bluuebunny/crossref_metadata_2025 huggingface dataset:
Natric Horizons on Some Erosional Landscapes in Northwestern South Dakota
Authors: Johnson W. F. , Mausbach M. J. , Gamble E. E. , Nelson R. E.
Published: July 2010

Soils with natric horizons, associated slickspots, and soils with argillic horizons were sampled to study landscape relationships. These soils occur in microtopographic sequences that recur in spacings of 15 m or more. At two sites soils were sampled from trenches that transected the microtopographic sequence. At each site soils had a continuous argillic/natric horizon that was exposed at the surface in slickspots. Slickspots have an upslope scarp and appear to be dynamic erosion surfaces that migrate upslope. Salt content in and below the argillic horizon was highest in the slickspot and in pedons closest to the slickspot and decreased with distance outward from the slickspot. Content of soluble salt also appears to vary in the parent rock. It is suggested that lateral movement of salts and content of salt in the parent material are important in formation of the soils and that salts may be redistributed by the movement of the slickspots.
Effects of Subsoiling and Irrigation on Corn Production
Authors: Cassel D. K. , Edwards E. C.
Published: July 2010

Deep tillage and irrigation are two soil management techniques that have been used separately to alleviate water shortages for crops growing on soils having root restricting tillage pans. The purpose of this study was to evaluate the effects of in‐row‐subsoiling (S), irrigation (I), and in‐row‐subsoiling plus irrigation on corn (Zea mays L.) production on Wagram soil (fine‐loamy, siliceous, thermic Arenic Paleudults) having a dense tillage pan. Main plot treatments were: CD (conventional tillage [double disking], dryland); CI (conventional tillage, irrigated when soil water pressure [SWP] at the 0.25‐m depth reached −40 kPa); SD (in‐row‐subsoiled and bedded, dryland); and SI (in‐row‐subsoiled and bedded, irrigation when SWP < −40 kPa at 0.30‐m depth). Total growing season precipitation in 1979, although poorly distributed, was near normal; 1980 and 1981 were both drought years. The 3‐yr mean amounts of irrigation water applied were 179 mm for the CI and 145 mm for the SI treatments. The CI, SD, and SI treatments always had significantly higher yields of grain and stover and lower numbers of barren plants compared to treatment CD. Maximum corn height was greatest (2.68 m) for treatment SI and leaf area indices for treatments CI, SD, and SI were 23, 28, and 36% greater, respectively, than the 2.56 value for CD. Mean grain yields for treatments CI, SD, and SI were 215, 197, and 277% greater, respectively, than the 2.58 Mg ha−1 CD yield. Root length and root mass in the 0.1 to 0.6‐m soil depth were greater for the dryland treatments. Apparent irrigation water use efficiencies were 0.031 and 0.014 Mg ha−1 mm−1 for treatments CI and SI, respectively. Estimates of subsoil water utilization using neutron attenuation and tensiometer data were 50 mm yr−1 which resulted in an apparent subsoil water use efficiency of 0.10 Mg ha−1 mm−1.
A Modified Miscible Displacement Technique for Investigating Adsorption‐desorption Kinetics in Soils
Authors: Carski T. H. , Sparks D. L.
Published: July 2010

The use of miscible displacement techniques to study kinetics of ion exchange in clay minerals and soils is increasing. Although only 1 g or less of adsorbent is often used, some of the adsorbate solution will always be retained by the adsorbent. The dilution of the incoming solution by the retained solution is easily mistaken for either adsorption or desorption, resulting in an overestimation of either process. A device that ensures constant dilution volumes, regardless of adsorbent, was developed to differentiate the adsorption‐desorption process from the dilution process.
Plant Response to Mycorrhizal Fungi: Host, Endophyte, and Soil Effects
Authors: Bethlenfalvay Gabor J. , Ulrich Jane M. , Brown Milford S.
Published: July 2010

Interactions and growth responses in soybean [Glycine max (L.) Merr.] and sorghum [Sorghum bicolor (L.) Moench] colonized by the vesicular‐arbuscular mycorrhizal (VAM) fungi [Glomus fasciculatum (Thaxt. sensu Gerd.) Gerd. and Trappe] or [Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe] as grown in three northern California soil types were investigated in a 2 by 2 by 3 factorial experiment. Growth and development of both symbiotic partners were significantly influenced by all three factors (host plant, endophyte, soil). Growth responses to VAM‐fungal colonization varied with soil type from −10 to 400%. Phosphorus concentrations increased significantly in all soybean and some sorghum plants relative to non‐VAM controls as a result of VAM‐fungal colonization. Shoot dry matter as percent of fresh weight increased significantly in only those VAM plants which had also experienced a significant growth enhancement. Root/shoot ratios of most VAM plants were lower than those of the controls. Changes in root/shoot ratios were inversely related to changes in dry weight. The results show that soil type, as well as the host‐endophyte combination, is a significant factor in modifying the VAM growth effect independently of mineral nutrient availability.
Synthesis and Characterization of Lansfordite and Nesquehonite
Authors: Ming Douglas W. , Franklin William T.
Published: July 2010

