bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mineralogy of the Major Soils of the Gezira Scheme (Sudan)
Authors: Adam A. I. , Anderson W. B. , Dixon J. B. 
Published: July 2010

AbstractThe major soil series comprising the Gezira scheme are Hosh, Suleimi, and Laota. These soils are calcareous, dark brown to grayish brown clays with low organic matter contents (< 1%). The mineralogical properties of these soils were studied by X‐ray diffraction (XRD), dissolution, and Ca/Mg and K/NH4 cation exchange capacities. Some complementary data were obtained using infrared (IR) spectroscopy. The results of the study reveal that these soils have similar sand, silt, and clay mineralogy. The sand fractions are composed of quartz, plagioclase, K feldspars, anatase, and amphiboles. The silt fractions contain, in addition to the above minerals, kaolinite, mica, and chlorite. The coarse clay is composed of chlorite, kaolinite, smectite, plagioclase and K‐feldspars, quartz, and mica. The fine clay is predominantly smectite (a mixture of montmorillonite and beidellite), kaolinite, and mica. Calcite is the dominant mineral in the gray hard nodules. The uniform physiographic position and similar mineralogy of these soils suggest that they have a common origin. The similarity in mineralogical composition to that of the recent sediments of the Blue Nile and its tributaries, supports the contention that the Gezira soils have inherited their mineralogical properties from the source area of the sediments in Ethiopia.
Rapid Estimation of Iron Oxides in Soils and Clays by Spectrophotometric Analysis
Authors: Fey M. V. , Dixon J. B. 
Published: July 2010

AbstractA simple, rapid method is presented for the determination of Fe in soils and other ferruginous materials involving hot 6M HCl digestion followed by colorimetric analysis of the ferric chloride complex at 365 nm. Absorbance is linear up to Fe concentrations of at least 40 mg/L. An interference by oxalate in solution was found to be small enough to permit the analysis of iron oxide residues after acid ammonium oxalate treatment. No other significant interferences were found.
Sampling Volume Effects on Determining Salt in a Soil Profile
Authors: Hassan H. M. , Warrick A. W. , Amoozegar‐Fard A. 
Published: July 2010

AbstractThe effects of soil sampling volume for determining salt present were investigated in situ. Six 2.2‐m2 plots were hand sprinkled over a 5‐d period with a total of 10 cm of water containing 1000 mg/L of chloride as CaCl2. Soil samples were taken at three locations within each plot at 10‐cm increments to 100 cm and at 20‐cm increments to the 160‐cm depth. Two different samplers, 7.9‐ and 2.1‐cm diameter, were used. The salt concentration was measured on a 2:1 extract. The measurements for the larger samples were less variable than the smaller samples. The coefficient of variability (CV) for the total chloride recovered was 8 and 14% for the large and small samples, respectively. In order to compare favorably to the known amount added, the effective radius of the sampling tool was critical. The CV for the chloride concentration calculated in the soil water ranged from 5 to 54% and 12 to 199% for large and small samples by depth.
Potassium‐Calcium Exchange in a Multireactive Soil System: II. Thermodynamics
Authors: Jardine P. M. , Sparks D. L. 
Published: July 2010

AbstractThermodynamics of K exchange were investigated in Ca‐saturated samples from the Ap horizon of an Evesboro soil from Delaware. At 283 and 298 K the selectivity curves (lnkv vs. X̄K) showed preference for K at low values of NK (mole fraction of K in solution) and for Ca at higher values. This selectivity reversal may be attributed to exchange sites of varying reactivity for K and Ca ions and supports the hypothesis of the multireactive nature of the soil. Although K was selectively bound at low NK, the soil exhibited an overall Ca preference as noted by the positive standard free energy values (ΔG°). The standard enthalpy of exchange (ΔH°) was negative, which indicated very strong binding of K ions with some sites of the soil. This may be associated with the presence of vermiculitic clay minerals that predominated in the <2‐µm clay fraction. A thermodynamic investigation was also initiated on the various size fractions of the soil (i.e., sand, silt, and clay) and on soil that was treated with cetyltrimethylammonium bromide (CTAB) or NaOCl‐DCB. These treatments explained the differences in ionic selectivity observed in the Evesboro soil.
Net Aerial Primary Production and Dynamics of Soil Organic Matter Formation in a Tidal Marsh Ecosystem
Authors: Hsieh Y. P. , Weber O. J. 
Published: July 2010

