bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Straw Mulch Rates on Soil Water Storage during Summer Fallow in the Great Plains
Authors: Greb B. W. , Smika D. E. , Black A. L.
Published: July 2010

Net gains in soil water storage during fallow due to increased quantities of wheat (Triticum aestivum L.) straw mulch varied from 1.0 to 4.3 cm at Sidney, Mont., from 2.1 to 4.1 cm at Akron, Colo., and from 1.3 to 3.3 cm at North Platte, Nebr. These gains were made primarily during the spring months of the 14‐month fallow season. More than 70% of the net gains in soil water under heavier amounts of mulch was found below the surface 61 cm of the soil profile at all experimental locations, thereby minimizing potential evaporation losses. Storage of water tended to increase with the delayed date of straw burial in Nebraska. Additional soil water was conserved at Akron, Colo. during the first fall by subtillage of wheat stubble at harvest when compared with spring subtillage; however, by the end of the fallow there was no significant difference between treatments. Fallow efficiencies averaged 22, 30, and 32% for all treatments at the Montana, Colorado, and Nebraska locations respectively.
The Chemical Composition of Sphagnum Species and the Influence of Drainage on its Location
Authors: Maas E. F.
Published: July 2010

Drainage of a sedge swamp containing islands of Sphagnum species resulted in a shift of new sph gnum growth on to the sedge around the perimeter of the islands. The new sphagnum deposit developed on a substratum of sedge peat was higher in exchangeable Ca and Mg, total N, percent ash and pH than that produced in its original location on the lower nutritional substratum of sphagnum peat.
Osmotic Effects on Water Flow Through a Ceramic Filter
Authors: Jackson Ray D.
Published: July 2010

Non‐Darcy type flow of water through a porous ceramic filter of 0.1µ pore diameter was shown to be caused by osmotic effects. When osmotic effects were accounted for, the flow rate through the filter was proportional to the pressure gradient, indicating that water flow was viscous and not plastic as has been previously reported. Threshold effects, if present, were small. The permeability, calculated by using the viscosity‐density ratio for bulk water, was invariant with temperature.
The Measurement of the Hydraulic Conductivity of Unsaturated Porous Materials Utilizing a Zone of Entrapped Air
Authors: Watson K. K.
Published: July 2010

A steady‐state method for determining the major portion of the hydraulic conductivity‐water content relationship of reasonably coarse‐grained unsaturated porous materials is presented. In the method, an initially saturated column of the material, in the process of draining to a water table at its base, is rewet at an appropriate time at its upper surface from a ponded supply. This occasions an increase in the pore air pressure in the zone of air entrapped in the profile between the wetting and draining fronts. Two physical consequences of this flow system, the formation of a bell‐shaped water content profile and the rapid attainment of steady‐state conditions, allow the determination of the conductivity‐water content relationship. Precautions to be taken in using the method are outlined, and experimental details are discussed. Two sets of experimental results are documented.
Soil Water Diffusivity from Horizontal Infiltration
Authors: Whisler F. D. , Klute A. , Peters D. B.
Published: July 2010

A method has been developed for the measurement of soil water diffusivity. The method is based on gamma ray absorption measurements of the water content as a function of time at a fixed position in a horizontal infiltration system. The calculation of diffusivity is based on the assumption that the water content is a function of position divided by the square root of time. The variability of the data led to scatter in the diffusivity function especially at high water contents. This variability in the data can be traced mainly to the inability to obtain sufficiently accurate data from the recordings of the gamma ray counting system. When the diffusivity function thus obtained was used to predict the water content time relationship in the column, even though the function had been fit statistically, the results were largely dependent upon the wet end of the relationship.
Flocculation of Clays and Soils by Organic Compounds
Authors: Chang C. W. , Anderson J. U.
Published: July 2010

The effectiveness of 15 substituted benzene ring compounds in flocculating < 2µ Gila clay was evaluated by measuring flocculation percentage and by observation after reaction in water suspension. In general the flocculation percentages were in the order: calcareous clays > noncalcareous, calcium‐saturated clays > noncalcareous sodium‐saturated clays. Effectiveness of organic compounds on carbonate containing clays increases sharply as the pH value drops to about 6.0. In carbonate‐free systems the effect of decreasing pH is not evident until the pH drops to < 4, and is not consistent. Calcium appears necessary for flocculation in all sodium, calcium‐clay systems studied. Interlayer absorption does not insure flocculation, and naturally existing organic matter did not increase flocculation by the organic compounds tested. The effectiveness of the compounds used appeared to depend on the number of active groups, and on the number of unshared electrons. Reactive groups of benzene ring compounds were more effective in the meta than in the ortho or para positions.
Cationic Diffusion in Clay Minerals: I. Homogeneous and Heterogeneous Systems
Authors: Lai T. M. , Mortland M. M.
Published: July 2010

Models of homogeneous and heterogeneous cationic diffusion systems were applied to clay minerals. The diffusion of Na and Cs ions in expanded Na‐vermiculite, which has both internal and external surface available for cationic diffusion, decreased with increasing diffusion time, a characteristic of heterogeneous systems. Diffusion of those ions remained essentially constant in collapsed K‐vermiculite which has only external surface available for diffusion and can thus be described as homogeneous. The property of homogeneity was further confirmed with cationic diffusion in the vermiculite whose exchange sites were clogged by p‐phenylenediamine cation, and in Na‐ and K‐kaolinite; while the heterogeneous property was observed for Na‐ and K‐bentonite. The diffusion of Na ion in Na‐vermiculite was related to a model originally derived for mathematical analysis of grain boundary problems. The evaluation of diffusion coefficients of external surface (De) and of interlayer surface (Di) was made, and De of Na ion in Na‐vermiculite was found to be about 5 times larger than that of Di. The importance of considering the homo‐ and heterogeneity of the system in the study of cationic diffusion in clay minerals is suggested.
Further Evidence for a P‐Zn Imbalance in Plants
Authors: Boawn Louis C. , Brown J. C.
Published: July 2010

