bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Field Study Using Dyes to Characterize Preferential Flow of Water
Authors: Ghodrati Masoud , Jury William A. 
Published: July 2010

AbstractCharacterization of preferential flow in soils through normal water tracer studies are, in most cases, inconclusive because of the inability of most solute sampling devices to detect the spatial pattern of preferential flow pathways. In this study, a number of field‐plot experiments were performed to provide direct observation of the preferential flow of water and solutes by adding soluble dye to stain the flow pathways. In addition to characterizing the spatial structure of preferential flow pathways, the dye trace patterns were used to investigate the interactive role of soil structure and irrigation methods on the preferential flow patterns of water and solutes. A narrow pulse of an anionic water‐soluble dye, Acid‐Red 1, was applied to the surface of a number of 1.5 by 1.5 m field plots, some of which had the top layer completely disturbed to the depth of 30 to 40 cm. The distribution patterns of the dye in these plots were examined after the plots received 100 mm of irrigation water, under either ponding or daily sprinkler irrigation. The observed vertical and horizontal distribution patterns of the water‐soluble dye clearly indicated the preferential flow patterns for each experimental condition. These include vertical fingering of dye traces 5 to 20 cm wide, which extended more than twice as deep as the mean displacement of the dye, as well as isolated patches of dye indicating lateral flow.
Steady‐State Aerobic Microbial Activity as a Function of Soil Water Content
Authors: Skopp J. , Jawson M. D. , Doran J. W. 
Published: July 2010

AbstractSoil physical properties often regulate aeration‐dependent microbial activities important to nutrient cycling, soil fertility and environmental quality. Microbial activity depends on soil water content and is maximum at a water content where the limiting effects of substrate diffusion and O2 supply are equal. The mechanism whereby this occurs and predictions of the soil water content where aerobic microbial activity is a maximum were the objectives of this study. In particular, this study predicted the shape of the microbial activity vs. water content function from soil physical concepts. Soil physical processes are assumed to influence microbial activity by limiting the steady flux of a required substrate or O2 to sites of microbial activity. Steady‐state flux relations are used to define the activity function. The dependence of diffusion coefficient on water content or air‐filled porosity is assumed. With these assumptions, it is possible to show that a maximum in the activity function exists. The predicted shape of the activity curve is consistent with experimental observations. The relationship between aeration‐dependent microbial activity and soil water content facilitates evaluating the indirect effects of soil management practices, such as tillage, on microbial activity.
Factors Affecting Rice Growth on Acid Sulfate Soils
Authors: Moore P. A. , Attanandana T. , Patrick W. H. 
Published: July 2010

AbstractRice (Oryza sativa L.) yields on acid sulfate soils, which comprise a sizable portion of the rice‐growing area in Southeast Asia, are constrained by soil parameters. The objective of this study was to identify those parameters most strongly related to rice growth. Metal availability and uptake by rice were evaluated in the Central Plains of Thailand using 134 flooded acid sulfate soils and in a growth chamber utilizing 50 of them. Nutrient‐uptake data indicated that uptake of divalent cations was most closely correlated to the divalent activity ratio (Ametal). Although many individual parameters were correlated with rice growth, results from multiple correlation analysis indicated that AFe (the ratio of Fe2+ activity to the sum of the activities of all other divalent cations), pH, and ionic strength provided the best three‐variable model describing dry‐matter production in the growth‐chamber study. In the field, the best two‐variable model describing yields included pH and AFe. Therefore, the most important constraints to rice growth on acid sulfate soils were (i) acidity, which includes the combined effects of pH, Al toxicity, and P deficiency, and (ii) Fe stress, which is due to the combined effects of Fe toxicity and deficiencies of other divalent cations such as Ca. This study indicates the importance of divalent activity ratios such as AFe when studying metal uptake or modeling plant growth. In a micronutrient fertility trial conducted under greenhouse conditions, the only significant yield response occurred when Si was applied to a limed acid sulfate soil.
Soil Inorganic Phosphorus Fractions and Their Uptake Relationships in Calcareous Soils
Authors: Yang Jae E. , Jacobsen Jeffrey S. 
Published: July 2010