AbstractRelationships between net aerial primary production (NAPP) and soil organic matter formation in a tidal marsh environment were analyzed using a dynamic model. Four basic parameters were considered in the model: NAPP, disappearance rate of dead standing crop, and rates of plant decomposition in soil and air. The model was tested in a sawgrass (Cladium jamaicense) tidal marsh of north Florida. Net aerial primary production was estimated to be 2643 g m−2 y−1 using a paired‐plot method. The mean annual disappearance rate of dead standing crop was estimated to be 1.965 g g−1 y−1. The disappearance rate of sawgrass in soil was estimated to be 4.308 g g−1 y−1 for the labile portion and 0.105 g g−1 y−1 for the resistant portion. The sawgrass consists of 34% labile and 66% resistant portions. The soil organic matter due to NAPP was estimated to be 12.5 kg m−2. The actual soil organic matter under the marsh was found to be about 100 kg m−2. Most of the soil organic matter was preserved by constant submergence in water and, therefore, did not actively participate in the carbon cycle. Only about 20 kg m−2 of the soil organic matter that had an average thickness of 30 cm was considered to be actively participating in the carbon cycle. The dynamic model predicted 30 y is needed for soil organic matter to be stabilized, and < 2 years is needed for dead standing crop to be stabilized under the environment. Ninety‐eight percent of the soil organic matter was from the resistant pool of sawgrass. The mean fraction remaining (MFR) of the soil organic matter was 0.36. Two carbon cycles were defined in the marsh soil: the short one (mean retention time = 0.73 y) is probably important to the food and energy supply of the ecosystem; the long one (mean retention time = 10 y) comprises the major portion of the soil organic matter.
Mineralizable Soil Nitrogen: Amounts and Extractability Ratios
Authors: Juma N. G. , Paul E. A. 
Published: July 2010

AbstractStudies were conducted on a 15N‐labeled Weirdale loam, a Dark Gray Chernozemic soil (Boralfic Boroll) to (i) determine the amounts of N released by several methods previously used to obtain an estimate of potentially mineralizable N, (ii) determine their 15N enrichment and extractability ratios, and (iii) compare the results from the above with the N mineralized during incubation and NH+4 released by the chloroform fumigation incubation technique. The NH+4‐N accumulated during 10 d in fumigated soils accounted for ∼1% of total N, was highly labeled, and had extractability ratios of 6.6 to 7.4. These ratios were similar to ones obtained for N mineralized during incubation of unfumigated soils. Ammonium‐N extracted with dilute acidic permanganate solution (0.01M KMnO4 in 0.1 or 0.5M H2SO4) accounted for 0.72 to 0.84% of total N and had extractability ratios ranging from 3.4 to 3.9. A stronger solution of acidic permanganate extracted more N that was less enriched. Dilute sulfuric acid extracted NH+4 and organic N that had extractability ratios of < 3. Ammonium‐N released by autoclaving the soil accounted for ∼1% of total N and had extractability ratios ranging from 0.6 to 0.9. Acid hydrolysis showed that 72% of total N was hydrolyzable, 32% was amino acid‐N and 20% was NH+4 released on hydrolysis. The extractability ratio for NH+4 released on hydrolysis was 1.7 and was significantly (P < 0.01) greater than extractability ratios of hydrolyzable N and amino acid‐N. The similarity and high extractability ratios of NH+4 released after fumigation and NO‐3‐N accumulating during aerobic incubation indicated that the fumigation extracted a biologically meaningful fraction. The biomass was responsible for only 15 to 25% of the net N mineralized during a 12‐week incubation. Results indicated that (i) extraction of a highly labeled N pool in soil can only partly explain the source of N being mineralized, (ii) N is mineralized from several pools, and (iii) there is a remote possibility that a single extractant can extract the variety of N compounds undergoing mineralization and immobilization in soil.
Nitrogen‐15 Balance and Residual Effects of Urea‐N in Wetland Rice Fields as Affected by Deep Placement Techniques
Authors: Cao Zhi‐hong , De Datta S.K. , Fillery I.R.P 
Published: July 2010

