bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Differential Aluminum Tolerance among Varieties of Wheat and Barley
Authors: Foy C. D. , Fleming A. L. , Burns G. R. , Armiger W. H.
Published: July 2010

Aluminum‐sensitive ‘Monon’ wheat (Triticum aestivum, spp vulgare (Vill. Host) Mac Key and ‘Kearney barley (Hordeum vulgare) (L. emend. Lam) varieties had higher root cation exchange capacities and induced lower pH levels in nutrient solutions than did Al‐tolerant ‘Atlas 66’ wheat and ‘Dayton’ barley varieties. Sensitive varieties contained higher concentrations of Al (and usually P) in their roots and lower concentrations of Ca in their tops than tolerant varieties, when grown in solutions containing Al. Furthermore, roots of Al‐sensitive varieties made less growth and contained higher concentrations of Al than those of tolerant varieties, even when the two were grown in the same container of vigorously aerated nutrient solution. This suggests either that zones of differential pH still exist around the roots of different varieties or that sensitive varieties absorb more Al at the same pH or both. Whether the lower Al tolerance of certain varieties is simply the result of greater accumulation of Al by roots, greater sensitivity to the same concentration of Al already absorbed, or both, cannot be determined from the present study. Differential Al tolerance of varieties was not closely related to differences in the Al or P contents of plant tops.
Soil Losses and Crust Formation as Related to Some Soil Physical Properties
Authors: Epstein E. , Grant W. J.
Published: July 2010

Soil loss curves of six soil types were obtained using a laboratory rainfall simulator. During the first 10 min of rainfall, soil losses increased to a maximum and then decreased sharply for the Marshall silty clay loam, Dunkirk silt loam, Caribou loam, and Nicholville silt loam soils. There was no peaking effect with the Hartland sandy loam and Winooski silt loam soils and the rate of soil loss was constant after 10 min. A linear relationship was obtained between clay content and soil loss during the 5‐ to 10‐min period. Detailed studies on the Dunkirk and Winooski soils suggest that the peaking effect may be due to the rate and extent of crust formation in the early stages of rainfall wetting. Bulk density of the 0‐ to 5‐mm layer increased from 1.15 to 1.65 g/cc for the Dunkirk soil and from 0.83 to 1.14 g/cc for the Winooski. The amount and distance of splash from a Caribou soil was measured using two drop sizes, 5.1 mm and 3.2 mm. Splash soil losses from the soil pans for the six soils was as much as three to four times those found in the runoff water.
The Establishment and Growth of Loblolly Pine Seedlings on Compacted Soils
Authors: Foil R. Rodney , Ralston C. W.
Published: July 2010

Loblolly pine (Pinus taeda L.) seedlings were grown from seed on core samples collected from surface soils of Lakeland loamy sand, Coxville loam, and Bayboro clay that had been compacted, puddled, or loosened. Seed germination was not affected by soil type or treatment, but seedlings became established with difficulty on clay cores and on heavily compacted cores of lighter texture. Top height and root length were not related to soil type, but seedlings grown on clay were significantly lighter than the other groups. Loosening the soil from its normal structure reduced growth on light‐textured soils, but stimulated it on clay soils. Compaction, whether at 3.5 or 10.5 kg cm‐2 of surface pressure, greatly reduced seedling size and weight. Small growth differences between compaction treatments indicated that even the smallest pressure applied reduced soil aeration and increased mechanical impedance to root growth to infavorable levels. There were negative linear relationships between root weight and penetration and densities ranging from 0.8 to 1.4 g cm‐3.
Fractionation of Soil Inorganic Phosphate by a Modification of Chang and Jackson's Procedure
Authors: Williams J. D. H. , Syers J. K. , Walker T. W.
Published: July 2010

A modified version of the phosphate fractionation procedure of Chang and Jackson (1957) included the determination of “residual inorg. P” and introduced a revised nomenclature for the other fractions. Added phosphate sorbed during the fluoride extraction was usually completely recovered in the succeeding sodium hydroxide extraction; this enabled mutually compensating corrections to be applied to NH4F‐P and 1st NaOH‐P values. A second acid treatment increased the amount of Ca‐P extracted. Further modifications simplified the colorimetric determinations of inorganic phosphate in several of the extracts. A measure of the reproducibility of fractionation results was also obtained.
Patterns Observed for the Oxidation of Ammonium to Nitrate by Soil Organisms
Authors: Morrill L. G. , Dawson J. E.
Published: July 2010

Ammonium sulfate solutions were percolated for 28 days through samples from the top two horizons of 55 soils derived from several classes of glacial tills and through six calcareous horizons influenced by sodium. Four general nitrification patterns were observed:

(I) Ammonium rapidly oxidized to nitrite which accumulated over a long period before being oxidized to nitrate. (II) Ammonium and the produced nitrite both rapidly oxidized. (III) Ammonium slowly oxidized to nitrate without nitrite appearing. (IV) Ammonium oxidation not detectable by either nitrite or nitrate formation.

The occurrence of the four patterns was correlated with soil reaction and other acidity related properties. Nitrosomonas spp. and Nitrobacter spp. organism numbers and proliferation characteristics influenced by soil environment accounted for the four nitrification patterns observed except insufficient Nitrobacter spp. organisms were detected to produce the nitrate formed in type III soils.

