bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Control of Soil Water Content in the Vicinity of Root Hairs
Authors: Hsieh J. J. C. , Gardner W. H. , Campbell G. S.
Published: July 2010

A technique for controlling water content in the root hair zone of growing plants has been developed which involves growing plants on a fine screen placed over soil in such a way that only root hairs can extend through the screen into soil beneath. Gamma‐ray attenuation is used to monitor the supply of water in the root hair zone. By means of controlling either the length of a hanging water column or the rate of water supply, the rate of water flow to the soil lamina beneath the screen can be so adjusted as to just offset the loss due to transpiration. A predetermined soil water content can be maintained to within 0.015 cm3/cm3 in the root hair zone of a growing plant.

Plant growth was affected by soil water potential. Reduction in elongation rate of corn (Zea mays L.) leaves was observed at matric potentials higher than −1 bars. Elongation essentially ceased at matric potentials of about −22 to −30 bars within the root hair zone. A large water content gradient existed adjacent to the root hair zone and extended to a depth greater than 10 mm.
Rapid Determination of Exchangeable Bases, Acidity, and Base Saturation for Soil Characterization
Authors: Hajek B. F. , Adams F. , Cope, J. T.
Published: July 2010

Routine, rapid, soil‐testing procedures were used for measuring both exchangeable bases and exchangeable acidity. Exchangeable bases were extracted by a single wash with a dilute HCl + H2SO4 solution and analyzed by flame spectrophotometry and atomic absorption. Exchangeable acidity was determined by the pH change of a buffered solution‐soil suspension. The values obtained compared favorably with values determined by NH4OAc, NaOAc, and BaCl2‐triethanolamine and were suitable for separation of Ultisols from Alfisols and mollic from umbric epipedons.
Growth, Mineral Composition, and Seed Oil of Sesame (Sesamum Indicum L.) as Affected by NaCl
Authors: Yousif Yousif H. , Bingham Frank T. , Yermanos D. M.
Published: July 2010

The tolerance of sesame to NaCl salinity was studied first during germination (72 hours), and later during plant growth up to maturity. Germination was conducted in the laboratory at 25C. Sesame plants were tested for response to salinity using nutrient solution cultures with sodium chloride added when test plants were approximately 10 cm tall. Experiments were continued until mature seed pod formation. The data showed a high tolerance during germination but sensitivity at later growth stages.

Although seed yield was strongly reduced, the seed oil content and its fatty acids were not changed. Analyses of leaf blades at different growth stages did not reveal changes in Ca, Mg, K, P, and N indicative of a nutrient deficiency(s). Chlorides, however, accumulated to levels considered toxic. The chloride absorption isotherm showed a marked increase at all growth stages for the same substrate NaCl concentration. This increase was coincident with severe leaf injury and growth reduction. The Na levels in the leaf blades were very low relative to Cl. For example, Na and Cl levels of plants under the highest NaCl treatment at 6 weeks were 0.20% Na and 5.13% Cl. Growth was reduced approximately 50% by this NaCl treatment. The 0.20% Na level is not high enough to indicate Na toxicity.
Response of Rice to Nitrogen and Calcium Nutrition
Authors: Krasaesindhu Prateep , Sims J. L.
Published: July 2010

The influence of N and of Ca nutrition on growth and chemical composition of ‘Nova 66’ rice (Oryza sativa L.) was studied in the greenhouse. Rice plants were grown in soil supplied with four levels each of N (0, 100, 200, and 300 ppm) and Ca (0, 400, 800, and 1,200 ppm) fertilizer. The soil was submerged throughout the experiment.

Significant N × Ca interactions were obtained for both grain yield and straw weight. The interactions for grain yield revealed that yield increased as rate of N fertilizer increased, and increases were greatest when Ca levels increased simultaneously. In contrast, interactions for straw weight showed that N increased weight but the increases were lessened in the presence of Ca. Total dry weight (grain + straw) was significantly increased by N but was only slightly affected by Ca. Thus Ca increased grain yield, decreased straw weight, and markedly increased the grain:straw ratio.

Nitrogen content (g/pot) and Ca concentration of grain were greatly enhanced by both N and Ca fertilization. Greatest contents were obtained at the highest levels of N and Ca. In contrast, Ca lowered concentration of N (%) in both grain and straw and N content (g/pot) of straw. Total N contents (straw + grain) were also slightly lower in the presence of Ca. The reductions in N concentration and content increased with increasing Ca added. Evidence indicated that the effect of Ca may have been largely indirect, through its effect on K accumulation. The inhibiting effect of Ca was overcome partially when N fertilizer level was increased.
Clay Mineralogy of Soils Developed Partially from Volcanic Ash
Authors: Pettapiece W. W. , Pawluk S.
Published: July 2010

Luvisols (Alfisols) in the Front Ranges of the Canadian Rocky Mountains of west‐central Alberta have several distinctive features including surface horizons with a variable volcanic ash content and reddish Bt (B2t) horizons characterized by the presence of expanding clays. A study of the clay fractions indicates a marked increase in the content of smectitic clay in the sola and particularly in the Bt (argillic) horizons compared with the parent materials. Also, the expanding component is poorly organized and appears to result from the synthesis of amorphous material, probably from a volcanic ash source, accompanied by some degradation of primary chlorite and illite. The clay mineral profile does not fit the concepts generally held for lessivé soils (Luvisols, Alfisols, Sols Lessivé, pseudo‐podzolic soils) and in some portions of the sola is similar to that noted in true podzols.
Weathering of Mica Flakes in Two Soils in Northern Greece Evaluated by Mössbauer and Conventional Techniques
Authors: Yassoglou N. J. , Nobeli Catherine , Kostikas A. J. , Simopoulos A. C.
Published: July 2010