AbstractCrop responses to recommended P‐fertilizer applications are erratic in high pH, calcareous soils of Montana. The objective of this research was to evaluate relationships between soil inorganic P (P1) fractions, Olsen‐P, and plant uptake. Soil‐incubation and plant‐growth experiments were conducted on samples of six calcareous soils from P‐responsive locations in Montana. Rates of P were 0, 11, 22, and 33 mg P kg−1 applied to soils in a randomized complete‐block design with four replications. Spring wheat (Triticum aestivum L. cv. Newana) was grown successively during three, 4‐wk growing periods. Fertilized soils were incubated without plants during the same period. Soils were subjected to a sequential‐fractionation procedure (resin‐P, NaHCO3‐P, NaOH‐P, and HCl‐P). Soil P1 quantities were HCl‐P > NaOH‐P > NaHCO3‐P (bic‐P) > resin‐P. Higher Olsen‐P soils had higher summation of P1 fractions than lower Olsen‐P soils. Changes in resin‐P accounted for most of P1‐fraction differences induced by P application and plant uptake. Cropped soils generally contained lower amounts of P1 in each fraction than noncropped soils. Highly significant (P > 0.01) correlations were found for Olsen‐P vs. resin‐P, P uptake vs. resin‐P, and P uptake vs. Olsen‐P, but not for Olsen‐P vs. bic‐P, resin‐P vs. bic‐P, and P uptake vs. bic‐P. Resin‐P was the best indicator of P‐uptake responses on these soils to P applications and should be considered in the prediction of crop responses.
Statistical Comparison of Soil Map‐Unit Boundaries
Authors: Nash M. H. , Daugherty L. A. 
Published: July 2010

AbstractLocating the exact boundaries of soil map units is one of the primary objectives for soil surveyors. Statistical methods were used to assure the most accurate location. Soil spatial variability, autocorrelation function, and soil boundary locations were examined along a 2700‐m transect in southern New Mexico. Eighty‐nine observation points were equally spaced along the transect. Selected physical and chemical characteristics through the transect were determined. A multivariate method of principal‐component analysis was used to produce one set of data. These data were first inspected for stationary manner, i.e., that the mean and variance of each property remain fairly constant for each data set. Log‐normal transformation was used to detrend the data. The stationary manner of autocorrelations was tested with semivariograms. The range of dependence obtained from the autocorrelations and semivariograms was used in a squared‐Euclidean‐distance procedure to locate the soil boundaries. These boundaries were compared with those obtained by conventional soilsurvey methods. Some of the calculated boundaries agreed with those obtained by conventional soil survey. The latter method is more economical and more productive than the statistical method.
Soil Erosion and Deposition Evidence in a Small Watershed Using Fallout Cesium‐137
Authors: Soileau J. M. , Hajek B. F. , Touchton J. T. 
Published: July 2010

AbstractSoil measurements of 137Cs, a fallout component of nuclear testing, were made within a 3.8‐ha research watershed in the Limestone Valley of northern Alabama. Objectives of the study were to: (i) compare 137Cs activity in soil profiles on eroded and depositional landscape positions, and (ii) relate soil erosion and deposition calculated by 137Cs methods to erosion estimated by the Universal Soil Loss Equation (USLE) and to sediment discharge measured at the watershed outlet. Triplicate soil profiles were analyzed for 137Cs activity to a 46‐cm depth in cultivated sites representing slightly eroded ridgetop, eroded side‐slope, and depositional downslope positions. These data were compared with baseline 137Cs measurements in undisturbed adjacent woodland. Erosion calculated by 137Cs activity losses from baseline values were compared with the USLE estimates on slope transects. Mean total 137Cs activities on baseline, eroded, slightly eroded, and depositional sites were 4860, 1804, 2807, and 5367 Bq m−2, respectively. Peak 137Cs activity and depth to zero activity were much greater in depositional than in eroded and slightly eroded sites. Estimated mean annual (1954–1987) soil‐erosion rates were similar between 137Cs and USLE methods for a slope transect with slight erosion (28 and 26 Mg ha−1 yr−1). On eroded side‐slopes, 137Cs estimates of erosion were 27 to 80% higher than the USLE estimates. This may be due to rill erosion unaccounted for by the USLE. The USLE estimated losses between 9 and 52 Mg ha−1 yr−1 for uplands during 1984 to 1988 cotton production. Sediment losses measured below the downslope depositional area of the small watershed (Gilbert Farm Research Watershed) were only 1 to 4 Mg ha−1 yr−1. This indirect evidence of extensive sediment deposition in a representative small watershed of karst terrain was supported by 137Cs activity in depositional soil profiles.
Comparison of Two Static Chamber Techniques for Determining Carbon Dioxide Efflux from Forest Soils
Authors: Raich J. W. , Bowden R. D. , Steudler P. A. 
Published: July 2010

