bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crop Residue Influences on Soil Carbon and Nitrogen in a Wheat‐Fallow System
Authors: Rasmussen Paul E. , Allmaras R. R. , Rohde C. R. , Roager N. C. 
Published: July 2010

AbstractSeven crop residue treatments were initiated in 1931 to measure long‐term residue management effects on soil organic matter in a wheat‐fallow cropping system on Pacific Northwest semiarid soils. There was evidence at this time of substantial organic matter (OM) loss during the first 50 years of wheat cultivation in the Great Plains. Organic carbon (C) and total (N) were measured at approximately 11‐year intervals over a 45‐year period to determine residue effects on the rate of change in soil OM content.Only the addition of 22.4 metric tons of manure/ha to straw residue before incorporation prevented a decline in soil N and C. The addition of 45 or 90 kg fertilizer N or of 2.2 metric tons of pea vines/ha to straw residue before incorporation reduced N and C loss when compared to straw only incorporation. Burning of straw in the fall following wheat harvest accelerated the loss of N but not C. Burning of straw in the spring just prior to tillage had no effect on N or C loss.Changes in N and C were primarily confined to the top 20 cm of soil. Soil C/N ratios in 1976 differed between treatments proportional to the rate of N loss; they were highest in burn or straw only treatments and lowest in the manure treatment.In all treatments, changes in soil N were best described by a linear function of time; slope within the linear function depended upon residue treatment. This linear function of time over a 45‐year period following approximately 50 years of previous cultivation suggests that 100 or more years may be required before N levels become stationary. Residual effects confirm that the new stationary level will depend on past crop residue management practices.Changes in soil C correlated highly with the amount of organic C supplied by each treatment, regardless of the different kinds of residue applied. Thus, changes in soil organic matter levels were controlled primarily by the amount of organic C supplied in crop residue. Regression equations indicate that approximately 5 metric tons of mature crop residue ha−1 year−1 are needed to maintain soil organic matter at its present level when cropped in wheat‐fallow rotation in this climatic zone.
Nitrogen Mineralization, Immobilization, and Nitrification Following Urea Fertilization of a Forest Soil Under Field and Laboratory Conditions
Authors: Johnson D. W. , Edwards N. T. , Todd D. E. 
Published: July 2010

AbstractFollowing a 200‐kg urea‐N/ha fertilization in a loblolly pine stand (Pinus taeda), soil mineral N levels (almost entirely NH4+) declined from 200 ppm 20 days after fertilization to < 10 ppm within 161 days. Similar patterns had been previously observed following urea fertilization in a Douglas‐fir stand. After the decline in soil mineral N, 20% (40 ppm) of fertilizer N was mineralized within 4 weeks of aerobic incubation in the laboratory at 25°C. Nitrogen mineralization in control soils did not occur after 7 weeks incubation.In contrast to field results, urea additions to control soils in the laboratory resulted in rapid net N mineralization. The difference between laboratory and field fertilization results is thought to be due principally to differences in available C supplies, i.e., large (> 2 mm) litter and roots were excluded from laboratory tests.The maximum rate of nitrification during incubation was related to the supply of NH4+ substrate, whereas the delay period was probably related to the initial populations of nitrifiers.Additions of 100 kg P/ha as triple superphosphate in the field and equivalent additions of NaH2PO4 in the laboratory had little or no effect on results.
Characterization of Hydroxy‐Aluminum Solutions
Authors: Bersillon J. L. , Hsu Pa Ho , Fiessinger F. 
Published: July 2010

AbstractHydroxy‐Al solutions were prepared and characterized with sulfate precipitation, resin treatment, and rate of Al‐ferron color development. The results suggest that the soluble Al species can be grouped into at least four categories: (i) high OH‐Al polymers — these have a residual positive charge of 0.33 or less per Al atom and are rapidly precipitable by Na2SO4, giving rise to the formation of noncrystalline basic aluminum sulfate; (ii) medium OH‐Al polymers — these form crystalline basic aluminum sulfate of composition Al(OH)2.50(SO4)0.22 · xH2O slowly and enter resin slowly; (iii) low OH‐Al polymers — these are not precipitable with Na2SO4, and they enter resin rapidly; and (iv) monomeric ions — these enter resin rapidly and react with ferron rapidly.
Some Accurate Numerical Solutions of the Soil‐Water Diffusion Equation
Authors: Braddock R. D. , Parlange J.‐Y. 
Published: July 2010