Chemically pure lansfordite (MgCO3·5H2O) and nesquehonite (MgCO3·3H2O) were synthesized from CO2‐saturated Mg(HCO3)2 solutions by degasation with air for varying periods of time depending upon equilibration temperature. Crystalline and chemical properties of the synthesized minerals were determined and the results were compared with the properties reported for geologic specimen minerals. Crystalline data determined for synthesized lansfordite are: monoclinic; a = 1.249 nm, b = 0.762 nm, c = 0.743 nm, β = 1.785 ± 0.002 rad, a/b/c = 1.638:1:0.976, Z = 4. Nesquehonite is monoclinic (pseudo‐orthorhombic); a = 1.199 nm, b = 0.769 nm, c = 0.537 nm, β = 1.573 ± 0.012 rad, a/b/c = 1.557:1:0.697, Z = 4. Lansfordite is unstable when exposed to the atmosphere at temperatures > 10°C. Large lansfordite crystals (>150 µm) were observed with scanning electron microscopy (SEM) to undergo dehydration above 10°C. X‐ray diffraction data and SEM observations indicate that upon dehydration large lansfordite crystals convert to nesquehonite but remain pseudomorphic after lansfordite. Small lansfordite crystals (<20 µm) appeared to dissolve upon an increase in temperature above 10°C when viewed with SEM. Crystal forms of nesquehonite, lansfordite, and dehydration states of lansfordite are shown in SEM microphotographs.
A Pneumatic Fracture Method for Measuring the Tensile Strength of Unsaturated Soils
Authors: Snyder V. A. , Miller R. D.
Published: July 2010

A new technique for measuring tensile strength of unsaturated soils is discussed, wherein applied stress, pore‐air pressure, and pore‐water pressure can be simultaneously and independently controlled. The method essentially involves enclosing the test sample in an adhesive membrane which is impervious to air, and then decreasing the external applied stress relative to the pore‐air pressure until the sample ruptures or literally explodes due to the pressure difference across the adhesive membrane. Applied stress is hydrostatic, eliminating the need for knowing sample dimensions and ensuring the absence of unwanted bending moments which are a common source of error in most direct tension procedures. The system is designed in such a way that sample equilibration and tensile strength measurements are carried out in the same apparatus, avoiding dangers associated with the transfer of very weak samples from one apparatus to another. The method is shown to produce comparable results to those obtained by a direct tension procedure.
Lanthanide Solid Phase Speciation
Authors: Essington M. E. , Mattigod S. V.
Published: July 2010

The solid phase speciation of La, Ce, and Nd in the Ln2O3‐CaO‐SO4‐PO4‐F‐O2‐CO2‐H2O (where Ln = La, Ce, and Nd) equilibrium system were evaluated using three‐dimensional activity diagrams. Diagrams were constructed from thermodynamic data and interpreted with a knowledge of the ligands associated with La, Ce, and Nd in sewage sludge and sludge‐amended soil particles as characterized by scanning electron microscopy. Throughout a wide range of equilibrium conditions at 298.15 K and 0.101 MPa, the activities of dissolved lanthanides were controlled by a small number of solid phases. These solids were cerianite [CeO2], lanthanite [La2(CO3)3·8H2O] and Nd‐lanthanite [Nd2(CO3)3·8H2O], and La and Nd sulfates [(La,Nd)2(SO4)3·8H2O] in the presence of gypsum. In general, the stable lanthanide solid phases predicted from the thermochemical evaluation were consistent with those directly observed in chemically well‐defined sewage sludge and sludge‐amended soil; thus, illustrating the applicability of such an evaluation when applied to well characterized environments.
Optimizing Phosphorus Fertilization Rates for Soybeans Grown on Oxisols and Associated Entisols
Authors: Lins I. D. G. , Cox F. R. , Nicholaides J. J.
Published: July 2010

Although soils vary considerably in their P sorption characteristics, this factor is often not considered in a soil test interpretation. One soil property closely related to P sorption is clay content. Residual P studies were conducted for 4 yr on three tropical soils of similar clay mineralogy, two Oxisols of 63 and 27% clay, and a Quartzipsamment of 12% clay. The Mehlich 1 (1:10) extractable P level was described as a function of time, initial soil P level, and P fertilization rate. One crop of soybeans [Glycine max (L.) Merr.] was grown each year and the yield related to extractable P, which, in turn, was related to the initial P soil level and P fertilization rate for a period of 1 yr. Based on a soybean price of $0.23/kg and a fertilizer P price of $1.23/kg, rates of P were calculated for each of the three soils that would maximize net returns for various initial levels of extractable P. As these rates differed markedly with clay content, a soil test interpretation was created by multiple regression based upon both Mehlich 1 extractable P concentration and clay percentage to predict a recommended rate of fertilizer phosphorus (R) as follows: R = 80 − 2.57(soil P) + 0.01386(clay)2 − 0.003281(soil P)(clay2). This function should be applicable to many soils with similar clay characteristics.
Effect of Clay Content in Soil on Boron Uptake and Yield of Wheat
Authors: Keren R. , Bingham F. T. , Rhoades J. D.
Published: July 2010

The effect of total B content in soil on B uptake by wheat (Triticum aestivum L.) and its effects on yield were studied for three soil‐sand mixtures at soil‐to‐soil + sand ratios of 1:3, 2:3, and 1. The results indicate that the higher the clay content of a soil, the lower is the B activity in solution for any given amount of B added. It was suggested that the soil adsorption sites act as a pool to which B can be stored or removed depending on the change in solution B concentration in soil. The B uptake by the plants is higher as the sand content increases, for any total amount of B added. However, the experimental results from all three soil‐sand mixtures lie on the same line when the B content in the shoot is plotted against B activity in soil solution (r2 = 0.9695). The dry matter of the plants was decreased with both an increase in total amount of B added and an increase in the sand content for any given amount of total B. As found for B uptake, the relative dry matter weight and the relative yield values lie on the same linear line when they are plotted against B activity in soil solution from all three soil systems. This indicates that the yield responds to B activity in soil solution only.
Late Season Heat Flux and Water Distribution in Summer‐fallowed Haploxerolls
Authors: Pikul J. L. , Allmaras R. R. , Waldman S.E.
Published: July 2010

