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Articles 1 - 11 of 11

Full-Text Articles in Life Sciences

Confounding Factors And Tertiary-Phase Control By A Surfactive Agent On Smectite Sorption Of Atrazine , Mark Albert Chappell Jan 2004

Confounding Factors And Tertiary-Phase Control By A Surfactive Agent On Smectite Sorption Of Atrazine , Mark Albert Chappell

Retrospective Theses and Dissertations

Atrazine is a widely used commercial pesticide applied to soil for the control broadleaf weeds in agriculture. Frequent detection of atrazine in surface and subsurface waters and the potential for adverse effects on toxicity to aquatic and terrestrial life have generated numerous investigations into the mechanisms governing atrazine sorption by soils. This dissertation seeks to add to that body of knowledge by elucidating basic mechanisms and processes that influence sorption of atrazine on clays in the presence and absence of surfactants commonly used in commercial formulations. Sorption studies showed that air-dried (AD), resuspended K+-saturated PC (KPC) exhibited a significantly ...


Population Genetic Studies Of The Tsetse Fly, Glossina Pallidipes (Diptera: Glossinidae) , Johnson Ouma Odera Jan 2004

Population Genetic Studies Of The Tsetse Fly, Glossina Pallidipes (Diptera: Glossinidae) , Johnson Ouma Odera

Retrospective Theses and Dissertations

Tsetse flies transmit trypanosome species that cause sleeping sickness in humans and nagana in livestock. In the absence of a vaccine against trypanosome parasites and given the high cost of treatment, vector control remains the most effective method for reducing the incidence of trypanosomiasis. In anticipation of area-wide control of G. pallidipes by using genetic methods, a thorough understanding of its breeding structure is required.;Capture release-recapture data show that G. pallidipes has a high capacity for dispersal, but genetic data indicate surprisingly high differentiation among populations. Studying local patterns of genetic variation and examining how such variation changes temporally ...


Land Preservation Decisions: Theoretical And Empirical Analysis , Shikha Marwah Jan 2004

Land Preservation Decisions: Theoretical And Empirical Analysis , Shikha Marwah

Retrospective Theses and Dissertations

There is a great concern that human actions are leading to increased rates of extinction of species. Ecologists have pointed out that the most important threat to wildlife comes from habitat alteration. The rapidly increasing human population and the resulting pressing demand for food and living space are pushing highly diverse natural areas into agriculture and other alternative uses. Recognizing this, the Federal agencies and private organizations, such as the Nature Conservancy, are becoming increasingly engaged in programs for conservation of species, where habitat restoration is an important component. However, this conservation is costly and there is uncertainty in the ...


Corridors And Some Ecological And Evolutionary Consequences Of Connectivity , John Lee Orrock Ii Jan 2004

Corridors And Some Ecological And Evolutionary Consequences Of Connectivity , John Lee Orrock Ii

Retrospective Theses and Dissertations

By connecting disjunct patches, corridors may offset the effects of fragmentation by promoting gene flow and population persistence. However, the ultimate effect of corridors on a focal species may hinge upon two considerations: how corridors may affect ecological interactions that impinge upon that species, and how corridors might affect the fixation of novel alleles that ultimately determine fitness and persistence. Using an experimental landscape, I show that corridor-mediated changes in patch shape change seed predation in connected and unconnected patches, and shift the behavior, abundance, and distribution of seed predators. Rodent seed predators removed more seeds in connected patches, arthropod ...


The Conservation Landscape: Trees And Nature On The Great Plains , Joel Jason Orth Jan 2004

The Conservation Landscape: Trees And Nature On The Great Plains , Joel Jason Orth

Retrospective Theses and Dissertations

In the past two centuries Americans have transformed the Great Plains. Farmers, politicians, scientists, and the state constructed and reconstructed the Plains to support their visions of a sustainable society. They transformed the region into a social and ecological space inextricably linked to the beliefs, agendas, and polices that have reshaped it. The new landscape blurred the social and the natural making these categories impossible to separate. The greatest task soil conservation on the Great Plains faces today is recognizing the hybrid space for what it is: a socially-constructed landscape, a conservation landscape.;This thesis traces the development of a ...