The weathering of the fine sand‐size mica flakes in two soils (I and II) developed in northern Greece under the same climatic, drainage, and age conditions, but under different vegetational cover, was investigated by chemical analysis, X‐rays, differential thermal analysis (DTA), infrared, and Mössbauer spectroscopy. It was found that hydrobiotite was inherited from the consolidated bedrock and underwent further pedogenetic oxidation, vermiculitization and kaolinitization in the soil. The oxidation of Fe seemed to take place preferentially in the larger and more symmetrical octahedral sites of the latice. Kaolinite was formed through transformation of the mica flakes in soil II which is now covered by scotch pine (Pinus sylvestris L.) and Vaccinium, while gibbsite was formed in the flakes of soil I, which has a spruce (Picea excelsa L.) cover. No detectable montmorillonite was found in the flakes examined in this study.

Rates of weathering and physical disintegration result in conditions which produce a more weathered appearance of the fine sand‐size flakes in the section of the profiles immediately below the surface in soil II compared to those in soil I.

The Mössbauer parameters of the flakes indicate that weathering of biotite to 2:1 minerals results in oxidation of the ferrous ions to ferric in the two octahedral sites of the lattice. Of these two sites the less symmetrical with hydroxyls in cis position is more resistant to oxidation.
Humic‐Fulvic Acid Content in Soils as Related to Ley Clipping Management and Fertilization
Authors: Tan K. H. , Beaty E. R. , McCreery R. A. , Powell J. D.
Published: July 2010

Studies on changes of humic‐fulvic acid content in a Eustis loamy sand due to weekly clipped Pensacola bahiagrass (Paspalum notatum Parodi) and fertilization showed that nitrogen fertilization encouraged formation of humic acid and decreased fulvic acid contents in soils. Longer clipping intervals tended to increase the amount of both humic and fulvic acid when nitrogen fertilization was applied.

A significant positive correlation between nitrogen or organic‐P contents of the soil and humic/fulvic acid ratios indicated that humic‐fulvic acid formation was affected by soil nitrogen content (or organic‐P). A correlation also existed between humic‐fulvic acid and pH, in which a decrease of soil pH resulted in an increase of humic/fulvic acid ratio.
Hydrolysis of Propazine by the Surface Acidity of Organic Matter
Authors: Nearpass D. C.
Published: July 2010

Propazine [2‐chloro‐4, 6‐bis (isopropylamino)‐s‐triazine] hydrolysis in acidic aqueous soil‐free systems was pH dependent, increasing with lower pH values. At a given pH, degradation followed first‐order kinetics. At 23.5C, the relationship was log t½ (days) = 0.59 pH −0.21. Adsorption of propazine by organic matter prepared from Michigan peat was also pH dependent, but both molecular and cationic adsorption occurred. An increased rate of degradation in the presence of organic matter was postulated as due to hydrolysis by ionized surface hydrogen. Increasing the calcium saturation resulted in decreased hydrolysis. Increasing the CaCl2 concentration of the propazine‐organic matter‐aqueous system had no effect on acid hydrolysis. In the salt‐amended systems, an increased hydrolysis, to be expected from the lower pH in the ambient solution, was apparently offset by a decreased hydrolysis due to the lowered amounts of ionized surface hydrogen.
Phytolith Size Characteristics Between Udolls and Ustolls
Authors: Yeck R. D. , Gray Fenton
Published: July 2010

To test a phytolith size‐annual rainfall relationship hypothesis, the sizes of opaline phytoliths from four Oklahoma soils were compared. Opaline phytoliths form in intimate association with plant cells and the variation of plant cell size with moisture stress forms the theoretical basis for the hypothesis. The soils sampled were St. Paul, a Typic Argiustoll; Zaneis and Vanoss, Udic Argiustolls; and Fitzhugh, a Typic Argiudoll. Opaline phytoliths were isolated from the 5–20µ, 20–35µ, and 35–50µ soil fractions. The relative amounts of phytoliths in these size fractions in the upper 10 cm of each soil was used to measure their size variation among soils. Phytoliths were further characterized by shape in each soil. Distribution of phytoliths with depth was also noted.

There was a higher incidence of the 5–20µ phytoliths in the Ustoll than in the Udoll (66.9% vs. 53.2%) and a correspondingly higher percentage of 35–50µ phytoliths in the Udoll compared to the Ustoll (14.8% vs. 4.4%). The Udoll‐Ustoll intergrades contained intermediate quantities of the 35–50µ phytoliths but not of the 5–20µ and 20–35µ phytoliths. It was concluded that the hypothesized relationship seemed to exist with further work required to understand the relationships in the intermediate areas. Such a relationship would be a very useful tool in paleosol and paleoclimate studies.
Field Test for Spodic Character Based on pH‐Dependent Phosphorus Adsorption
Authors: Bartlett R. J.
Published: July 2010