AbstractThe similarity of two commonly used methods of measuring CO2 fluxes from forest soils was assessed by directly comparing the sodalime method with a static chamber technique using gas chromatographic analysis of CO2 ‐concentration changes during short‐term incubations. A paired‐chamber sampling design was applied in 11 different forest stands to examine the two methods across a range of soil‐CO2 efflux rates. Carbon dioxide efflux rates were highly variable within sites, and showed no spatial autocorrelation. No consistent differences in measured rates of CO2 efflux were observed between the two methods, indicating that either method may be applied to the range of mean daily rates encountered in this study (1.7–11.4 g m−2 d−1). A large number of chambers can be deployed with the soda‐lime method, but no information on diel variations in efflux rates is obtained. The short‐term incubation technique, on the other hand, can be utilized to simultaneously monitor several trace gases and diel trends in flux rates. Selection between the methods should be based on the hypotheses being tested or on practical constraints.
Phosphate‐Fertilizer‐Induced Salt Toxicity of Newly Planted Apple Trees
Authors: Peryea F. J. 
Published: July 2010

AbstractMonoammonium phosphate (MAP) or triple superphosphate (TSP) added to planting holes often stimulates early growth of apple trees (Malus domestica Borkh.); however, high rates may stunt or kill trees. A greenhouse study was conducted on a Quincy sand (a mixed, mesic Xeric Torripsamment) and a Cowiche silt loam (a fine‐loamy, mixed, mesic Aridic Argixeroll) to examine effects of soil type, P source (MAP or TSP), and P rate (0–2.75 kg P/m3) on soil salinity, soil acidity, and apple tree growth in nonleaching soil systems during a 56‐d period after planting. Rootstock and old scion masses were not affected by soil type or P treatments. In the Quincy sand, new scion mass and root mass were inversely related to P rate in both MAP‐ and TSP‐amended soil; tree death occurred at P rates above 1.65 kg/m3. In the Cowiche soil, root mass was independent of and new scion mass was inversely related to P rate. At equivalent P rates, TSP produced lower soil salinity and greater soil acidity than MAP. For a given P source, soil salinity and acidity were positively related to P rate. Soil salinity decreased and soil pH increased over time. Relative new scion mass was inversely related to time‐integrated soil salinity; however, the relationships were soil‐specific. Total exchangeable soil acidity was positively related to P rate and was soil‐dependent. Exchangeable soil Al was detected only at the two highest TSP rates in the Quincy soil. Indirect evidence suggested that Mn, NH3, and NO2 phytotoxicities and any nutrient deficiencies were absent. The results suggest that transient soil salinization is the primary mechanism for MAP‐ and TSP‐induced apple tree phytotoxicity.
Modified‐Quadratic/Plateau Model for Describing Plant Responses to Fertilizer
Authors: Bock B. R. , Sikora F. J. 
Published: July 2010

AbstractAccurate estimation of optimal fertilizer rates is becoming more critical because of growing economic and environmental concerns associated with fertilizer use. Curve‐fitting techniques are often used to estimate optimal fertilizer rates, but significant problems exist in selecting a proper model for a particular cropping situation. One solution is to develop a model sufficiently general to preclude the need for selecting a proper model for each cropping situation. We developed a modified‐quadratic/plateau (MQ/P) segmented model (four or five parameters) and demonstrated its general applicability compared with the quadratic/plateau (MQ/P) segmented model (three parameters) for describing fertilizer responses. The MQ/P model contains an efficiency index (Ex) that is a quadratic function of the applied rate of nutrient X. In the Q/P model, Ex remains constant relative to the rate of nutrient X. The MQ/P and Q/P segmented models set yield equal to the maximum yield (Ym) when the rate of nutrient X is greater than that required to achieve Ym. The general applicability of the MQ/P model in comparison with the Q/P model was evaluated by determining how well these models fit hypothetical input data calculated with linear/plateau (L/P), Mitscherlich (M), and square root/plateau (SR/P) functions. The MQ/P model gave R2 values >0.99 and predicted economically optimum fertilizer rates (i.e., rates at which the first derivative of yield response functions equaled the fertilizer/crop price ratio) close to those calculated with the input functions. The Q/P model gave R2 values ranging from 0.95 to 0.99, but gave poor predictions of economically optimum fertilizer rates. The ability of the MQ/P model to fit functions as diverse as L/P, M, and SR/P, and to predict economically optimum N rates associated with these functions, suggests that the MQ/P model has utility as a general curve‐fitting technique for responses in which the right‐hand segment is a plateau. An advantage of the MQ/P model is that the regression parameters can be interpreted as physically meaningful constants.
Acidification and Liming Influence on Surface Charge Behavior of Kentucky Subsoils
Authors: Lumbanraja J. , Evangelou V. P. 
Published: July 2010