AbstractSome accurate numerical solutions are obtained for the soil‐water diffusion equation. The method replaces the two endpoint boundary value problem with a standard initial value problem and uses iteration to select the appropriate initial slope. The results obtained are accurate to seven significant figures and the solution exhibits a wetting front with a sharp corner and foot at the leading edge of the front. The corner and foot highlights our ignorance of the processes by which water percolates the soil at low concentrations.
The Swelling of Clay: II. Montmorillonites
Authors: Low Philip F. 
Published: July 2010

AbstractThe water content at equilibrium was determined as a function of applied pressure for 35 different Na‐saturated montmorillonites by means of a miniature pressure membrane apparatus. Then the data were used to develop a general, empirical equation in which the swelling pressure of the montmorillonite depends exponentially on the water content. The parameters in this equation were shown to be functions of the cation exchange capacity and specific surface area of the montmorillonite. The data were also used to develop semiempirical equations in which the swelling pressure depends exponentially on the distance between the superimposed layers of the montmorillonite. Depending on the assumptions used in their development, the latter equations involve constant coefficients or coefficients that depend on the surface charge density of the montmorillonite. Analysis of these equations indicated that swelling is due primarily to interaction between the layer surfaces and water.
Analytical Properties of the Soluble, Metal‐complexing Fractions in Sludge‐Soil Mixtures: V. Amino Acids, Hexosamines, and Other Carbohydrates in Fulvic Acid
Authors: Holtzclaw Kenneth M. , Schaumberg Gene D. , LeVesque‐Madore C. S. , Sposito Garrison , Heick J. A. , Johnston Cliff T. 
Published: July 2010

AbstractThe quantitative distribution of amino acids, hexosamines, and other carbohydrates was determined for three representative, purified fulvic acids extracted from anaerobically‐digested sewage sludges. The amino acid content ranged from 5 to 9 wt % in the three fulvic acids and the distribution of acidic, neutral, and basic amino acids generally was similar to that in soil‐derived fulvic acids. The principal difference between the two types of fulvic acid was with the S‐containing amino acids, which were more abundant in the sludge‐derived fulvic acids. The content of galactosamine was very high in the three fulvic acids studied, with the result that the glucosamine/galactosamine ratio was about an order of magnitude lower in these fulvic acids than what is typical for soil‐derived fulvic acids. The content of neutral and acidic sugars ranged from 12 to 25 wt % in the fulvic acids, with a distribution of neutral sugars that was similar to what is found typically in natural soil organic matter. Thus the amino acid, hexosamine, and carbohydrate components of sludge‐derived fulvic acid may account for up to 50 wt % of this material. The major differences among these components between sludge‐derived and soil‐derived fulvic acids appear to be related to the high sulfur content of the sludge‐derived fulvic acids and their expected high content of anaerobic bacterial residues.
Factors Influencing Oxygen Consumption Rates in Flooded Soils
Authors: Reddy K. R. , Rao P. S. C. , Patrick W. H. 
Published: July 2010

AbstractThirty‐seven surface soil samples varying in physico‐chemical properties were incubated under reduced (anaerobic) conditions to study the factors influencing oxygen consumption rates. Oxygen consumption rates were measured after introduction of a known amount of oxygen into a reduced (anaerobic) soil system and following the disappearance of oxygen as a function of time.The time dependence of oxygen consumption in all flooded soils could be described as a two‐phase first order reaction process. Rapid oxygen consumption during Phase I was followed by relatively slower consumption during Phase II. The first‐order rate coefficient (k1, hour−1) for Phase I was approximately the same for all 37 soils evaluated, whereas each soil was characterized by a different rate coefficient (k11, hour−1) for Phase II. The average value for k1 was 0.15 hour−1 (coefficient of variation = 20%) while the values of k11 ranged from 0.0027 to 0.054 hour−1. Step‐wise regression analysis of the data showed that NaOAc‐extractable Fe of a reduced soil was the single best predictor of k11 and also the fractional consumption associated with Phase I. Significant improvement in these regressions was obtained when total NH4‐N content of the reduced soil, in addition to reducible Fe2+ was considered.
Soil Microbial and Biochemical Changes Associated with Reduced Tillage
Authors: Doran John W. 
Published: July 2010

