bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acidic Zones from Ammonia Application in Conservation Tillage Systems
Authors: Robbins S. G. , Voss R. D. 
Published: July 2010

AbstractSubsurface soil acidity resulting from repeated NH3 applications in long‐term conservation tillage systems that do not disturb the NH3 injection zone was studied in six different crop‐fertilizer‐tillage systems by: (i) observation of the size, shape, and distribution of acidic zones in the field by using a pH color indicator method and (ii) intensive quantitative sampling of the upper 25‐ to 30‐cm soil layer with subsequent laboratory analysis for soil pH. Acidic soil zones created by the nitrification of the injected NH3 were roughly circular with 12‐ to 18‐cm diam. Soil pH of the acidic zones was generally 0.9 to 1.8 pH units lower than that of the surrounding bulk soil. In the ridge till‐plant and ridge slot‐plant systems studied, a distinct highly localized persistent acidic soil zone was detected in each interrow. On the basis of the extent and degree of acidity observed, it is concluded that yield‐limiting problems due to acidification by continuous NH3 applications are not likely in the ridge management systems studied. In the flat no‐till systems studied, numerous persistent acidic soil zones were observed scattered throughout each interrow. It is concluded that soil acidity problems due to long‐term NH3 usage potentially could develop in the no‐till systems studied where NH3 is not injected in the same vicinity each year. Efforts toward localized placement of N by the farm operator could effectively minimize potential problems due to the acidifying effects of NH3 in conservation tillage systems.
Measuring Nitrogen Losses from Lowland Rice Using Bulk Aerodynamic and Nitrogen‐15 Balance Methods
Authors: De Datta S.K. , Trevitt A.C.F. , Freney J.R. , Obcemea W.N. , Real J.G. , Simpson J.R. 
Published: July 2010

AbstractManagement practices, designed to reduce ammonia (NH3) volatilization and total N loss from flooded rice fields, after application of urea, were assessed in the dry season at Mabitac, Philippines. The assessment was made in replicated 4.8‐m × 5.2‐m plots by determining NH3 and total fertilizer N losses with bulk aerodynamic and 15N balance methods, respectively. The bulk aerodynamic method was first evaluated by comparison of ammoniacal‐N concentrations, pH values, and equilibrium NH3 concentrations for a 50‐m diam, circular area and small plots receiving the same fertilizer treatment. Good agreement was obtained so the bulk aerodynamic method was used to determine NH3 loss from the small plots receiving the different management treatments. Ammonia loss was high when urea was broadcast into floodwater 10 d after transplanting—48 and 56% of the applied N was volatilized as NH3 during the first 8 d after application of 53 and 80 kg N ha−1, respectively. Total N losses were 60 and 59%, respectively. Ammonia loss was reduced slightly (to a mean of 43% of the applied N for the two application rates) by broadcasting the fertilizer into 0.05‐m‐deep floodwater and incorporating it into the soil by harrowing before transplanting. Removal of the floodwater before applying urea onto saturated soil and incorporation by harrowing reduced NH3 loss to a mean of 9% and total fertilizer N loss to a mean of 33%. Fertilizer N recovery by rice plants was significantly increased by incorporation without surface water.
Two‐Site/Two‐Region Models for Pesticide Transport and Degradation: Theoretical Development and Analytical Solutions
Authors: van Genuchten M. Th. , Wagenet R. J. 
Published: July 2010

AbstractAnalytical solutions are presented for two convection‐dispersion type transport models useful for studying simultaneous pesticide sorption and degradation. One solution is for the familiar two‐site sorption model in which adsorption‐desorption proceeds kinetically on one fraction of the sorption sites, and at equilibrium on the remaining sites. Another solution holds for two‐region (or mobile‐immobile liquid phase) transport appropriate for aggregated or fractured media. The transport models account for degradation in both the solution and sorbed phases. The dimensionless analytical solutions for the two‐site and two‐region models are shown to be identical; they contain up to six independent dimensionless parameters: a column Peclet number, a retardation factor, a coefficient partitioning the soil/chemical system in equilibrium and nonequilibrium parts, a rate coefficient, and two dimensionless degradation coefficients. One of the two independent degradation coefficients may be eliminated when the solution and sorbed phase degradation rate coefficients are assumed to be identical, or when, with additional but reasonable assumptions, adsorbed phase degradation is assumed to be negligible.
Analysis of Water Flow under Trickle Irrigation: I. Theory and Numerical Solution
Authors: Lafolie F. , Guennelon R. , van Genuchten M.Th. 
Published: July 2010