The depth position and supply of water are especially critical soil management goals for fall‐sown crops in a semiarid climate such as the Pacific Northwest of the USA where precipitation during late summer and early fall is not a reliable source of water for germination. Soil heat flux and water distribution were measured from 1 August to 1 November in a summer‐fallowed soil which was cultivated several times with a rodweeder to create a loose soil mulch layer. Soil heat flux in the top 60 cm was measured using a combination of the temperature gradient method at 35 cm and calorimetry to obtain the flux at 1 cm. Daily soil heat energy at the 1‐cm depth ranged from 710 kJ/m2 on 2 August during clear weather (and with a dry soil mulch) to − 300 kJ/m2 on 3 October, a clear day following a 30 mm rain. An additional daily heat energy of about 1000 kJ/m2 was used on 2 August to evaporate 0.42 mm of water; on 3 October, the estimated additional daily heat energy to evaporate 0.98 mm of water was 2400 kJ/m2. Soil water evaporation was measured during a wet and dry late summer season when the 0‐ to 9‐cm mulch layer had respective average water contents of 0.15 and 0.05 cm3/cm3. Evaporation rates for comparable time periods during the dry year were generally one‐third of the evaporation rate measured during the wet year. Light rain during late summer and early fall did not add significantly to stored soil water, because recharge and evaporation occurred mainly above the seedzone depth. Soil water evaporation rate during the wet year did not change appreciably from early September to early October even though potential evaporation declined 40%; this comparison period had similar rainfall amounts and antecedent soil moisture. When there were no late season rains to consolidate the mulch layer, the evaporation rate during September and October ranged near 0.15 mm/d. Soil water conservation benefits of the soil mulch disappear following rains that consolidate the mulch layer.
Surface Soil Removal and Herbicide Treatment: Effects on Soil Properties and Loblolly Pine Early Growth
Authors: Tuttle C. L. , Golden M. S. , Meldahl R. S.
Published: July 2010

Neither soil removal nor herbicide treatment alone significantly increased loblolly pine (Pinus taeda L.) seedling height after 3 yr, although in combination they did increase height. Soil removal and herbicide treatments produced significantly higher 3‐yr volumes, apparently due to nonpine plant competition reduction. Removal of 2.54 or 7.62 cm of surface soil resulted in significant decreases in Ca, K, Mn, P, N, and organic matter in the surface 30 cm after three seasons. Mobile nutrients (Ca, Mg, and K) were also apparently leaching through the surface layers on the removal treatments. Surface soil bulk density was increased by soil removal. Soil nutrient concentrations decreased and bulk densities increased as the quantity of soil removed increased. The degree of nutrient and organic matter reductions imply that the total site potential may have been lowered, particularly on the heavy soil removal treatment.
Extractable Soil Nitrogen Following Clear‐cutting and Burning in a Beech Forest
Authors: Phillips M. J. , Goh K. M.
Published: July 2010

Nitrogen (N) mineralization was monitored in the humus layer and soil in an undisturbed and harvested beech (Nothofagus) spp. forest in the West Coast of the South Island of New Zealand. To assess the effects of different harvesting regimes and intensities of burning on N mineralization, treatments applied were (i) Podocarpus spp. clear‐cutting; (ii) Podocarpus spp. clear‐cutting and prescribed burning; (iii) harvesting to chipwood standard (10‐cm dbh); and (iv) chipwood logging and prescribed burning. Nitrate was found to be negligible in fresh and field‐incubated humus and soil samples in the undisturbed beech forest. Ammonium predominated in both the humus layer and soil. Clear‐cutting, and clear‐cutting and burning increased NH+4‐N. The burning effect was confined mainly to the humus layer.
Sampling Ports for An Instrumented Lysimeter System
Authors: Robbins C. W.
Published: July 2010

An improved method for mounting ceramic‐moisture sampling cups and soil‐atmosphere sampling tubes in lysimeters is described. The 0.31‐m diam by 1.18‐m deep lysimeters were constructed from low pressure polyvinyl chloride irrigation pipe (PVC) and contained soil 1.0‐m deep. Tensiometer tubes with attached cups, and open‐ended pyrex gas sampling tubes were installed at three depths, using sealing ports in the lysimeter walls. The sealing ports were constructed from half of a PVC pipe compression coupler. This system allows for inserting the sampling cups and tubes after the soil has been added and settled. The sampling equipment can also be removed before the soil is sampled and removed when studies are completed. Individual sampling units can also be removed for cleaning or repair during the study without disrupting lysimeter operation. This was not possible with earlier described lysimeter systems.
Calibrating Ground Penetrating Radar Data for Soil Applications
Authors: Zobeck T. M. , Lyon J. G. , Mapes D. R. , Ritchie A.
Published: July 2010

A ground penetrating radar system (GPR) was tested in two soils to determine the accuracy of GPR measurements and to demonstrate a simple technique to calibrate the instrument. The GPR was used to identify a buried auger in a relatively dry loamy‐skeletal and a relatively moist fine‐silty soil. Radar measurements, on the average, were within 3 cm of the actual depths measured in adjacent soil pits.
Evaluation of a Field Method for Determining the Gas Diffusion Coefficient in Soils
Authors: Jellick G. J. , Schnabel R. R.
Published: July 2010

