bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ammonia Volatilization from Flooded Soil Systems: A Computer Model. II. Theory and Model Results
Authors: Jayaweera G. R. , Mikkelsen D. S. 
Published: July 2010

AbstractOur theory to describe the process of NH3 volatilization from flooded systems is that the rate of NH3 loss is principally a function of two parameters, floodwater NH3(aq) concentration and the volatilization rate constant for NH3, kvN. These parameters are governed by five primary factors, floodwater NH4‐N concentration, pH, temperature, depth of floodwater, and wind speed. The NH3‐volatilization model is executed with five primary factors as input variables. With the input of time, it predicts the NH3 loss for a specified period. The interactive effects of these factors were studied by individually varying one factor while maintaining the four other factors at their mean values; the same factor was also studied by maintaining a second factor at its highest and lowest values while the other three factors were kept constant at their mean values. It is seen that, by changing the existing conditions, the NH3‐volatilization losses are increased or decreased appreciably. The sensitivity analysis shows that pH is the most sensitive and temperature and water depth are the least sensitive determinants affecting NH3 volatilization.
A Wick Tensiometer to Measure Low Tensions in Coarse Soils
Authors: Gee Glendon W. , Campbell Melvin D. 
Published: July 2010

AbstractA wick tensiometer was constructed to measure soil water pressures or tensions in coarse sands and gravelly soils. The tensiometer is similar in design to a conventional tensiometer except that a flexible wick material is used instead of a ceramic cup. Soil matric potential (reported as tension) or water pressure is sensed by the wick and monitored with a pressure transducer or hanging water column. Several wick materials were tested. Absorbent toweling, rolled to form a tight cylinder and sealed into a tensiometer body by a compression fitting, measured tensions up to 90 cm successfully. Glass‐fiber filter paper and wettable plastic sheeting were also tested successfully. Initial tests indicated that the wick sensor was as responsive to tension changes in gravelly soil as ceramic cup units and was less likely to break during placement.
Soil Denitrification and Nitrification Potentials during the Growing Season Relative to Tillage
Authors: Staley T. E. , Boyer D. G. , Caskey W. H. 
Published: July 2010

AbstractSoil management practice, through the alteration of various biological processes, can have a profound effect on nutrient availability to crops. During the growing season, the effect of no‐tillage (NT) or conventional tillage (CT), location (between or within row), and N rate (0 or 56 kg N ha−1) on soil potential denitrification activity (PDA) and potential nitrification activity (PNA) was investigated. A Gilpin silt loam (fine‐loamy, mixed, mesic Typic Hapludults) was selected and maize (Zea mays L.) was planted. For both PDA and PNA, most of the activity was concentrated in the soil surface (0–3.8‐cm) layer, especially under NT, and decreased to barely detectable levels in the deepest (15–30‐cm) layer examined. Significant main effects were found for tillage, season, and location for PDA in the soil surface layer. Tillage interacted only with season, resulting in an increase in PDA under NT, and a lack of response under CT, during the growing season in both the soil surface and the 3.8‐ to 7.6‐cm layers. For PNA in the soil surface layer, significant main effects were found for all treatments. Only location interacted with tillage, resulting in a 50% increase in PNA from within rows to between rows under NT, and a lack of response under CT. In the 3.8‐ to 7.6‐cm layer, the lowest order interaction was significant. In the 7.6‐ to 15‐cm layer, PNA increased more rapidly under CT than NT during the growing season. These results demonstrate the importance of considering spatial distribution and time when these microbial activities are examined in tillage studies, and suggest that N losses under NT should exceed those under CT.
Occurrence and Correction of Manganese Deficiency in Histosol‐Grown Rice
Authors: Snyder G. H. , Jones D. B. , Coale F. J. 
Published: July 2010