AbstractSpecific adsorption of ions onto soil clay surfaces influences the magnitude and behavior of the surface charge. This study evaluated the influence of acidification and liming on surface charge magnitude and behavior of three Kentucky subsoils (Eden and Lowell, fine, mixed, mesic Typic Halpludalfs; and Nicholson, a fine‐silty, mixed, mesic Typic Fragiudalf) that have consistently shown poor crop response to added fertilizer. Soil samples were adjusted to three pH values (4.0–4.3, 5.5–5.8 and 6.8–7.3) with either HCl or Ca(OH)2 and were titrated with either NH4OH or KOH as titrants and NH4Cl or KCl as background electrolytes. The titration procedure was a rapid stop‐and‐go technique. The soil samples initially adjusted with HCl to a pH range of 4.0 to 4.3 exhibited titration behavior similar to a clay surface loaded with trivalent Al. The KOH titration plots exhibited a common cross‐over point, a titration behavior commonly associated with variable‐charge surfaces, for two of the soils (Eden and Lowell). The same titration behavior was not apparent when titrated with NH4OH. For the samples initially adjusted with Ca(OH)2 to pH ranges of 5.5 to 5.8 or 6.8 to 7.3, titration behavior was influenced by the clay permanent negative charge. With increasing background electrolyte concentration, the titration plots were displaced to the right without an apparent cross‐over point. These samples also exhibited a pH‐buffering region in the range of 6.0 to 8.5. On most soils, this is often attributed to the CaCO3‐HCO3 buffer system. This buffer system cannot be implicated in this study, since CO2 and CaCO3 were excluded. It appears that in these soils, K and NH4 do not behave as analogs of each other; rather, each reacts with adsorption sites exhibiting certain ion specificity. The findings suggest that, when soils with vermiculite‐Fe oxide mineralogy change their pH, they also change their surface chemistry with respect to adsorption of K and NH4, but not in a predictable manner.
Binary and Ternary Exchange of Potassium on Calcareous Montmorillonitic Soils
Authors: Feigenbaum Sala , Bar‐Tal Asher , Portnoy Rita , Sparks Donald L. 
Published: July 2010

AbstractSimultaneous K exchange with Ca, Mg, and Na occurs in soils, but most of the published information is obtained from binary systems. The theoretical question of whether selectivity coefficients obtained in binary systems are valid for ternary systems has not yet been clarified; however, no significant difference has been found between selectivity coefficients in binary and ternary systems. Potassium exchange with Mg plus Ca was studied in two calcareous soils with variable concentrations of Na, using batch and miscible‐displacement methods. Preference for K over the divalent cations was found in both soils, regardless of Na concentration and the experimental methods. Modified Gapon (kG) and Vanselow (kV) selectivity coefficients were calculated for each cation pair in binary and ternary systems. In both soils, the kv and the kG decreased with increasing K fraction in the solution, but the kG value was less affected than the kv. A simple mathematical solution of the Gapon binary equations, K − (Mg + Ca) and Na − (Mg + Ca), in combination with an assumption of constant cation‐exchange capacity (CEC), was used to predict the amount of exchangeable K as a function of solution composition in a ternary system. The high correlation of predicted exchangeable K with the directly measured values shows that binary selectivity coefficients can be used in multicationic systems on calcareous montmorillonitic soils.
Ammonium Fixation, Release, Nitrification, and Immobilization in High‐ and Low‐Fixing Soils
Authors: Beauchamp E. G. , Drury C. F. 
Published: July 2010

