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Iowa State University

Agricultural Science

Theses/Dissertations

Agricultural engineering

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Integration Of Remote Sensing And Crop Growth Modeling For Nitrogen Management Decision Support In Corn , Kelly Robert Thorp Jan 2006

Integration Of Remote Sensing And Crop Growth Modeling For Nitrogen Management Decision Support In Corn , Kelly Robert Thorp

Retrospective Theses and Dissertations

This dissertation describes efforts to move toward a completely integrated remote sensing and crop growth modeling tool for developing precision nitrogen management recommendations for corn. Aerial hyperspectral remote sensing imagery collected throughout the 2004 growing season was used to estimate corn plant stand density, and a machine vision system was used to map corn population on the ground. Multiple linear regression analysis was used to assess the ability of all combinations of three reflectance bands to estimate corn plant population at resolutions of 2 m, 6 m, and 10 m. Coefficients of multiple determination of up to 0.82 were ...


Vegetative Filter Strip Assessment In The State Of Iowa, Manveen Bansal Jan 2006

Vegetative Filter Strip Assessment In The State Of Iowa, Manveen Bansal

Retrospective Theses and Dissertations

Vegetative filter strips (VFS) is one of the best management practices that uses natural processes to remove a portion of the sediment and other pollutants carried by runoff before the water enters a water-body. The project analyzes the flow accumulation of runoff with the help of Geographic Information Systems (GIS). The objectives for this project include (1) To determine the effectiveness of VFS by visual field observation and validation by flow mapping procedures in ArcGIS 9, (2) To compare the area ratios and percentage of flow along each stream segment at various resolutions for different sizes of the survey data ...


Analysis Of Spatial Yield Variability And Economics Of Prescriptions For Precision Agriculture: A Crop Modeling Approach , Joel Obien Paz Jan 2000

Analysis Of Spatial Yield Variability And Economics Of Prescriptions For Precision Agriculture: A Crop Modeling Approach , Joel Obien Paz

Retrospective Theses and Dissertations

Non-uniformity of soil properties, soil moisture and rooting depth, and other factors such pest and disease pressures can cause significant soybean and corn yield variability within a field. In this study, two crop growth models were used to characterize factors that cause spatial yield variability in soybeans and corn, and to evaluate economic consequences of variable rate management prescriptions. Analysis of yield data from 224 grids within a 16-hectare field in Boone, Iowa focused on water stress effects using CROPGRO-Soybean and CERES-Maize models for soybean and corn, respectively. Water stress explained 69% of the variability in soybean, and population and ...


Herbicide And Conservative Tracer Movement Through The Soil Profile And To Subsurface Drains Under No-Till And Chisel Plow Systems , Syed Imran Ahmed Jan 1999

Herbicide And Conservative Tracer Movement Through The Soil Profile And To Subsurface Drains Under No-Till And Chisel Plow Systems , Syed Imran Ahmed

Retrospective Theses and Dissertations

Adoption of conservation tillage has increased the role of macropore flow on the transport of agricultural chemicals to groundwater. Therefore, it is important to understand the role of macropore flow in the transport of water through the vadose zone and to the shallow groundwater. Two field studies were conducted at Iowa State University's Agricultural Research Center near Boone, Iowa, to determine the effect of two tillage practices (chisel plow and no-till) on the transport of herbicides and tracers, with applied water, through the soil profile and to the shallow groundwater. Two herbicides, atrazine [(6-chloro-N-ethyl-N-(1-methylethyl-1,3,5 triazine)-2-4-diamine ...


Use Of Site Specific Farming Systems And Computer Simulation Models For Agricultural Productivity And Environmental Quality , Allah Bakhsh Jan 1999

Use Of Site Specific Farming Systems And Computer Simulation Models For Agricultural Productivity And Environmental Quality , Allah Bakhsh

Retrospective Theses and Dissertations

Site specific farming systems have the potential to increase farmers' net income by reducing the use of agro-chemicals and applying variable rate technology for areas showing stable yield patterns. This study was designed to: (1) study yield patterns in given fields using variography; (2) seek correlation among soil attributes and yield data using GIS; and (3) simulate the effects of N-fertilizer and swine manure application rates on NO 3-N losses with subsurface drainage water and crop yields. The results of this study showed that the spatial correlation lengths were found to vary from 40 m for corn to about 90 ...