Beans (Phaseolus vulgarus) and potatoes (Solanum tuberosum) were grown using a split‐medium technique that permitted Zn to be supplied to the plants from a soil medium while variable levels of P were supplied from a solution. A balance between P and Zn levels was attained through trial and error so that only the highest level of P induced interveinal chlorosis and stunting.

In both crops, P induced the deficiency without causing a decrease in the Zn nutritional status of the plants. Increasing the soil Zn level at a given P level resulted in plants with normal growth. The results are interpreted to support the hypothesis that normal metabolism is dependent upon a physiological balance between P and Zn.
Soil Trends and Variability Across Selected Landscapes in Iowa
Authors: Walker P. H. , Hall G. F. , Protz R.
Published: July 2010

Soil profile features such as A horizon thickness, depth to subsoil mottles, depth to carbonates, and surface and subsoil pH were measured in sample grids on small loess and drift landscape segments. Trend analyses were made across the full range of topography, then soil variation was examined within topographic subareas that approximated detailed soil survey delineations. Comparison of standard errors and standard deviations showed that some increase in the precision of predictions was obtained for loess soils when using “trend” rather than “within delineation” analysis. The reverse was true for drift soils. The representation of data in polynomial trend equations is justified because of systematic variation observed across small landscape segments, and from a consideration of a soil landscape model that is generally applicable in Iowa. Using this model, maxima and minima of soil properties are expected along transects from upland to lower pediment slopes. Polynomials provide a statistical fit of soil landscape data and a suitable representation of maxima and minima of soil properties.
An Improved Method for Extracting Organic Matter from Soil
Authors: Gascho G. J. , Stevenson F. J.
Published: July 2010

A procedure is described which reduces the possibility of chemical alteration of soil organic matter during extraction, and which permits recovery of most of the solubilized organic matter as an acid‐insoluble material low in ash. The essential features of the method are: (i) destruction of hydrated silicate minerals by pretreatment of the soil with 0.3N HF, (ii) recovery of organic matter by extraction first with 0.02M Na4P2O7 and then with 0.03N NaOH, and (iii) removal of inorganic contaminants by dialysis against 0.3N HF.
A Vacuum System for Accumulating Runoff from Infiltrometers
Authors: Dixon R. M. , Peterson A. E.
Published: July 2010

A vacuum system for picking up and accumulating runoff from sprinkler and overland‐flow infiltrometers is described. This system is much simpler than the runoff recirculation system of the Purdue sprinkler infiltrometer. Costs of fabrication, operation, and maintenance are greatly reduced and inherent errors of a malfunctioning recirculation system are avoided. Sampling for subsequent runoff‐quality determinations is facilitated by the vacuum system since no sedimentation occurs in the collection and transfer parts of the system.
Simultaneous Flow of Water and Heat under Periodic Heat Fluctuations
Authors: Hadas A.
Published: July 2010

Theoretical Predictions of thermally induced moisture transfer have been compared ot measured quantities. Soil samples at different initial moisture contents were subjected to sinusoidal heat waves having an amplitude of 6C, and various periods of time. Temperatures were measured at various distances from the heat source, using copper‐constantan thermocouples and recording the emf output.

The mositure distribution after the 1st, 2nd, 6th, and 16th cycle was determined gravimetrically.

The measured net transfer quantities were found to be larger than the theoretically predicted values by factors ranging from 0.8 to 8.0. The discrepancy between predicted and measured values of ent transfer may be attributed to the incompleteness of the theoretical models.
Hydraulic Properties of a Clay Loam Soil and the Field Measurement of Water Uptake by Roots: II. The Water Balance of the Root Zone
Authors: van Bavel C. H. M. , Brust K. J. , Stirk G. B.
Published: July 2010

Soil water depletion rates in a 115‐cm and a 170‐cm deep profile of Adelanto clay loam were compared with lysimetrically obtained consumptive use rates for periods of many days after measured water applications. When the soil was bare, the depletion rates were always higher than the rate of loss to the atmosphere, and the inferred flux at the 170‐cm depth was as high as 2 mm/day 8 days after irrigation. When the test plot was planted to sorghum (Sorghum vulgare Pers.) an initially strong downward flux at the 170‐cm depth reversed itself after about 10 days and became as high as 4 mm/day, representing upward flow of water from wet soil into the root zone above. The data imply that indiscriminate use of soil water depletion rates as representing consumptive use rates can be highly misleading at any time in an irrigation cycle. Further analysis shows that a rational and satisfactory correction of depletion data is not likely feasible, and, at any rate, unworkable for the condition of the experiment.
Mathematical Simulation of Water Movement through Unsaturated Nonhomogeneous Soils
Authors: Wang Flora Chu , Lakshminarayana V.
Published: July 2010

The general states of flow of water through unsaturated nonhomogeneous soils have been simulated by the nonlinear diffusion equation. A numerical technique is developed and programed for the IBM 7094 to solve the explicit‐implicit difference scheme analogue of the nonlinear partial differential equation of parabolic‐type.

