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Articles 1 - 13 of 13

Full-Text Articles in Life Sciences

Field And Laboratory Investigations Of Solute Transport Through Soil , Francis Xavier Mckeon Casey Jan 2000

Field And Laboratory Investigations Of Solute Transport Through Soil , Francis Xavier Mckeon Casey

Retrospective Theses and Dissertations

Two single tracer methods (basic and variance) and one multiple tracer method were developed to simultaneously estimate soil hydraulic properties and mobile/immobile solute transport parameters in situ. In this study, immobile water contents (thetaim) and mass exchange coefficients (alpha) were estimated with the multiple tracer method and the single tracer methods on the same five field sites. The theta im values estimated by the basic single tracer method were consistently lower than the multiple tracer method values. This was attributed to the assumption that alpha = 0 for the basic single tracer method. Furthermore, alpha values estimated by multiple tracer ...


Interactions And Transformations Of Chlorpyrifos In Aqueous And Colloidal Systems , Jigang Wu Jan 2000

Interactions And Transformations Of Chlorpyrifos In Aqueous And Colloidal Systems , Jigang Wu

Retrospective Theses and Dissertations

Chlorpyrifos [o,o-diethyl o-(3,5,6-trichloro-2-pyridyl) phosphorothioate] is a broad-spectrum organophosphorus insecticide widely used in agricultural, industrial, and residential environments. Understanding interaction of chlorpyrifos with colloidal materials is fundamental for assessing fate and toxicity of chlorpyrifos in soil and aquatic environments. The objectives of this study were: (1) to quantify sorption and desorption of chlorpyrifos on colloidal materials in aqueous systems; (2) to investigate hydrolysis of chlorpyrifos in aqueous systems; (3) to evaluate the effects of colloidal materials on the fate of the sorbed chlorpyrifos in aqueous systems; and (4) to study abiotic transformation of chlorpyrifos in water;Six ...


A Historical Profile Of Valamo Monastery's Agricultural Practices, With Implications For Agricultural And Extension Education , Andrei Vladimirovich Khomoutov Jan 2000

A Historical Profile Of Valamo Monastery's Agricultural Practices, With Implications For Agricultural And Extension Education , Andrei Vladimirovich Khomoutov

Retrospective Theses and Dissertations

The purpose of the study was to create a vision to empower monks and civilians to make their decisions about developing a renewed agricultural extension and demonstration system for the Valamo Archipelago based on agricultural technology transfer in time. In other words, the purpose was to propose better ways to educate people of the described area about how to live in harmony with the environment;Two research questions guided the study: (1) What components of an informal agricultural education system were in use at Valamo Monastery prior to World War II; and (2) What basic elements can be applied to ...


Floristic Analysis Of Central Iowa Woodlands, And Comparison Of Reproduction And Regeneration In Common And Restricted Herbaceous Species , Catherine Mary Mabry Jan 2000

Floristic Analysis Of Central Iowa Woodlands, And Comparison Of Reproduction And Regeneration In Common And Restricted Herbaceous Species , Catherine Mary Mabry

Retrospective Theses and Dissertations

I studied the distribution and abundance of the plant species of forests in central Iowa, emphasizing the effect of cattle grazing on the vegetation. I used traits to identify groups of species that may function as guilds, and to address whether species' frequency was related to traits. To understand the difference between species that were common compared to those relatively less common (restricted species), I examined whether the two groups differed in reproductive output and allocation, seed viability, and seedling emergence;Understory species and canopy trees were generally distributed along the same environmental gradients. These were landform, soil phosphorous and ...


Methane Cycling In Soils , Alvarus Sang Keong Chan Jan 2000

Methane Cycling In Soils , Alvarus Sang Keong Chan

Retrospective Theses and Dissertations

Methane (CH4) is an important greenhouse gas which captures heat in the atmosphere by absorbing infrared radiation and thereby contributing to global warming. Atmospheric CH4 concentration has been increasing since the industrial age and recent data suggest that the growth rate may be on the rise. This increase of CH4 in the atmosphere may have a significant impact on future global warming. It has been estimated that 50% of annual CH4 comes from terrestrial environments. The role of natural and agricultural ecosystems in terms of their contribution to the atmosphere is unclear. This study was conducted to: (i) evaluate methodology ...


The Influence Of Habitat Features On Grassland Birds Nesting In The Prairie Pothole Region Of North Dakota , David Joseph Horn Jan 2000

The Influence Of Habitat Features On Grassland Birds Nesting In The Prairie Pothole Region Of North Dakota , David Joseph Horn

Retrospective Theses and Dissertations

Results of habitat fragmentation studies on grassland and wetland birds are not consistent. Some studies have found positive relationships among abundance, nest success, field size, and distance to edges, whereas others have found no relationship. One reason for differing results may be the landscape composition in which the study took place. I examined how landscape composition influenced relations among: (1) occurrence and abundance of grassland songbirds and field size, and (2) nest success of ducks, field size, and edges. I also investigated the effects of mowing on grassland songbirds, and how landscape features, such as amount of perennial grassland, and ...


