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Articles 1 - 10 of 10
Full-Text Articles in Physical Sciences and Mathematics
An Integrated Crop- And Soil-Based Strategy For Variable-Rate Nitrogen Management In Corn, Darrin F. Roberts
An Integrated Crop- And Soil-Based Strategy For Variable-Rate Nitrogen Management In Corn, Darrin F. Roberts
Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research
Nitrogen (N) management in cereal crops has been the subject of considerable research and debate for several decades. Historic N management practices have contributed to low nitrogen use efficiency (NUE). Low NUE can be caused by such things as poor synchronization between soil N supply and crop demand, uniform application rates of fertilizer N to spatially variable landscapes, and failure to account for temporally variable influences on soil N supply and crop N need. Active canopy reflectance sensors and management zones (MZ) have been studied separately as possible plant- and soil-based N management tools to increase NUE. Recently, some have …
Nutrient Leaching In Undisturbed Cores Of An Acidic Sandy Podosol Following Simultaneous Potassium Chloride And Di-Ammonium Phosphate Application, Ian Phillips, Edward Burton
Nutrient Leaching In Undisturbed Cores Of An Acidic Sandy Podosol Following Simultaneous Potassium Chloride And Di-Ammonium Phosphate Application, Ian Phillips, Edward Burton
Associate Professor Edward D Burton
In south-east Queensland, Australia, extensive areas of sandy soils (Podosols) with shallow (<1>m) watertables are used for exotic pine tree production. Despite concerns that surface-applied fertilisers (di-ammonium phosphate (DAP) and potassium chloride (KCl)) may be contributing to a decline in local groundwater quality, published information on nutrient leaching in these Podosols is scarce. Large (0.3 m i.d. · 0.85 m long) undisturbed soil cores were intermittently leached with deionised water following a single surface application of KCl in combination with DAP. Potassium was applied at rates (equivalent on a surface area basis) of 0 (K0), 50 (K50), 100 (K100) …
Effects Of Diffusion And Resuspension On Nutrient Release From Submerged Sediments, Ian Phillips, Edward Burton, Darryl Hawker
Effects Of Diffusion And Resuspension On Nutrient Release From Submerged Sediments, Ian Phillips, Edward Burton, Darryl Hawker
Associate Professor Edward D Burton
Nutrient release from a coarse-sand (CS) and a fine-sand (FS) estuarine sediment into the overlying water column was studied under static (diffusion-controlled) and dynamic (resuspension) conditions. Resuspension increased the amounts of NH4+, NO3- and P released from the sediment cores compared to those released by diffusion alone due to direct release of these nutrients from the readily available pore-water and ion exchange fractions. The average effective NH4+, NO3- and P diffusion coefficients (De) were found to be similar for both sediments, and did not vary significantly between static and dynamic conditions. Values of De were typically of the order of …
Characterization Of An N2 Flowing Microwave Post-Discharge By Oes Spectroscopy And Determination Of Absolute Ground-State Nitrogen Atom Densities By Talif, Et. Es-Sebbar, Y. Benilan, A. Jolly, M-C. Gazeau
Characterization Of An N2 Flowing Microwave Post-Discharge By Oes Spectroscopy And Determination Of Absolute Ground-State Nitrogen Atom Densities By Talif, Et. Es-Sebbar, Y. Benilan, A. Jolly, M-C. Gazeau
Dr. Et-touhami Es-sebbar
A flowing microwave post-discharge source sustained at 2.45 GHz in pure nitrogen has been investigated by optical emission spectroscopy (OES) and two-photon absorption laser-induced fluorescence (TALIF) spectroscopy. Variations of the optical emission along the post-discharge (near, pink and late afterglow) have been studied and the gas temperature has been determined. TALIF spectroscopy has been used in the late afterglow to determine the absolute ground-state nitrogen atomic densities using krypton as a reference gas. Measurements show that the microwave flowing post-discharge is an efficient source of N (4S) atoms in late afterglow. In our experimental conditions, the maximum N (4S) density …
Nitrogen Transport, Transformation And Cycling Through A Mountain Lake, Bull Trout Lake, Idaho, Usa, Ryan Settle Lockwood