The data utilized in this study for the simulated soil profile are obtained from the experimental work of Nielsen et al. (1964) for vertical drainage and infiltration. Computed cumulative loss and average rate are in reasonable agreement with their field measurements. The results indicate that the average rate of drying and wetting are controlled largely by the physical properties of the soil and their corresponding boundary conditions.
Effect of K+‐Uptake by K+‐Depleted Micas on the Basal Spacing
Authors: Weed S. B. , Leonard R. A.
Published: July 2010

Potassium was introduced into expanded, i.e., K+‐depleted, micas by (i) adding about 0.5 symmetry of KCl to a chromatographic column of expanded mica plus sand and (ii) by equilibrating suspensions of Ca2+ or Mg2+‐saturated expanded mica with 0.5, 1.0, 1.5, or 2.0 symmetry of KCl. Two expanded biotites readily formed a regular alternation of 10 and 14A spacings whereas two muscovites did not develop such a phase. A phologopite yielded this phase only at the lowest concentration of K+ tested. Regular alternation developed most readily in the Ca2+‐saturated minerals. Development of regular interstratification did not appear to be related to the gross surface‐charge‐density of the minerals, but did seem to be positively related to the content of octahedral Fe.
Retention of Boron by Layer Silicates, Sesquioxides, and Soil Materials: III. Iron‐ and Aluminum‐Coated Layer Silicates and Soil Materials
Authors: Sims J. R. , Bingham F. T.
Published: July 2010

Boron retention as a function of pH was determined for Fe‐ and Al‐coated layer silicates using a previously described procedure (15). Treating the Na+ and K+ forms of South Africa vermiculite material with Al3+ prior to B treatment resulted in equivalent B retention by the two forms. Coating kaolinite with hydroxy iron compounds initially decreased B retention in comparison to uncoated kaolinite. However, as the amount of coating was increased to 4.2% Fe2O3 the amount of B retained was slightly greater than that retained by uncoated kaolinite. Boron retention by the Al‐coated kaolinite and by both Fe‐ and Al‐coated montmorillonite was significantly greater than B retention by the uncoated clays. A single regression line represented B retention as a function of Fe2O3 content for both clays. Boron retention as a function of Al2O3 content for the two coated clays fell on two lines which led to the conclusion that hydroxy Fe and Al compounds in the layer silicates dominate over clay mineral species per se in determining B retention characteristics and that B retention characteristics may be conditioned by clay mineral species.

Boron retention at pH 6 by nine soil materials was determined from the difference in the initial and final B concentrations of the saturating solutions. Relationships between B retention and various chemical properties of the soil materials were examined statistically. The highest correlations with B retention were found with free iron oxide content and 1.0N KCl (pH2) extractable Al2O3. It was concluded that B retention by these soil materials was in response mainly to their free iron oxide and Al2O3 contents.
Use of the Stanford‐DeMent Bioassay to Study Atrazine‐Soil Reactions
Authors: Tompkins G. A. , McIntosh T. H. , Dunigan E. P.
Published: July 2010

Quantitative detection of atrazine in soil was accomplished using a modified Stanford‐DeMent type bioassay. The technique should be easily adaptable for analysis of other herbicides in soil. The uptake of atrazine by oat plants (Avena sativa, var. Swedish Victory) was directly proportional to the amount of atrazine applied to the soil and inversely proportional to the clay and soil organic matter content. Using 14C labeled atrazine it was found that only a very small amount of atrazine was removed from the soil by one oat crop. The bioassay was used to examine the adsorptive effects of certain model compounds which represented different fractions of soil organic matter. One percent activated charcoal in sand completely inactivated atrazine applied in the range 1.0 to 11.3 ppm. One percent lignin in sand was moderately effective in reducing atrazine phytotoxicity in oats. One percent cellulose in sand was relatively ineffective in adsorbing atrazine. The Stanford‐DeMent type bioassay should be a useful tool for a study of chemical or microbial transformation of herbicides in soil.
Micromovement Mechanisms of s‐Triazines in Soil
Authors: Lavy T. L.
Published: July 2010

In situ autoradiography of corn (Zea mays L., var. WF9 × Hy) roots grown in bands of three different soils treated with 14C ring‐labeled s‐triazines showed that both mass flow and diffusion of the herbicides occur. Mass flow was the most important means of moving the herbicide to the absorbing root in the case of 2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine (atrazine) the most water soluble of the herbicides studied. Movement of the soil‐applied herbicides to the corn roots did not insure uptake of the chemical. Mass flow patterns were clearly present around roots growing in the band of 2‐chloro‐4, 6‐isopropylamino‐s‐triazine (propazine) treated Sharpsburg silty clay loam soil; however, the least amount of 14C uptake occurred on this soil‐herbicide combination indicating restrictive herbicide uptake by the plant root.

Adsorption of the s‐triazines on the three soils increased as the soil acidity, organic matter, and clay content increased. Plant uptake of 14C decreased as the soil acidity, organic matter, and clay content increased.
Availability of Exchangeable and Nonexchangeable Mg in Sandy Coastal Plain Soils
Authors: Rice H. B. , Kamprath E. J.
Published: July 2010

The chemical forms of Mg in five sandy Coastal Plain soils were determined. The total Mg ranged from 0.73 meq. to 2.48 meq/100g. The percentage of the total Mg in the exchangeable form varied from 3.8 to 9.4% and generally increased as the total increased. Soils containing an expansible lattice clay had the highest Mg content per gram of clay.