An in situ method, based on spherical diffusion of gas from an injection point, was evaluated for determining the diffusion coefficient of N2O in field soils. It was found that the analytical solution for spherical diffusion used previously with this method assumes unrealistic initial conditions to calculate concentration of gas at the injection point with time. A finite‐difference model was developed that incorporated initial conditions based on experimental data. Concentrations predicted by the model matched measured concentrations of N2O more closely than concentrations predicted by the analytical solution as determined by the mean absolute difference between predicted and measured concentrations. Mean absolute differences using the numerical model avg 2.4% as compared to 5.2% using the analytical model. Diffusion coefficients determined with the method were reproducible and compared well with those determined by a common laboratory core technique using sand and undisturbed soil cores. The in situ method is a rapid, nondistructive procedure for the determination of gas diffusion coefficients. The method gives reproducible results and is especially useful when many data are needed to determine the spatial or temporal variability of diffusion coefficients in the field.
Ammonia Volatilization from Nitrogen Sources Applied to Rice Fields: II. Floodwater Properties and Submerged Photosynthetic Biomass
Authors: Fillery I. R. P. , Roger P. A. , De Datta S. K.
Published: July 2010

The effects of (NH4)2SO4, urea, and urea amended with the urease inhibitor, phenyl phosphorodiamidate (PPD), on floodwater properties were studied concurrently as part of a field NH3 volatilization study. In the (NH4)2SO4 treatment the maximum concentration of ammoniacal‐N in the floodwater (≃ 50 g N m−3) occurred immediately after its application to the floodwater. Thereafter, floodwater ammoniacal‐N concentrations declined rapidly and were negligible 6 d after the application of (NH4)2SO4. Ammoniacal‐N concentrations in the urea treatment reached maxima of ≃ 12 g N m−3, 3 to 5 d after urea was applied and then declined steadily to negligible concentrations in 7 d. Application of PPD (1% wt/wt) along with urea delayed the buildup of ammoniacal‐N in floodwater until 5 to 7 d after N was applied although the maximum ammoniacal‐N concentration in the floodwater was comparable to that obtained in the urea treatment. Floodwater pH displayed a marked diurnal pattern throughout the experiment in the urea‐amended and background fields. In contrast, pH in the floodwater in the (NH4)2SO4‐amended field was buffered at ≃ 8.00 for the first 2 d, probably because high concentrations of NH4HCO3 formed in floodwater. Diurnal fluctuations in pH prevailed after 3 d when ammoniacal‐N concentrations had declined substantially. The partial pressures of NH3 (pNH3) in the floodwater in all treatments were synchronized with diurnal temperature and pH changes in the floodwater. The maximum pNH3 in floodwater was similar in both the (NH4)2SO4‐ and urea‐amended fields even though ammoniacal‐N concentrations were initially significantly higher in the former. Total titratable alkalinity in floodwater increased after urea and urea/PPD were applied but declined following the application of (NH4)2SO4. The initial levels of alkalinity in floodwater were double the content of alkalinity in irrigation water, and it is surmised that evaporation and/or respiration contributed significantly to alkalinity in the floodwater. Enumerations of algae present in the flooded soil showed the biomass to be small and dominated by non‐N2‐fixing blue‐green algae (Syanophyceae). This biomass, however, was associated with marked diurnal fluctuations in floodwater pH, which coupled with the accumulated alkalinity, were the major factors contributing to the rapid NH3 loss following the application of (NH4)2SO4 and urea to the floodwater.
Nitrogen Release from Urea and Sulfur‐coated Urea in Jack Pine Forest Humus
Authors: Foster N. W. , Beauchamp E. G.
Published: July 2010

Urea and sulfur‐coated urea (SU) were each applied in the spring at a rate equivalent to 200 kg N ha−1 to a separate set of replicated 1‐m2 plots in a 50‐yr‐old boreal jack pine (Pinus banksiana Lamb.) forest. Fertilizer N recovery in L, F, and H horizons was determined periodically over 4 yr. Urea was completely hydrolyzed in soil within 10 d, whereas incompletely dissolved SU pellets, containing N equivalent to approximately 10% of the amount added, were recovered from the humus horizons 447 d after fertilization. In urea‐treated humus, NH+4‐N concentrations significantly greater than those in controls were observed for 57 d. In SU‐treated humus, NH+4‐N concentrations significantly greater than those in a control were maintained for 477, 336, and 115 d in L, F, and H horizons, respectively. Initial (3 d) NH3 volatilization from SU‐treated soil was only 17% of that observed in the urea treatment, presumably because slower release from SU granules resulted in lowere initial pH increases in L and F horizons.
Laboratory Apparatus for Preparing and Dispensing Nitrogen‐15‐labeled Anhydrous Ammonia
Authors: Norman R. J. , Kurtz L. T.
Published: July 2010

