1,720,983 research outputs found
The Impact of Cover Crops on Soil Microbial Population and Soil Physical and Chemical Properties
Get PDFConventional farming on Ultisols that are dominant in Southeast US has resulted in the loss of soil organic matter over time. Conservation tillage farming practices that incorporate different cover crops are shown to increase soil organic matter. Soil organic matter is the lifeblood and basis of soil health. Soil microorganisms play a critical role in the breakdown and mineralization of cover crops that are incorporated into soil. Different types of soil microbes are involved in mineralizing different cover crops. Relationships between soil microbes’ diversity and activities in soil are dependent on soluble organic sources. Although the impact of cover crops on soil physical, biological, and chemical properties in general are well established, there are still many gaps in our knowledge on the effects of specific cover crops on soil microbial diversity and populations and, soil physical-chemical properties under specific environmental conditions. Hence, the objectives of our studies were to evaluate three cover crop species, cereal rye (Secale cereale), crimson clover (Trifolium incarnatum), and forage radish (Raphanus sativus L.) and their mixtures in a soybean (Glycine max L.)–corn (Zea mays.) rotation under strip tillage on selected soil properties; investigate the impact of the cover crops on nematode population and phonology, microbial activities, and soil properties at different soil depths. The field experiment was a randomized complete block design with four replications. Treatments were fallow (no cover crop), clover, rye/clover, rye/radish, clover/radish, and rye/clover/radish (3-way mixtures) mixtures. Cover crops had significant impacts on soil respiration, active carbon, labile amino nitrogen, C:N ratio, compaction, bulk density, predator, and bacterial feeding nematodes by soil depths. Cover crops did not significantly affect total organic carbon and nitrogen, organic matter, plant parasitic nematode, fungal feeding nematode, and omnivore in all depths by year. Nematode populations for all feeding groups were considerably high at 0-10 cm depth compared to lower soil depths. This study will contribute to our understanding of the impact of cover crops on Ultisols of Alabama
Irrigation Scheduling to Promote Corn Productivity in Central Alabama
Get PDFAgriculture is the largest consumer of water in the United States. Results from previous studies have shown thatit is possible to substantially reduce irrigation amounts and maintain corn yield. The objectives of this study wereto evaluate the advantages and disadvantages of two irrigation scheduling methods for corn production inAlabama. Two irrigation scheduling methods evaluated were: a) Checkbook, which is one of the conventionalmethods used by farmers that is based on the soil water balance estimated using water lost by evapotranspirationand its replacement through rainfall or irrigation, and b) Sensor-based, which was based on soil matric potentialvalues recorded by soil moisture tension sensors installed in the field. The experimental field was divided intotwo irrigation management zones (zone A and zone B) based on soil properties of each field. During the 2014season in zone A, significant grain yield differences were observed between the two irrigation methods. TheCheckbook plots exhibited greater yield than Sensor-based plots: 10181 kg ha-1 and 9696 kg ha-1, respectively.The greater yield on the Checkbook plots could be associated with higher irrigation rate applied, 148 mm more,compared with the Sensor-based plots. In zone B, there were no significant yield differences between bothirrigation methods; however, Sensor-based plots out yielded Checkbook plots, with 9673 kg ha-1 and 9584 kgha-1, respectively. Even though the irrigation amount applied in Checkbook located in zone B was higher, 102mm more, there were no significant yield differences. Therefore, it suggests that the Sensor-based method waspromissory irrigation scheduling strategy under the conditions of zone B. In 2015, there were no significant grainyield differences between zone A and zone B when the data from the Checkbook plots were analyzed. However,the Sensor-based treatment produced a statistically significant difference of grain yield of 13597 kg ha-1 in zoneA and 11659 kg ha-1 in zone B, also both zones received the same amount of irrigation. Overall results of bothgrowing seasons indicated that the use of the Sensor-based irrigation scheduling treatment resulted in similarvalues of total profit per hectare when compared to Checkbook method. The Sensor-based method seems apromising strategy that could result in water and financial savings, but more research is required.Fil: Da Cunha Leme Filho, Jose F.. Virginia Polytechnic Institute; Estados UnidosFil: Ortiz, Brenda V.. Auburn University.; Estados UnidosFil: Damianidis, Damianos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Oliveros; ArgentinaFil: Balkcom, Kipling S.. Usda-soil Dynamics Research; Estados UnidosFil: Dougherty, Mark. Auburn University.; Estados UnidosFil: Poschel, Thorsten. Auburn University.; Estados Unido
Quantifying and Modeling Preferential Flow and Nutrient Loss from Agricultural Soils Fertilized with Poultry Litter.
No full textFertilizing agricultural fields with poultry litter to meet crop nutrient requirements and using cover crops to improve soil health are important agricultural management practices. Excessive loss of contaminants via surface runoff and subsurface flow pathways from fields fertilized with poultry litter can cause water quality impairment. Further, recent research has shown that cover crops, while beneficial for soil health, can increase macroporosity in soil layers, the size of the large pores, the interconnectivity, and connection probability of larger pores, which may significantly enhance the transport of contaminants via preferential flow pathways. Therefore, it is crucial to understand the dynamics of the transport of pollutants (e.g., phosphorus and trace metals (copper, zinc, and nickel)) in agricultural fields. Specific objectives of this study were to (1) investigate the effect of cover crops and poultry litter application on phosphorus, zinc, copper, and nickel losses via leaching and (2) model the degree of preferential flow occurring and transport of trace metals (copper and zinc) in undisturbed soil columns with surface-applied poultry litter in pastures.
For objective 1, ten intact undisturbed soil cores (150 mm diameter and 500 mm length) collected from E.V. Smith Research Center, near Shorter, Alabama, were used for laboratory-based leaching experiments. For the leaching experiments, the treatments included cover crop and no-cover crop soil columns with and without (control) poultry litter application. The leachates collected during the rainfall simulation experiments were analyzed for total metals, dissolved metals, colloidal metals, and dissolved reactive phosphorus (DRP). The results showed preferential flow in the columns due to the presence of macropores. The total, colloidal, and dissolved phosphorus concentration was significantly higher in columns with cover crops fertilized with poultry litter than in columns with no-cover crops fertilized with poultry litter. Similar trends were observed in trace metal losses. The preferential flow through soil macropores increased the mobility and velocity of solute movement in cover cropping systems.
For the second objective, a numerical model (HYDRUS-1D) was used to model the tracer and trace metal flow through the soil columns collected from the Sand Mountain region in northern Alabama. The inverse parameter optimization technique was used to obtain parameters that can shed light on the physical and chemical processes occurring in the flow media. The results showed that soil cores, though collected from the same pasture field, varied in their pore structures, which led to different degrees of preferential flow and solute transport in the vadose zone. The preferential flow occurring in the columns causes physical nonequilibrium (PNE). The mobile immobile model (MIM) in the HYDRUS-1D program successfully described the tracer transport and preferential flow occurring in the columns. Trace metal transport was accompanied by chemical nonequilibrium (CNE) due to the reactive nature of trace elements. A dual porosity model with PNE and CNE could model the preferential flow and kinetic desorption. PNE and CNE occurring simultaneously are difficult to distinguish as they affect each other in natural soils. However, numerical modeling allowed us to differentiate between the types of nonequilibrium and understand the factors affecting these nonequilibrium processes. Overall, understanding the mechanism of solute transport through the macropores is of utmost importance to develop appropriate management practices
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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