AbstractRice (Oryza sativa L.) production is seldom limited by availability of Mn in mineral soils. Manganese deficiency of seedling rice was suspected, however, in drained Histosols with pH values near or exceeding 7.0 in the Everglades Agricultural Area. Several greenhouse and field studies were conducted to verify the occurrence of Mn deficiency, to document its effect on rice growth, and to explore methods for alleviating the deficiency in Histosols. Manganese deficiency was determined to limit the growth of rice seedlings drill‐planted in several drained Histosols having pH values ranging from 6.9 to 7.7. Approximately 3 wk after seedling emergence, deficiency symptoms were evident as interveinal chlorosis on fully expanded leaves. Affected seedlings were shorter, had fewer leaves, weighed less, and had less root mass and length than unaffected seedlings. Affected seedlings contained <20 mg Mn kg−1 tissue. The deficiency also reduced grain yield in the field. In the greenhouse, several methods were investigated for preventing the deficiency. These included soaking seeds in Mn solutions, foliar application of Mn, flooding, or placing Mn fertilizer with the seed at planting. The latter proved to be the best method for preventing the deficiency. The results of the field studies indicated that application of approximately 15 kg Mn ha−1 as MnSO4 with the seed prevented the deficiency and provided near‐maximum grain yields.
Origin of Silt‐Enriched Alpine Surface Mantles in Indian Basin, Wyoming
Authors: Munn L. C. , Spackman L. K. 
Published: July 2010

AbstractThree soil profiles developed over different bedrock (intrusive mafic pods and granite gneiss) in the Wind River Range, Wyoming were examined to determine the origin of their high‐silt‐content surface horizons. Particle‐size distributions and clay mineralogy support the hypothesis that the soils have formed in surficial deposits derived from local bedrock materials. The soils are the product of physical (gelifraction) and chemical weathering, influenced by colluvial and (local) eolian transport processes. Mineral weathering has produced vermiculite and illite with an alteration or loss of chlorite and interstratified smectite‐kaolinite. The silt‐enriched mantles are distinctly different from loess. Frost action has resulted in silt and clay production in surface horizons and in mixing of materials throughout the profiles.
Acidification Induced by Different Nitrogen Sources in Columns of Selected Tropical Soils
Authors: Stumpe John M. , Vlek Paul L. G. 
Published: July 2010

AbstractSustainability in agriculture is a rising concern in the tropics where fertilizers are introduced to meet increasing food demands. The adverse effects of long‐term fertilizer use were monitored through changes in the soil exchange complex in packed columns of an Oxic Paleustalf, a Typic Paleudult, and a Tropeptic Haplustox. Following each application of N at rates of 0, 50, or 100 kg ha−1 as urea, ammonium sulfate (AS), or calcium ammonium nitrate (CAN), the soils were flushed with distilled water, representing the water draining from these soils in their respective tropical environments during a growing season. The procedure was repeated 30 times during 2 yr with 6‐wk rest periods after each five cycles. The rate of acidification reflected the rate of application and acid‐producing capacity of the N source. In the Oxisol and Ultisol, further acidification resulted in an increase in exchangeable Al and Mn, which were eventually found in the effluent, suggesting mineral dissolution. In the Alfisol, acidification resulted in a loss of cation‐exchange sites and the increasing predominance of Al and Mn. This acid‐consuming process caused the development of a descending acidification front, in which soil pH dropped from 6.7 to 5.0. Leachates remained neutral until the acidification front reached the bottom of the soil column. Applied N was quantitatively recovered in the leachates of all soils. Although plant growth would moderate these processes, the results show that indiscriminate N use on such fragile soils may eventually cause soil degradation and groundwater pollution.
Temporal Effects of Subsoil Compaction on Soil Strength and Plant Growth
Authors: Lowery B. , Schuler R. T. 
Published: July 2010