Consecutive extractions with 1N NaOAc solution of pH 1 removed almost twice as much Mg as consecutive extractions with a solution of 1N NaOAc pH 7. This indicates that a portion of the nonexchangeable Mg is quite soluble in a dilute acid. The soils which released the highest amount of nonexchangeable Mg per gram of clay also were the ones containing some expansible clay minerals.

The exchangeable Mg in the range 0.05 to 0.23 meq/100 g of soil appeared to be equally available as indicated by plant uptake. In four of the soils a large part of the Mg taken up by corn (Zea mays L.) came from the nonexchangeable form.
Adsorption of Calcium and Strontium by Crandallite
Authors: Kunishi H. M. , Taylor A. W.
Published: July 2010

Samples of the phosphate mineral crandallite, CaAl3(PO4)2 (OH)5 · H2O were equilibrated with solutions containing calcium and strontium chlorides labelled with 45Ca and 85Sr. The apparent selectivity coefficient for the equilibrium system, calculated from the isotopic dilution, varied from 1.5 at pH 9.3 to 8.2 at pH 4.7. The mineral has limited value as a scavenging agent for the removal of strontium from soil.
Movement of Water Tagged With 2H, 3H, and 18O Through Acidic Kaolinitic Soil
Authors: Corey John C. , Horton J. H.
Published: July 2010

Miscible displacement techniques were used to compare the behavior of deuterium, tritium, and oxygen‐18 as water tracers. Displacement of a 170‐ml portion of triply tagged water through a 186‐cm‐long column of water‐saturated acidic kaolinitic soil by distilled water revealed no differences in the relative rates of movement of deuterium‐, tritium‐, and oxygen‐18‐tagged water.
Extraction of Cations from Silicate Minerals During the Determination of Exchangeable Cations in Soils
Authors: Rhoades J. D. , Krueger D. B.
Published: July 2010

The extent to which silicate minerals release Ca, Mg, Na, and K during the determination of exchangeable cations in soils by the ammonium‐acetate‐extraction procedure was evaluated. The method of exchangeable‐sodium evaluation used by the US Salinity Laboratory was employed for this study with the exception that soil samples were replaced with reference mineral samples. Amounts of cations equivalent to 0.3 to 21.8 meq/100 g were extracted from the minerals by ammonium acetate. In general, the proportions of cations extracted decreased in the order Ca + Mg>> Na> K. Because of this phenomenon, complications are expected to occur in the evaluation of exchangeable Ca and Mg in arid‐land soils, but not for exchangeable Na except under unusual circumstances. The latter circumstances are described and the general extent of error that may occur is estimated.
Reaction Products of Applied Phosphate in Limed Soils
Authors: Murrmann Richard P. , Peech Michael
Published: July 2010

A study was made of the solubility of phosphate in limed soils to which liberal amounts of superphosphate had been added over a long period of time but to which no phosphate had been applied for at least 5 years prior to sampling. The control limed soils to which no phosphate had been applied were also included for comparison. A 20‐g sample of soil was extracted with 200 ml of 0.01M CaCl2 for 108 hours and the concentration of phosphate and pH were determined in the clear supernatant solution after centrifugation. Although the extracts of all soils were found to be undersaturated with respect to hydroxyapatite, most of the extracts were found to be supersaturated with respect to fluorapatite in the presence of solid phase CaF2. By assuming the formation of an ideal solid solution with fluorapatite and hydroxyapatite as end‐members, it was shown that fluorapatite should be the stable phase even in the absence of solid phase CaF2 provided that the F‐ concentration in the soil solution is > 10‐8 M. Consistent with this deducation, the solubility of phosphate in many of the limed soils examined in this study agreed well with that expected for fluorapatite in the presence of 10‐5M F‐ solution, which was the concentration of F‐ found in several of the extracts that were examined. It may be concluded, therefore, that fluorapatite was the ultimate reaction product of the applied superphosphate in these limed soils.
Anaerobic Conversion of DDT to DDD and Aerobic Stability of DDT in Soil
Authors: Guenzi W. D. , Beard W. E.
Published: July 2010

14C‐DDT and carrier DDT were added to nonamended and to 1% alfalfa‐amended Pawnee silt loam. One set of sterile and nonsterile soil samples was incubated anaerobically, and another set was incubated aerobically. After predetermined periods of incubation, the soil samples were extracted, the extracts chromatographed on thin layer plates, and the separated radioactive DDT and decomposition products transferred into vials for quantitative determination by liquid scintillation counting.

DDT was converted to DDD (TDE) in an anaerobic soil system by microorganisms; only traces of six other degradation products were detected. Amending the soil with 1% alfalfa increased the rate of conversion, and less than 1% of the applied DDT was recovered in the soil extract as the original molecule after 12 weeks of incubation.