A field method based on P adsorption is proposed for measuring the relative amounts of reactive organic Al in suspected spodic horizons. A soil sample to be tested is equilibrated by shaking with a pH 9.1 phosphate solution. If high in reactive Al, the sample will remove the P from the solution as indicated by the absence of blue‐colored molybdophosphate in the filtrate. Phosphorus adsorbed by soil samples under the test conditions was found to be correlated with Al extracted by pH 4.8 NH4OAc, but not by neutral KCl. It is suggested that soils be initially screened for presence of reactive hydroxy Al by testing with NaF and alizarin yellow, with the expressed caution that occasional high organic spodic horizons may give negative NaF tests.
Soil Morphology and Water Table Relations: I. Annual Water Table Fluctuations
Authors: Boersma L. , Simonson G. H. , Watts D. G.
Published: July 2010

Water table positions with respect to the soil surface and precipitation were measured daily over a 2‐year period at representative sites of five soil series comprising the Willamette association of nearly level soils with good to poor natural drainage. All soils had water tables present for some period during the winter. Perched water tables were present near the surface of the two most poorly‐drained series most of the winter.

A mathematical model was developed for predicting water table positions on the basis of rainfall input and soil physical characteristics. The model was calibrated with measurements made during the 2 years and then used with rainfall data from the previous 29 years, to reconstruct water table positions as they had occurred in the past. The computer procedure did not apply to the two poorly‐drained series because of the presence of an impermeable soil horizon (clay B) near the surface. However, water table positions of these series were estimated satisfactorily by correlation with water table positions on the better‐drained series. The average percent of time the water table was above a given level during each month, calculated for the period of 1929 to 1957 showed that for a specific depth and month, the percent of time the water table was above a given level increased as the natural drainage conditions became poorer. The percentages for the 30.4‐cm depth during April for example were 1.8, 15.4, 66.7, 81.5, and 92.0, respectively, for the five series. Thus, particular water table regimes are associated with drainage conditions of specific soil series.
Soil Phosphorus Level Adequate for Growth of Ocala Sand Pine Seedlings, A Greenhouse Evaluation
Authors: Baker James B. , Brendemuehl R. H.
Published: July 2010

A greenhouse study was conducted to determine the level of soil P adequate for satisfactory growth of Ocala sand pine (Pinus clausa (Chapm.) Vasey) seedlings. Various quantities of Lakeland sand with low and high P contents were blended to provide soil mixtures with a range of available P. Ocala sand pine seedlings were grown in these mixtures for 10 months. On the basis of the seedlings' dry matter production, the level of soil P adequate for satisfactory growth of Ocala sand pine is in the neighborhood of 1 ppm available [NH4OAc (pH 4.8)‐extractable] P. Seedlings growing in soils containing < 1 ppm available P showed a marked reduction in dry weight. Tissue analyses indicate that concentrations of foliar P of < 0.15% may denote a deficiency of available soil P.
Amorphous Material in Some Papua New Guinea Soils
Authors: Parfitt R. L.
Published: July 2010

The clay fraction of five tropical soils was extracted successively with dithionite‐citrate‐bicarbonate, 2% sodium carbonate and, 0.5M sodium hydroxide. Large amounts of clay were dissolved from all soils except the solodic soil. Differential infrared spectroscopy showed that allophane was dissolved from the volcanic ash soils together with iron and alumina gels. Goethite and disordered kaolinite were extracted from the latosol. No amorphous silica was present in the solodic soil.
Effect of Ion‐Pair Formation on the Solubility Product
Authors: Babcock K. L. , Marion G. M.
Published: July 2010

Two treatments of electrolyte solutions in which ion‐pair formation occurs are possible: one as a strong electrolyte, the other as a weak electrolyte. It is demonstrated, however, that the value of a solubility product is independent of the method of treatment.
Potentiometric Titration of Sulfate in Water and Soil Extracts Using a Lead Electrode
Authors: Goertzen J. O. , Oster J. D.
Published: July 2010

Sulfate concentrations in natural waters and soil‐water extracts were determined semiautomatically using a lead‐ion electrode to indicate the solution potential change at the endpoint, a constant flow device to deliver the titrant, a pH‐mV meter to measure the potential, and a strip chart recorder to plot the solution potential thus indicating the endpoint. Sulfate concentrations as low as 0.5 meq/liter in the sample solution were determined by the potentiometric titration system. This semiautomated direct titration of sulfate has the advantages of increased sensitivity and speed as compared with the precipitation method.
The Transport of Cations in Soil Columns at Different Pore Velocities
Authors: Lai Sung‐ho , Jurinak J. J.
Published: July 2010

The transport of Na+ and Mg2+ in Ca2+‐saturated Yolo loam soil column under saturated steady state flow of different pore velocities was studied. The cation solution was maintained at a concentration such that a linear adsorption isotherm described the cation adsorption. Experimental retention curves were compared to the theoretical solutions obtained from a linear equilibrium model. At low relative concentrations, the equilibrium adsorption of Na+ was significantly less than that of Mg2+. At high pore velocities, the agreement of the experimental retention curves with that of the theoretical calculation was good. At low pore velocity, the agreement was poor. The retention volumes of Na+ and Mg2+ were smaller than those theoretically calculated and those obtained experimentally at high pore velocity. Extensive tailing of Mg2+ observed in the experimental data was not described by the theoretical model.
Reactive Aluminum Estimated from the Formation of Magnesium‐Aluminum Double Hydroxide
Authors: Schalscha E. B. , Pratt P. F. , Gonzalez M. C.
Published: July 2010