AbstractEstimating the size of the ponded surface area is a major source of error in modeling water movement under trickle irrigation. After reviewing available approaches and models for simulating water flow under trickle irrigation, we present a new numerical solution of the governing partial differential equations that improves the prediction of the size of the ponded area at the soil surface. A common formulation could be used for both Cartesian and axicylindrical flow geometries. The spatial operator was approximated using finite differences, and time integration was performed with an implicit method. Nonlinearity was treated by means of a fixed point iterative algorithm. The proposed model is applicable to saturated‐unsaturated flow in layered soils having anisotropic hydraulic properties. Accuracy and stability of the solution are checked and comparisons made with previous numerical solutions for several trickle irrigation and other unsaturated flow problems.
Factors Influencing Early Performance of Leguminous Plants in Forest Soils
Authors: Schoeneberger M. M. , Volk R. J. , Davey C. B. 
Published: July 2010

AbstractSubterranean clover (Trifolium subterraneum L.), a winter annual, and big trefoil(Lotus pedunculatus Cav.), a summer perennial, are being studied for use in forestry operations. Establishment and performance of these plants with their associated rhizobia (+RHIZ) are adversely affected by the infertile, acid conditions generally encountered in forest soils. Using the 15N isotope dilution technique, we investigated the effects of N fertilization and inoculation with the vesicular‐arbuscular mycorrhizal fungus, Gigaspora margarita Becker and Hall (+VAMF) on early growth and N2‐fixing capabilities of these plants in a pasteurized acid forest soil containing low levels of both P and N. In clover, dual inoculation with + RHIZ, + VAMF at 10 kg N ha−1 enhanced N derived from the atmosphere (Ndfa), both on a per‐plant (350%) and a per‐gram total N (151%) basis, as well as plant biomass (68%) and flower production (100%) over the corresponding values for + RHIZ plants. Increasing N to 100 kg N ha−1 resulted in greater biomass (24%) in dual‐inoculated clover, but concurrently decreased the amount of Ndfa while increasing the amount of N derived from the soil (Ndfs). Compared to + RHIZ trefoil, dual inoculation of trefoil (+ RHIZ, + VAMF) resulted in greater biomass production at 100 kg N ha−1, but had no significant effect on Ndfa or Ndfs. Increasing soil N increased biomass production, but did not reduce Ndfa in dual‐inoculated trefoil. The difference in response to G. margarita inoculation may be a reflection of the annual vs. perennial nature of subterranean clover and big trefoil, respectively. The shift in biomass production and Ndfa in nodulated plants at the higher N level demonstrates the need to modify site management practices in order to maximize tree growth and leguminous plant‐biological N fixation benefit to the site.
Soybean Response to Phosphorus and Potassium Fertilizers as Affected by Soil Drying
Authors: Kaspar T. C. , Timmons D. R. , Zahler J. B. 
Published: July 2010

AbstractSoybean, Glycine max (L.) Merr., response to P and K fertilzers can vary with the amount of rainfall received during a growing season, but it is often difficult to determine whether growth is limited by unavailability of nutrients and/or water. A 2‐yr study was conducted in a rhizotron at Ames, IA, to determine whether drying of the fertilized, surface soil layer reduces plant growth and utilization of P and K fertilizers when subirrigation replenishes water below the fertilized surface layer. Low, medium, and high fertility levels were established on soil obtained from the upper 0.15 m of a Sparta loamy, fine sand (sandy, mixed, mesic Entic Hapludoll). Two surface‐drying treatments, one beginning during late flowering (dR2) and the other after the start of seed fill (dR5), and a control were imposed. Shoot tissue concentrations and dry weights at the fullseed stage (R6) and mature seed yield were measured. Surface drying reduced total shoot accumulation of P and K. Leaf and pod P concentrations were lower for the dR5 treatment than for the dR2 treatment. Shoot K concentrations of the dR2 treatment increased less than those of the other treatments as soil K levels increased. Shoot dry weights at R6 and mature seed yield were reduced at the low fertility level. Surface‐drying treatments reduced total shoot dry weight (42.8 and 40.9 g plant −1) compared with the control (49.5 g plant−1) in both years, but yield was reduced only in 1984. This study shows that drying of the fertilized soil layer reduced shoot growth and utilization of applied P and K fertilizers even though water was available at greater depths.
Water Table Fluctuation in Representative Immokalee and Zolfo Soils of Florida
Authors: Hyde Adam G. , Ford Richard D. 
Published: July 2010