AbstractIn recent years, scientists have become concerned that heavy farm equipment is causing soil compaction below the nominal depth of tillage. Compaction this deep may not be ameliorated after one season's freeze‐thaw and wet‐dry cycles. Experiments were conducted on a Kewaunee (fine, mixed, mesic Typic Hapludalf) and Rozetta (fine‐silty, mixed, mesic Typic Hapludalf) soil to determine the duration and effect of subsoil compaction on soil strength and corn (Zea mays L.) growth. Soil at two sites was compacted with 8 and 12.5 Mg axle loads in the spring of 1983. Cone‐penetration resistance of compacted soil was significantly higher than that of uncompacted soil below the plow zone. Plant heights, at physiological maturity averaged across both sites, were reduced 13 and 26% on the 8‐ and 12.5‐Mg compaction treatments, respectively, compared with the control in 1983. In 1984, average mature plant heights were 2.4, 2.3, and 2.3 m for the control, 8‐, and 12.5‐Mg compaction, respectively. Three years after the compaction was applied (1986), the average mature plant height for the 8‐ and 12.5‐Mg compacted sites were reduced 3.1 and 4.3% compared with the control. Nitrogen and K uptake was reduced by compaction. Iron, Al, and Mn uptake increased with increasing levels of compaction on the Kewaunee soil in 1983. In 1983, yields for the 8‐ and 12.5‐Mg treatments on the Rozetta soil were reduced 4 and 14%, respectively, relative to the control. Similarly, yields for the Kewaunee soil were reduced 14 and 43%. Yields for the Kewaunee soil were not reduced by compaction in 1984, although 5 and 9% reductions were observed at the Rozetta site. Yields were not affected the following 2 yr (1985 and 1986), whereas the resistance to cone penetration was significantly higher in the compacted plots compared with the control.
Productivity Index Model Modified to Estimate Variability of Montana Small Grain Yields
Authors: Wilson J. P. , Sandor S. P. , Nielsen G. A. 
Published: July 2010

AbstractThe productivity index (PI) model estimates crop productivity by characterization of the soil rooting environment and evaluates a soil's vulnerability by simulated removal of surface soil and consideration of three soil properties, available water‐holding capacity, bulk density, and pH. Although the PI model has performed well in the Corn Belt and elsewhere, further testing is required to demonstrate its applicability in northern Great Plains small‐grain environments. Evaluation of PI model performance in Cascade County, Montana, revealed a weak relationship between PI and small‐grain yield that may have been due to shortcomings in the SOILS‐5 database. Therefore, soils and crop data were collected in August and September 1987 from four fields in Hill and Jefferson Counties to evaluate model performance and indicate appropriate changes in the model's design to allow its use in Montana. Results indicate that model performance can be improved by addition of the content and location of organic matter and CaCO3 in the soil profile. Productivity indices were first generated with the original model. The regression of small‐grain yield against PI accounted for 64, 67, 63, and 1% of the variability in yield within Fields 1 through 4, respectively. When the modified PI values were used, R2 increased an average of 44% and accounted for 77, 69, 60, and 75% of the variation in grain yield within Fields 1 through 4, respectively. Moreover, R2 increased slightly (0.69 to 0.75) for all fields collectively when cropping history was considered. These results have encouraged further efforts to develop a modified and improved version of the PI model that uses the SOILS‐5 database for county‐scale assessments in northern Great Plains small‐grain environments.
Cover Crop Management of Polysaccharide‐Mediated Aggregation in an Orchard Soil
Authors: Roberson Emily B. , Firestone Mary K. , Sarig shlomo 
Published: July 2010

AbstractSoil carbohydrates, including microbial extracellular polysacchrides, stabilize soil aggregates and improve soil structure. This study examined whether short‐term managment of C inputs by cover crops and tillage affected polysaccharide‐mediated macroaggregation. Soil was sampled from a Californa prune (Prunus domestica L.) orchard where an experiment comparing four management techniques, permanent grass cover crop, mowed cover crop, no‐till herbicide, and conventional tillage, had been in place for two seasons. Cover crops significantly increased saturated hydraulic conductivity, acid‐ex‐tractable heavy‐ fraction carbohydrates (those in soil denser than 1.7 g/mL), and macroaggregate slaking resistance over clean‐cultivated or herbicide treatments. Heavy‐fraction carbohydrates are probably mainly composed of microbial extracellualr polysaccharides produced in response to cover‐crop C inputs. Heavy‐fraction carbohydrates were significantly correlated with aggregate stability and satureated hydraulic conductivity, while total organic C and lightfraction carbohydrates were not. There were no differences between soil under herbicide and clean‐cultivation treatments, showing that tillage alone did not measurably affect carbohydrate or soil structure. Heavy‐fraction carbohydrates were shown to be important in the initial improvement of soil structure by cover crops.
Nutrient Flux to Mixed‐Bed Ion‐Exchange Resin: Temperature Effects
Authors: Yang J. E. , Skogley E. O. , Schaff B. E. 
Published: July 2010