AbstractThe 15N balance at harvest, the residual effects of applied N fertilizer, and the distribution of N by depth in a wetland rice (Oryza sativa L.) soil (Alfisol) were determined in field experiments using 15N‐labeled urea. Nitrogen‐15 balance data show that with point, deep placement of urea supergranules (USG), only 4 to 5% of the applied N was unaccounted for after harvest of both the dry‐season and wet‐season crops. In contrast, when prilled urea was basally broadcast and incorporated and topdressed at panicle initiation (PI), 11 to 35% of the applied N was not recovered at harvest, indicating substantial loss of fertilizer N, especially when poor incorporation resulted in high floodwater mineral‐N levels. Uniform deep placement also resulted in high recovery of 15N (92–107%), confirming that the high total 15N recovery obtained with point deep‐placement of USG was largely a function of depth of placement. Band application of urea gave complete 15N recovery (102%) in the dry season and low recovery (61%) in the wet. Nitrogen‐15 balance data showed that 22 to 56% of the applied urea‐N still remained in the soil after the final harvest. The uptake by the wet season crop of the residual labeled soil N from the dry season experiment was about 5% of the initial applied N (87 kg N/ha) for all treatments. Placement method appeared to influence the actual recovery of residual soil 15N; the percentage recovery from the USG treatment was highest and that from the split urea treatment lowest. In neither the dry season nor the wet season was 15N enrichment significant in soil below 30 cm. Generally, the distribution of the residual 15N in soil reflected the placement pattern of urea.
Amino Sugar Distribution in Four Soils as Determined by High Resolution Gas Chromatography
Authors: Benzing‐Purdie Laure 
Published: July 2010

AbstractHigh Performance Gas Chromatography (HPGC) was used for the accurate determination of glucosamine and galactosamine in soil hydrolysate fractions of different particle sizes, the water soluble and plant residue fractions of four cultivated soils: a clay and clay loam soil with grain cover, a sandy loam and loamy sand with corn (Zea mays L.) cover. Results showed in all instances, a parallel between organic C, N, and amino sugar content, with a definite enrichment in organic matter and amino sugars in the small particle‐size fractions in the sandy loam and loam sand soils. An accumulation of amino sugars was observed in the smaller particle‐size fraction of the clay loam acid soil.
Leaching of a Soluble Chemical under Field Crop Conditions
Authors: Smith S. J. , Ahuja L. R. , Ross J. D. 
Published: July 2010

AbstractThe leaching pattern of surface‐applied bromide is examined in an active rootzone of a sorghum‐sudangrass [Sorghum sudanense (Piper) Stapf] crop in Southern Plains field plots. Data were collected for eight soils, comprising five soil orders, over three growing seasons. The position of the leaching front (solute center of mass) was better predicted generally by Burns' equation, which assumes chromatographic‐type, sequential mixing of solute with soil water, than by Levin's equation, which assumes the leaching front moves with the velocity of water flowing above field capacity. With both equations effective rainfall was used, by correction for the soil water deficit caused by evapotranspiration above the leaching front. The leaching pattern in the soil profile was described quite well by a simplified version of the convective‐dispersive solute transport equation, which assumed constant average values for the dispersion coefficient, D, a plant uptake factor, β, and flow velocity, V̄. Plant uptake of solute was assumed to be proportional to its concentration in soil water during passage through the root zone, with an effective average value of the proportionality constant applicable on a seasonal basis. The average value of D among soils was fairly uniform, 1.36 ± 0.56 cm2 d−1. Therefore, in practice a single value of D will probably suffice for many soils and conditions. Necessary inputs for obtaining V̄ can be obtained from plant growth and water balance components of CREAMS, or other appropriate models. In the case of β, some additional information is needed regarding its relationship to specific growth factors.
Effects of Fertilization on Soil Solution pH and Manganese Concentration
Authors: Petrie S. E. , Jackson T. L. 
Published: July 2010

