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Full-Text Articles in Engineering

Effects Of Shallow Water Tables On Soil Aeration, Water Quality, And Physiological Growth Of Soybean , Tahir Sarwar Jan 1995

Effects Of Shallow Water Tables On Soil Aeration, Water Quality, And Physiological Growth Of Soybean , Tahir Sarwar

Retrospective Theses and Dissertations

This study was conducted to investigate the effects shallow water table depths on soil aeration, groundwater quality and on some physiological growth and yield parameters of soybean. The experiments were conducted in two environmentally controlled growth chambers using sixteen lysimeters. Water table (WT) treatments were established on 37 day after planting (DAP), at depths of 0.15-, 0.30-, 0.45- and 0.60-m below the soil surface. Soil aeration status was determined by measuring soil oxygen concentrations at 0.15-, 0.30-, 0.60-m depths in the lysimeters. Effects of water table depths on groundwater quality were determined by ...


Amino Acid Composition Of Soil Organic Matter And Nitrogen Transformations In Soils Under Different Management Systems , Zachary Ngewoh Senwo Jan 1995

Amino Acid Composition Of Soil Organic Matter And Nitrogen Transformations In Soils Under Different Management Systems , Zachary Ngewoh Senwo

Retrospective Theses and Dissertations

Studies of amino acid composition of soil organic matter extracted from 10 Iowa surface soils and from surface soils of two long-term rotation experiments showed that, with the exception of asparagine plus aspartic acid and glutamine plus glutamic acid, the other 13 amino acids, expressed as percentages of total amino acid extracted, were very uniform among the soils. The total amino acid extracted was significantly correlated with organic C (r = 0.79[superscript]\*\*) and clay content (r = 0.76[superscript]\*\*), but not with total N. Expressed as percentages of organic C and N in soils, the amounts extracted ranged from ...


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 ...


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 ...