Toxicity Of Chlorpyrifos Adsorbed On Clay And Humic Acid To Larval Walleye , Todd Alan Phillips Jan 2000

Toxicity Of Chlorpyrifos Adsorbed On Clay And Humic Acid To Larval Walleye , Todd Alan Phillips

Retrospective Theses and Dissertations

Agricultural production poses one of the most serious threats to the continued ecological integrity of environmental systems and has been charged as the activity most responsible for loss of fish species in streams. Although all anthropogenic stressors affecting aquatic ecosystems have not been isolated, suspended solids, sediment, and pesticides are believed to be major factors. The objectives of this dissertation were to: (1) evaluate sources of variability in measuring cholinesterase activity, (2) determine the most sensitive life stage of walleye exposed to chlorpyrifos, (3) evaluate the bioavailability of chlorpyrifos adsorbed on humic acid (HA) and Panther Creek (PC) clay to ...


Historical Alterations Of Surface Hydrology In Iowa's Small Agricultural Watersheds, Katherine Louise Andersen Jan 2000

Historical Alterations Of Surface Hydrology In Iowa's Small Agricultural Watersheds, Katherine Louise Andersen

Retrospective Theses and Dissertations

Iowa's headwater prairie streams, once meandering within a landscape of tall grasses, marshes and wooded riparian borders, today exist in direct contact with an agricultural matrix. This study determined historic changes in surface water features of four small agricultural watersheds. Bear Creek watershed was once part of the "wet prairie" region located in the Des Moines Lobe landform of north-central Iowa. Storm Lake watershed, located in the Northwest Iowa Loess Prairies landform, was of a similar original condition with limited stream channel development. The Walnut Creek and Three Mile Creek watersheds are located in the Southern Iowa Rolling Loess ...


Effects Of Liquid Swine Manure Placement And Rate On Phosphorus Loss With Runoff Water , Hadi Tabbara Jan 2000

Effects Of Liquid Swine Manure Placement And Rate On Phosphorus Loss With Runoff Water , Hadi Tabbara

Retrospective Theses and Dissertations

There is an increasing concern on the use of nitrogen (N) based manure application rate for corn production and its impact on soil phosphorus (P) buildup and the potential to release P to the environment. Therefore a field study was conducted to evaluate the effects of manure application rate and method of application on soil erosion and P loss with runoff water and sediment. Simulated rainfall was applied to 24 runoff plots to study two variables in triplicate. The first variable was application rate: liquid swine manure was applied at N recommended rate and twice the rate, and inorganic liquid ...


Biomass, Carbon, Nitrogen And Soil Respiration Dynamics Within Riparian Buffers And Adjacent Crop Fields , Aydin Tufekcioglu Jan 2000

Biomass, Carbon, Nitrogen And Soil Respiration Dynamics Within Riparian Buffers And Adjacent Crop Fields , Aydin Tufekcioglu

Retrospective Theses and Dissertations

Natural and re-established riparian buffers reduce nonpoint-source pollutants derived from upland agricultural lands and enhance terrestrial and aquatic habitat. This study was conducted in multi-species riparian buffers, cool-season grass buffers and adjacent crop fields to determine biomass, carbon, nitrogen and soil respiration dynamics. The multispecies buffers were composed of poplar (Populus x euroamericana' Eugenei ) and switchgrass (Panicum virgatum L.). Crop fields were under annual corn-soybean rotation. Aboveground biomass was determined by clipping grasses in 25 x 25 cm quadrats. The dynamics of fine (0--2 mm) and small roots (2--5 mm) were assessed by sequentially collecting 5.4 cm diameter, 35 ...


Maternal Effects In The American Coot: Consequences For Offspring Growth And Survival , Wendy Louise Reed Jan 2000

Maternal Effects In The American Coot: Consequences For Offspring Growth And Survival , Wendy Louise Reed

Retrospective Theses and Dissertations

Life history theory predicts, and empirical studies indicate, that egg size can be an important determinant of fitness for a variety of species. The premise of these studies is that energy for reproduction is limited, and as parents increase energy investments in individual offspring, those offspring should accrue fitness benefits. The work presented in this dissertation addresses how energetic and hormonal resources vary with egg size and the consequences of these investments for offspring growth and survival in a free-living population of American coots (Fulica americana). Eggs vary in size at three levels: at the population level, among females and ...


Mobility And Bioavailability Of Heavy Metals In Selected Soils Of Iowa And Nigeria , Monday Ochu Mbila Jan 2000

Mobility And Bioavailability Of Heavy Metals In Selected Soils Of Iowa And Nigeria , Monday Ochu Mbila

Retrospective Theses and Dissertations

Environmental pollution due to release of heavy metals from various sources is a widespread problem throughout the world. This research was conducted to investigate the behavior of heavy metals released to soils from sewage-sludge application and ore mining. The distribution, chemical forms, bioavailability and microenvironment of Zn, Cu, Pb, and Ni in sewage-sludge-amended Ultisols from southeastern Nigeria, and Pb and Zn in Alfisols of an abandoned mine in northeast Iowa, were investigated using field studies and microanalytical techniques to complement standard bulk analytical methods. After 37 years of sludge amendment, the soil chemical properties had changed enough to wan-ant a ...


Hydrological Variation Along The Missouri River And Its Effect On The Fish Community , Mark Alan Pegg Jan 2000

Hydrological Variation Along The Missouri River And Its Effect On The Fish Community , Mark Alan Pegg

Retrospective Theses and Dissertations

The Missouri River has been subjected to human alteration for over 150 years and the flow regime is one physical attribute that has drastically changed as a result of alteration. Likewise, using flow characteristics has been identified as a driving variable to describe fish community structure in lotic systems. Therefore, my goal was to assess fish community structure in the Missouri River system in relation to flow. I first used a time series approach to examine daily mean flow data from 10 gauging stations on the Missouri River, and tested for differences associated with human alteration. Daily mean flow over ...