After six months of aerobic incubation, 75% of the added DDT was recovered in both the sterile and nonsterile soils. A maximum of 4% DDE and a trace of DDD was detected during the incubation period. Less than 1% of the carbon‐14 in the phenyl ring of DDT was oxidized to CO2 in the nonsterile soil. No radioactivity was found in n‐hexane traps, indicating no loss of DDT in the vapor phase.
Effect of Controlled Air and Soil Temperature and Starter Fertilizer on Growth and Nutrient Composition of Corn (Zea mays L.)
Authors: Ketcheson J. W.
Published: July 2010

Grain corn (Zea mays L.) yielded higher when grown to maturity under a 22‐12C controlled air‐21C controlled soil temperature combination than when grown under other factorial combinations with 26‐16C air and 17C soil. Lowering air temperatures lengthened the time, whereas increasing soil temperature shortened the time to reach maturity, indicating that growth rates stimulated by air temperature can reduce yields, but growth rates stimulated by soil temperature can increase yields. Starter fertilizer effects on yield were greatest with the temperature conditions giving lowest yield (higher air temperature‐lower soil temperature). Yields correlated negatively with tissue NPK concentration at maturity. Variations in leaf area corresponded to variations in yield.
Ant (Formica exsectoides) Pedoturbation in a Forest Soil
Authors: Salem M. Zarif , Hole Francis D.
Published: July 2010

Twenty‐five active mounds of the common eastern moundbuilding ant (Formica exsectoides) had an average height of 0.37 m and basal diameter of 1.1 m in a long, narrow neverplowed clearing of 1,040 m2 on the edge of a woodland in southern Wisconsin. The mound volume ranged from 0.01 to 0.6 m3 and averaged 0.13 m3. The ant nests, extending at least 160 cm below the soil surface occupied 1.9% of the area of the surface of a Typic Hapludalf (Gray‐Brown Podzolic), Dubuque silt loam, formed in thin loess over reddish cherty clayey residuum on dolomitic limestone. Mounds were virtually bare and were largely composed of silty clay. Detailed studies were made of a soil profile through a large mound and of an intermound soil profile nearby. Calculations indicated that the ants have moved to the surface the equivalent of 1.25% of a plow layer or 2,500 kg of soil (dry wt) per 1,040 m2 and in the process have reduced the bulk density of the material from 1.5 to 0.8 g/cm3 and increased the contents of available nutrients in the soil. Voids 0.2 to 2.3 cm in diameter, on the average occupied 20% by volume of the mound and about 10% of the buried A horizons. The mound contained about 50% silt, 46% clay, 4% sand; 4% free iron oxides, and 3% organic matter. Corresponding figures for the A2 and IIB23 horizons of the Dubuque are: 78, 18, 4; 2 and 3; 15, 83, 2; 6 and 0.3. Disturbance of soil profiles by this species of ant is restricted to small areas, apparently because colonies are established and mounds developed only in temporary openings in forests.
Linear Extensibility as Calculated from Natural‐Clod Bulk Density Measurements
Authors: Grossman R. B. , Brasher B. R. , Franzmeier D. P. , Walker J. L.
Published: July 2010

Use of a coating that is flexible permits measurement of bulk density of natural clods at more than one moisture content. Linear extensibility, expressed as a coefficient (COLE) or as change in horizon thickness, can be calculated from the increase in bulk density between the water content at ⅓‐bar tension and oven dryness. Extensibility data are given for a Marias soil (Entic Chromoxerert). Composition of the Marias soil remains similar with depth but the structure changes. COLE values are affected by the change in structure as are also PVC test results, but liquid and plastic limit values are affected little.
Soil Water Storage During Fallow in the Central Great Plains as Influenced by Tillage and Herbicide Treatments
Authors: Smika D. E. , Wicks G. A.
Published: July 2010

Soil water storage during the fallow period of winter wheatsorghum‐fallow (Triticum aestivum and Sorghum vulgare) and alternate winter wheat‐fallow rotations was measured during three fallow periods. Storage was greater when herbicides rather than conventional tillage practices were used to control weeds. The storage increase of nearly 4 cm of available water as a result of treatments was distributed throughout the profile in the 3‐year rotation, but the greatest increase occurred in the upper 60 cm of soil. In the 2‐year rotation the nearly 14‐cm increase in available water due to treatment was also present in the entire profile, but most of the storage increase occurred to a depth of 210 cm, with soil water content to a depth of 180 cm being at or near field capacity.

Soil water storage for the total fallow period of the 3‐year rotation ranged from 18.6 to 22.3 cm, having corresponding storage efficiencies of 35.4 and 42.4%, for conventional tillage and complete herbicide treatments, respectively. Water storage for the complete fallow period of the 2‐year rotation ranged from 18.6 cm with spring plowing (bare soil) to 23.8 cm with tillage stubble mulch to 32.5 cm with complete use of herbicides, and had storage efficiences of 25.0, 32.0, and 43.7%, respectively.
Automatic Control of Water Table Level in Soil Tanks
Authors: Willey C. R.
Published: July 2010

Thermistors are used as in situ water‐level sensors in an automatic control system that maintains water tables by supplying water to soil tanks directly from a high‐pressure water line.
Effects of Salts on Oxygen Diffusion Rate Measurements in Unsaturated Soils
Authors: Rickman Ron W.
Published: July 2010

Current‐voltage curves determined with tips of platinum electrodes touching a solution surface were used to evaluate the effect of solution electrical conductivity and specific ions on measurements of oxygen diffusion rates in unsaturated soil. Current was found to be dependent upon electrical conductivity in pure monovalent cation solutions. In divalent cation solutions, or mixed monovalent‐divalent cation solutions, current was only slightly affected by electrical conductivity of the solution. The presence of divalent cations caused a lower measured current with identical solution‐electrode geometry and measured electrode potential than when only monovalent ions were in solution. Based upon the assumption that these determinations reflect at least the magnitude of such phenomena that occur in soils, conditions are described under which the platinum electrode should operate most satisfactorily or have a minimum interference from salt.
Hydraulic Load‐Cell Lysimeter, Construction, Calibration, and Tests
Authors: Black T. A. , Thurtell G. W. , Tanner C. B.
Published: July 2010