Reactive Al in volcanic ash soils of Chile was estimated from the buffering in the pH interval of 8.2 to 8.5 for potentiometric titration curves obtained from serial titrations of 5‐g samples of field‐moist soil suspended in 50 ml of 0.5N MgCl2 using NaOH as the base. The period of time allowed for reaction was 24 hours. Reactive Al thus measured was highly correlated with the Al extracted by 1N NH4OAc at pH 4.8, with the ratio of Al2O3 to SiO2 dissolved by NaOH, with phosphate fixation, and with the CEC measured by saturating with KH2PO4, but not with organic matter content. The reactive Al in A horizons was highly correlated with that in B horizons. An alkaline soil containing no volcanic ash showed no buffer capacity in the pH 8.2 to 8.5 range when titrated in MgCl2 solution. Volcanic ash soils titrated without MgCl2 showed no buffering in this pH range. This method of measuring reactive Al appears to be promising but needs to be further tested.
Calcium and Strontium Transport to Plant Roots
Authors: Elgawhary S. M. , Malzer G. L. , Barber S. A.
Published: July 2010

Mass‐flow and diffusion of Ca and Sr to tomato (Lycopersicon esculentum) roots were studied in two exchange resin rooting media. Six harvests were made from plants grown over a 26‐day period under low and high humidities in a growth chamber. With low humidity, the rate of supply of Ca and Sr by mass‐flow exceeded uptake rate during the entire growth period. Under high humidity, the rate of mass‐flow supply exceeded uptake only until the second harvest, thereafter diffusion became the dominant supply mechanism.

The Ca/Sr ratio of uptake was compared with the Ca/Sr ratios on the resins and in solutions to determine the source of Ca and Sr. Supply by mass‐flow came from the solution, where‐as supply by diffusion apparently came mainly from the exchangeable fraction indicating exchange diffusion was important. Both log of root length and log of water uptake were linearly correlated with time for the 26‐day growth period investigated. The rate of water absorption ranged from 1.1 × 10‐7 to 6.0 × 10‐7 cm3/cm of root per sec.

The root uptake coefficient for Ca uptake varied between 1.43 × 10‐6 and 2.72 × 10‐6 cm/sec and for Sr 1.0 × 10‐6 to 2.38 × 10‐6 cm/sec where an average root radius of 0.015 cm was used in the calculations.
Relationships Among Physical and Chemical Properties of Representative Soils of the Tropics from Puerto Rico
Authors: Philipson Warren R. , Drosdoff Matthew
Published: July 2010

In an investigation of the extent to which predictive soil property relationships can be relied upon in characterizing soils of the tropics classified at the reconnaissance level, 9 to 15 soil properties, of 370 horizons, from 84 Puerto Rican profiles, were studied by correlation and multiple linear regression. The soils represented six orders of the new US Soil Taxonomy (7th Approximation): Vertisols, Mollisols, Alfisols, Inceptisols, Ultisols, and Oxisols. Multiple regression equations were formed from the data of each order, with 15‐bar moisture content, CEC, organic carbon, extractable iron, and base saturation as dependent variables. The results indicate that, although it is possible to eliminate certain properties from tropical soil data acquisition and still adequately characterize the soil, the specific properties that can be successfully eliminated depend on the soil order.
Influence of Sand on the Amount of Water‐Dispersible Clay in Soil
Authors: Ashford E. M. , Shields L. G. , Drew J. V.
Published: July 2010

Water‐dispersible clay in soils from a number of geographic locations increased in relation to clay measured by a standard procedure as the proportion of sand in the soils increased. Additions of sand to soils containing relatively small amounts of water‐dispersible clay relative to “regular” clay markedly increased the yield of water‐dispersible clay; medium sand and coarse sand were the most effective. Conversely, the removal of sand from soil containing large amounts of sand reduced the yield of water‐dispersible clay. The abrasive action of sand during agitation associated with water dispersion evidently breaks down aggregates containing clay.
Improved Mercury Well for Multiple Tensiometer Systems
Authors: Doering E. J. , Harms J. P.
Published: July 2010

Details are presented for the fabrication of an improved mercury well for multiple tensiometer systems. The well is mounted on the back of the manometer support and is so designed that individual manometers can be repaired without disturbing the other manometers. Scale zero is visible and low moisture tensions can be read.
Total Mercury Content in Morrow Plot Soils over a Period of 63 Years
Authors: Jones Robert L. , Hinesly T. D.
Published: July 2010

Over a 63‐year period, Hg varied from 0.1 to 3.92 ppm in samples from surface horizons of soils from Plots on the University of Illinois campus. The dominant secular trend has been to lower levels in recent time. Neither changes in organic carbon content nor agronomic practices were related to Hg levels. Large amounts of coal burned in a nearby power plant did not contribute a fallout of Hg to the soils. A change toward improved internal soil drainage caused by tile drainage is thought to be the major factor causing the trend.
Growth, Mineral Composition, and Seed Oil of Sesame (Sesamum indicum L.) as Affected by Boron and Exchangeable Sodium
Authors: Yousif Yousif H. , Bingham Frank T. , Yermanos D. M.
Published: July 2010

A solution culture boron experiment was conducted with sesame (Sesamum indicum L.) to show the effects of excessive B. The boron content of leaf blades, petioles, and stems was highly correlated with substrate boron. The leaf blades contained the highest amount of boron, and the stems the least. Concentrations of 5 mg B/liter or higher inhibited growth, seed production, and resulted in a leaf necrosis and premature leaf drop. Foliage of plants receiving excess B contained > 700 µg B/g on a dry weight basis.