Nitrification patterns were modified by altering the soil properties and the number of nitrifying organisms consistent with the above interpretations. Ammonia, nitrite, nitrate, and pH affected Nitrobacter spp. lag in type I soils.
Mica Genesis in Hawaiian Soils
Authors: Juang T. C. , Uehara G.
Published: July 2010

A soil mica having a formula Na0.11 NH40.06 K1–24 (Al, Si) (Al, Fe, Mg) O20 (OH)4 has been identified in soils of the wet uplands in the Hawaiian Islands. It contains 7.2% potash and is predominantly a mixer‐layered mica with vermiculite‐montmorillonite and chlorite. The mica is concentrated in the surface horizons, and its concentration increases with soils formed under increasing rainfall and elevation. Biological recycling of potash is proposed as a mechanism for its formation.
Phosphorus‐Zinc Interaction in Two Soybean Varieties Differing in Sensitivity to Phosphorus Nutrition
Authors: Paulsen Gary M. , Rotimi Olusegun A.
Published: July 2010

Two soybean varieties (Glycine max (L.) Merr.) differing in sensitivity to phosphorus nutrition were grown in nutrient solutions containing various levels of P and Zn. Low P levels decreased growth and P concentration in leaves more than in other plant parts. High P levels decreased growth of the P‐sensitive variety more than the P‐tolerant variety but decreased Zn concentration in both varieties equally. Added Zn overcame the effect of P on the tolerant variety but not on the sensitive variety, indicating two different detrimental effects of P. Zinc deficiency affected growth of all plant parts similarly but had little effect on P content of plants except that when Zn was added to deficient plants P concentration in leaves decreased.

Interaction of P with Zn decreased Zn concentration of leaves most and roots least. The effect of P on Zn appeared to originate in the roots, however, and to occur on translocation of Zn to the upper plant parts.
Potassium Exchange Equilibria and Yield Responses of Oats, Barley, and Corn on Selected Quebec Soils
Authors: Zandstra H. G. , MacKenzie A. F.
Published: July 2010

Potassium:calcium + magnesium activity ratios were used to calculate availability indices on eight Quebec soils. These were compared to available potassium measurements and related to yield responses of oats (Avena sativa L.), barley (Hordeum vulgare L.), and corn (Zea mays L.) to potassium fertilizers in field experiments. Crop growth did not change the potential buffering capacities (PBCK) of two selected soils, which indicated that the quantity‐intensity relation regulated the release of potassium although the activity ratio was greatly reduced. The potassium potential was obtained by multiplying the total amount of exchangeable potassium (−ΔK°) with the potential buffering capacity to place soils on a comparative basis. The potassium potential fully defined the quantity‐intensity relation and correlated more closely to crop responses than the activity ratio measurement, the PBCK, or the available potassium determination.
Bulk Density Measurements on Certain Soils High in Coarse Fragments
Authors: Cunningham R. L. , Matelski R. P.
Published: July 2010

Bulk density methods were employed in repetitious sampling of Millheim silt loam containing high amounts of soft shale coarse fragments. The bulk density of a 377,560 cm3 soil volume was also determined as a reference for evaluating the samples collected. Statistical analyses of the data indicate that the 347.5 cm3 core sample best evaluates bulk density. However, in soils containing fragments harder than shale, cores are impossible to collect. Clod samples closely approximate 347.5 cm3 core samples in evaluating bulk density and can be taken in almost any soil. Thus, they are a useful sample for the determination of bulk density with the advantage that it can be used for moisture retention measurements.
Oxidation‐Reduction Potential of Saturated Forest Soils
Authors: Bonner F. T. , Ralston C. W.
Published: July 2010

Large decreases in redox potentials of saturated soil over a 25‐day incubation period were favored by high temperature and the addition of sucrose, loblolly pine needles (Pinus taeda L.), or yellow‐poplar leaves (Liriodendron tulipifera L.). The addition of a complete nutrient solution had no effect in soils incubated with sucrose, but it reduced the drop in potential in soils incubated with tree litter at 21–27C. The data suggest the need for care when evaluating soil aeration by means of redox potentials and the dominant role of soil microorganisms in activating redox systems.
Bulk Volume and Hydraulic Conductivity Changes during Sodium Saturation Tests
Authors: Waldron L. J. , Constantin G. K.
Published: July 2010

Fragmented samples of 1 organic and 5 mineral California soils were permeated with salt solutions while confined in cylinders under a constant axial stress of 0.05 bar. Continuous and precise measurement of bulk volume changes during sodium saturation with 1M NaCl followed by 0.25M NaCl showed that while hydraulic conductivity always decreased upon changing to the more dilute solution, the bulk volume increased with some soils and decreased with others. Such bulk decreases occurred only in the first passage of 0.25M NaCl following sodium saturation and were attributed to aggregate failure. If 1M NaCl was re‐introduced, hydraulic conductivity increased with all soils so tested and bulk volume decreased. Further successive permeations with 1M and 0.25M solutions produced hydraulic conductivity increases with bulk volume decreases on changing from 0.25M to 1M, and hydraulic conductivity decreases with bulk volume increases on changing from 1M to .025M NaCl. A mechanical explanation is given which is based on a bimodal pore model of the soil and on the way in which variation of stress from point to point within the soil affects volume changes of the swelling material and the soil pore‐size distribution.
Factors Influencing Hydraulic Conductivity of Soils in the Presence of Mixed‐Salt Solutions
Authors: McNeal B. L. , Layfield D. A. , Norvell W. A. , Rhoades J. D.
Published: July 2010

