1,720,966 research outputs found
A New Spin on an Old Crop for Bioenergy: Sorghum
Get PDFAccording to Renewable Fuels Standard (RFS) – Energy Policy Act of 2005, the U.S. must reduce foreign oil dependence, where the target is to produce 36 billion gallons of oil equivalent in 2022 (RFA, 2010). Cellulosic material is considered an alternative source for bioenergy production, because it is renewable and environmentally friendly (Peters and Thielman, 2008). Annual crops, such as sorghum (Sorghum bicolor L.) can be cultivated in current row-crop production systems, which could provide grain and cellulosic feedstock production in Southeastern U.S. However, the impacts of removing cellulosic biomass on agricultural soils must not be ignored, and sorghum biomass has relatively high moisture content which should be dried before transported to reduce costs. Different experiments were established at the E.V. Smith Research Station, Shorter, AL to evaluate quantity and quality of sorghum biomass production, to monitor soil impacts due to biomass production/removal, and determine the best approach to drying sorghum biomass. Three types of sorghum: grain sorghum – NK300 (GS), high biomass forage sorghum – SS 506 (FS), and photoperiod sensitive forage sorghum - 1990 (PS) and a forage corn (Zea mays L.) – Pioneer 31G65 were grown for two consecutive years (2008 and 2009) under irrigated and non-irrigated treatments, and under two different tillage systems: conventional (total disked area, 0.15 m depth) and conservation tillage (in-row subsoiling, 0.30 m depth). The results indicated that irrigation affected aboveground dry matter (ADM) positively in both years, but conservation system
improved ADM production only in 2009. Holocellulose, lignin and ash content differences among crops for both evaluated years were lower than 8.3%, 2.0% and 1.9 % respectively, and they were considered minor. PS was considered the best crop for ADM production, respectively, 26.04 and 30.13 Mg/ha at 18 and 24 weeks after planting in 2008. ADM production in 2009 decreased due to leaf losses caused by Anthracnose (Colletotrichum graminicola) disease which affected all sorghum varieties. Furthermore, changes in soil characteristics were detected after 2 years of cropping. Soil organic carbon (SOC) increased near soil surface (0.10 – 0.15 m), but it decreased from 0.40 – 0.45 m. SOC losses were higher in conventional than conservation tillage. Total nitrogen in soil (N) drastically increased in deep layers due to percolation. Additionally, bulk density (Bd) values increased at all evaluated depths. Irrigated plots had higher Bd than non-irrigated plots at both 0.05 – 0.10 and 0.20 – 0.25 m soil layers. And cone index (CI) values showed restrictive layers at depths of 0.15 m for conventional plots. Therefore, conservation tillage and photoperiod sensitive sorghum (1990) – PS were recommended. In another experiment, sorghum-sudan hybrid was harvested with two different headers on a self-propelled windrower: a Massey Ferguson 9145 (sickle) and a Massey Ferguson 9185 (disc). The disc header was comprised of two pairs (rear/front) of metal conditioner rollers which used three different pressures (0, 3500, and 7000 kPa), and two different gaps (0 and 0.02 m). Sorghum-sudan biomass moisture content (%) was evaluated daily until it remained constant. Results revealed that the higher pressures and smaller gaps resulted in faster drying of biomass. The best settings for the disc header were “7000 kPa – 0 m” or “7000 kPa – 0.02 m” which showed, respectively, moisture content levels of 13.6 % and 16.8 % after 14 days. These results indicate that proper setting of the disc header including properly setting the pressures and gaps are important to achieve optimum drying of sorghum biomass
An Automatic Depth Control System for the On-the-Go Soil Strength Sensor
Get PDFHardpans are areas of soil compaction formed by vehicle traffic or natural processes. These compacted areas beneath the topsoil can hinder successful crop production. A novel sensor for measuring soil strength was presented in an earlier work, and patented as the OSSS (On-The-Fly Soil Strength Sensor). The focus of this thesis is the design and evaluation of a control system for this new method of sensing soil strength. The graphical user interface has been implemented with National Instrument’s LabVIEW R software, and drives an analog PID-type (proportional, integral, and derivative) position controller for a hydraulic cylinder. This controller causes the strength sensor to vertically oscillate in the soil at consistently spaced distance intervals, regardless of tractor speed variations. Successful development enables this system to collect soil strength information over an entire field at all desired depths in a short period of time
Modeling and Validation of Hitched Loading Effects on Tractor Yaw Dynamics
No full textThis thesis develops a yaw dynamic model for a farm tractor with a hitched
implement, which can be used to understand the effect of tractor handling characteristics
for design applications as well as for new automated steering control systems. A model is
found in which hitched implement conditions can be accounted for, and an improvement
in yaw rate tracking prediction in both steady state and dynamic conditions is seen vs.
traditional models. This model is termed the “3-wheeled” Front and Hitch Relaxation
Length (“3-wheeled” FHRL) Model. Experimental data from a hitch force dynamometer
are used to validate the way the hitched implement forces are derived in the “3-wheeled”
FHRL Model and to determine if differential hitch forces can be ignored. Steady state
and dynamic chirp data taken for a variety of implements at varying depths and speeds
are used to quantify the variation in the hitch parameter and to find the front and hitch
relaxation length values. Finally, a model which accounts for four-wheel drive forces is
derived, and experiments are taken which provide a preliminary look into the effect of
four-wheel drive traction forces on the yaw dynamics of the tractor.