Soybean Quality Loss During Constant Storage Conditions , Ibni Hajar Rukunudin Jan 1997

Soybean Quality Loss During Constant Storage Conditions , Ibni Hajar Rukunudin

Retrospective Theses and Dissertations

A modified method for determining free fatty acid (FFA) in crude and refined soybean oils from 0.3 to 6.0 g oil sample size was developed. Good correlation between the modified and official methods was established for crude and refined soybean oils with R2 of 0.9995 and 0.997, respectively. The slopes were 1.01 and 0.99 for the crude and refined oil, respectively.;The number of days soybean lost 0.5 and 1.0% dry matter, for low and high harvest moisture content (MC) soybeans both mechanically and manually harvested, were determined. Soybeans manually harvested at ...


Measuring And Modeling Alachlor Dissipation In Soil , Dee Anna Jo Weed Jan 1995

Measuring And Modeling Alachlor Dissipation In Soil , Dee Anna Jo Weed

Retrospective Theses and Dissertations

Field and laboratory experiments evaluated the overall dissipation of alachlor (2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl) acetamide) and the effect of no-till and chisel-plow tillages on alachlor leaching and dissipation. In the top 30-cm layer of field soil, the time to 50% dissipation (half-life) was 2 to 3 d, and the time to 90% dissipation ranged from 17 to 30 d. In no-till soil, alachlor dissipated slightly faster, and more was transported into the 10-to-30-cm soil layer. The tillage effect depended on weather that favored movement into and dissipation within the soil, rather than dissipation on plant residues and the soil ...


Seed Furrow Sidewall Smearing By Double Disk Openers , Muhammad Iqbal Jan 1995

Seed Furrow Sidewall Smearing By Double Disk Openers , Muhammad Iqbal

Retrospective Theses and Dissertations

Seed furrow sidewall smearing by planter double disk openers in clay loam and loam soils was investigated in field and growth chamber experiments. Treatment variables were row preparation, soil moisture, and planting period. Evaluation parameters were soil bulk density, air permeability, cone index, emergence rate index and total emergence, and plant dry matter weight. The experiments were conducted in somewhat poorly drained soils near Ames, Iowa. The fields were not cultivated before planting and the residue from the previous year's corn was removed. Experiments were conducted in two cropping seasons. Each experiment consisted of a factorial design of three ...


Knowledge And Decision Support For Variable Rate Application Of Materials In Prescription Farming , Jack Robert Ambuel Jan 1995

Knowledge And Decision Support For Variable Rate Application Of Materials In Prescription Farming , Jack Robert Ambuel

Retrospective Theses and Dissertations

One major goal of prescription farming is to optimize application rates for seed fertilizer, and other agricultural inputs as a function of location within a field. There are four main components of a variable rate application system: (1) A method of determining the location of farm equipment (e.g. combines, tractors) within a field. (2) A system for controlling the application rate of materials (seeds, fertilizers, pesticides). (3) The capability to measure the results using a real time yield monitor. (4) An algorithm or prescription for determining what rates of materials to apply at each location. In this dissertation it ...


Soil Compaction Loosener , Kamal Mohamed Adam Jan 1993

Soil Compaction Loosener , Kamal Mohamed Adam

Retrospective Theses and Dissertations

Soil compaction is a potential problem in many agricultural soils due to the increasing mass of agricultural vehicles and equipment and tendency of farmers to work fields when soil is wet. A review of literature showed that some control measures can be taken such as controlling traffic to reduce compaction or use of tillage to remove the effects of compaction. Many implements have been used to loosen compacted soil, but in their design compaction depth was not considered and also these implements are designed for full width tillage as opposed to tillage only in the zone that has been compacted ...


Measurement And Simulation Of Water Table Management Effects On Groundwater Quality , Prasanta Kumar Kalita Jan 1992

Measurement And Simulation Of Water Table Management Effects On Groundwater Quality , Prasanta Kumar Kalita

Retrospective Theses and Dissertations

The goal of this study was to investigate the effect of various water-table management (WTM) practices on corn growth and yield and agricultural chemical concentrations in shallow groundwater. Field experiments were conducted for three years (1989-91) at the research sites near Ames and Ankeny. Water-table depths of 0.3, 0.6, and 0.9 m were maintained in field lysimeters at the Ames site, and variable water-table depths were maintained in a subirrigation field at the Ankeny site;Photosynthesis measurements were made regularly during the growing season, and yield data were collected at harvest. In 1989, a relatively dry year ...