For a group of soils having variable clay content but nearly uniform clay‐fraction mineralogy, relative hydraulic conductivity in the presence of mixed‐salt solutions decreased markedly with increasing clay content, particularly at the lowest salt concentrations employed. The stability of a group of Hawaiian soils under high‐sodium, low‐salt conditions was greatly reduced by partial removal of the free iron‐oxides. Replacing the Ca in percolating NaCl‐CaCl2 solutions with Mg measurably decreased soil hydraulic conductivity, although the effect was often negligible when comparisons were made at equivalent exchangeable‐sodium‐percentages.
Prediction of the Effect of Mixed‐Salt Solutions on Soil Hydraulic Conductivity
Authors: McNeal B. L.
Published: July 2010

A procedure is described for predicting the hydraulic conductivity of soils in the presence of mixed‐salt solutions, after first measuring the absolute hydraulic conductivity of the soil with a single high‐salt, high‐sodium solution, and then measuring the relative hydraulic conductivity of the same sample with a low‐salt solution. Calculated interlayer swelling values for soil montmorillonite serve as a frame of reference for the predictions. Swelling values are obtained using a simplified domain model for characterizing the exchangeable‐cation distribution on Na‐Ca montmorillonites. Reliability of the procedure is established with a group of soils having variable clay content but constant clay‐fraction mineralogy. The effect of soil texture on relative hydraulic conductivity to mixed‐salt solutions appears to be adequately accounted for through the interlayer swelling values used for the predictions.
Chemical and Physical Properties of Iron and Aluminum Phosphates and Their Relation to Phosphorus Availability
Authors: Juo Anthony S. R. , Ellis Boyd G.
Published: July 2010

Synthetic, colloidal ferric and aluminum phosphates were crystallized in aqueous medium to form variscite, AlPO4 · 2H2O and strengite, FePO4 · 2H2O. The compounds were identified and characterized by X‐ray, infrared analysis, and electron microscopy. Iron phosphate crystallized at a much faster rate than aluminum phosphate under the same temperature and pressure conditions. Variscite and strengite which were crystallized at 105C for 40 days had specific surface areas of 24.9 m2g‐1 and 1.98 m2g‐1, respectively. The strengite consisted of single spherical crystals with an average diameter of 6 microns and the variscite consisted of reniform crystalline aggregates with an average diameter of 1.5 micron. In quartz sand cultures, with sudan‐grass (Sorghum vulgare sudanese) as the indicator crop, the relative availability of P from the synthetic compounds was: strengite < variscite ⋘ colloidal Fe‐P ⋍ colloidal Al‐P.
Iron Deficiency in Cotton in Relation to Growth and Nutrient Balance
Authors: Vretta‐Kouskoleka Helen , Kallinis Thomas L.
Published: July 2010

Iron deficiency symptoms were developed in cotton (Gossypium spp.) growing in nutrient solutions. The first symptoms appeared when the plants were 15 days old, while a general chlorosis developed by the time the plants were 8 weeks old. The deficiency was first observed on the upper young leaves. These leaves became chlorotic and progressively their margin turned necrotic and curled upwards. Addition of Fe in the nutrient solution of the deficient plants corrected all deficiency symptoms within 1 week. Two ranges of Fe concentration, 85–112 ppm for the young cotton blades, and 57–88 ppm for the old cotton blades were found to be the critical concentrations of Fe for cotton.
Parent Material Uniformity and Origin of Silty Soils in Northwest Arkansas Based on Zirconium‐Titanium Contents
Authors: Chapman S. L. , Horn M. E.
Published: July 2010

Uniformity of parent material studies were made of 15 soils overlying various geologic materials, utilizing petrographic and X‐ray spectographic techniques. Zr and Ti contents were used as tests for a “loess” versus a “residual silt” hypothesis for the origin of silty soils in northwestern Arkansas. The lack of significant deviations with depth in Zr and Ti contents and ratios points to an absence of lithologic discontinuities in soils suspected of having an upper loess parent material. It is concluded that these soils are formed in local materials and not from extra‐regional loess. It is proposed that prolonged weathering of local rocks together with reworking by mass movements, water, and wind on a local basis has resulted in a rather homogeneous regolith on the older gently sloping landscapes over cherty limestones and siltstones. The local nature of the soil parent materials is also indicated by the fact that Zr and Ti contents in the very fine sands were found to be related to underlying rocks being highest (ZrO2, 0.30%; TiO2, 0.26%) in soils over sandstone and lowest (ZrO2, 0.03% TiO2, 0.10%) in soils over cherty limestone. Zr was most abundant in coarse silts except for two soils over sandstone in which it was most abundant in the very fine sands. Ti increased as particle size decreased. In several soils Ti was present as leucoxene coatings on quartz and chert grains of very fine sand size. This indicates the probable translocation of Ti in soils and its general unsuitability as a stable constituent in soil genesis studies.
Root Cation‐Exchange Capacity and the Mineral Nutrition of Eastern White Pine and Eastern Redcedar
Authors: Vimmerstedt John P.
Published: July 2010

A field study showed that redcedar (Juniperus virginiana L.) foliage had a lower monovalent to divalent cation ratio than foliage of white pine (Pinus strobus L.). It was hypothesized that this difference resulted from redcedar roots having a higher cation exchange capacity (CEC) than white pine roots. Greenhouse experiments with seedlings grown on natural soils of contrasting fertility, and synthetic soils composed of crushed quartz and kaolinite, failed to support the hypothesis. The experiment with natural soils showed no interspecific difference in root CEC. In the experiment with synthetic soils, white pine roots had the higher CEC but redcedar had the lower monovalent‐divalent cation ratio. It was concluded that root CEC was not the factor causing the difference in cation ratios between species and that cation ratio in the soil had a strong influence on cation ratio in the trees.
Hydraulic Properties of a Clay Loam Soil and the Field Measurement of Water Uptake by Roots: III. Comparison of Field and Laboratory Data on Retention and of Measured and Calculated Conductivities
Authors: Brust K. J. , van Bavel C. H. M. , Stirk G. B.
Published: July 2010

Soil water characteristics obtained on soil cores in the laboratory at air pressures < 1 bar agreed substantially with pressure‐water content relations determined in the field. Thus, in field studies of soil hydraulics, measurement of either water content or pressure potential may suffice.