An apparatus and a procedure are described for preparing liquid anhydrous NH3 (LAA) of a desired 15N concentration and a cold‐jacketed syringe for dispensing the LAA. Preparation of LAA was accomplished by reacting 15N‐labeled (NH4)2SO4 (30‐50 atom % 15N) with a 2 M NaOH solution and allowing the resultant 15N‐labeled NH3 gas to mix with reagent grade anhydrous NH3 gas dispensed from a lecture bottle (38.5‐ by 5.1‐cm cylinder). The resulting gas mixture was condensed and drained into a collection vessel from which it could be withdrawn, measured, and dispensed with specially built cold‐jacketed syringes. With the apparatus and procedure described here, 10 mL of LAA containing 0.7 to 2.0 atom % 15N can be prepared and applied quantitatively in amounts ranging from 25 (15.21 mg NH3‐N) to 500 µL (296.98 mg NH3‐N). A detailed description of how to construct and operate the 15N‐labeled LAA preparation apparatus and dispensing syringes are discussed.
A Stainless‐Steel Soil Solution Sampler for Monitoring Pesticides in the Vadose Zone
Authors: Smith C. N. , Carsel R. F.
Published: July 2010

A design for an in situ soil solution sampler (suction lysimeter), consisting of a stainless steel tube with a 0.1 MPa (−1.0 bar), high‐flow, porous ceramic cup, is presented for use in monitoring pesticide or other dissolved chemical leaching in the vadose (unsaturated) zone. The sampler is of one piece construction with the porous ceramic cup attached by epoxy adhesive. The design permits collection of a total volume of up to 0.5 L of soil solution per sample. Laboratory studies indicated that pesticide sorption on the sampler was insignificant and no analytical interference problems were observed. The samplers were designed to monitor leaching of pesticides and inorganic tracers in an on‐going field study in southwest Georgia. Successful field performance of 60 installed samplers (depths of 1.5, 2.1, and 2.7 m) was demonstrated during the 1984 cropping year. Soil solution sample volumes of 10 to 500 mL were obtained during one 24‐h sampling period with vacuums of 0.015 and 0.020 MPa.
Characterization of Compacted Soil Using Sorptivity Measurements
Authors: Walker Jon , Chong S. K.
Published: July 2010

Research was conducted on reconstructed soil cores compacted at varying levels of water content and static pressure. The pressure levels were chosen in an effort to simulate the static conditions that might occur during field cultivation and forest logging operations. Sorptivity, So, and void ratio, e, were measured from the soil cores. The statistical analysis showed that both sorptivity and void ratio showed similar responses to different degrees of soil compaction and there was a correlation coefficient of 0.89 between So and e. The result also showed that sorptivity was more sensitive to the change in soil structure than in soil‐water content.
Models for Predicting Potentially Mineralizable Nitrogen and Decomposition Rate Constants
Authors: Deans J. R. , Molina J. A. E. , Clapp C. E.
Published: July 2010

Two equations, a single exponential: Nt = No (1 − e‐kt) and a double exponential: Nt = No S (1 − e‐kt) + No (1 − S)(1 − e‐kt), were used to compare mineralization potentials of soils, where Nt is the N mineralized in time (t), No is the potentially mineralizable N, and S and (1 − S) are the fractions of the labile and recalcitrant organic N compounds decomposing at specific rates h and k, respectively. Data were obtained from the published and unpublished incubation studies of Stanford and Smith (MD), Smith et al. (WA), Deans et al. (MN), El‐Haris et al. (US), and Griffin and Laine (CT). The double exponential equation provided the “best fit” of the N mineralization‐time (Nt/t) curve as determined by the estimated mean square error (MSE). With long‐term (>84 d) incubations, Nt/t curves for the double exponential equation resulted in an avg MSE of 6 compared with the single exponential equation (avg MSE of 79) for CT, MN, and MD data sets (n = 20). For short‐term (≤84 d) incubations, Nt/t curves were better estimated by the double exponential (avg MSE = 4, n = 21) than by the single exponential (avg MSE = 12, n = 13) for WA, US, and MN data.
Soil Sorting by Forty‐five Years of Wind Erosion on a Southern New Mexico Range
Authors: Hennessy J. T. , Kies B. , Gibbens R. P. , Tromble J. M.
Published: July 2010

This paper presents the fractional composition of soil lost from wind erosion for a 45‐yr period on mesquite sand dune rangeland in south‐central New Mexico. In addition, an equation was developed for defining the soil loss by particle size. Three arbitrarily chosen groups (deposition, noneroded, and eroded) were used to categorize the sampling locations. Net soil loss was in excess of 4.6 cm/ha. Maximum deposition was 78.6 cm and maximum erosion was in excess of 61.9 cm. The sand fraction was divided into three particle size classes. There was a significantly greater amount of the 0.5‐ to 0.05‐mm sand fraction in the deposition site than in either the eroded or non‐eroded sites. No net loss of sand from the experimental site was measured. The silt fraction was significantly greater in the noneroded and eroded sites than in the deposition site, indicating removal of the silt fraction by wind erosion. Wind erosion occurring on the site is resulting in a more sandy textured soil.
Development of Particle‐size Distributions in Some Alfisols of Southeastern Australia
Authors: Walker P. H. , Chittleborough D. J.
Published: July 2010