The construction and calibration of two 35‐metric ton, hydraulic load‐cell lysimeters with suction drainage systems are described. The butyl‐nylon load cells contain an ethylene glycol‐water mixture and pressures are measured with a capacitive pressure transducer. Lysimeter sensitivity is 0.02 mm evaporation. Daily evaporation from the lysimeter and the two independent micrometeorological methods agreed to within 5%. On a June day, lysimeter measurements of evaporation from bare soil lagged measurements using the two other methods by almost 1.5 hours. Differences between the lysimeter thermal regime and that in the surrounding soil accounted for the lag. By using foam plastic insulation of the tank walls, thermal regime differences were minimized.
Leaching Requirement for Exchangeable‐Sodium Control
Authors: Rhoades J. D.
Published: July 2010

A method is described for estimating the leaching fraction required to keep the sodium‐adsorption‐ratio (SAR) at the lower limit of the plant‐rooting zone below some limiting value. The choice of the limiting SAR depends on plant tolerances to sodium and on soil permeability. The method is based on an equation that satisfactorily predicts the SAR values of waters draining from a calcareous soil under various leaching regimes.
A Portable Injector for Dispensing Liquid Anhydrous NH3 in the Field
Authors: Smiley R. W. , Papendick R. I.
Published: July 2010

A portable injector for metering and dispensing small aliquots of anhydrous NH3 rapidly and with good precision in the field has been constructed and tested. The device is versatile and should be equally suitable for dispensing other high‐pressure solutions in the field. The portable injector is simple in design, easily operated, and readily transportable. Injecting liquid NH3 with the portable injector produces little soil disturbance compared with usual application methods.

The absolute mass of a single injection of anhydrous NH3 in the field may be determined by direct calibration in the field or by a laboratory calibration and a calculated correction for temperature. The latter method appears to be more practical and involves no more error than that involved in a direct field calibration.

A procedure for sampling soil by taking successive hemispheres around the injection point was found to be satisfactory for characterizing NH3 concentrations and pH in the retention zone.
The Drying Through the Top Surface of a Vertical Porous Column
Authors: Heller J. P.
Published: July 2010

Microscopic and macroscopic descriptions are given of the process of drying from a long porous and permeable column, initially saturated fully with a liquid which wets its grains. A comparison is made with the process of drainage, and it is shown that the “first stage of drying” corresponds with the extension down into the pack of a saturation profile derived from the capillary pressure curve. In the second stage of drying this profile penetrates still deeper; its upper end coincides with a “bone dry front,” the progress of which down the pack is controlled by diffusion of vapor to the surface. Results of the analysis are compared to measurements of front position during the drying of unconsolidated fluorite packs.
Iron‐Rich Montmorillonite Formation in Soils Derived from Serpentinite
Authors: Wildman W. E. , Jackson M. L. , Whittig L. D.
Published: July 2010

Montmorillonite, identified by X‐ray diffraction, is the predominant clay mineral in the B horizons of four widely separated California soils (Henneke, Dubakella, and Fancher series and one from the New Idria area) derived from serpentinite. The < 0.2µ fractions contain respectively, 81, 68, 71, and 33% montmorillonite as determined by CEC determination. These fractions contain 57.5, 54.9, 62.5, and 50.0% SiO2; 17.2, 18.4, 17.6, and 7.5% combined Fe2O3 (by chemical analysis after removal of free Fe2O3); 7.2, 4.3, 8.7, and 25.0% MgO; and 4.3, 10.4, 1.0, and 6.1% Al2O3. Much of the MgO can be attributed to < 0.2µ serpentine minerals, identified by electron microscopy. The montmorillonite has a high content of Fe in octahedral position, represented by the range in octahedral sheet formula, Fe1.8–2.7Al0.2–1.8Mg0–1.1, calculated for the four soil clays. Mg is the predominant exchangeable cation in the < 2 mm soil (67–96% of the total exchangeable cations). The parent serpentinite contrasts with the soil clays in having lower SiO2 (43.3, 38.1, 40.0, and 39.8%) and Fe2O3 (6.6, 3.6, 8.9, and 3.1%, after magnetite removal from the parent rock samples), higher MgO (33.7, 41.0, 42.2, and 40.3%), and lower Al2O3 (0.4, 2.4, 1.5 and 0.7%). Leaching of serpentinite removed much of the Mg; concurrently Si, Fe, and Al were enriched in the pedogenic montmorillonite which formed.
Effect of Moisture Regimes and Harvests on Efficiency of Water Use by Ten Forage Crops
Authors: Powell R. D. , Kardos L. T.
Published: July 2010

The total amounts and rates of depletion of soil water required to produce dry matter by 10 crops were studied. Two experiments with forages were conducted, one being managed to simulate pasture and the other being managed for hay. Three levels of soil moisture management were used in each experiment: control (M0), irrigation when the available soil water at the 10 cm depth was 85% depleted (M1), and irrigation when available soil water at the 10 cm depth was 30% depleted (M2).

On the basis of total harvest for all the species, most efficient use of water occurred at the M0 irrigation level. Also, most efficient use of water occurred prior to the first harvest and least efficient use usually occurred during the period after the first harvest but prior to the second harvest. Ladino clover and ladino‐orchardgrass (Trifolium repens‐Dactylis glomerata) harvested to simulate pasture were less efficient in using water than the other forages which were managed for hay. Alfalfa swards (Medicago sativa) managed for hay were more efficient than the other swards and the legume‐grass combinations differed only slightly from legumes alone.