When the laboratory data were supplemented with a doubletube measurement of the saturated conductivity, the relation between water content and conductivity was calculated using two methods. Of these, the one due to Millington and Quirk gave less accurate agreement with actual field measurements than did the method proposed by Laliberte, Corey and Brooks. The latter method, when based on double‐tube measurements in the field and pressure cells or similar measurements on cores in the laboratory, appears useful.

Retention values measured with the pressure membrane method on disturbed soil samples were out of line with both field and core results, even when the disturbing treatments were minimized.
Calibration and Field Test of Soil Heat Flux Plates
Authors: Fuchs M. , Tanner C. B.
Published: July 2010

Soil heat flux plates were calibrated in the laboratory in steady‐state conditions and checked in the field vs. the soil temperature gradient thermal conductivity measurements of heat flux density. Good agreement was obtained after correcting for the flux divergence in the layer of soil where the temperature gradient was measured. Soil heat flux density measurements in a bare soil indicated that the heat storage in a 5‐cm layer of soil above the flux plates contributes significantly to the diurnal soil heat flux wave.
Clay Accumulation in Some Hapludalfs as Related to Calcareous Till and Incorporated Loess on Drumlins in Wisconsin
Authors: Allan R. J. , Hole F. D.
Published: July 2010

A distinct boundary (γ) between the dark‐colored, acid solum and the paler calcareous dolomitic sandy loam till in 24 representative Hapludalf profiles on drumlins in southeastern Wisconsin is related to carbonate content of the till (b′ = 0.61 and r = 0.75) and depth of a silty covering (b′ = 0.68), (R2 = 67). In the absence of a silty covering, clay accumulation above the γ was apparently not influenced by the carbonate content of the till (r = 0.16 and R2 = 3) because the solum deepened by leaching of the till at the same rate as clay accumulated.

Clay accumulation is also attributed in part to the admixture into till of loess different from that of the discrete silty coverings and attributable, on the basis of mineralogical studies of five profiles, to a distant source. Coarse silt of the silty coverings is mineralogically similar to the coarse silt of the till beneath the sola, except for that indicated by a higher content of Zr in the coverings.

Eluviation of clay of the loess has been important in the genesis of the argillic horizon in these soils.

Leaching of the till usually has resulted in the concentration of coarser and less weatherable fractions in the lower B horizon adjacent to the γ boundary. In most profiles clay did not accumulate notably immediately above the coarser of the sandy loam calcareous tills. Dolomite content of the Carbonate fraction of the till 5 cm below the γ boundary of six profiles averaged 95.6% compared with 97.0% at 55 cm still lower, indicating that the dissolved carbonate from the solum did not form a distinct Cca horizon.
Mechanism for Soil Potassium Release by Drying
Authors: Scott A. D. , Smith S. J.
Published: July 2010

When large flakes of edge‐weathered biotite were air‐dried, some of the silicate layers were forced apart while others were brought closer together. Since the space between the separated layers developed into visible cracks that penetrated the inner mica core, the dry flakes provide visual evidence for a mechanism by which interlayer K can be released when soils are dried. The collapse of part of the lattice can give rise to a simultaneous occurrence of K fixation.
Transport in Soils: The Balance of Momentum
Authors: Raats P. A. C. , Klute A.
Published: July 2010

The mechanics of the fluid phase(s) of a soil is discussed on the basis of a balance of momentum for each phase. Saturated as well as unsaturated soils are considered. It is shown that with certain assumptions the balance of momentum for a fluid phase reduces to Darcy's law. The meaning and some possible generalizations of the various assumptions are considered. The form of Darcy's law appropriate to soils whose solid phase undergoes a deformation is deduced.
Adsorption and Desorption of Diquat, Paraquat, and Prometone by Montmorillonitic and Kaolinitic Clay Minerals
Authors: Weber J. B. , Weed S. B.
Published: July 2010

The adsorption of diquat, paraquat, and prometone by montmorillonite and kaolinite clays and their desorption using several extracting solutions has been investigated. Diquat and paraquat were adsorbed by the clay minerals to approximately the cation‐exchange capacity of the clays. Approximately 80% of each of the herbicides was displaced from kaolinite clay with Ba2+ ions. A total of 5% of each of the compounds was removed from montmorillonite using 1M BaCl2 solutions. The two herbicides were found to exchange for one another on both clay minerals in a one‐for‐one manner. Paraquat was preferentially adsorbed over diquat by both clays in competitive ion studies and was also found to be more difficult of the two herbicides to displace.