An exchangeable sodium experiment using clay soil with and without a synthetic soil conditioner showed that yields were sharply reduced at an ESP level of 15 or greater. Leaf blade sodium was higher for the treatments without the soil conditioner but in both series (± conditioner), 50% growth depression was associated with leaf values of about 0.4% Na. Potassium and Mg in the leaf blades did not vary significantly, and although calcium was decreased 50% with increasing ESP, no visual deficiency symptoms were detected. The oil content of the seed was decreased slightly with ESP levels of about 25.
Predicting Soil Moisture in the Southern Appalachians
Authors: Helvey J. D. , Hewlett J. D. , Douglass J. E.
Published: July 2010

Soil moisture was measured for 3.5 years on forested slopes in the mountains of western North Carolina to develop equations for predicting soil moisture content of watersheds. Predictors used were precipitation and easily measured topographic, seasonal, and soil physical factors; among these, sand content and moisture retention at 1‐bar suction were the best predictors of moisture content. Position on slope (height or distance from the stream channel) appeared to be an important factor only in the lower 25% of the slope. The annual cycle of soil moisture in the top 213 cm approximated a sine wave with a maximum during mid‐April and a minimum during mid‐October. As expected, moisture changes in surface layers were correlated best with rainfall weighted toward days immediately preceding observation; changes in deeper layers were better correlated with rainfall during previous weeks. Seasonal changes in soil moisture content at all depths were greatest upslope and least in the lower slope. Equations developed account for about 88% of the variation in soil moisture (standard error approximately 2–3% by volume) and can be used to predict antecedent moisture distribution for hydrologic and other purposes. Results support the “variable source area” concept of streamflow, but even with the neutron method slope gradients in field moisture were not easy to detect.
Manganese and Iron Solubility Changes as a Factor in Tile Drain Clogging: I. Observations During Flooding and Drying
Authors: Grass L. B. , MacKenzie A. J. , Meek B. D. , Spencer W. F.
Published: July 2010

A field study of waterlogging and subsequent drying of the soil profile has shown that under irrigation culture in Imperial Valley reducing conditions became prevalent. Reducing conditions, as indicated by declining Eh values, became most favorable for dissolution of Mn and Fe near the soil surface. However, the concentrations of Mn2+ and Fe2+ were lowest near the surface, probably because of their leaching from this zone, and the shorter time of contact between soil solution and soil particles. The concentration of Fe2+ and Mn2+ were higher in the deeper horizons of the soil profile.

In the plow layer, the reducing intensity increased, beginning 9 m away from the tile and reaching a maximum 18‐ to 23‐m from the tile drain. The Eh levels in the soil profile declined immediately after irrigation began and rose immediately after irrigation stopped indicating the importance of atmospheric oxygen to the oxidation‐reduction status and, therefore, to the solubility of iron and manganese compounds. Soluble organic carbon apparently was not related to the concentration of Mn2+ or Fe2+ in the soil solution even though the decomposition of soil organic matter is important in oxidation‐reduction reactions in the soil profile.
Manganese and Iron Solubility Changes as a Factor in Tile Drain Clogging: II. Observations During the Growth of Cotton
Authors: Grass L. B. , MacKenzie A. J. , Meek B. D. , Spencer W. F.
Published: July 2010

Various levels of oxidation‐reduction develop in the soil profile during the irrigation and growing season of the cotton (Gossypium hirsutum L.) crop. Reducing intensity increased with depth during the growing season and reached maximum intensity at the 6.10‐m depth. Reducing conditions favorable to increased solubility of Fe and Mn were observed in the surface horizons of the profile during most of the season.

Changes in the solubility of manganese and iron occurred with changes in the oxidation‐reduction status in the soil profile. Manganese began to dissolve at 400 mV and became significant at less than 300 mV. Increased concentration of nitrate retarded reduction of oxidized Fe and Mn compounds. The salinity of the soil solution affected the concentration of soluble manganese and iron. The presence of NO3‐ ‐N in the soil solution in amounts >0.2 ppm retarded the dissolution of Mn compounds.

The solubility of manganese and iron can probably be controlled by controlling or regulating the oxidation‐reduction status of the soil profile by reducing the waterlogging period after irrigation to a minimum.
The Dissolution of Complex Ferric Phosphates Under Controlled Eh and pH Conditions
Authors: Williams B. G. , Patrick W. H.
Published: July 2010

The dissolution of complex ferric phosphates, CaFe2H4(PO4)4 · 8H2O and KFe3H14(PO4)8 · 4H2O, was studied in a reduced chemical system. Both salts dissolved incongruently to release calcium and phosphorus in a molar ratio of 1:2 and solid FePO4. Below an Eh of — 200 mV further P was released due to FePO4 dissolution. Potassium ferric phosphate crystals dissolved rapidly with complete release of K, whereas dissolution of calcium ferric phosphate was retarded probably due to interference by precipitated FePO4. The solubility of precipitated FePO4 differed slightly from that observed with crystalline strengite and at pH 6 and 7, ferric hydroxides apparently entered into the reaction.
Selective Distribution and Labile Pools of Micronutrient Elements as Factors Affecting Plant Uptake
Authors: Graham E. R.
Published: July 2010

A study of the selective distribution of the nutrient elements Mn, Fe, Zn, Co, and Cu and plant response for soils from Colorado, Nebraska, Missouri, and Florida showed that selective distribution was related to plant response.