Particle‐size distributions of 20 soils in southeastern Australia were studied to determine whether Alfisols had consistent characteristics, and to examine the changes in clay and nonclay fractions with soil age. Particle‐size intervals, based on the logarithmic phiscale, were chosen to give adequate details of size distributions. The A horizons of three Alfisols with strong textural contrast from erosional and depositional landscapes (group I) had essentially one size mode in the nonclay range. The Bt horizons had bimodal particlesize distributions with a strong mode in the 0.06‐ to 0.12‐ or 0.12‐ to 0.24‐µm size classes and another in the nonclay range. Other subsoil horizons were less clearly bimodal. Seventeen soils from four river terrace sequences (group II) ranged from unmodified alluvium of valley floors (Fluvents) to soils with strong textural contrast (Us‐talfs) on Pleistocene terraces. The A horizons of these soils generally had one particle‐size mode in the nonclay range. With increasing soil age and textural differentiation, the particle‐size distributions of B horizons were more strongly bimodal with clay‐size populations similar to the Bt horizons of soils in group I. Only one clay‐size population occurred in Bt horizons with an upper size limit close to 2 µm. Although enriched, the fine clay fraction (<0.2 µm) was not identified as a size population separate from coarse clay (0.2‐2 µm). Development of Bt horizons is envisaged here as progressing from an initial translocation of the clay inherited from parent materials to intensive weathering and size reduction of clay particles in response to strong seasonal fluctuations in soil moisture.
Wheat Residue Loss for Chemical and Stubble‐mulch Fallow
Authors: Tanaka D. L.
Published: July 2010

Surface placement of wheat (Triticum aestivum L.) residue can be an effective practical method for erosion control in the semiarid Plains. Therefore, a study was conducted to determine the effect of chemical and stubble‐mulch fallow on residue orientation and decomposition, N and P concentrations, C/N ratios, and to compare straw weight per unit length and stalk population of standing winter wheat residue on chemical fallow plots to that of spring wheat. the study was conducted on a Williams loam (fine‐loamy, mixed Typic Argiborolls) in eastern Montana. Chemical fallow plots were sprayed four times, whereas stubble‐mulch fallow plots were tilled with sweeps, followed by three additional tillage operations with a rod weeder to control weeds. Residue samples were collected and analyzed periodically during 426‐d (14 months) winter wheat fallow and 638‐d (21 months) spring wheat fallow periods. Quantities of winter and spring wheat surface residue on stubble mulch plots decreased 70% from May through July of the year following harvest, while on chemical fallow plots, standing residue decreased and flat residue increased at constant rates. Chemical fallow plots had three times more surface residue for erosion control after 426‐ and 638‐d of fallow than stubble‐mulch fallow plots. About 27 and 8% of the initial winter and spring wheat total residue, respectively, were standing at the end of fallow on chemically fallowed plots. Nitrogen concentration was about 1.3 times greater, and P concentration two times greater for flat residue, than for standing residue.
Debris Avalanching in the Southern Appalachians: An Influence on Forest Soil Formation
Authors: Neary D. G. , Swift L. W. , Manning D. M. , Burns R. G.
Published: July 2010

In early November 1977, a storm system that formed in the Gulf of Mexico moved northeast into the Appalachian Mountains of North Carolina. It produced intense (30–120 mm h−1), heavy rainfall (200–320 mm), which triggered debris avalanching in steep terrain of the Pisgah National Forest. Soil material displaced by the mass wasting was in the order of 2 to 3 × 103 ha−1 along avalanche tracks, which exceeded 1 km in length. Peak stormflows had recurrence intervals ranging from 20 to >100 yr. Factors prominent in development of the storm were evaluated using infrared satellite imagery and rain gauge data. Most debris avalanches on one well‐documented basin originated in shallow Umbric and Typic Dystrochrepts soils on upper slopes and ran out onto Typic Haplumbrepts, Typic Hapludults, and Typic Fluvaquentic Dystrochrepts soils in lower gradient deposition zones. Although debris avalanching in the Appalachian Mountains is a rare phenomenon in human history (100–1000+ yr return period), it is a major and frequent geomorphic process influencing soil formation.
Long‐term Effects of Mesquite Removal on Soil Characteristics: II. Nutrient Availability
Authors: Klemmedson J. O. , Tiedemann A. R.
Published: July 2010

Previously we reported differences in nutrient availability of desert grassland soils under mesquite [Prosopis juliflora (Schwartz) DC] trees and adjacent open areas. In a related study conducted at that same time (1967), several mesquite trees were removed to measure shading effects. Since then about half of the harvested trees have sprouted and regrown. Now after 13 yr, we report the long‐term effects of mesquite removal on nutrient availability of these soils. In a greenhouse pot test, dry weight yield of shoots plus roots of Arizona cottontop [Digitaria californica (Benth.) Chase] and barley (Hordeum vulgare L. var. gustoe) was used to measure availability of nutrients. Variables in the pot test were mesquite history (mesquite intact, mesquite removed‐sprouted, mesquite removed), location (canopy, open), and nutrients (N, P, S, K). In the analysis of variance, the main effects and all interactions were significant. Yield responses confirmed results of our earlier study that nutrient availability of mesquite canopy soils was significantly greater than that of adjacent open areas. Removal of mesquite resulted in a significant decline in nutrient availability. For sites where mesquite had been removed but then sprouted and regrew, nutrient availability of soils was intermediate between that of mesquite‐intact and mesquite‐removed sites. Removal of mesquite resulted in a large decline in available soil N; smaller losses of available P, K, and S were noted.
Solubility of Aluminum Fluoride, Fluorite, and Fluorophlogopite Minerals in Soils
Authors: Elrashidi M. A. , Lindsay W. L.
Published: July 2010