Prometone which was adsorbed by the montmorillonite clay was more readily desorbed with deionized water than with 1M BaCl2. Small amounts of prometone which were adsorbed by the kaolinite clay were also readily desorbed by deionized water.
Behavior of Sulfate Sulfur and Elemental Sulfur in Three California Soils in Lysimeters
Authors: Jones M. B. , Martin W. E. , Williams W. A.
Published: July 2010

Three soils from diverse climatic regions of California were placed in free‐draining lysimeters, and sulfur was applied as gypsum, fine elemental S (particles <0.1 mm), or pelleted elemental S (0.5 to 0.9 mm in diameter), at the rate of 56 kg S/ha (1,135 mg S per lysimeter). All S fertilizers were tagged with radioactive S. Sulfur uptake by soft chess (Bromus mollis), and S in leachate, and in runoff was measured. Recovery of S by the plant was greater in the fine elemental S treatment than in the gypsum treatment on the two soils where the loss of gypsum S by leaching was greater. Concentrations of S in the leachate were generally highest in the gypsum treatment in the first year after treatment. Timewise, concentrations were generally highest when the first percolate of the rainy season came through the soil. From 80 to 90% of the applied gypsum S, about 50% of the fine elemental S, and 10 to 15% of the pelleted elemental S was accounted for in a 4‐year period. Most of the gypsum S was accounted for in the first year. In contrast, most elemental S was recovered in subsequent years. Willits loam held gypsum S against leaching much better than did soils of the “Hebron” or Sehorn series, and the uptake of gypsum S was higher from Willits soil than from the other two soils.
Soil Swelling: Laboratory Measurement and Relation to Other Soil Properties
Authors: Franzmeier D. P. , Ross S. J.
Published: July 2010

Soil swelling is measured using saran‐coated natural‐fabric samples to obtain the coefficient of linear extensibility (COLE) in soil genesis and characterization studies. It is measured using crushed and sieved samples to obtain the potential volume change (PVC) for on‐site investigations of potential building sites. For 30 samples from various horizons of soils in 10 states, the two measurements have the general relationship COLE × 60 = PVC. In coarse‐textured soils and in clayey soils high in kaolinite or mica but with no montmorillonite COLE ranges up to 0.03, and PVC up to 2.9; in clayey soils high in montmorillonite COLE ranges from 0.03 to 0.18, and PVC from 1.5 to over 9.0. The range of swelling potential in the montmorillonitic samples is related to the amount of clay and the fabric of the soil.
Tracing Soil Movement with Fluorescent Glass Particles
Authors: Young R. A. , Holt R. F.
Published: July 2010

Fluorescent glass particles with a density similar to that of natural soil particles were developed and tested under simulated rainfall for their effectiveness in tracing soil particle movement. From 10 to 38% of the various size ranges of particles used were successfully traced on the test plots. During a simulated rainstorm of 6.35 cm of rainfall in one hour, 11.8, 2.9, 0.7, and 0.6% of the largest to smallest size range of particles used, respectively, moved a distance of 10.37 m to the bottom of the plots. Lateral movements of up to 182.9 cm and upslope movements of up to 61.0 cm, as a result of raindrop splash action, were also detected.

From the field test, glass particles appear to be potentially useful in work where knowledge of the movement of soil sized particles is desired.
Clay Mineralogy of Certain Soils of Colombia
Authors: Mejia G. , Kohnke H. , White J. L.
Published: July 2010

Allophane was found to predominate in the soil derived from volcanic ash in the Colombian Andes. The allophane is transformed into halloysite. The soils of the superhumid tropical forests derived from marine deposits are high in kaolinite and low in gibbsite. Other clay minerals found in Colombian soils include vermiculite, montmorillonite, chlorite, and illite.
Effect of Topsoil Removal on Nitrogen‐Supplying Ability of Pullman Silty Clay Loam
Authors: Eck Harold V.
Published: July 2010

Under irrigation, removal of the surface 10, 20, 30, and 41 cm of soil decreased N yields 40.6, 47.5, 58.7, and 64.7%, respectively. Respective decreases under limited moisture were 20.0, 36.3, 53.9, and 62.4%. Total N in the surface 15 cm of soil and N yields were closely related.

Relationships among drymatter yields of grain sorghum (Sorghum vulgare), associated N uptake, and N treatments (soil NO3‐N + fertilizer N) were used to estimate maximum yields attainable and to determine the internal N requirement of grain sorghum. That requirement was almost a constant (1.0%) despite the widely different yield maxima attained under the contrasting moisture regimes.

Under irrigation, similar yield potentials were attained on all except the treatment with the greatest topsoil removal (41 cm). Undefined factors, other than N, P, or water, reduced the yield potential on that treatment. Under limited moisture, fertilizer treatments did not restore drymatter yields on any depth of soil removal. Differences are attributed to differences in water storage and use.

Efficiency of uptake of available N was not directly affected by topsoil removal but was affected by the N status of the plants. It remained relatively constant until the plant N requirement was met, and then declined.
Influence of Soil Structure on Water Relations in Low Humic Latosols: I. Water Retention
Authors: Sharma M. L. , Uehara G.
Published: July 2010

Experiments were carried out to study the effect of two aspects of soil structure, macrofabric and microfabric, on the water retention characteristics of two latosolic soils. The soils were selected because of similarity in composition but differences in structure.