Nitrogen Transport, Transformation And Cycling Through A Mountain Lake, Bull Trout Lake, Idaho, Usa, Ryan Settle Lockwood
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
The effects of a mountain lake on nitrogen dynamics in a sub-alpine watershed were examined via watershed monitoring, mesocosm experiments, microcosm experiments, and enzymatic assays during spring and summer of a single year. Our study addressed the questions: (1) How does hydrologic transport through the lake affect the net fluxes of dissolved nitrogen (N) species? (2) What are the net effects of the littoral zone biota on dissolved N fluxes? (3) What are the seston and benthic uptake rates of nitrate? (4) What is the magnitude of N retention in littoral zone sediments? (5) What role does microbial hydrolysis of …
Nutrient Uptake And Mineralization During Leaf Decay In Streams – A Model Simulation, J. R. Webster, J. D. Newbold, Steven A. Thomas, P. J. Mulholland
Nutrient Uptake And Mineralization During Leaf Decay In Streams – A Model Simulation, J. R. Webster, J. D. Newbold, Steven A. Thomas, P. J. Mulholland
School of Natural Resources: Faculty Publications
We developed a stoichiometrically explicit computer model to examine how heterotrophic uptake of nutrients and microbial mineralization occurring during the decay of leaves in streams may be important in modifying nutrient concentrations. The simulations showed that microbial uptake can substantially decrease stream nutrient concentrations during the initial phases of decomposition, while mineralization may produce increases in concentrations during later stages of decomposition. The simulations also showed that initial nutrient content of the leaves can affect the stream nutrient concentration dynamics and determine whether nitrogen or phosphorus is the limiting nutrient. Finally, the simulations suggest a net retention (uptake > mineralization) of …
Development And Application Of A System For The Analysis Of Atmospheric, Water And Sediment Nitrogen And Carbon, Ann Stavert, Stephen R. Wilson, Dianne F. Jolley
Development And Application Of A System For The Analysis Of Atmospheric, Water And Sediment Nitrogen And Carbon, Ann Stavert, Stephen R. Wilson, Dianne F. Jolley
Faculty of Science - Papers (Archive)
Eutrophication and climate change, key environmental concerns, are both linked to the carbon and nitrogen cycles hence the improved understanding of these cycles is essential. Currently, there is no system that simultaneously measures the fluxes of the three key gas phase products of nitrogen and carbon cycling (CO2, CH4 and N2O) in submerged ecosystems with hourly time resolution. A “Lake-in-a-box” (mesocosm) was developed in the laboratory which allowed the monitoring of key components of the carbon and nitrogen cycles within the air, water and sediments. The approach is automated, simple and time efficient and novel in its ability to examine …
Nutrient Limitation Of Phytoplankton By Nitrogen And Phosphorus: Erosion Of The Phosphorus Paradigm, Wayne A. Wurtsbaugh, William M. Lewis Iii
Nutrient Limitation Of Phytoplankton By Nitrogen And Phosphorus: Erosion Of The Phosphorus Paradigm, Wayne A. Wurtsbaugh, William M. Lewis Iii
Watershed Sciences Faculty Publications
No abstract provided.
Freshwater Responses To Nitrogen And Phosphorus Pollution And A Case Study Of Cutler And Dingle Marsh Wetlands, Wayne A. Wurtsbaugh
Freshwater Responses To Nitrogen And Phosphorus Pollution And A Case Study Of Cutler And Dingle Marsh Wetlands, Wayne A. Wurtsbaugh
Watershed Sciences Faculty Publications
No abstract provided.
Soil Carbon And Nitrogen Accumulation In A Forested Debris Flow Chronosequence, California, Judith K. Turk, Robert C. Graham
Soil Carbon And Nitrogen Accumulation In A Forested Debris Flow Chronosequence, California, Judith K. Turk, Robert C. Graham
Conservation and Survey Division
The role of forest soils in the biogeochemical cycling of C and N is most dynamic during the early stages of soil development. To define C and N trends that occur with soil development in a mixed coniferous forest, a chronosequence formed by debris flows was studied. The accumulation rates of total organic C (TOC) and total N (TN) were evaluated in soils on 10 debris flow deposits, ranging from depth, since this was the depth of the shallowest debris flows. Carbon was found to accumulate in the organic horizons at a rate of 26.5 g m−2 yr−1 …