AbstractThe physical, chemical, and biological soil environment for reduced or no‐till farming differs greatly from that for conventional tillage. Evaluation of the soil microbial and biochemical environment greatly aids predictions of N availability to crop plants and in optimizing management practices for reduced and no‐till soils.Surface soils from long‐term no‐till and conventional tillage plots at seven U.S. locations were characterized for microbial and biochemical components. The counts of aerobic micro‐organisms, facultative anaerobes, and denitrifiers in the surface (0–7.5 cm) of no‐till soils were 1.14 to 1.58, 1.57, and 7.31 times higher, respectively, than in the surface of plowed soil. Phosphatase and dehydrogenase enzyme activities and contents of water and organic C and N in the surface of no‐till soil were also significantly higher than those for conventional tillage. However, at the 7.5‐ to 15‐cm and 15‐ to 30‐cm depths these trends were reversed and microbial populations, enzyme activities, and water and organic C and N contents were the same or higher for conventional tillage than for no‐till. The trends in microbial populations with both tillage treatments were closely paralleled by soil enzyme activities and were also regulated by soil pH and levels of organic C and N. The surface 0‐ to 7.5‐cm of no‐till soil contained more potentially mineralizable N—20 to 101 kg/ha—than did that of plowed soils. This increased labile N reserve is apparently related to the higher microbial biomass present under no‐till soils.Maximum aerobic microbial activity with conventional tillage extends to a greater depth than with no‐till. Microbial populations under no‐till decrease rapidly below the 7.5‐cm depth. At the 7.5‐ to 15‐cm depth counts of aerobic microor‐ganisms and nitrifiers were 1.32 to 1.82 times higher on the conventionally tilled soils. However, counts for facultative anaerobes and denitrifiers were 1.23 to 1.77 times higher for no‐till soil. Also, the proportion of the total aerobic population represented by facultative anaerobes and denitrifiers for no‐till was twice that for conventional tillage. Consequently the potential rate of mineralization and nitrification is higher with conventional tillage while that for denitrification is higher with no‐till.Microbial population counts and the relative abundance of various microbial types suggests that the bochemical environment of no‐till soils is less oxidative than that under conventional tillage. Changes in tillage and fertilizer management practices required for no‐till soils should reflect the increased potential for immobilization of surface applied N and the lower levels of plant available NO3‐ as compared with those under conventional tillage.
Sulfur‐coated Urea and Urea Compared as Nitrogen Sources for Irrigated Corn
Authors: Sander D. H. , Moline W. J. 
Published: July 2010

AbstractSulfur‐coated urea (SCU) was compared to urea (U) to determine their value as N fertilizers for irrigated corn (Zea mays L.) production. Two soils were studied from 1970 through 1972, Cass sandy loam (Fluventic Haplustoll) and Holder silty clay loam (Udic Arguistoll). Comparisons were made with different rates of the two fertilizers and the results interpretated in terms of yields, N uptake, and residual NO3‐‐N in the root zone.Results of the study indicated little difference between the performance of the two N fertilizers in terms of grain, forage yields, or in N uptake although N from SCU tended to be less available than from U. After 3 years of application, more NO3‐‐N was found in the root zone with SCU than U. This was especially apparent on the fine‐textured Holder soil and to a lesser extent on the sandy Cass soil. While the increased NO3‐‐N found after 3 years in the root zone did not affect fertilizer N need, data does suggest that SCU has potential for increased N efficiency by reducing leaching under moderate leaching situations.The data emphasizes the need for more accurate N recommendations that will access NO3‐‐N in the root zone, N mineralization potential of the soil, and N in the irrigation water. It was possible to grow 92 to 94% of maximum corn yields without losses of N to the groundwater.
Evaluation of EDTA‐extractable Phosphorus as a Soil Test Procedure
Authors: Onken Arthur B. , Matheson Richard , Williams E. Jay 
Published: July 2010