Measured values for rates of moisture depletion per day of all unirrigated forages were generally smaller than values computed by using the Blaney‐Criddle formula. The measured values of the irrigated forages approached the Blaney‐Criddle values more closely.
Effect of Initial Clod Size on Characteristics of Splash and Wash Erosion
Authors: Moldenhauer W. C. , Koswara Jajah
Published: July 2010

Wash erosion increased as initial clod size increased from 0.5–2 mm to 8–30 mm on a Marshall silty clay loam except in the case of clods from continuous bromegrass (Bromus inermis). Wash losses increased as size increased despite a drop in runoff from the 8–30‐mm clods. Final splash loss rates were higher from the 8–30‐mm than from the smaller size clods from continuous corn (Zea mays). Splashed material was larger than washed material and both were larger than material forming the seal.
A Machine for Taking Soil Samples and Placing Access Tubes for Soil Moisture and Density Measurements
Authors: Hipp Billy , Gerard C. J. , Edwards B.
Published: July 2010

The Bull hydraulic sampler has been mounted to provide greater mobility in soil sampling and can also be used for placing neutron probe access tubes.
A Welding Technique for Peltier Thermocouple Psychrometers
Authors: Campbell G. S. , Trull J. W. , Gardner W. H.
Published: July 2010

A welding technique is described for making improved themocouples for use in Peltier‐type thermocouple psychrometers. Junctions welded using this technique are compared with a commercial welded thermocouple and soldered thermocouples. Thermocouples produced (i) are more stable than soldered junctions, (ii) have greater range and sensitivity than available commercial welded thermocouples, and (iii) are more uniform in response than soldered junctions.
The Effect of Osmotic Pressure Gradients on Water Movement in Unsaturated Soil
Authors: Letey J. , Kemper W. D. , Noonan L.
Published: July 2010

Water movement, in response to osmotic pressure gradients, was measured in clay loam and sandy loam soils at soil water suctions from 0.08 to 15 bars. Movement in response to osmotic pressure gradients were compared to movement in response to hydraulic pressure gradients in the soil water suction range from 0.08 to 0.65 bars. At suction less than 0.5 bars, the amount of water moved by osmotic pressure gradients was generally less than 4% of the water moved by hydraulic gradients of equal magnitude.
Analyzing Steady‐State Flow in an Inclined Soil Slab with an Electric Analog
Authors: Whisler F. D.
Published: July 2010

An electrical resistance network analog was used to analyze the steady‐state flow in sloping land modeled as an inclined soil slab for both saturated and unsaturated conditions. At saturation the equipotentials and surface fluxes are symmetrical about the vertical midplane of the slab and agree with an analytic solution. For “rainfall” rates lower than that necessary to saturate the slab, this symmetry is lost. For unsaturated flow a step function representation of the pressure head‐conductivity relationship gives comparable results to a more complicated function. As the angle of slope is increased, even though part of the slab may be unsaturated, the internal flow rate increases, especially at the lower outflow end of the slab. Although the results are presented for homogenous‐isotropic soils, they can be used for anisotropic soils by using a transformation process.
EDTA‐Ammonium Carbonate Soil Test for Zinc
Authors: Trierweiler J. F. , Lindsay W. L.
Published: July 2010

A soil test was developed for the diagnosis of Zn‐deficient soils. The test consists of shaking 10 g soil with 20 ml of extractant (pH 8.6) containing 0.01M EDTA (ethylenediaminetetraacetic acid) and 1M (NH4)2CO3. After 30‐min shaking period the suspension is filtered, and Zn is determined directly in the filtrate by means of atomic absorption spectrophotometry. The new soil test was evaluated on 42 Colorado neutral and high lime soils whose response to Zn was determined in the greenhouse with corn (Zea mays) as the test crop. A critical level of 1.4 ppm of extractable Zn separated the Zn‐deficient from the nondeficient soils. The new Zn soil test compares favorably with the dithizone method and is an improvement over the 0.1N HCl method. Unlike strong‐acid extractants, the new procedure suppresses the dissolution of carbonates and oxides, and thereby avoids extraction of occluded Zn.
Equilibrium Relationships of Zn2+, Fe3+, Ca2+, and H+ with EDTA and DTPA in Soils
Authors: Lindsay W. L. , Norvell W. A.
Published: July 2010

A general approach is developed by which the equilibria between chelating agents and metal ions in soils can be predicted from formation constants. Mole‐fraction diagrams are derived for EDTA (ethylenediaminetetraacetic acid) and DTPA (diethylenetriaminepentaacetic acid) in soils when the competing cations are either Fe3+, Ca2+, and H+, or Zn2+, Fe3+, Ca2+, and H+. These diagrams give the specific metal‐ligand complexes that form in soils and show how the concentration of each complex changes with pH. Evidence is presented to support the hypothesis that Zn reacts with amorphous SiO2 in soils to form ZnSiO3. The concentration of Zn2+ in equilibrium with solid phase ZnSiO3 and amorphous SiO2 is approximately 10‐6M at pH 6, and decreases 100‐fold for each unit increase in pH. This concentration of Zn2+ is approximately 100,000 times lower than that in equilibrium with ZnO or ZnCO3.
Iron Uptake Dependent upon Genotype of Corn
Authors: Brown J. C. , Bell W. D.
Published: July 2010