AbstractDepth and duration of the seasonal high water table in soils are important factors affecting land use. Most water‐table statements are based on soil properties and field observations; very few long‐term measurements have been recorded. This study was conducted to determine how well current water‐table statements agree with the actual data on the representative Immokalee (sandy, siliceous, hyperthermic Arenic Haplaquod) and Zolfo (sandy, siliceous, hyperthermic Grossarenic Entic Haplohumod) soils. The water table depths were measured approximately every 2 wk from 1977 to 1986. Rainfall was also measured. Water‐table statements can be improved with long‐term data on key soils. Long periods of more than two consecutive years have high‐water tables below that given in the water‐table statements used in this study. Short‐term measurements taken during these long periods of low water tables could be misleading.
Detecting Soil Information on a Native Prairie Using Landsat TM and SPOT Satellite Data
Authors: Su Haiping , Ransom M. D. , Kanemasu E. T. 
Published: July 2010

AbstractComputer pattern recognition techniques were used to discriminate soil information from the Landsat Thematic Mapper (TM) and the French Systeme Probatoire d'Observation de le Terre (SPOT) satellite data on a native prairie near Manhattan, KS. Digital Elevation Model (DEM) data were merged to Landsat TM and SPOT data to delineate soil mapping units within the study area. Soil mapping units from a conventional soil survey were compared with a classified soil spectral map obtained from Landsat TM or SPOT, and DEM derived elevation, slope, and aspect data, using an overall accuracy assessment. The overall accuracy of soil spectral classes from TM and SPOT data was improved after DEM data were merged. A higher average accuracy for soil mapping units was obtained with a low frequency filtering transformation of the data. For Landsat TM data, Band 5 (middle infrared, 1.55–1.75 µm) was most useful for soil information extraction, and a higher overall accuracy was obtained in the dormant season compared with the accuracy in the growing season. The overall accuracy (about 57%) from SPOT data was slightly higher than the accuracy (about 53%) from Landsat TM at a similar wavelength range. Our results indicate that high resolution Landsat TM and SPOT satellite data can be used to aid second‐order soil surveys in areas where the dominant land use is rangeland.
Litter Decomposition Across an Air‐Pollution Gradient in the San Bernardino Mountains
Authors: Fenn Mark E. , Dunn Paul H. 
Published: July 2010

AbstractAir pollution may affect forest ecosystems by altering nutrient cycling rates. The objective of this study was to compare decomposition rates of L‐layer litter of ponderosa pine (Pinus ponderosa Laws.) and Jeffrey pine (Pinus jeffreyi Grev. & Balf.) collected from across an air‐pollution gradient in the San Bernardino Mountains in southern California. Litter from the more polluted western areas decomposed at a significantly (P = 0.01) faster rate than litter from plots in areas exposed to moderate or low pollution levels. The Shannon diversity index values for litter fungi were 1.41, 1.84, and 2.25 for plots in areas exposed to low, moderate, and high pollution levels. Nitrogen content of litter was greatest in the high pollution plots and was positively correlated with litter decomposition rate. Higher N and lower Ca content of litter at the more polluted western sites suggest that litter in the western plots originates from younger foliage than litter at the less polluted sites, possibly because of ozone (O3)‐induced needle abscission. Possible factors contributing to increased decomposition and fungal diversity in the western plots include: higher litter nutrient content because litter originates from younger foliage, higher soil N levels which may result in higher foliar N content, greater input of N from air pollution, and O3 damage to needles creating favorable sites for microbial decomposers.
Nitrogen Source, Rate, and Application Method for No‐Tillage Corn
Authors: Howard Donald D. , Tyler Donald D. 
Published: July 2010

