respectively, remained in the soil. The effect of carriers on these amounts of residual fertilizer N was not significant. The removals in crops during the second season plus those amounts remaining in the soil at the end of the second season were essentially equal to the residual fertilizer N which had been in the soil at the end of the first season. Thus, no evidence was found for loss of residual N by leaching, denitrification, or other processes during the second cropping season. Since removals of N in crops were considerably greater than the additions in fertilizers, it is hypothesized that nearly all inorganic fertilizer N was taken out of the soil and most of the residual fertilizer N was in relatively stable organic forms. Conditions for these experiments had been selected to conserve N, and as a consequence the deficits of fertilizer N reported here may be expected to be smaller than might occur under other practices.
Anomalies and Sampling Variation in Forest Soil Water Measurement by the Neutron Method
Authors: Sartz Richard S. 
Published: July 2010

AbstractSampling errors were determined for neutron meter measurements of soil water content in a heterogeneous forest soil. Water content variance at individual 30‐cm depths on uncut plots increased with depth at a high water content but was uniform at a low water content. The variation was greater at a low than at a high water content on uncut plots, but was about equal on cut plots. Water content changes over a period of time were more variable than water content at a single point in time. Coefficients of variation for individual depths ranged up to 76% for uncut plots and up to 137% for cut plots. Coefficients of variation for total profile storage were a little lower for change in water content than for total water content on uncut plots, but the relationship was reversed on cut plots. Soil depth differences contributed substantially to the variance of total storage changes, but variable soil depth must be considered in sampling schemes designed to determine total water use under different cover conditions.
Effects of Hydroxyl‐Containing Organics on the Strength‐Energy Characteristics of Montmorillonite
Authors: Dowdy R. H. 
Published: July 2010

AbstractThe effect of polyvinyl alcohols and glucose on the tensile strength and tensile strain energy (rupture energy) of montmorillonite was studied by utilizing direct tensile strain of oriented clay films. Polyvinyl alcohol (PVA) dramatically increased the tensile strength of homoionically saturated montmorillonite in the following order: Na ≥ Ca >> Al. The intermediate molecular weight PVA8 (70,000–80,000 MW) increased strength significantly more than did the lower molecular weight PVA9 (14,000 MW). The strength of Na clay increased from 120 to 560 kg cm‐2 with the addition of 30 g PVA8/100 g clay. Increases in strength were also noted at lower rates of polymer applications; 0.5 g PVA8/100 g clay doubled the strength of Ca clay. Glucose did not change the strength characteristics of montmorpillonite. The data suggest that long, linear, uncharged, polyhydroxylic polymers, such as PVA, are very effective in bridging clay domains. The tensile strain energy required to rupture montmorillonite increased with added PVA in a pattern similar to tensile strength increases.
Rate and Extent of Inorganic Phosphate Exchange in Lake Sediments
Authors: Li W. C. , Armstrong D. E. , Williams J. D. H. , Harris R. F. , Syers J. K. 
Published: July 2010

AbstractThe exchangeability of sediment inorganic P was investigated by adding carrier‐free 32P inorganic phosphate to steady‐state lake sediment‐water systems and measuring the rate and extent of 32P incorporation into the sediment phase. The effects of sediment properties (calcareous and noncalcareous), oxygen status, and addition of inorganic P on exchangeability were evaluated. Exchangeable P comprised from 19 to 43% of the total native inorganic P of the sediments investigated. Although inorganic P was released into solution in anaerobic systems due to reduction of iron from the ferric to the ferrous state, the total pool of exchangeable P (sediment phase plus in solution) was not greatly altered. Sorbed added inorganic P (equilibrated 2 weeks) showed approximately the same degree of exchangeability as native inorganic P in noncalcareous sediments but was more exchangeable in calcareous sediments. Exchangeable P exhibited exchange rates which were resolved into three separate first‐order reactions by a graphical procedure. A major portion of exchangeable native sediment P (45 to 87%) participated in the rapid exchange reaction characterized by an exchange rate constant ranging from 7.4 to 46 hours‐1. These results show that a large pool of sediment inorganic P has a high potential for interaction with the overlying lake water and for biological assimilation.
Anion Adsorption in Ferruginous Tropical Soils
Authors: Mekaru T. , Uehara G. 
Published: July 2010

AbstractThe difference in pH of a soil suspension prepared with 1N KCl and with water was used to determine net charge of colloids with constant potential type surface. The quantity (pHKCl‐pHH2O) called delta pH had a positive, zero, or negative value corresponding to the net surface charge. Negative and positive adsorption of chloride or nitrate ions were measured in soil suspensions with negative and positive delta pH, respectively. Increasing the nitrate ion concentration increased sulfate adsorption in suspensions with negative delta pH values. Negative adsorption of nitrate and chloride ions was measured when sulfate ions were added to a soil colloidal suspension which was initially net positively charged. This supports the present belief that specifically adsorbed anions render a surface more negative by displacing the zero point of charge to lower pH values. This was substantiated by a measured increase in CEC from an initial value of 26 meq/100 g in a phosphated soil. Each millimole of adsorbed phosphate increased CEC by 0.8 meq.