Moisture retention curves of the soils and also of their water stable aggregates were obtained. On the basis of results it was concluded that for strongly structured soils, water retention was greatly influenced by macrofabric in the tension range between 0 to 0.3 bar, while the effect of microfabric was more prominent beyond this range. The influence of microfabric was also demonstrated by applying the surface tension, radius of curvature, pressure relationship on selected aggregate fractions.
Denitrifying Activity in Solodized Solonetz Soils of Eastern Australia
Authors: McGarity J. W. , Myers R. J. K.
Published: July 2010

Denitrifying activity was studied in 17 solodized solonetz profiles from eastern Australia using a Warburg manometric technique. Three distinct depth‐distribution patterns of activity were observed. In the first pattern, denitrifying activity declined with depth from a maximum in the Al horizon; this decline was positively correlated with decreasing organic C and total N contents. In the second pattern, denitrifying activity increased in the upper Bt horizons to levels slightly in excess of the A2 horizon above. The significant relationship between denitrification rate and organic matter was less consistent in these profiles. In the third type, denitrifying activity increased in one or more Bt horizons to levels greatly in excess of the A2 horizon above. No significant correlations were obtained between denitrifying activity and organic matter parameters for profiles of this group. It is suggested that high denitrifying activities in subsoil Bt horizons may be a transient property affected by environmental influences, and consequent on accumulation of small quantities of energy rich available organic matter.
Ammonium and Nitrate as Nitrogen Sources for Pinus radiata and Picea glauca
Authors: McFee W. W. , Stone E. L.
Published: July 2010

The relative value of ammonium and nitrate as N sources for Pinus radiata D. Don seedlings was determined under various conditions. Short‐term experiments varying from 3 weeks to 6 months' duration were conducted utilizing three growth media: solution, soil, and exchange resin beads. In the solution cultures N sources were compared at two levels of acidity (pH 3.6 and pH 5.9), three root‐zone temperatures (15, 20, and 25C), and three N levels (2.8, 11.2, and 22.4 ppm N). In the soil cultures N was added at five levels as NaNO3 or NH4Cl with a nitrification inhibitor. Three levels each of ammonium and nitrate were used in a factorial arrangement in the resin cultures.

Radiata pine seedlings grown either in soil, solution culture, or exchange resins exhibited greater growth and N uptake with an ammonium source than with nitrate. This was true in experiments at several levels of acidity, in all three growth media and regardless of the root zone temperature or N level maintained. Increases in root zone temperature in solution cultures increased growth and N uptake and increased the differential response to N source.

Eight‐fold differences in N concentration in the solution cultures produced only small differences in growth and N uptake. N levels of approximately 2.0 ppm N in solutions proved satisfactory for normal growth.

Picea glauca (Moench) Voss seedlings were tested concurrently in the solution cultures and exhibited the same favorable response to ammonium N source.
Morphological Classification of Grass Phytoliths
Authors: Twiss P. C. , Suess Erwin , Smith R. M.
Published: July 2010

Opal phytoliths derived from epidermal cells of grass leaves have been identified in atmospheric dust, soils, paleosols, Pleistocene loess, and deep‐sea sediments. By comparing oriented shapes of phytoliths in spodograms of 17 common grass species, four classes and 26 types are proposed which distinguish three groups of subfamilies of Gramineae. The Festucoid class contains eight types that are circular, rectangular, elliptical, or oblong forms. The Chloridoid class contains two types of saddle‐shaped bodies. The Panicoid class contains 11 types that are variations of crosses and dumbbells. The Elongate class contains five types that have no subfamily implications and occur in all 17 species. Because phytoliths of native tall grasses (Panicoid), short grasses (Chloridoid), and common domestic grasses of the humid regions (Festucoid) can be distinguished, it is possible to determine whether phytoliths in dust, soils, and sediments were derived from local or remote sources.
Argillic Horizons Without Clay Skins
Authors: Nettleton W. D. , Flach K. W. , Brasher B. R.
Published: July 2010

Although the clay in some moderately fine and fine‐textured Bt horizons of soils of arid and mediterranean climates of the southwestern United States is highly oriented, no distinct illuvial clay skins can be recognized. The distribution of clay skins is related to shrink‐swell potentials. Clay skins are absent in horizons having a shrink‐swell potential of more than 4% or a masepic or omnisepic plasmic fabric; they are present in equivalent horizons having low shrink‐swell potentials and an insepic or mosepic plasmic fabric. The clay content, mineralogy, and moisture regime of a Bt horizon in turn largely determine its potential to shrink and swell and hence determine its plasmic fabric.

Evidence that clay illuviation has indeed taken place in these finer textured Bt horizons is based on four pairs of geographically associated soils with horizons of clay accumulation. Bt horizons of the coarser textured members of pairs have clay skins and the finer textured members do not. The distribution of biotite pseudomorphs in some of these pairs parallels the distribution of clay skins, suggesting that oriented bodies of clay can be destroyed. Clay orientation in one of the horizons was reformed experimentally to show that the highly oriented soil fabrics do not acquire their orientation by illuviation of clay.

The studies further indicate that bodies of oriented clay in medium and fine‐textured B horizons have been erroneously described as clay skins.
Contribution of Humic Acid and a Polysaccharide to Water Repellency in Sand and Soil
Authors: Savage S. M. , Martin J. P. , Letey J.
Published: July 2010

A silica sand and Pachappa sandy loam were treated at various pH's with aqueous suspensions of three microbial humic acids, a soil and peat humic acid, a microbial polysaccharide, and metallic salts of the tested organic substances. Of all the substances tested, only one, a humic acid isolated from a Stachybotrys atra culture, caused water repellency in the sand and soil. The Fe3+ and Al3+ salts of this humic acid rendered the sand and soil practically impermeable to water. The organic matter content of the extremely water repellent sands was less than .05%. The final conclusion of the paper is that humic acid‐like substances and polysaccharides probably do not contribute much to water repellency in soils.
The Absence of Threshold Gradients in Clay‐Water Systems
Authors: Miller Raymond J. , Overman Allen R. , Peverly John H.
Published: July 2010