AbstractSurface applying urea‐containing N fertilizers may result in greater N losses by volatilization of NH3 as urea hydrolyses than nonurea containing materials. The objective of this study was to evaluate the N efficiency of urea‐ammonium nitrate (UAN), urea and urea‐urea phosphate (UUP) at 56, 112, 168, and 224 kg ha−1 N rates applied broadcast, surface banded, and injected for no‐till corn (Zea mays L.). Yield, ear‐leaf N concentration, and N uptake were used to estimate N availability. Broadcast ammonium nitrate (AN) and injected anhydrous ammonia (AA) were used as controls for evaluating N efficiency of urea‐containing N sources and their application methods. The method of applying the urea‐containing N sources has a significant effect on apparent N fertilizer availability. Injecting UAN and urea resulted in significantly higher yield, leaf N concentration, and N uptake when compared with broadcast and surface band application methods. Surface banding UAN at 168 and 224 kg ha−1 resulted in higher yields than urea or UUP. Yield, leaf N concentration and N uptake differences among the three urea‐containing N sources were not observed when broadcast applied. Broadcasting AN at 168 and 224 kg ha−1 resulted in higher yields than UAN, urea or UUP. Injecting the N sources resulted in higher yields when compared with broadcasting AN.
Electro‐Optic Detection of Liquid in Translucent Porous Material
Authors: Cary J. W. , McBride J. F. , Simmons C. S. 
Published: July 2010

AbstractThe amount of light transmitted through translucent porous materials can be accurately and inexpensively measured with a phototransistor or a CdS resistance cell. The results presented here suggest that light attenuation measurements in fritted glass or fibrous filters may be more easily calibrated to soil‐water content than the electrical resistance blocks that are commercially available because of reduced sensitivity to salt concentration. Light attenuation measurement in porous polyethylene offers a practical and inexpensive way to detect an organic liquid in the vadose zone or on the surface of the groundwater table. Light attenuation measurements also correlate with changes in water content in plant leaves.
Soil Surface Salty Crusts and Water Loss by Evaporation
Authors: Galizzi Fernando A. , Peinemann Norman 
Published: July 2010

AbstractWater evaporation measurements in small soil columns saturated with different salt solutions show that the surface salty crusts affect the water content as well as the water movement in the soils in the order: NaCl < Na2CO3 < Na2SO4 < MgSO4. Morphological observations suggest that these differences are due to the deposited salt crust.
Subsurface Occurrence of Mirabilite in a Mollisol of Southern Alberta, Canada: A Case Study
Authors: Beke G. J. , Palmer C. J. 
Published: July 2010

AbstractAn efflorescent mineral, occurring at about 1 m depth in a moderately well‐drained soil of southern Alberta, had a chemical composition which corresponded to that of mirabilite, a hydrated sodium sulfate mineral. The x‐ray diffraction analysis of dehydrated crystals identified the anhydrous sodium sulfate mineral thenardite. The mirabilite crystals occurred in unsaturated soil beneath a melting frozen layer. Saturation extracts of bulk soil samples identified two zones of high ionic concentration, at the depth of mirabilite occurrence and below the water table. The dominant ions in these zones were sulfate and sodium and, to a lesser extent, magnesium. All saturation extracts and soil solutions from below the frozen layer and the groundwater were found to be saturated with respect to calcite, dolomite, and gypsum. Only the soil solutions from the 90 to 120 cm depth showed saturation with mirabilite. Mirabilite formation was attributed to the low soil temperatures, high soil water contents, and concentration of ions below the frozen layer.
Phosphorus Behavior in Flooded‐Drained Soils. III. Phosphorus Desorption and Availability
Authors: Sah R. N. , Mikkelsen D. S. , Hafez A. A. 
Published: July 2010