AbstractThe phytoavailability soil test (PST) is designed to assay plant‐available nutrient quantity as a function of diffusive ion movement to a spherical, mixed‐bed ion‐exchange resin sink. Temperature is known to alter many parameters relating to nutrient availability and plant uptake. This study was conducted to determine PST sensitivity to temperature‐induced changes in availability of NO‐3‐N, NH+4‐N, P, K, and S. Nutrient flux to resin accumulators was measured during 96 h at 25, 35, and 45 °C. Fluxes of P, K, S, and NH+4‐N all increased with increasing temperature, while the flux of NO‐3‐N decreased. The size of the temperature effect was nutrient and soil specific. Nutrient‐accumulation characteristics were significantly represented by quadratic equations, corresponding to diffusion‐controlled processes. Initial flux (0.5 h) of each nutrient to the resin was rapid and highly related to nutrient ion activity in saturated‐paste soil solutions equilibrated for 24 h. The slope of the accumulation curve decreased after the initial rapid flux. This is interpreted to suggest that diffusion characteristics of the soil control, to a large degree, the flux of nutrients to the resin accumulator after an initial rapid phase related to high nutrient activity in the soil solution. These results provide strong evidence that the PST system is diffusion controlled and that it is sensitive to conditions known to influence nutrient availability in soils, such as temperature and nutrient ion activities.
Potassium Trends in Red Pine Plantations at Pack Forest, New York
Authors: Nowak C. A. , Downard R. B. , White E. H. 
Published: July 2010

AbstractTrees are believed to cause improvement of nutrient availability in impoverished soils; however, evidence for this ameliorative capacity has generally been only circumstantial. Long‐term monitoring of chemical changes in forest soils on nutrient‐poor, agriculturally degraded sites may provide evidence of amelioration by trees. At the Pack Forest in the southeastern Adirondack Mountains of New York, soil and foliar K were periodically measured from 1949 to 1987 in red pine (Pinus resinosa Ait.) plantations established in the late 1920s to early 1930s. These plantations were established two decades after the area had been abandoned following a century of exploitive agriculture, when the inherently nutrient‐poor site was further impoverished for K by crop removal. For unfertilized plantations, both Ap horizon exchangeable K and K in current‐year foliage increased from the 1950s to the 1980s; the rate of soil K increase was 250 g ha−1 yr−1. For K‐fertilized stands, Ap horizon and foliar K were constant throughout the measurement period. High potential for the parent material to supply K, coupled with conservative biogeochemical cycling, can account for the increase and maintenance of K in this agriculturally degraded system.
Seasonal Variation in Solution Composition and Mineral Stability of Two Kentucky Alfisols
Authors: Karathanasis A. D. 
Published: July 2010

AbstractSeasonal variations in the soil solution composition of two Maury soils (fine, mixed, mesic Typic Paleudalf) of the inner bluegrass region in Kentucky were investigated by monitoring solution chemistry changes of Ap, Bt, and BC horizons during the spring, fall, and winter of 1988. During the summer, the soils were too dry for soil solution extraction. Temporal soil moisture variations accounted for only a small portion of the variability in solute activities. The resultes demonstrated that, for most solutes, there were significant seasonal differences as well as differences between horizons and between soils. Many solute activities spanned a temporal range of ≈ ±5 times the mean, with Al showing one of the highest (≈10 times) and H4SiO4 one of the lowest (≈3 times) variations. The highest solute activities were attained during early fall and the lowest during the spring or winter seasons. The contrasting behavior of pH and certain solutes (Al, Na, Mn, H2PO4) within and between soils was attributed to stratification effects of the weathered limestone beds. Seasonal fluctuations of Al, Si, Mg, K, and H in solution apparently have moderate effects on illite → vermiculite/smectite → kaolinite weathering relationships, with kaolinite formation being favored during Si‐depleted spring periods and vermiculite/smectite during Si‐enriched fall (and probably summer) months. Temperature decreases during the winter appeared to enhance the stability of lower order kaolinite, gibbsite, and quartz mineral phases. Even though the consistency of the observed relationships is subject to the uncertainty of the thermodynamic data used and the variability from year to year, the results of this study point out that temporal variations in solution chemistry have indeed a significant impact on chemical weathering and nutrient‐availability patterns.
Measurement of Cadmium Activities in Slightly Acidic to Alkaline Soils
Authors: El‐Falaky A. A. , Aboulroos S. A. , Lindsay W. L. 
Published: July 2010