The transient pressure transducer technique was used to test for threshold gradients in 9, 30, 40, and 50 weight percent montmorillonite and <2µ and 2–20µ size fraction kaolinite. Threshold gradients were not found in any of the samples tested.
Soil Degradation of Malathion, a Phosphorodithioate Insecticide
Authors: Konrad J. G. , Chesters G. , Armstrong D. E.
Published: July 2010

Rates of malathion degradation in soils were related directly to extent of malathion adsorption, suggesting that degradation occurred by a chemical mechanism which was catalyzed by adsorption. Malathion degradation was rapid (50 to 90% in 24 hours, depending on the type of soil) in both sterile and nonsterile soil systems, and no lag phase occurred prior to degradation. In aqueous soil‐free systems inoclulated with a soil extract, a lag phase (7 days) occurred, followed by rapid malathion loss, likely due to microbial degradation. Thus in soils, complete chemical degradation of malathion occurred prior to microbial adaptation to malathion. To obtain information on the pathway and products of malathion degradation, chemical hydrolysis in soil‐free systems was investigated using liquid:liquid partition techniques with 14C‐labeled malathion. Hydrolysis did not occur in acid systems (> pH 2), was slow at pH 9 (< 50% in 20 days) and rapid at pH 11 (> 99% in 1 day). At pH 9 the hydrolysis resulted in formation of thiomalic acid and dimethyl thiophosphoric acid as final products with accumulation of diethyl thiomalate as an intermediate due to unequal rates of hydrolysis of the ester linkages. In soils, both ester linkages are hydrolyzed, although not at the same rate, resulting in the accumulation of diethyl thiomalate in some soils.
Steady State Studies of Nitrification in Soil: Theoretical Considerations
Authors: McLaren A. Douglas
Published: July 2010

Equations are set up for consecutive reactions in an idealized soil column and solved for concentrations of metabolites as functions of time and depth within the column under steady state conditions. The reactions NH+4 → NO‐2 → NO‐3 were so expressed for columns with maximum numbers of nitrifying organisms.

These equations for an open system can be modified to accommodate rates of metabolism for reperfusion experiments for the condition of maximum enrichment of nitrifiers.
Vapor Density of Soil‐Applied Dieldrin as Related to Soil‐Water Content, Temperature, and Dieldrin Concentration
Authors: Spencer W. F. , Cliath M. M. , Farmer W. J.
Published: July 2010

Vapor densities of dieldrin (principal constituent HEOD‐hexachloro‐epoxyoctahydro‐endo, exo‐dimethanonaphthalene) in dieldrin‐soil mixtures increased with temperature and dieldrin concentration but were not affected by soil‐water content until the water content decreased below that equivalent of one molecular layer of water. Vapor densities dropped to very low values when the water content fell below this level, but increased again as water was added to the dry soil, indicating that the drying effect is reversible. When more than a monomolecular layer of water was present in the soil, vapor density increased with increasing soil dieldrin (HEOD) concentration until a saturation vapor density equal to that of HEOD without soil [54, 202, and 676 ng HEOD/liter at 20, 30, and 40C, respectively (9)] was reached at approximately 25 ppm HEOD. This implies that surface applications of dieldrin and probably other similar chlorinated hydrocarbon insecticides will volatilize as rapidly from mineral soils as from the pure materials until the concentration at the surface falls to relatively low levels.

The data indicate that loss of water, per se, is not required for significant rates of volatilization to occur from soils or other surfaces on which water can successfully compete for adsorption sites.
Nitrification in Soil: Systems Approaching a Steady State
Authors: McLaren A. Douglas
Published: July 2010

Equations are set up for the consecutive reactions NH4+ → NO2‐ → NO3‐ in an idealized soil column and solved, for an open system with a constant rate of entry of a solution of ammonium, for concentrations of ions as functions of time of flow and distance within the column. The equations take into account growth of nitrifying organisms but it is assumed that diffusion and ion exchange within the soil and fixation of nutrients by the nitrifiers are of secondary importance.
Leaching of Added Selenium From Alkaline Soils as Influenced by Sulfate
Authors: Brown M. J. , Carter D. L.
Published: July 2010

A BaSO4‐BaSeO4 mixture (S:Se = 10) and BaSeO4 alone were applied at 1.60 and 3.20 mg Se per column to two soils and leached with water or gypsum solution. Eight hundred milliliters (10‐cm depth) of leaching solution were added to columns containing 2,100 g of Portneuf silt loam and 2,500 g of Gooding loamy sand at 4‐week intervals for 20 weeks. More Se was leached by gypsum solution than by water from all columns. Where 1.60 mg Se per column was applied, more Se was leached from Gooding loamy sand than from Portneuf silt loam soil with both water and gypsum solution. Where 3.20 mg Se per column was applied, more Se was leached by water from Gooding than from Portneuf soil, but the reverse was true with gypsum solution. The Se leached from the Portneuf soil treated with the BaSO4‐BaSeO4 mixture ranged from 0.34 mg, where 1.60 mg Se per column was applied and soils leached with water, to 2.32 mg, where 3.20 mg Se per column was applied and soils leached with gypsum solution.