AbstractDiagnostic techniques involving complex systems such as soils and plants are rarely infallable. Thus, a constant research effort is underway to improve decision making by adding information to presently used methods and/or developing new techniques.Predicting crop response to applied P requires a suitable extractant and a model that satisfactorily describes the yield response. A number of extractants and yield response models have been proposed and evaluated over the last 50 years. The objectives of the research reported here were to (i) develop a satisfactory procedure for extraction of P using one of these extractants (EDTA), (ii) evaluate this procedure using current mathematical and statistical models, and (iii) compare this procedure (by use of the models) with current procedures in order to determine if decision‐making could be improved.Soil samples of four soil series from 23 location‐years of irrigated fertilizer response trials with grain sorghum (Sorghum bicolor L. Moench) were extracted with ammonium acetate, sodium bicarbonate, and EDTA. Extraction time for EDTA was established utilizing soils from two locations of known P response. The extraction procedures were evaluated by the following models: linear, quadratic, logarithmic, Mitscherlich, and the Cate‐Nelson analysis of variance method.For the soils used, an extraction time for EDTA of 1.0 hour was established as a reasonable compromise between ability to distinguish with a high degree of certainty between soils on a P needs basis and an extraction time suitable for a routine analysis procedure. The Cate‐Nelson ANOVM (Analysis Variance Method) for partitioning soils for expected P response was found to be superior to the other models tested for all three extractants. For five of six models tested, the EDTA‐extraction procedure resulted in better predictability of P fertilizer needs than either the ammonium acetate or sodium bicarbonate extraction procedures. The combination of the EDTA‐extraction procedure and the Cate‐Nelson three‐class model resulted in the highest R2 value (0.71) of all combinations of models and extractants evaluated.
Effects of Banded and Residual Fertilizer Phosphorus on Dryland Spring Wheat Yield in the Northern Plains
Authors: Alessi J. , Power J. F. 
Published: July 2010

AbstractAlthough phosphate fertilizers are commonly applied either by surface broadcasting or banding with the seed to dryland spring wheat (Triticum aestivum L.), data are limited on the residual effects of previous fertilization on plant growth and grain yield. This is especially true in regions where there are drought periods during the growing season. Therefore, the residual effects of P fertilization on spring wheat grown on Parshall fine sandy loam (Pachic haploboroll) were determined in a field study at Mandan, North Dakota. Fertilizer rates of 0, 20, 40, 80, and 160 kg P/ha were broadcast in 1968 to establish several levels of residual P in the soil. In 1969 subplots were established on each of the broadcast P plots, to which P was banded with the seed at the rate of 15 kg/ha either (i) repeated to the same subplot each year for 6 years, (ii) on a new subplot (previously unfertilized) each year, or (iii) not at all.After 6 years of cropping, the residual effects of 160 kg P/ha broadcast in 1968 resulted in an average increase in grain yields of about 10% (200 kg ha−1 year−1. Banding of P with the seed resulted in an additional 10% increase in grain yields, with about half this increase due to current‐year banding and about half due to residual effects of banding in previous years. Residual effects of banding and broadcast treatments were additive, with little interaction. Average plant P concentrations (1969–1974) were significantly increased by both the P initially applied and by the banded‐P treatments at all growth stages. NaHCO3‐soluble P levels in the 0‐ to 15‐cm soil depth decreased with time for all broadcast P treatments, but repeated banding of P on the same plot each year increased NaHCO3‐soluble P levels during the 6 years of study. An exception was the 160‐kg P/ha broadcast‐P treatments where NaHCO3‐soluble P level was still decreasing. The addition of banded P decreased percent fertilizer P recovery in grain, especially when P was repeatedly banded each year on the same site. Since yield increases resulted from banding P with the seed even when soil test levels were high, it was concluded that banding P may be beneficial for spring wheat in the cool springs of the northern Great Plains no matter what soil test level is present.
Minesoil Genesis and Morphology in a Spoil Chronosequence in Montana
Authors: Schafer W. M. , Nielsen G. A. , Nettleton W. D. 
Published: July 2010