AbstractThe objective of this study was to determine if competing sinks for added NH4 (i.e., immobilization and nitrification) affected NH4 fixation and release. Low‐ and high‐fixing soils, N rate, K preaddition, and temperature were variables chosen for studying these processes. Labeled (15NH4)2)SO4 was added to soils and they were aerobically incubated. At the end of each incubation, fixed 15NH4 and KCl‐extractable 15NH4 and 15NO3 were determined. Ammonium fixation was mainly responsible for the disappearance of extractable 15NH4 in a high‐fixing soil. The fixed 15NH4 fraction comprised 68% of the nonextractable 15N fraction in the high‐fixing soil, and 28% in the low‐fixing soil. In both soils, about half of the 15NH4 fixation occurred within 6 h after application. The maximum quantity of fixed 15NH4 occurred after 30 d. An 15NH4‐addition rate of 150 mg N kg−1 doubled the fixed 15NH4 concentration over that at 75 mg N kg−1. Low temperature did not affect the quantity of added 15NH4 fixed. Potassium preaddition reduced fixed 15NH4 concentration at 6 h, but did not appear to affect it subsequently. Immobilization of 5.7% of the added 15NH4 occurred in the high‐fixing soil, and 3.9% in the low‐fixing soil. Extractable‐ and fixed‐NH4 fractions were interrelated pools. When fertilizer NH4 was added to the soil, a proportional amount was fixed by the clay minerals. When nitrification and immobilization depleted extractable NH4, fixed NH4 was released. The fixed‐NH4 pool appeared to be a slow‐release reservoir, with fixed‐NH4 release being slower than the rate of fixation.
Reactivity of Phosphorus in Northeastern Brazilian Soils Assessed by Isotopic Dilution
Authors: Salcedo I. H. , Bertino F. , Sampaio E. V. S. B. 
Published: July 2010

AbstractTo diagnose fertilizer requirements in regions of high soil variability where P‐fixing capacities can vary 100‐fold, single‐extraction P tests must be complemented by an evaluation of P sorption. The isotopic‐dilution kinetics of 32P was tested for its potential to measure available P and to predict the degree of soil‐fertilizer P reactivity. Six soils from northeastern Brazil were fertilized with P, incubated (1, 42, and 84 d) and then seeded with pearl millet [Pennisetum glaucum (L.) R. Br.]. Soil samples were analyzed for water‐soluble P (Pw), resin P, 32P in solution 1 min after addition over 32 P added (R1/R0), rate of 32P disappearance from solution between 1 and 100 min (n), reversible P (Prev, determined by double isotopic dilution), mobile P (Pm = Pw + Prev), and isotopically exchangeable P (E1 and E‐value [E] for 1‐min and 24‐h equilibrium periods, respectively). Use of R1/R0 successfully differentiated soils in terms of net fertilizer effects on Pw and Pm with time. We found that Pw and Pm were better predictors of plant P uptake than resin P, E1, and E, since the latter quantities overestimated available P in a high‐P‐fixing Oxisol. Based on this and published data, we propose a critical value of R1/R0 (0.26) below which E values consistently overestimated labile P, while Pw correlated satisfactorily with available P. A modified technique overcomes limitations of measuring very low concentrations of Pw in such soils. To diagnose labile P and fertilizer responses in soils with R1/R0 > 0.26, we propose a simplified methodology that avoids the double isotopic dilution.
Some Andisols from Savai'i, Western Samoa
Authors: Morrison R. J. 
Published: July 2010

AbstractFive pedons in the lowlands and foothills of Savai'i were studied in detail to determine whether or not they were Andisols. All five met the requirements proposed by the International Committee for the Classification of Andisols (ICOMAND) for the designation of Andisols, as recently accepted into the soil taxonomy. Four of the pedons were Hapludands at the great group level, with subgroup differences due to base status, depth to lithic contact, and water‐retention properties being observed. The fifth pedon was a Thaptic Fulvudand with imogolite present. The results obtained indicate that Andisols are likely to dominate the landscape of Savai'i. This is rather unexpected, as Savai'i is the oldest island of the Samoa chain. Recent volcanism associated with the approach of Savai'i to the edge of the Tonga trench has “rejuvenated” much of the island, leading to the formation of young soils. Since certain soils on Savai'i and the adjacent island of Upolu are mapped as the same series, reexamination of the soils on both islands would appear necessary to determine whether or not the soils are sufficiently different to warrant the establishment of new series.