Remote Sensing Of Moisture And Nutrient Stress In Turfgrass Systems , Jason Keith Kruse Jan 2004

Remote Sensing Of Moisture And Nutrient Stress In Turfgrass Systems , Jason Keith Kruse

Retrospective Theses and Dissertations

Management of irrigation and fertility on a golf course or other large turfgrass area requires a significant amount of time scouting for and identifying problem areas to maintain optimum turfgrass quality. The objectives of these studies were to evaluate the relationship between remotely sensed reflectance data collected from a turfgrass canopy and the associated phosphorus and nitrogen content of turfgrass tissue, and to determine the relationship between reflectance data and soil moisture content as determined by time domain reflectometry (TDR). Phosphorus deficiency symptoms decreased and biomass production increased at P rates above 1.0 g m-2 with a single application ...


Soil And Runoff Phosphorus As Affected By Fertilizer And Manure Application , Brett Lee Allen Jan 2004

Soil And Runoff Phosphorus As Affected By Fertilizer And Manure Application , Brett Lee Allen

Retrospective Theses and Dissertations

Fertilizer or manure applications are increasing soil P in agricultural fields. This study assessed the impact of P application on soil P fractions and P loss with surface runoff based on P rate field trials and both indoor and field rainfall simulations. Bray P, Mehlich-3 (M3) P, Olsen P, total P (TPS) and soil P saturation (Psat) estimated by M3 or oxalate extractable P, Fe, and Al molar ratios increased with cumulative P application (0 to 1098 kg P ha-1 after 4 to 23 yr) at plots from 11 trials. Soil test P, TPS, and Psat were linearly correlated. Routine ...


Education And Water Conservation In Tucson, Arizona: Towards An Educational Model For Saudi Arabia , Mohammad Sh Al-Shayaa Jan 2004

Education And Water Conservation In Tucson, Arizona: Towards An Educational Model For Saudi Arabia , Mohammad Sh Al-Shayaa

Retrospective Theses and Dissertations

Saudi Arabia and Tucson, Arizona are both surrounded by desert and rely on groundwater. Both places also suffer from similar types of water shortage problems. The average water usage, in gallons per person per day, in Tucson is 160. In contrast, in Saudi Arabia this figure is 260. Respectively, these factors encouraged the researcher to investigate the educational roles in Tucson. The findings and experience gleaned from Tucson will be used in Saudi Arabia where the researcher is planning to pursue his career.;Information circulated to the Tucson public about water conservation demonstrates effectiveness in addressing issues related to water ...


Riparian Land-Use Impacts On Stream And Gully Bank Soil And Phosphorus Losses With An Emphasis On Grazing Practices , George Nick Zaimes Jan 2004

Riparian Land-Use Impacts On Stream And Gully Bank Soil And Phosphorus Losses With An Emphasis On Grazing Practices , George Nick Zaimes

Retrospective Theses and Dissertations

The tall-grass prairies, wetlands and forests that dominated the Iowa landscape have been replaced by annual row-crops and grass pastures that occupy more than 90% of the landscape today. Because of these changes, water reaches streams and gullies much faster and has led to incised streams and an extensive growth of gully networks. Stream and gully banks are major contributors of non-point source sediment and phosphorus. Reducing these pollutants is a priority to maintaining healthy streams. The objective of this study was to compare stream and gully bank soil and phosphorus losses under different land-use practices in three Iowa regions ...


Insuring Uncertainty In Value-Added Agriculture: Ethanol, Nicholas David Paulson Jan 2004

Insuring Uncertainty In Value-Added Agriculture: Ethanol, Nicholas David Paulson

Retrospective Theses and Dissertations

A wide variety of insurance products are currently available for agricultural producers to insure against yield or price risks in the markets for the raw commodities they produce. Value-added enterprises, such as ethanol production, have become increasingly popular among farmers over the last decade; however, insurance against declines in the value-added portion of their crops is not yet available. This paper outlines the development of an insurance product aimed at corn producers who are members of an ethanol production cooperative. The product mimics the gross margin level of a typical ethanol production facility, and has the potential to provide producers ...


The Economic Potential Of Switchgrass As A Viable Biofuel Alternative, Jennifer E. Reutzel Jan 2004

The Economic Potential Of Switchgrass As A Viable Biofuel Alternative, Jennifer E. Reutzel

Retrospective Theses and Dissertations

To be commercially viable as a bioenergy feedstock, switchgrass must be cost-competitive. Switchgrass production and delivery costs are calculated for the Chariton Valley Switchgrass Biomass Project located in the Chariton Valley, Iowa. Sensitivity analyses are performed to determine which variables have the greatest impact on cost. Switchgrass production costs would require higher than expected market prices, and therefore various incentive payment options are considered. The incentive payments attempt to encapsulate the positive environmental attributes from the production of switchgrass as well as using switchgrass as a clean energy coal substitute. A modified CRP payment, carbon payment, and green tag payment ...