AbstractThe effects of fertilizers on the soil solution pH and Mn concentration were studied in a laboratory experiment. A Tulana silt loam variant (medial, nonacid, mesic, Mollic Andequepts) with 18% organic matter was placed in incubation trays. Simulated fertilizer bands were made in the soil and marked with washed white silica sand. Nitrogen (N) was applied at 0 or 22 kg/ha as (NH4)2SO4, NH4Cl, or urea. Phosphorus (P) was applied at 0 or 19 kg/ha as Ca(H2PO4)2 and manganese (Mn) was applied at 0 or 5.6 kg/ha as MnSO4. All fertilizer rates were based on 0.25‐m row spacing. An unaltered portion of the soil solution was removed by centrifugation. The soil solution pH and Mn concentrations were measured in samples collected in the fertilizer band and 0.025 m from the band at 7, 14, and 28 d after fertilization. At 7 d after fertilization the soil solution pH in the fertilizer band was lowered from 8.12 to 7.30 by (NH4)2SO4 and from 7.75 to 7.21 by NH4Cl. In contrast, urea fertilization increased the soil solution pH from 7.75 to 8.01. Application of Ca(H2PO4)2 with N fertilizers lowered the soil solution pH regardless of N source. The soil solution pH tended to remain depressed at 14 and 28 d after fertilization when (NH4)2SO4 plus Ca(H2PO4)2 or NH4Cl plus Ca(H2PO4)2 were applied but increased when urea plus Ca(H2PO4)2 were applied. The pH changes at 0.025 m from the fertilizer band were approximately one half those occurring in the fertilizer band. The soil solution Mn concentration in the fertilizer band increased from 7.3 × 10−7 mol/L in the band receiving no fertilizer to 3.28 × 10−6, 5.82 × 10−6, and 2.18 × 10−6 mol/L in the (NH4)2SO4, NH4Cl, and urea bands, respectively, at 7 d after fertilization. At 28 days after fertilization the Mn levels were 4.55 × 10−6, 4.19 × 10−6, and 5.5 × 10−7 mol/L in the (NH4)2SO4, NH4Cl, and urea bands, respectively. When Mn was included with N fertilizer the soil solution Mn concentration increased from 7.3 × 10−7 to 4 × 10−4, 3 × 10−4, and 4.8 × 10−4 mol/L in the (NH4)2SO4, NH4Cl, and urea bands, respectively, at 7 d after fertilization. The Mn concentration in the (NH4)2SO4, NH4Cl, and urea bands fell to 2.8 × 10−4, 2.2 × 10−4, and 9 × 10−5 mol/L, respectively, at 28 d after fertilization.
Soil Test Phosphorus and Solubility Relationships in Calcareous Soils
Authors: Havlin J. L. , Westfall D. G. 
Published: July 2010

AbstractIrrigated alfalfa (Medicago sativa L.) was established in 1976 on two Colorado Soils [Keith clay loam (Aridic Argiustolls) and Ravola loam (Typic Torrifluvents)] to determine the residual value of fertilizer P. Triple superphosphate was applied annually at rates of 25 and 50 kg P ha−1, with 75 kg P ha−1 applied triennially and at seeding. Phosphorus solubility (in 0.01M CaCl2) and NaHCO3 ex tractable P were measured initially and in the third and sixth years of the study. The resulting calcium hydroxide (Ca(OH)2) and monocalcium phosphate (Ca(H2PO4)2) potentials were related to known solubility products for distinct mineral phases. Phosphorus solubility in the 0‐ to 7.5‐cm depth increased in all fertilized treatments after three years in both soils. No further increases in P solubility, NaHCO3‐P, or P uptake were observed over the next 3 yr. According to solubility diagrams residues of octacalcium phosphate (OCP) were apparently accumulating in the surface 7.5‐cm layer at NaHCO3‐P levels >32 mg kg−1. Below this extractable P level β‐tricalcium phosphate (TCP) apparently controlled P solubility.
Six Years of Phosphorus and Potassium Fertilization of Irrigated Alfalfa on Calcareous Soils
Authors: Havlin J. L. , Westfall D. G. , Golus H. M. 
Published: July 2010

AbstractLong‐term irrigated alfalfa (Medicago sativa L.) field experiments at two locations in Colorado [Keith clay loam (Aridic Argiustolls) and Ravola loam (Typic Torrifluvents)] were established to (i) determine the magnitude and frequency of P and K fertilization required to maintain initial soil tests, and (ii) evaluate the residual value of soil and fertilizer P and K. Ten P and K treatments (3 annual, 1 triennial, and 1 initial application) were used. Alfalfa yield, P and K uptake, NaHCO3‐extractable P, and NH4C2H3O2‐exchangeable K were measured over 6 production years. Soil test P declined in both soils to levels where significant yield responses to fertilizer P were expected, but none were observed. Organic P mineralization and/or an extensive mycorrhizal association were suggested as contributing factors to P availability. Generally, application of 50 kg P ha−1 maintained initial NaHCO3‐P at both locations, while soil P declined below the initial level for all other P rates. Phosphorus uptake was significantly increased by P fertilization on the Keith soil, due to lower NaHCO3‐P level, but not on the Ravola soil. Soil test K remained at high levels in both soils and no yield responses to fertilizer K were observed. Application of 380 and 5 kg K ha−1 were calculated to maintain initial NH4C2H3O2‐K in the Keith and Ravola soils, respectively. The low maintenance requirement of the Ravola soil was due apparently to a high nonexchangeable K release rate which buffered exchangeable K near 100 mg kg−1. Potassium uptake was significantly increased by K fertilization in the Ravola soil, due to a lower exchangeable K level, but not in the Keith soil. The results indicate very large P and K reserves exist in both soils and unless improved forage quality influences the economic benefit from P and K fertilizer application, fertilization of these soils would not be recommended.
Effect of Fertilizer Phosphorus Placement on the Availability of Phosphorus
Authors: Sleight D. M. , Sander D. H. , Peterson G. A. 
Published: July 2010