The solubilities of AlF3(c), CaF2 (fluorite), and KMg3AlSi3O10F2 (fluorophlogopite) were investigated. Equilibrium was approached from both undersaturated and supersaturated conditions. The average equilibrium constant (K°) determined was 10−17.37 for AlF3(c), 10−10.3 for CaF2, and 107.94 for KMg3AlSi3O10F2. Nine soil samples each of strongly acid, slightly acid, and alkaline soils were used for AlF3(c), CaF2, and KMg3AlSi3O10F2 studies, respectively. The 1:5 soil/water suspensions, with and without added mineral, were shaken for 150 d. The F‐ solubility for strongly acid and near neutral soils without added minerals was undersaturated with respect to AlF3(c) and CaF2, respectively. The F‐ solubility for alkaline soils was close to that of KMg3AlSi3O10F2.
A Rapid Routine Method for Obtaining Soil Solution Using Vacuum Displacement
Authors: Wolt Jeff , Graveel John G.
Published: July 2010

Vacuum displacement, a modification of traditional column displacement utilizing 75‐g soil samples and a mechanical vacuum extractor, was compared to centrifugation as a method for obtaining unaltered soil solution for comprehensive analysis. Soil solutions were displaced by the two procedures from field‐moist Lily (Typic Hapludults), Memphis (Typic Paleudalfs), and Etowah (Typic Paleudults) soil samples having varied chemical and physical properties. Solutions obtained were analyzed for volume of solution recovered, pH, EC, Ca, Mg, Mn, K, Na, NH4, Cl, NO3, SO4, P, and percent ion difference. Vacuum displacement was more efficient than centrifugation in terms of man‐hour requirements and sample turn‐around time. Smaller volumes of soil solution (usually <5 mL) were obtained by vacuum displacement compared to centrifugation, necessitating analytical techniques adapted to uL‐volumes of solution. For the most part, both methods resulted in analate concentrations with coefficients of variation <5% and ion differences <12%. Exceptions were NH4, K, and Na, which were sometimes present at concentrations approaching the limits of detection for the procedures employed. Although significant differences in analate concentrations between the two methods were observed, few of the measured differences would lead to interpretive difficulties for the solution components and soils considered.
Genesis and Classification of Some Paleborolls and Cryoboralfs in Northern Utah
Authors: Jalalian Ahmad , Southard A. R.
Published: July 2010

Three soil series in northern Utah were studied to determine if the apparent surface mantle is a depositional discontinuity. Field descriptions show a dark gray silty deposit overlying thick E horizons and reddish brown, clayey skeletal B horizons. Laboratory results show an abrupt change in texture and mineralogy with amphiboles and Ca‐feldspar and zeolites in the surface deposit or upper sequum and quartz, chlorite, mica, and kaolinite in the lower sequum. The fine clay in the upper sequum of all three soils is dominated by amorphous material suggesting an early stage of weathering. Results of these studies suggest that the older soils (lower sequum) were Alfisols. Recent additions of eolian material from Lake Bonneville sediments and Snake River plain have covered the Alfisols and mollic epipedons have developed in the eolian material. These soils are now classified as Paleborolls. We suggest that Thapto extragrade classification would help identify more of the characteristics of these soils than the present classification.
Modeling Corn Grain Yield in Relation to Soil Erosion Using a Water Budget Approach
Authors: Timlin D. J. , Bryant R. B. , Snyder V. A. , Wagenet R. J.
Published: July 2010

The effect of long‐term soil loss on corn (Zea mays L.) grain yields in shallow soils of the Northeast is evaluated using a simple computer simulation model. Easily obtainable soil and meteorological data are used as input. The model relates the change in soil productivity to the reduction of available water holding capacity caused by long‐term soil loss by erosion. Depth to an impermeable layer, which limits the total available water in the soil profile, is considered a nonrenewable soil property. Renewable soil properties such as surface soil structure and fertility, which can be maintained through optimum management, are not considered to limit yields. The model is based on the established relationship between relative yields and the relative transpiration ratio. A simple water budget estimates actual transpiration on a daily basis and calculates stress as a function of relative transpiration ratio. Yields are predicted from total seasonal stress and accumulated heat units. The model has been run using 16 yr of meteorological data to simulate varying climatic conditions, and correlations between actual and predicted yields on deep to moderately deep soils are good. Soil erosion is simulated by removing increments of soil depth. For each soil depth, the model predicts both mean yield and variance. Mean yield values are used to generate productivity curves that graphically depict the relationship between soil productivity and soil erosion. For medium textured soils in New York State, the model predicts that soil erosion will decrease mean yield and increase variability in annual yields when the depth to a root restricting horizon is <70 cm.
A Stochastic Approach to the Crop Yield‐Irrigation Relationships in Heterogeneous Soils: I. Analysis of the Field Spatial Variability
Authors: Russo David
Published: July 2010

When a deterministic irrigation regime is applied to a heterogeneous field, soil‐water content, soil salinity, and crop yield will vary in space because of the inherent spatial variability in the soil properties. It is important, therefore, to analyze their spatial distributions in the field in order to suggest improved irrigation management schemes for spatially‐variable fields. A stochastic approach was used to analyze the spatial variability of four parameters of the soil‐water retention curve as well as that of the initial soil‐water content and soil salinity, using actual measured field data. These properties were used as inputs for a simplified crop yield‐soil‐water model which, in turn, was coupled with the conditional simulation method to analyze the spatial distribution of the calculated soil‐water content (θ), soil salinity (C), and relative crop yield (Y) in an irrigated field, for various combinations of irrigation water quantity and quality (salinity). Analysis of the results showed that both irrigation water quantity and quality affected the spatial variability in θ, C, and Y but essentially did not affect the spatial dependence of these properties. Although the average (spatial) response of the field was similar to that of a fictitious equivalent homogeneous field, the response of different sites in the field was quite different. For some combinations of irrigation water amount and salinity, the relative difference between relative crop yield obtained at different sites in the field exceeded 100%.
A Stochastic Approach to the Crop Yield‐Irrigation Relationships in Heterogeneous Soils: II. Application to Irrigation Management
Authors: Russo David
Published: July 2010