In comparisons with other traditional models, the “3-wheeled” FHRL Model is
shown to be superior in its steady state yaw rate tracking ability with an RMS error of
.245 deg/s vs. 1.96-2.07 deg/s for other models at a certain depth and also superior in its
dynamic tracking ability with an RMS error of .675 deg/s vs. .748-1.37 deg/s for the
other models. The experimental results from the hitch force dynamometer show that the
implement performs according to the linear tire model and that the moment caused by
differential forces at the hitch can be ignored. The hitch parameter, Cah , ranges from 452-
3385 N/deg for various implements and depths tested in this thesis. The front tire
relaxation length is found to be .37 m and the hitch relaxation length is found to be .4 m.
The four-wheel drive experiments show that using four-wheel drive provided an increase
in yaw rate from 9-21%, depending on the implement depth and speed
Reduction of Soil Compaction in a Cotton and Peanut Rotation Using Conservation Systems
Get PDFSouthern Coastal plain soils have a long history of intensive continuous monoculture cropping, and are highly weathered due to geoclimatic conditions. These soils pose a challenge to the adoption of conservation agriculture due to subsoil compaction (densification of subsurface layers). This problem is usually addressed with adoption of non-inversion deep tillage. However, with ever-increasing prices of fuel this operation is often questioned by farm managers as too costly. Another problem facing farmers in this region is the lack of a good rotation system. In recent years, rotations of cotton (Gossypium hirsutum L.) and peanuts (Arachis hypogaea L.) have increased substantially in Southern Coastal plain due to reduced disease pressure and increased
economic benefits provided by this rotation. Nevertheless many farmers are skeptical about adopting conservation tillage practices for peanut production due to fear of depressed yields caused by pests and diseases.
We attempted to develop a conservation tillage system that included several methods of subsoil disruption. Three subsoiling implements were evaluated against a non-subsoiled treatment with and without a rye (Secale cereale L.) cover crop on a 4-yr cotton/peanut rotation at the Wiregrass Research Station in Headland, AL on a Dothan loamy sand (fine loamy, kaolinitic, thermic Plinthic Kandiudult). Plant, soil, and machinery parameters were evaluated: crop yield, cover crop biomass, cotton leaf temperature, soil moisture, bulk density, cone index, total soil carbon and nitrogen, saturated hydraulic conductivity, and tillage energy. Results showed consistently lower yields for non-subsoiled (11 and 51% lower, for peanuts and cotton, respectively) treatments. In one year of the study which was dramatically affected by drought, a cover crop provided a 26% increase in seed cotton yield. No differences between implements were found. Soil strength was greatly reduced by in-row subsoiling. During the 2006 cotton season, the no-till treatment had cone index of 3.6 MPa at the 10 cm depth which was significantly greater than any of the other in-row subsoiling treatments; Strip-till (0.9MPa), Paratill (1.4 MPa), and Worksaver (1.2 MPa). Our yield and economic results demonstrate that it is highly recommendable to in-row subsoil and plant a winter cover crop as they significantly boost productivity to competitive levels, increase net economic return, and improve system sustainability
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Development of a More Sustainable Sweetpotato Production System in Alabama
No full textField experiments were conducted from 2003-2005 to evaluate the influence of grass and legume cover crops, no-tillage, and varying rates of nitrogen on commercial sweetpotato production. Cover crops used for the no-till operation were crimson clover, hairy vetch, winter rye, and winter wheat, along with a bareground treatment, which was conventionally planted. Applied nitrogen rates were 50 kg•ha-1 or 100 kg•ha-1. The experimental design was a randomized complete block design. Each experimental unit consisted of one of the four cover crops at one of the two nitrogen rates. These eight treatments were compared to two bareground treatments at one of the two nitrogen rates. Each treatment was planted with ‘Beauregard’ sweetpotato. Biomass samples were taken from the cover crops for biomass, carbon, and nitrogen analysis. Cone index measurements were taken after transplanting to determine soil compaction for each treatment. Soil temperature and percent soil moisture were taken for each treatment throughout the growing season. Soil samples were taken to determine organic matter content pre and post treatment. When the sweetpotatoes were harvested, yield data was taken from each treatment.
All of the cover crops produced significant quantities of biomass compared to the bareground treatment. Hairy vetch and crimson clover produced desirable C:N ratios. Cone index measurements were reduced in 2005 compared to 2004. Rye, crimson clover, and wheat cover crops conserved soil moisture. There was an increase in organic matter from 2003 to 2005. Highest yields of sweetpotato were obtained when no-tilled into crimson clover or hairy vetch cover crops. Highest yields of sweetpotato was also obtained when either 50 kg•ha-1 or 100 kg•ha-1 of nitrogen was applied. Using crimson clover or hairy vetch cover crops with 50 kg•ha-1 of applied nitrogen yielded higher net returns compared to the conventional bareground method with 100 kg•ha-1
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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