AbstractGreenhouse studies were conducted with oats (Avena sativa L.) to determine why band applications of fertilizer P are often more effective than broadcast applications of equal rates. Phosphorus fertilizer solutions tagged with 32P were applied to the soil with different spacing distances between solution application points. All the P fertilizer was applied at approximately equal distance from oat seeds (48 mm), while application points were spaced 0, 16, 32, and 48 mm from one another. Investigations were conducted using two soils, a Uly silt loam subsoil (fine‐silty, mixed, mesic Typic Haplustolls) with soil pH 8.4, a calcium carbonate equivalent of 4.2%, and 1.2 mg kg−1 NaHCO3‐extractable P; and a Thurman loamy fine sand (sandy, mixed, mesic Udorthentic Haplustills) with soil pH 5.9 and 11 mg kg−1 Bray and Kurtz no. 1‐extractable P. On the high pH calcareous silt loam soil, yield and P uptake were greatest when application points were spaced far apart. However, on the acid loamy fine sand, no relationship was found between the spacing of the application points and P uptake. It was concluded that on the loamy fine sand, movement of P from a single spot increased the probability that root‐fertilizer contact would occur, whereas no such movement occurred in the silt loam. The amount of P uptake by oats was nearly proportional to the volume of soil containing the applied P fertilizer. Apparently, the early beneficial effects of banding are obtained mainly from placing all of the fertilizer where contact by active roots is likely, rather than from any increase in availability that may be obtained from decreased soil‐fertilizer contact associated with banding. If this is the case, then soils in which P is relatively immobile, most efficient use of P fertilizer will be made by the young plants if the fertilizer is mixed thoroughly with the soil near the seed into which a high concentration of roots will grow.
Soil Loss Reductions from Conservation Tillage Practices
Authors: Cogo N. P. , Moldenhauer W. C. , Foster G. R. 
Published: July 2010

AbstractSoil loss reductions by residue cover (mulch) under field conditions were verified by deriving a mulch factor for no‐till, chisel plowing plus disking, and spring sweep tillage using anchored and unanchord corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] residues on a 4.5% slope 10.5 m long on Russell silt loam soil. A mulch factor was also derived for sweep tillage using anchored wheat residue on a 6.5% slope Martinsville loam soil, for simulated slope lengths of 35, 60, 85, 110, and 135 m. Both soils are Typic Hapludalfs. The studies were conducted using simulated rainfall and field plots. A crop residue mulch was relatively more effective than roughness alone in reducing soil loss on smoother soil surfaces and on the longer slopes. Corn residue was more effective in reducing erosion than soybean residue, and residues partially incorporated into the soil were more effective in reducing soil loss than residues loose on the surface. The findings showed that the b‐value in the mulch factor (Fm)‐% residue cover (M) equation Fm = e‐bM varied appreciably depending on roughness, and type and incorporation of the residue.
Shallow‐Layer Soil Water Potential Changes Due to Waterdrop Impact
Authors: Cruse R. M. , Francis P. B. 
Published: July 2010

AbstractSoil shear strength is inversely related to soil water matric potential (ψm), which changes in the soil during a rainstorm. An understanding of surface soil ψm changes due to rainfall may give an insight in soil erosion dynamics. Changes in soil water matric potential (ψm) under 1‐ and 3‐mm simulated soil surface seals were monitored following single waterdrop impacts on the soil surface. Selected ψm's were applied to the base of the seals with a hanging water column during the tests. After waterdrop impact, changes in ψm were detected within 2 to 3 s under 1‐mm surface seals and within 6 to 10 s under 3‐mm surface seals. The time required for ψm to equilibrate with the preimpact ψm (that ψm applied continuously with the hanging water column) ranged from 160 to 280 s. Equilibration time decreased slightly with increasing preimpact ψm's and was significantly affected by the type of soil material used to make the seal, the applied ψm, and the thickness of the seal. Increases in ψm under the 1‐mm surface seal due to waterdrop impact ranged from 0.3 to 0.5 kPa depending on ψm applied via the hanging water column. Smaller ψm changes were observed under the 3‐mm surface seal.