Much less Se was leached where only BaSeO4 was applied to Portneuf soil. The amount leached ranged from 0.07 mg, where 1.60 mg Se was applied and water used for leaching, to 0.64 mg Se, where 3.20 mg Se was applied and gypsum used for leaching. The Se recovery from the Gooding soil was within these ranges for the same treatments. The Se leached increased with application rate, but not proportionately. The data indicate that addition of SO42‐ increases the solubility of BaSeO4 in these soils.
Phosphorus Adsorption Sites in Soils
Authors: Harter Robert D.
Published: July 2010

Regression analysis of phosphorus adsorption as a function of five soil characteristics indicates that organic matter is important in the initial bonding of phosphorus by soils. It is, therefore, proposed that phosphorus is initially bonded to anion exchange sites on organic matter, and subsequently transformed into less soluble iron and aluminum phosphates.
Effects of Petroleum Mulch on Soil Water Content and Soil Temperature
Authors: Kowsar Ahang , Boersma L. , Jarman G. D.
Published: July 2010

Changes in soil temperature and soil water content of mulched and unmulched soil, subjected to the same radiation load, were measured at 2‐hour intervals under controlled laboratory conditions. Soil was packed into boxes with inside dimensions of 40.0 by 4.0 by 50.0 cm at a pre‐determined water content. Part of the soil surface was covered with petroleum mulch. The soil was subjected to a diurnal temperature cycle by varying the output of infrared heat lamps.

At a depth of 1 cm the mulch‐covered soil was 5C warmer than the bare soil at the time the soil temperatures attained their maximum value. At all other times the temperature difference between mulched and bare soil was smaller. The bare soil rapidly lost water in the upper 4 cm. The mulch‐covered soil lost water in the upper 1 cm of soil but gained water at depths below this zone. This gain in water in the zone where seedlings are normally placed, indicates that the beneficial effect of petroleum mulch on germination and seedling growth must be attributed to improved soil water conditions as well as to improved soil temperature conditions.
Conductivity Instrumentation for In Situ Measurement of Soil Salinity
Authors: Enfield C. G. , Evans D. D.
Published: July 2010

A transducer has been developed which is capable of assessing, in situ, the electrical conductivity of soil water. The transducer is constructed of porous glass with platinum electrodes and operates over the entire field moisture range. The transducer is accurate to within 10% when measured with an associated soild state meter in a conductivity range of 1–20 millimhos/cm @ 25C and a temperature range of 5–45C. Typically, the time required to achieve 63% of equilibrium response, in aqueous solutions, is less than 2 hours.
A Simple X‐Ray Fluorescence Technique for the Determination of Iron and Manganese in Soils and Concretions
Authors: Barnhisel R. I. , Phillippe W. R. , Blevins R. L.
Published: July 2010

A simple technique for the determination of Fe and Mn in concretions and soils was developed using X‐ray fluorescence. A 25 mg sample was suspended in a 1% glue‐methyl alcohol solution and transferred to a 4.25‐cm circle of filter paper. The filter paper containing a thin layer of uniformly distributed sample was placed in an X‐ray emission spectrograph for analysis, and highly reproducible and accurate results were obtained. Precision was achieved over a wide range of Fe and Mn oxide contents.
Suction Apparatus for Mounting Clay Specimens on Ceramic Tile for X‐Ray Diffraction
Authors: Rich C. I.
Published: July 2010

A simple suction apparatus for preparing clay mineral specimens for X‐ray diffraction on unglazed ceramic tile is described. A large rubber stopper is modified by forming a molded recess with silicon rubber to reduce air leakage about the tile. Specimens of proper thickness can be prepared quickly with the apparatus.
Reactions of 12 s‐Triazines with Soil Clays
Authors: Brown Cyril B. , White Joe L.
Published: July 2010

Twelve herbicides—chloro, methoxy and methyl‐thio compounds—of the s‐triazine family were reacted with chloroform and water suspensions of soil clays of varying mineralogical composition, and also with Wyoming bentonite. IR spectra of air‐dried KBr pellets of the reacted samples were made. NMR data of a chloro and methoxy s‐triazine were studied.

Data showed that protonation and hydrolysis of the triazine had occurred in certain samples. The highly acidic environment of montmorillonitic clay surfaces provided conditions suitable for the hydrolysis. The order of hydrolysis of the chloro s‐triazines used in the study is trietazine > chlorazine > propazine > ipazine > simazine = atrazine. The corresponding methoxy or methyl‐thio compound hydrolyzed less than the chloro analogue. Protonation and adsorption are directly related to the basicity of the triazine but hydrolysis has an inverse relation. NMR data can be used to obtain the relative basicities of s‐triazine herbicides and thus be an indicator of ease of hydrolysis.
Locus of Urease Activity in Soil
Authors: Paulson K. N. , Kurtz L. T.
Published: July 2010

A model is proposed to determine the location of active urease in soil; that is, whether the urease was associated directly with soil microorganisms or free from microorganisms and adsorbed on the soil colloids. An indirect approach was used which consisted of making periodic measurements of urease activity during a period of time when the microbial population was undergoing change. Multiple regression analysis was applied to the data to determine the relationship between urease activity and microbial population. Under steady state conditions, 79–89% of the urease activity of the soil examined was due to urease adsorbed on soil colloids. An increase in microbial population reduced this percent temporarily until a new steady state was reached. Addition of a small amount of urea (13 ppm of urea‐N) to the soil induced microorganisms to produce more urease.
Determination of Opal in Soil by Alkali Dissolution Anaylsis
Authors: Jones Robert L.
Published: July 2010

Boiling the 20–50 µ fraction of soil for 20 min in 0.5N NaOH and subsequent colorimetric determination of dissolved silica gives results comparable in precision to the liquid density‐separation method. The main advantage is economy of time.