In a heterogeneous field in which the soil properties vary, under a deterministic irrigation regime, the crop yield might also differ from place to place in the field. These differences may, in turn, reduce the average (over the field) yield relative to that which would be obtained if the soil properties were uniform throughout the field. The simplified crop yield‐soil response model coupled with the conditional simulation method, presented in part I of this study, was used here to evaluate the spatial distribution of the amount of irrigation water required to maintain a prespecified relative crop yield, uniform throughout the field, for a given irrigation water salinity. By considering the water irrigation amounts at different sites in the field, rather than that of the entire field, it was shown that the amount of irrigation water required to obtain a given relative crop yield (for a given irrigation water salinity) can be reduced by 7 to 34%. The amount of water that could be saved increased as the level of the required crop yield increased and as the salinity of the irrigation water decreased. The spatial distributions of the amount of irrigation water required to maintain a given relative crop yield were combined with economic considerations in order to evaluate the spatial distribution of the optimal amounts of irrigation water for a given irrigation water salinity. It was shown that the optimal amounts of irrigation water can be reduced by 6 to 29%, when the responses of different sites in the field is considered rather than the average response of the entire field. Irrigation schemes based on imposition of engineering requirements on the spatial distributions of the optimal irrigation water amounts, increased the net benefit (price of the crop yield minus cost of the irrigation water) by 5.5 to 42% relative to that obtained under deterministic conventional water application schemes. The differences between the two schemes decreased as the irrigation water salinity increased.
Factors Affecting Anion Movement and Retention in Four Forest Soils
Authors: Johnson Dale W. , Cole Dale W. , Van Miegroet Helga , Horng F. W.
Published: July 2010

Three hypotheses concerning the movement and retention of anions in forest soils were tested in a series of laboratory and field studies on two Tennessee Ultisols with mixed deciduous forest cover and two Washington Inceptisols, one with deciduous (red alder Alnus rubra Bong.) and one with coniferous [Douglas‐fir, Pseudotsuga menziesii (Mirb.) Franco] forest cover. The first hypothesis, that sulfate and phosphate retention was related to adsorption to free Fe and Al oxides, which were in turn related to soil parent material and degree of weathering, was not supported by results of laboratory and field studies. The young, relatively unweathered Washington Inceptisols adsorbed more phosphate and sulfate than the older, highly weathered Tennessee Ultisols, apparently because of greater amorphous (oxalate‐extractable) Fe and Al in the former. The second hypothesis, that NO‐3 retention was governed primarily by biological uptake, was supported. Nitrate adsorption by soils in laboratory column studies was negligible, but subsequent field studies showed that tree uptake in field plots greatly reduced the leaching of applied NO‐3 in all but the N‐rich red alder plot. The third hypothesis, that inputs of mobile anions will reduce pH and concentrations of bicarbonate and adsorbing anions (e.g., sulfate), were supported by application of chloride as both acid and Na and Ca salts to soil columns in the laboratory. Sulfate concentration as well as bicarbonate concentrations in soil solutions were sensitive to solution pH.
Solid‐State Decomposition Kinetics of Phenyl Phosphorodiamidate
Authors: Gautney J. , Barnard A. R. , Penney D. B. , Kim Y. K.
Published: July 2010

Kinetic studies were conducted to determine the effect of temperature, phenyl phosphorodiamidate (PPDA) production impurities, and relative humidity on the solid‐state decomposition of the urease inhibitor, PPDA, alone and in urea‐PPDA mixtures (960 g kg−1 of urea and 40 g kg−1 of PPDA). In general, the solid‐state decomposition of pure PPDA obeys first‐order reaction kinetics, whereas the decomposition of the urea‐PPDA mixtures obeys zero‐order kinetics. Rate constants (d−1) for pure PPDA ranged from 0.05 at 70°C to 4.78 at 100°C. Rate constants (decomposition d−1) for urea‐PPDA mixtures ranged from 7.26% at 50°C to 1200% at 90°C. The activation energy (kJ mol−1) is 164 for pure PPDA and 127 for urea‐PPDA mixtures. The presence of production impurities, ammonium chloride (NH4Cl) and diphenyl phosphoramidate (C6H5O)2·PO·NH2, increased the decomposition rate for pure PPDA, but did not significantly affect the decomposition of the urea‐PPDA mixtures. Increasing relative humidity dramatically increased the decomposition rate for PPDA. These results suggest that researchers should minimize the time between preparation and testing of urea‐PPDA mixtures, because at room temperature over half of the PPDA can be lost in 1 yr.
Problems with the Sandy Loam Subclass Definition
Authors: Mays M. D. , Brasher B. R.
Published: July 2010

There are undefined particle‐size distributions that are within the definition of sandy loams but not within the definitions of any of the subclasses of sandy loams according to the 1981 draft of chapter 4 of the Soil Survey Manual. These undefined particle‐size distributions can be accommodated by appending the following phrase to the sandy loam subclass definition: “or less than 15 percent very coarse, coarse and medium sand and less than 30 percent either fine or very fine sand.”