AbstractThe solid phases that control Cd2+ solubility in soils are poorly understood. This study was made to measure Cd2+ activity in nine slightly acidic to alkaline soils using competitive chelation, which avoids errors that may be caused by unknown Cd‐organic complexes that may be present. The Cd2+ activities measured in these soils varied widely, ranging from 10−6.61 to 10−9.31 M, and were inversely related to soil pH with a correlation coefficient (r2) of 0.95. The activities of Cd2+ in the soils could be predicted from the equation (Cd2+) = 106.5(H+)2. A solubility diagram was constructed for various Cd minerals using the thermodynamic data selected from the literature. The equilibrium constant (Ko) for the reaction of CdFe2O4(c) was derived assuming that the entropy (So) value of CdFe2O4(c) is similar to that of ZnFe2O4(c). The diagram suggests that CdFe2O4(c), in equilibrium with soil Fe, is a likely solid phase controlling Cd2+ activities in these soils.
Diffusion and Automated Nitrogen‐15 Analysis of Low‐Mass Ammonium Samples
Authors: Kelley K. R. , Ditsch D. C. , Alley M. M. 
Published: July 2010

AbstractConventional steam‐distillation techniques for concentrating inorganic N in soil extracts prior to 15N analysis are time‐consuming and labor‐intensive procedures. Diffusion procedures have been proposed as alternatives to steam distillation, but incomplete recovery and isotope dilution have been reported. We evaluated a procedure for diffusing low masses of 15NH4‐N from 2 M KCl solution to determine the effects of NH4 and 15N concentrations on recovery and isotope‐ratio analysis of diffused N. A series of solutions were prepared containing from 0.5 to 2.5 mg N L−1 at 1.1461 atom % 15N. Forty‐milliliter aliquots were placed in plastic containers, equipped with acidified glass‐fiber disks, and allowed to diffuse for either 6 d at room temperature or 5 d at 55 °C. Nitrogen recovery in glassfiber disks averaged 100.5% of the added N. Quantitative recovery of added N was also obtained in a second study in which 30‐mL aliquots of standard solutions containing from 25 to 100 µg N at 15N concentrations varying from 0.1030 to 1.1461 atom % 15N were diffused for 10 d at 55 °C. Significant dilution of 15N concentration for low‐mass N samples occurred. Differences in 15N concentrations between diffused and nondiffused samples were attributed to background N at a 15N concentration of natural abundance. Close agreement was obtained between diffused and nondiffused samples when an isotope‐dilution equation was used to calculate the atom % 15N concentration of the sample N. These studies indicate that the diffusion method is suitable for preparing low‐mass N samples for 15N analysis if appropriate blanks are determined and used to correct for background N.
Soil Phosphorus Extracted By Iron‐Aluminum‐Oxide‐Impregnated Filter Paper
Authors: Sharpley Andrew N. 
Published: July 2010

AbstractThe use of Fe‐Al‐oxide‐impregnated paper strips may allow estimation of plant‐available P contents of soils with widely differing properties. Little information is available on the forms of P extracted by paper strips (SP). Relationships between SP and Olsen, Bray I, Mehlich III, and P fractions were investigated for 203 surface soils representing all soil orders. Soils were divided into calcareous, slightly weathered, and highly weathered groups, based on taxonomy and weathering. Amounts of P extracted by paper strips were closely correlated (r2 of 0.89 to 0.93, P > 0.001) with soil‐test P (Olsen, Bray I, and Mehlich III), for soils on which use of the test is recommended. It is suggested that the paper strips removed primarily physically bound extractable P from all soils (approximate 1:1 relationship), with little extraction of amorphous Al and Fe or Ca compounds indicated. A potential general applicability of Fe‐Al‐oxide‐impregnated paper strips to estimate plant‐available soil P is suggested.