Modeling Spatial Variability And Transport Processes In A Glacial Till Soil , Binayak Prasad Mohanty Jan 1992

Modeling Spatial Variability And Transport Processes In A Glacial Till Soil , Binayak Prasad Mohanty

Retrospective Theses and Dissertations

The objective of this study was to investigate the spatial variability of different physical and chemical properties of soils, and their role on transport processes of chemicals to groundwater sources in a glacial till soil of central Iowa;Measurements were made to determine the in-situ saturated hydraulic conductivity (K[subscript] sat) of a glacial till soil at sixty six sites in a tillage established plot. One hundred thirty-two data points on K[subscript] sat collected at two soil depths along two bisecting perpendicular transects, were used to develop semivariogram models, in conjunction with split-window median polish approach. Nested structure with ...


Efficient Herbicide Application To Reduce Environmental Losses , Steven Kent Mickelson Jan 1991

Efficient Herbicide Application To Reduce Environmental Losses , Steven Kent Mickelson

Retrospective Theses and Dissertations

A point-injection system has successfully been designed to inject and incorporate herbicides applied with water into the soil profile in a band. This point-injection cylinder (PIC) can incorporate herbicides in a single pass through the field while leaving the soil surface virtually undisturbed. The PIC functions effectively on both bare soil surfaces and soil surface covered with crop residue;The relative persistence of banded herbicides (alachlor, atrazine, and propachlor) using the PIC and a band sprayer was compared in a field study. A bare soil surface and a soil covered with an average of 79 percent corn residue were used ...


Changes In Soil Microtopography By Tillage With A Cultivator Sweep , Harold Mark Hanna Jan 1991

Changes In Soil Microtopography By Tillage With A Cultivator Sweep , Harold Mark Hanna

Retrospective Theses and Dissertations

The ridging effect of cultivator sweeps modifies soil microtopography affecting root environment and soil erosion potential. The effects of sweep rake angle (13.5°, 16° and 44°), speed (5, 7, and 9 km/hr), and depth (50 and 100 mm) on lateral soil movement into a ridge, ridge height and changes in surface elevation were measured. Dependent variables soil shift, ridge height and change in surface height were defined as measures of the change in soil microtopography;Techniques were developed and used to measure soil aggregate movement during sweep tillage. A comparison was made of actual soil flow to that ...


Tillage-Induced Changes In The Physical Properties Of Soil , Syed Hasan Ali Rizvi Jan 1991

Tillage-Induced Changes In The Physical Properties Of Soil , Syed Hasan Ali Rizvi

Retrospective Theses and Dissertations

Four tillage systems were used to measure the effects of tillage-induced changes on bulk density, penetration resistance, soil temperature, moisture content, surface roughness, and aggregate mean weight diameter. The four systems included, five passes with a cultivator, one pass with rotavator, two passes with disk, and one pass each with moldboard and disk. Wheat emergence count and yields were evaluated. Field experiments were conducted in three different agro-ecological regions of Pakistan. Soil types varied from sandy clay loam to clay loam. Wheat (Triticum aestivum L.) was used at all sites. Prior to tillage, base line data for the above related ...


Monitoring High Water Table Effects On Corn Growth And Water Quality In Growth Chambers And Field Lysimeters , Niaz Ahmad Jan 1991

Monitoring High Water Table Effects On Corn Growth And Water Quality In Growth Chambers And Field Lysimeters , Niaz Ahmad

Retrospective Theses and Dissertations

The general purpose of this study was to investigate the effects of different degrees of stress due to excessive wetness on root and shoot growth, yield of corn, plant uptakes of nitrogen, phosphorous, and potassium; and on nitrogen leaching;Experiments were conducted in both environmentally controlled chambers and field lysimeters. Four stress levels due to excessive wetness, equivalent to 90, 180, 270 and 360 cm-days (Sieben's SEW[subscript]30 concept), were applied to growing corn by surface flooding for 3, 6, 9, and 12 days, and for 6, 12, 18, and 24 days when the water table was maintained ...


Ridge Farming And Plant Root Environment, Wesley Fisher Buchele Jan 1954

Ridge Farming And Plant Root Environment, Wesley Fisher Buchele

Retrospective Theses and Dissertations

No abstract provided.