Genetic variants are responsible for a differential uptake of Fe by ys1 and Pa 54 corn (Zea mays). Different degrees of iron stress were developed in the plants by supplying them with increasing amounts of FeHEDTA. Iron stress enhanced Fe uptake more in Pa 54 than in ys1 corn. Enhanced Fe uptake was also associated with the ability of the plant to lower the pH of the nutrient solution, Pa 54 > ys1. Uptake of P was accentuated more in ys1 than Pa 54 by adding CaCO3, or by adding KCl instead of K2SO4 as a source of K to the nutrient solution. Phosphate reduced Fe uptake more in ys1 than in Pa 54, and increased the incidence of chlorosis in ys1.
Studies of Clay Skins in a Cecil (Typic Hapludult) Soil: II. Effect on Plant Growth and Nutrient Uptake
Authors: Khalifa E. M. , Buol S. W.
Published: July 2010

A greenhouse experiment was conducted to study the effect clay skins may have on plant growth and N, P, and K uptake. Wheat (Triticum vulgare, var. Wakeland) plants were grown in uncoated aggregates and in large and small clay skin‐coated peds from the B22t horizon of a Cecil (Typic Hapludult) soil for 4 weeks. Data obtained for dry weight and total N, P, and K content of the plants were statistically analyzed. Plants grown in the uncoated aggregates had higher dry weights and more total N, P, and K than those grown in either the large or small coated peds. Most of the plant roots grew outside of the coated peds with a concentration of fine roots on the surface of the clay skin. It is hypothesized that the clay skins reduced plant growth and nutrient uptake (especially P and K) either by serving as a barrier for root growth and/or by slowing ion diffusion from the soil peds into the inter‐ped soil solution.
Clay Mineralogy of Soils Formed on Mazama Pumice
Authors: Chichester F. W. , Youngberg C. T. , Harward M. E.
Published: July 2010

Amorphous components predominated in the clay size fraction of samples taken across a climatic transect of soils from Mazama pumice in central Oregon. The amounts were greatest in the less intensely weathered horizons, i.e., in lower horizons and at drier sites of the transect. Crystalline minerals were present in relatively small percentages and were unexpectedly complex. The phyllosilicates included beidellite, montmorillonite, vermiculite, a micaceous component, chloritic intergrades, and chlorite. Non‐phyllosilicate minerals of the suite were gibbsite, plagioclase feldspars, and quartz. The amount and distribution of the individual clay size minerals varied within and between profiles.

Results of clay mineral identification were evaluated with respect to environmental data available for the transect sites. The factors primarily controlling the processes responsible for 2:1 clay mineral genesis were hypothesized to be the vesicular structure and chemical composition of the pumice material. Other factors such as climate and vegetation were believed to govern local weathering intensity.
The Role of Vertic Subgroups in the Comprehensive Soil Classification System
Authors: DeMent James A. , Bartelli Lindo J.
Published: July 2010

The application of soil surveys to nonfarm as well as to farm uses is reflected in recent modifications of the Comprehensive Soil Classification System. A case in point is the creation of vertic subgroups. Soils of vertic subgroups fail Vertisols primarily because they lack gilgai relief, intersecting slickensides, and parallelepiped structural aggregates. However, in having cracking properties peculiar to Vertisols, they are inappropriate to typic subgroups of other soil orders. Data from selected soils indicate that the cracking properties are related primarily to mineralogy and clay content. Soils dominated by montmorillonitic clay and having a clay content exceeding 40% are most common to the vertic subgroups. In addition, these soils most commonly have a Unified Soil Classification of CH or MH. They have unstable behavior with regard to engineering structures and are referred to by engineers as having a high content of “fat” clays. The Comprehensive Soil Classification System allows discussion of this unique group of soils at the subgroup level.
Relation of Soil Properties to its Erodibility
Authors: Wischmeier W. H. , Mannering J. V.
Published: July 2010

A soil's inherent erodibility, which is a major factor in erosion prediction and land‐use planning, is a complex property dependent both on its infiltration capacity and on its capacity to resist detachment and transport by rainfall and runoff. The relations of these capacities to soil physical and chemical properties were investigated in a 5‐year field, laboratory, and statistical study including 55 selected Corn Belt soils. Properties that contributed significantly to soil‐loss variance included percentages of sand, silt, clay, and organic matter; pH, structure and bulk density of plow layer and subsoil; steepness and concavity or convexity of slope; pore space filled by air; residual effects of sod crops; aggregation; parent material; and various interactions of these variables. An empirical equation was derived for calculating the universal soil‐loss equation's erodibility factor K for specific soils. Tests of the equation against soils of the older erosion‐research stations, for which the erodibility factor is known, substantiated its general applicability over a broad range of medium‐textured soils.
Weight and Nitrogen, Phosphorus, Potassium, and Calcium Content of Forest Floor Humus of Lodgepole Pine Stands in Colorado
Authors: Moir W. H. , Grier H.
Published: July 2010

The pine‐derived organic matter of the forest floor was sampled by horizon from eight Pinus contorta stands of contrasting densities, site indices, average dbh, and stand height. Tabular data are given for loss‐on‐ignition, mineral and ash content, and N, P, K, and Ca content of these horizons. Total quantities of forest floor humus ranged from 2.54 to 4.21 kg/m2 irrespective of stand density. Expressed as g/m2 the N content of the forest floor humus ranged from 31–54, P from 2–5, K from 7–17, and Ca from 10–25. The proportion of N increased with progressive decomposition of organic material. The most mobile nutrients, K and P, were generally most concentrated in the lowest of the four forest floor humus horizons whereas Ca concentrations differed little among each of the horizons.