AbstractMinesoils from 1 to 50 years old in southeastern Montana were compared to adjacent natural soils. Due to their maninfluenced origin, minesoils had several unique morphological properties which made them difficult to classify. Weakly consolidated rock fragments, common in minesoils, acted in part like soil in supplying water and in part like rock in preventing root penetration. Low chroma mottles were common in minesoils without the influence of a high water table. Organic C content from 0–10 cm soil depth reached levels found in natural soils within 30 years, but will not reach equilibrium at 20–50 cm for 400 years or more. Litter accumulation was common under pioneer vegetation on minesoils resulting in wide C/N ratios; reduction in available N; successional stagnation; and reduced plant community production. Soluble salts were leached downward in minesoils in tens of years, but thousands of years will probably be required for carbonate removal to occur in the upper 50 cm. Soil structure developed more quickly near the soil surface (10–50 years) than below 10 cm (50–200 years), and was attained sooner in clayey than in sandy minesoils. Many characteristics of minesoils are expected to always be different from natural soils. Well‐designed minesoils can be highly productive, however, in a few cases perhaps exceeding the potential of natural soils.
Wheat Straw Composition and Placement Effects on Decomposition in Dryland Agriculture of the Pacific Northwest
Authors: Douglas C. L. , Allmaras R. R. , Rasmussen P. E. , Ramig R. E. , Roager N. C. 
Published: July 2010

AbstractField‐measured characteristics of cereal residue decomposition under semiarid dryland agriculture are needed for systematic management of residue in reduced tillage systems. Straw placement, loading rate, and nutrients are all important characteristics. Straw composition and placement, at a moderate loading rate, were evaluated for their effects on decomposition. Wheat straw with three different N and S contents was contained in fiberglass cloth bags which were placed above, on, and below the soil surface to simulate, respectively, standing stubble, straw matted on the surface, and straw plowed under. Weight loss and changes in N and S content were measured during a 26‐month period in a winter wheat (Triticum aestivum L.)‐pea (Pisum sativum L.) rotation. After 26 months exposure residue losses were 25, 31, and 85% for placements above, on, and in the soil, respectively. Above‐surface and on‐surface straw showed a nearly constant decomposition rate with little response to weather variables; decomposition rate of buried straws responded to both soil moisture and temperature. Mineralization or immobilization of N and S were sensitive to placement and initial nutrient content of the straws. Net N mineralization in buried straw varied from 17 to 2 kg N/ha as straw composition varied from 0.78 to 0.20% N. When placed above or on the surface net N mineralizations ranged from 6 to −4 kg N/ha as straw varied from 0.78 to 0.20% N. Net S mineralization paralleled N mineralization, however, magnitudes were smaller. First‐order rate constants for weight loss successfully characterized the placement and straw composition effects.
Effects of Fire on Soil Nutrients in Clearcut and Whole‐tree Harvest Sites in Central Michigan
Authors: Adams Paul W. , Boyle James R. 
Published: July 2010

AbstractSurface‐mineral soil samples from adjacent northern red oak (Quercus rubra L.)‐bigtooth aspen (Populus grandidentata Michx.) sites harvested by contrasting methods were evaluated for available Ca, Mg, K, P, and total N before and after a wildfire. Abundant slash from clearcutting contributed to significant and persistent increases in Ca, Mg, K, and N following fire. Sample data grouped by variations in estimated surface burn intensity revealed no significant differences, indicating that slash windrows did not appreciably localize nutrient increases. Minimal residues from whole‐tree harvest released smaller quantities of Ca, Mg, and K, and total N exhibited no significant change. Significant increases in soil Ca, Mg, K, and P at both sites occurred within a month after burning. Five months after the fire, soil Ca, Mg, K, and P at both sites generally decreased, in some cases to prefire levels. Cation leaching losses from the surface soils, monitored by porous cup lysimeters at the 1‐m depth, increased within 2 months after the fire, but losses appeared to stabilize within 5 months. Leaching losses of Ca were significantly greater in the clear cut site. Although short‐term soil nutrient changes following fire were generally positive, the long‐term effects on site quality remain in question due to the probable net loss of organic matter and nutrients through volatilization and accelerated leaching.