AbstractFour California soils that showed wide variability in soil properties and P sorptivity under flooded‐drained (FD) conditions were selected for this study. The soils were flooded for 0 to 90 d at two levels of organic matter (OM, 0 and 10 g kg−1) and two temperatures (23 and 35 °C). They were subsequently drained and used for P‐sorption studies at 0.3, 1.2, and 2.0 mM initial P concentrations. The P desorption from P‐sorbed soils were carried out in three consecutive extractions with 0.1 M NaCl. The effect of FD conditions on P availability to corn (Zea mays L.), was studied at three levels of P (0, 5, and 20 mg P kg−1 soil). Without OM treatment, FD conditions decreased P desorption in three of four soils examined. Added OM and higher temperature further decreased P desorption and the period of flooding (FP) required to reach the minimum P desorption. Organic matter markedly decreased P desorption even in Soil 3, which was unaffected by FD conditions. Under FD conditions, plant‐tissue P concentration of corn was decreased to a variable extent depending on soil type. The desorption of added fertilizer P in a given FD soil correlated well with changes in the amorphous FeA fraction under comparable conditions. Phosphorus sorption and desorption were controlled by the changes in amorphous FeA and, in some cases, amorphous FeB fractions.
Reasons for Differences among Soils in Placement of Phosphorus for Maximum Predicted Uptake
Authors: Kovar J. L. , Barber S. A. 
Published: July 2010

AbstractPrevious research on placement of phosphate fertilizer has shown that the fraction of the soil fertilized with P affected P uptake by the crop, and that the fraction fertilized for maximum P uptake varied among soils. Placement effects on P uptake have been successfully simulated with a mechanistic uptake model. Values of parameters in the model describing P supply to the root depend on Pli, the initial concentration of P in the soil solution, and Psi, the initial P concentration of the solid phase that rapidly equilibrates with Pli. The objective of this research was to determine the importance of differences among soils in changes in Pli and Psi with increasing rate of P added, on the effect of P placement. Previous research has shown that, as P rate in the fertilized soil increases proportionally with a reduction in the fraction of the soil fertilized, Pli increased curvilinearly and Psi increased linearly. These relations were de‐on calculated P uptake with differing P placements was examined rate of P added, a, c and h are constants and d and g are predicted values of initial Pli and Psi, respectively. The effect of varying the coefficients a and c for the Pli function and of h for the Psi function on calculated P uptake with differing P placements was examined in this study. Standard deviations for c and h of 25% of the mean for 33 diverse soils were obtained from previous research. However, these data also showed that log a was correlated negatively with c (r = −0.92). Hence, in a study of curvilinearity of Pli with P added, it was necessary to adjust log a as c was changed. When log a was decreased as c was increased, the fraction of the soil to fertilize for maximum uptake decreased and predicted P uptake with optimum placement increased. When h was increased while holding c and log a constant, there was only a small increase in predicted P uptake and no change in fraction of the soil to fertilize for maximum P uptake. Hence, changes in Pli had a greater effect on predicted P uptake with changes in P placement than changes in Psi.
Winter Legume Effects on Soil Properties and Nitrogen Fertilizer Requirements
Authors: McVay K. A. , Radcliffe D. E. , Hargrove W. L. 
Published: July 2010

AbstractWinter legume cover crops have been shown to provide significant amounts of N to subsequent nonleguminous crops, but benefits beyond those directly attributed to N are rarely cited. A 3 yr field study at two Georgia locations utilizing a randomized, complete‐block, split‐plot design with four replications was begun in 1985 to measure the equivalent fertilizer N supplied by winter annual legumes and to monitor changes in soil physical and chemical properties. Corn, Zea mays L. was grown on a Rome gravelly clay loam soil (fine‐loamy, mixed, thermic Typic Hapludult) at the Limestone Valley location, and grain sorghum [Sorghum bicolor (L) Moench] on a Greenville sandy clay loam soil (clayey, kaolinitic, thermic Rhodic Paleudult) in the Coastal Plain. Main plots were cover crops of hairy vetch (Vicia villosa Roth.), crimson clover (Trifolium incarnatum L), berseem clover (Trifolium alexandrinum L), winter pea [Pisum sativum subsp. arvense (L) poir], wheat (Triticum aestivum L), and fallow. Subplots were broadcast NH4NO3 fertilizer of varying rates. Hairy vetch and crimson clover replaced the greatest amount of fertilizer N averaging 123 and 99 kg N ha−1, respectively. More water‐stable aggregates were found following cover crops than fallow in the 0‐ to 0.025‐m depth at the Coastal Plain location. Higher infiltration rates were found following cover crops than fallow at both locations and infiltration rates were greater following hairy vetch than following wheat at the Coastal Plain site. An adapted winter legume cover crop can replace all of the fertilizer N necessary for optimum rain‐fed grain sorghum and up to two‐thirds of that required for corn production, and improve soil physical properties.