Webo Dasto Task Chair

http://deepblue.lib.umich.edu/bitstream/2027.42/108435/1/wwittry_1366948833.pd

Dual cathode system for electron beam instruments

An electron beam source having a single electron optical axis is provided with two coplanar cathodes equally spaced on opposite sides from the electron optical axis. A switch permits selecting either cathode, and a deflection system comprised of electromagnets, each with separate pole pieces equally spaced from the plane of the cathodes and electron optical axis, first deflects the electron beam from a selected cathode toward the electron optical axis, and then in an opposite direction into convergence with the electron optical axis. The result is that the electron beam from one selected cathode undergoes a sigmoid deflection in two opposite directions, like the letter S, with the sigmoid deflection of each being a mirror image of the other

Evaluation of soil sampling strategies for soil tests and of variable-rate fertilization for phosphorus in Iowa soils

http://www.worldcat.org/oclc/4027259

Gaussian Models for the Energy Distribution of Excitation in Solids: Applications to X-Ray Microanalysis and Solid State Electronics

Gaussian models for the depth distribution of excitation in a solid bombarded by an electron beam have been successfully applied to the interpretation of data obtained in electron probe x-ray microanalysis (spatial resolution and absorption effects) and to the study of voltage dependence of cathodoluminescence and the voltage dependence of electron beam induced currents at Schottky barriers. In these applications, it was assumed that the distribution of excitation with depth can be scaled in depth according to the range-energy equation: R = CEno. The physical basis for this range-energy equation is the Bethe equation for electron energy loss, which yields the Bethe range when integrated over the electron\u27s path in the target. The Bethe range was previously shown by Hoff and Everhart to be of the form R = CEno over the range of energies useful in most experiments with electron beam excitation

Uniform and variable-rate fertilizer and manure phosphorus for the corn-soybean rotation

Precision agriculture has evolved from a concept into an accepted management practice. The challenge now is how to best utilize these technologies for the benefit of agriculture. Nutrient management could be improved and spatial variability reduced by variable-rate (VR) application. The objectives of this dissertation were to assess the value of VR P fertilization and P-based liquid swine manure application for corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] production compared with the traditional uniform-rate (UR) application. On-farm research methods based on replicated, long narrow strips were adapted to precision technologies. These technologies included grain yield monitors, differential global positioning systems, and geographical information systems. Treatments consisted of a non-fertilized control, a UR method based on average soil-test P (STP) for the entire field and a VR method based on STP from 0.2 to 1.7 ha grid cells. Grain yield and temporal changes in STP were used to assess treatment differences in both studies. In addition, plant dry weight, P concentration, and P uptake (V5 growth stage) were used in the fertilizer study.;Phosphorus fertilization and manure often increased whole-field crop grain yield in fields in which average STP values were below the Optimum interpretation class for corn and soybean production. Analyses of yield for field areas with contrasting STP values often showed significant responses to fertilizer or manure P in field areas testing Optimum or less, but rarely in high-testing areas. Phosphorus fertilization increased early plant growth and P uptake more frequently than grain yield. Although the method of P application did not influence whole-field or within-field plant responses, VR reduced soil P variability compared with UR by increasing STP in low-testing areas and decreasing or not affecting STP of high-testing areas.;This research showed precision farming technologies are useful tools for improving nutrient management. Fertilization or manure application programs that vary the nutrient application rate may not result in increased yield compared with UR application methods. However, use of VR technology will result in better nutrient management and perhaps better water quality because of more efficient distribution of fertilizer or manure

Use of DGPs, Yield Monitors, Soil Testing, and Variable Rate Technology to Improve Phosphorus and Potassium Management

New technologies such as differential global positioning systems (DGPS), yield monitors and other sensors, variable rate technology, and associated practices (such as grid soil sampling) have potential to improve soil fertility management. Soil sampling in the field is one of the most important sources of error in soil testing. A very small amount of soil needs to appropriately represent thousands of tons of soil and usually there is significant spatial variability of nutrient levels. The expectation of many producers and agronomists is that grid sampling will adequately describe field nutrient availability and that variable rate fertilization will result in better soil fertility management and increased profits to producers. Many also believe that variation in nutrient levels explains much of the yield variability within fields. Studies of the spatial variability of nutrient supplies, sampling methods, and relationships between nutrient levels and crop yields are essential to assess if these expectations are reasonable. Once reliable and cost-effective sampling schemes are identified, the agronomic and economic advantage of variable rate fertilization can be reasonably estimated from amounts of fertilizer applied, expected yield responses, and the costs involved

How Can We Make Intensive Soil Sampling and Variable-Rate P and K Fertilization Cost-Effective?

Precision agriculture technologies have potential for improving soil fertility evaluation and nutrient management. Global positioning systems (GPS), yield monitors, various forms of remote sensing, geographical information system (GIS) software, and variable rate technology are available to producers. Intensive soil sampling, crop scouting, and other practices complete the new technological package. Soil testing is a diagnostic tool that adapts well to site-specific management because it can evaluate nutrient availability of areas of different sizes. However, the spatial variation of nutrients within fields makes soil sampling one of the most important sources of error in soil testing. Intensive soil sampling, soil test mapping, and variable-rate application of fertilizers or manure can improve the efficacy of the conventional practice of collecting soil samples from large areas and applying a uniform fertilizer rate over a field. Although variable-rate fertilization can be used on the basis of sampling areas identified according to soil map units, topography, and/or previous management, many believe it should be based on grid sampling. The conventional sampling by soil map unit may not be appropriate for precision agriculture because available soil survey maps may not have the required precision and often there is high nutrient variation within soil map units. This presentation discusses soil sampling methodology and summarizes results of ongoing Iowa research. The research compares various soil sampling methods and fixed-rate versus variable-rate P or K fertilization conducted in various producers\u27 fields. The research is not based on simulations based just on soil test data. It evaluates the effectiveness of intensive grid sampling schemes and the effectiveness of current variable rate technology

Soil Sampling Strategies for Variable Rate P and K Fertilization and Liming

Soil fertility management can be greatly improved with the use of precision agriculture technologies. Differential global positioning systems (DGPS), yield monitors, aerial photographs, and variable rate technology can improve both soil fertility evaluation and fertilizer or lime application. Soil sampling in the field is the most important source of error in soil testing. A very small amount of soil needs to appropriately represent thousands of tons of soil and usually there is large spatial variability of nutrients. Intensive soil sampling and variable-rate fertilization can improve the efficacy of fertilization and liming compared with the conventional practice of collecting soil samples from large areas and using single-rate fertilizer applications. Although variable-rate fertilization can be used on the basis of the traditional sampling of areas identified on the basis of soil types, landscape, or previous management, many believe that it should be based on intensive grid sampling. Conventional soil sampling may not be appropriate for precision agriculture because one composite sample, even if it is collected from one soil mapping unit, may not adequately represent apparently uniform areas with long histories of cropping and fertilization. This presentation discusses the advantages and disadvantages of various soil sampling methods and summarizes ongoing research on the spatial variability of phosphorus (P) and potassium (K) and the cost-effectiveness of variable-rate fertilization or liming for corn and soybean crops