The labile pool expressed in ppm for the elements Mn, Fe, Zn, Co, and Cu may be plotted against the selective distribution resulting in the best relationship between soil characteristics and plant uptake. It appears that the selective distribution labile pool plot will have universal application as a diagnostic method for assessing the fertility level of Mn, Fe, Zn, Co, and Cu.
Scanning Electron Microscopy of Hydrous Metal Oxide Crusts Intercalated in Naturally Weathered Micaceous Vermiculite
Authors: Jackson M. L. , Lee S. Y. , Brown J. L. , Sachs I. B. , Syers J. K.
Published: July 2010

Scanning electron microscopy (SEM) of the weathering products of trioctahedral mica, chemically weathered in nature to micaceous vermiculite (14 and 10Å spacings by X‐ray diffraction), revealed occasional deposition of hydrous metal oxide crusts on intermittent cleavages interspersed at intervals among chemically clean (001) surfaces. Examination by SEM of layers through pores or holes, and along (hkO) fractures through the (001) planes, revealed that the intercalated crusts were 1–15µm thick with sequences of hundreds of clean 14Å crystallographic layers between each crust layer. The pores may represent weathering out of 238U fission tracks resulting from impurities in the original micas.

Treatment of a micaceous vermiculite flake with citratebicarbonate‐dithionite (CBD) produced a large number of smooth, thin phyllosilicate flakes which had planar areas at least one‐half that of the original untreated flake; hundreds of smaller flakes were released by this treatment. Natural weathering apparently formed cracks in the large flakes both in the (001) and (hkO) crystallographic directions. The metal oxides removed by CBD cemented the mica pseudomorphs in the untreated sample. The holes and fractures along (hkO) planes apparently permitted a diffusion of Fe3+ and Al3+ from the octahedral positions into the crusts during the geochemical conversions of biotite to micaceous vermiculite and may relate to the associated lowering of layer charge.
Effect of Two Nonionic Surfactants on Adsorption and Mobility of Selected Pesticides in a Soil‐System
Authors: Huggenberger F. , Letey J. , Farmer W. J.
Published: July 2010

The effect of two nonionic surfactants on the adsorption and mobility of lindane, diuron, and atrazine in soil columns was studied. A wide range of surfactant concentrations was used in this study. Adsorption of the pesticides by soil from a surfactant solution was inversely related to the leaching of the pesticides through the soil in presence of the surfactants. Low concentrations of both surfactants did not influence adsorption and mobility of the pesticides. A marked increase in the adsorption and reduction in the mobility of the pesticides was observed with 500 ppm Aqua Gro and 2,000 ppm Soil Penetrant. At concentrations of 5,000 ppm and 10,000 ppm, both surfactants decreased the adsorption and increased the mobility of lindane and diuron, but did not influence the adsorption and mobility of atrazine. An attempt was made to explain the mechanisms by which the two surfactants influence adsorption and mobility of the pesticides using the concept of micelle formation and critical micelle concentration.
Carbohydrases in Soil as Affected by Successional Stages of Revegetation
Authors: Pancholy Sunil K. , Rice Elroy L.
Published: July 2010

Addition of plant materials from the first successional stage of old‐field succession caused a continuous increase in the microbial population and in activities of amylase, invertase, and cellulase for 45 days, the duration of the experiment. On the other hand, addition of plant materials from an intermediate successional stage or the climax stage resulted in an initial increase in the microbial population and in the activities of the three carbohydrases with a leveling off or decrease after 30 days. Type of organic matter added appeared to be responsible for the higher activities of the carbohydrases during the early stages of old‐field succession.
Loess Distribution as Revealed by Mineral Variations
Authors: Kleiss H. J. , Fehrenbacher J. B.
Published: July 2010

The apparent physical uniformity of various loess deposits has often led in the past to conclusions of uniform composition and constant rate of deposition for loess formations. These assumptions have been used in many evaluations of soil development and in explaining the distribution of various soils. The existence of identifiable increments of characteristic composition within Peoria Loess not only indicates compositional variations but permits evaluation of the regional distribution of individual loess increments. Unique mineralogy (particularly clay‐mineralogy) of the loess increments is attributed to major changes in the origin of valley loess source sediments.

The consistent identification and pattern of four distinct zones within Peoria Loess in Illinois east of the Illinois River Valley reveal that the rate of loess deposition has not been constant. Rather, the upper younger loess increments are most dominant and more widely distributed and therefore most important as soil forming material. This implies that the soils of the maturity or development sequence in Illinois have all formed in the same relatively young increment of Peoria Loess. The characteristies of these soils which vary from weakly‐ to moderately‐developed Udolls to very strongly‐developed Albaqualfs cannot be attributed to their age differences.
Quantitative Calcium Carbonate Equivalent Determination in the Field
Authors: Holmgren George G. S.
Published: July 2010

A simple volume calcimeter can be constructed from a 50‐cc and a 20‐cc plastic syringe. To operate, a weighted quantity of soil is placed in the large syringe and 5 cc of 10% HCl is drawn into the small syringe. The tips are then joined together through a connecting sleeve and the acid is injected into the soil. The volume of CO2 produced is measured in either or both syringes, depending on the amount.

An array of sample weights to yield 1 cc CO2 for 1% CaCO3 equivalent at various temperatures and elevations is provided. This array is approximated by the relation W = (118‐13h)/T where W = weight of sample in grams, h = elevation in kilometers, and T = temperature, oK. Soluble CO2, ranging from 7.3 cc at 5C to 3 cc at 35C, must be added to the observed volume to obtain the true volume of CO2 released.

An alternate procedure using a constant sample weight of 0.33 grams is also described. Directions are given for constructing a simple hand balance to weight this amount in the field, and a nomograph is provided to facilitate calculations.

With these procedures, CaCO3 equivalent can be determined within 1–2% absolute over the range 0–50%. These errors may be reduced at lower CaCO3 equivalent values by increasing the sample size.
Simultaneous Transport of Chloride and Water During Infiltration
Authors: Kirda C. , Nielsen D. R. , Biggar J. W.
Published: July 2010

Displacement of chloride during infiltration was studied using soil columns for two cases: chloride initially spread on the soil surface; and chloride initially mixed with the soil. Chloride was applied as CaCl2 labeled with 36Cl. Its activity in counts per minute was scanned with a GM counter along a 2.5‐cm wide window slit in the columns. In conjunction with the chloride activity measurement, gamma‐ray attenuation measurement was used for monitoring the water content distribution during the simultaneous flow of chloride and water. Treatments included different levels of initial soil water content and different levels of water saturation at the soil surface during infiltration. With a numerical method the equations describing vertical water flow and miscible displacement of chloride were solved simultaneously. Experimental and calculated chloride distributions were in agreement. Chloride apparent diffusion coefficients estimated for pore water velocities less than 0.01 cm min‐1 were nearly equal to that for moleculer diffusion only. Initial soil water content did not influence the depth of chloride displacement for a given quantity of water infiltrated; whereas, keeping the water content at the soil surface below saturation resulted in a deeper and more complete displacement of chloride.
Chemical Properties of Acid‐Sulfate Soils Recently Reclaimed from Florida Marshland
Authors: Calvert D. V. , Ford H. W.
Published: July 2010

Acid soil layers, with pH as low as 3.0, were found in the subsurface horizons of soils derived from marine sediments and have been recently developed into citrus groves. Soil layers with acidity varying from pH 3.0 to 7.7 and sulfate content from 0.5 to 39.0 meq/100 g of soil were compared for their capability of producing acid‐sulfates. Lime requirements of selected acid layers were found to be as high as 4.5 meq of CaCO3 equivalent per 100 g of soil. The acid‐sulfate potential (oxidation of reduced sulfur to H2SO4) accounts for the reduction of pH of the reclaimed soils. The sulfate content of soil layers was often in excess of 2,000 ppm when the soil pH after oxidation with H2O2 was below 3.0 and was dependent on oxidizable sulfur content of the sample and buffering capacity of the soil. Oxidized soil layers with pH values below 3.5 released soluble Al and Fe up to 275 ppm and 100 ppm, respectively.
Evaluation of Various Extractants for Available Soil Sulfur
Authors: Hoeft R. G. , Walsh L. M. , Keeney D. R.
Published: July 2010

The S status of 49 Wisconsin soils was evaluated in field studies using alfalfa (Medicago sativa) as the test crop. The effectiveness of six soil S extractants for predicting yield and S uptake response to applied S were evaluated by means of correlation analyses. The best extractant, considering all dependent variables and the S range, mean and standard deviation for each procedure, was 2N HOAc containing 500 ppm P as Ca(H2PO4)2 · H2O [Ca(H2PO4)2‐HOAc]. The correlation between extractable S and response to applied S was not improved by inclusion of percent organic matter, percent sand, or subsoil SO4‐S in the regression equation. However, inclusion of soil pH with extractable S did significantly improve the prediction of S response.

The best equation for prediction of yield response to applied S in the field was: Yield response (metric tons/ha) = 50.81 − 7.22 pH − 8.19 S + 1.171 (pH × S) + 0.167 (S)2 − 0.00341 (pH × S)2 where S is the ppm of S extracted with Ca‐(H2PO4)2‐HOAc. Significant response to applied S would be expected on soils having a calculated yield response of 0.40 metric tons/ha or greater when extractable S is between 6 and 10 ppm S. Soils testing less than 6 ppm would be expected to respond and those testing greater than 10 ppm S would not be expected to respond to application of S, regardless of the calculated response value. Use of the regression equation and the limits of 6 and 10 ppm S resulted in correct prediction of S response at 77.6% of the field sites.
A Precision Dispenser for Dry Fertilizer Materials
Authors: Onken Arthur B. , Sunderman Herbert D. , Brashears Alan D.
Published: July 2010

Equipment for the rapid and accurate dispensing of dry fertilizer materials is described. The dispensers consist of acrylic plastic cylinders containing a cylindrical cavity and are powered by a combination of hydraulic cylinders and solenoid valves. Hydraulic and electrical power are supplied by the transporting tractor. Three dispensing cylinders of different sizes are assembled to form a unit. One such unit is used for each row. The cylinders are designed with adjustable volume and may be used in various combinations, thus giving a high degree of flexibility. The amount of material dispensed with this equipment, though less precise than obtained by weighing, is more precise than obtained by using hand‐manipulated containers. The use of this equipment has sharply reduced the time and labor required to apply treatments.

With the system described, either three rates of the same material or three different materials may be dispensed for application to each of four rows. Because of the modular design of the system, adaptations for specific needs can be constructed.
Flood and Seepage Water Sampling Techniques in Rice Fields Under Different Water Management Practices
Authors: Tanji K. K. , Biggar J. W. , Mehran M. , Henderson D. W.
Published: July 2010

Sampling equipment reported herein enables collection of flood and seepage waters to determine persistence and transport of chemicals applied in flooded rice culture (Oryza sativa L.). This system gives a capability of evaluating the effects of different chemical application methods (water‐applied, soil‐incorporated) and water management systems (static, flow‐through, and recycled).
Persistence and Competition Aspects of Rhizobium japonicum Observed in Soil by Immunofluorescence Microscopy
Authors: Bohlool B. B. , Schmidt E. L.
Published: July 2010

Fluorescent antibody was used to study persistence and competition of Rhizobium japonicum in soils. Strain 110 (USDA) attached to microscope slides was studied by FA‐staining after recovery of the slides from soil at various intervals. In the Clarion soil, reactive cells dropped from 32/microscope field, with 100% of the fields being positive, to 0.15/field, with only 10% positive fields in 120 days. In the Ulen soil, the drop was from 53/field (100% positive fields) to 2.5/field (40% positive fields) over the same period.

The question of competition was approached first by varying the numbers of strain 110 added to constant but low numbers of the resident rhizobia flora of Clarion soil. Each treatment was used to inoculate plants and each nodule was tested separately with the homologous FA. Relatively high inoculant/resident ratios were needed to overwhelm the resident population. When the log of the numbers of introduced 110 was plotted against the percentages of 110 nodules, a sigmoidal curve emerged which may reflect a region of resistance characteristic for the resident R. japonicum population of that soil. A second approach involved the competitive ability of a known number of the introduced strain in the soil over a period of time. An initial population of 2.2 × 103 R. japonicum 110/g of Clarion soil, capable of initiating 85% of the nodules, formed only 55% and 45% of the nodules after 10 and 30 days, respectively, of incubation in the soil. This probably was a reflection of the inability of the initial added population to persist and maintain its numbers in the soil.
The Dynamic Character of a Chloritized Vermiculitic Soil Clay
Authors: Lietzke D. A. , Mortland M. M.
Published: July 2010

Interlayer removal experiments using a chloritized vermiculitic soil clay showed its dynamic character by rapid alteration to vermiculite. The Ca/Mg cation exchange capacity of one sample dispersed ultrasonically and treated with dilute NaOH at pH 10 increased from 33 to 169 meq/100 g while the K/NH4 CEC remained in a range of 25 to 35. This particular sample contained all of the organic matter and the natural surface oxides. On standing for 12 days at lower pH, interlayer material was redeposited as indicated by Ca/Mg CEC reduction. Another sample of the same soil clay was pretreated in a conventional manner. The Ca/Mg CEC also increased from 24 to 113 and the K/NH4 CEC increased from 20 to 31 meq/100 g when treated with NaOH in the same manner. A standard prochlorite showed small but equal upward increases of both kinds of CEC. Deuteration experiments using a chloritized vermiculitic soil clay, a vermiculitic soil clay, and a standard prochlorite showed the easy accessibility of interlayer OH groups to deuteration at moderate temperatures. The interlayer OH groups of chloritized vermiculite showed deuteration at 68C, while the OH groups in the 2:1 structure of the vermiculitic soil clay started deuteration at 150C and those of the prochlorite at 200C.
Response of Corn in the Greenhouse to Soil Applied Zinc and a Comparison of Three Chemical Extractions for Determining Available Zinc
Authors: Coffman C. B. , Miller J. R.
Published: July 2010

The response of corn (Zea mays L.) to applied Zn on 12 Maryland soils was investigated in the greenhouse. Zinc was thoroughly mixed with soils at the rate of 0, 1.25, 2.5, 5, 10, 20, and 40 ppm Zn as zinc sulfate. Corn was grown for 30 days after emergence and dry matter yields were determined. The plant tissue was analyzed for Zn, Ca, Mg, K, and P.

The application of Zn increased the dry matter yield of corn on only one of the 12 soils. As the Zn rate was increased, the Zn content of the corn usually increased. The level of Zn in the corn tissue above which no further significant increase in yield was obtained was about 12 ppm.

Three chemical soil extractants were compared for determining available soil Zn. The Zn extracted by each of the three chemical extractants was correlated with the Zn content of the above ground portions of the corn plants. The correlation coefficient for the 0.05N HCl plus 0.025N H2SO4 extractant was 0.834, the 0.1N HCl extractant 0.854, and the 0.01M EDTA plus 1.0M (NH4)2CO3 extractant 0.787, respectively. The r values for all three extractants were statistically significant at the 1% level.

The level of extractable Zn in an Othello soil which gave a significant dry weight increase in corn following the application of Zn was 0.3 ppm for the HCl plus H2SO4 extractant, 0.2 ppm for the HCl extractant, and 0.1 ppm for the EDTA plus (NH4)2CO3 extractant, respectively.