Open Access. Powered by Scholars. Published by Universities.®

Earth Sciences Commons™

Open Access. Powered by Scholars. Published by Universities.®

2021

Discipline
Institution
Keyword
Publication
Publication Type
File Type

Articles 61 - 90 of 16206

Full-Text Articles in Earth Sciences

Physical Modeling Of Seismic Response For The Coal Seams Of Yan'an Formation In Loess Tableland Of North China, Xing Tingdong, Xue Shigui, Li Xiaowei, Suo Chonghui, Wang Huiming, Jiao Yanyan Dec 2021

Physical Modeling Of Seismic Response For The Coal Seams Of Yan'an Formation In Loess Tableland Of North China, Xing Tingdong, Xue Shigui, Li Xiaowei, Suo Chonghui, Wang Huiming, Jiao Yanyan

Coal Geology & Exploration

A seismic physical simulation is carried out for the complex seismic response of the coal seam of Yan'an Formation in the loess tableland. First, the physical model materials for the dry layer near the surface of the loess tableland and the coal seam are developed. After several tests, a mixture of silicone rubber with silicon aerogel powder is selected to simulate the surface of the loess tableland, and the mixture with ultra-fine carbon powder added to silicone rubber is used to simulate the low-speed and low-density coal seam. Through the methods of molds control layer, layer by layer pouring, three-dimensional …


Design And Construction Of A Seismic Physical Model Of Room-Pillar Goafs In Shallow Coal Seams, Wang Pan, Zhu Shujie, Jia Qian, Jian Benqi, Lian Miaomiao, Dong Ruijing Dec 2021

Design And Construction Of A Seismic Physical Model Of Room-Pillar Goafs In Shallow Coal Seams, Wang Pan, Zhu Shujie, Jia Qian, Jian Benqi, Lian Miaomiao, Dong Ruijing

Coal Geology & Exploration

In view of the problem of low detection accuracy of room-pillar goafs in shallow coal seams in northern Shaanxi, the seismic physical model is designed for physical simulation according to the principle of similarity ratio of geometry size and wave impedance. Through a large number of ratio tests of similar materials, the ratio of epoxy resin and silicone rubber is determined as 1 : 1.2 for similar materials of low velocity loess layer, 1 : 0.2 : 0.6 for epoxy resin, silicone rubber and talc for mudstone, 1 : 0.4 for epoxy resin and silicone rubber for coal seams, 1 …


Discussion On The Recommended Models For Resource Reuse Of Closed Coal Mines In Main Mining Areas Of Hebei Province, Yin Quanzeng, Chen Zhongshan, Feng Qiyan, Geng Lijuan, Lian Lixun, Li Fang, Liu Ning Dec 2021

Discussion On The Recommended Models For Resource Reuse Of Closed Coal Mines In Main Mining Areas Of Hebei Province, Yin Quanzeng, Chen Zhongshan, Feng Qiyan, Geng Lijuan, Lian Lixun, Li Fang, Liu Ning

Coal Geology & Exploration

The evaluation and the utilization of the resources of the closed coal mines have dual benefits of resources and environment, and can provide a transformation and development path for coal mining enterprises. Based on the investigation of the resources of the closed coal mines in the main mining areas of Hebei Province, through the summary of the typical cases of the resources reuse of the closed coal mines at home and abroad and in Hebei Province, this paper sums up 7 types and 19 kinds of recommended modes of the resources reuse of the closed coal mines in Hebei Province, …


Deformation Characteristics Of Coal Measures And Gas Occurrence Law Of Coal Mines In North China, Wang Wei, Wei Yanzhao, Jia Tianrang, Yan Jiangwei Dec 2021

Deformation Characteristics Of Coal Measures And Gas Occurrence Law Of Coal Mines In North China, Wang Wei, Wei Yanzhao, Jia Tianrang, Yan Jiangwei

Coal Geology & Exploration

Gas is not only one of the important disaster-causing factors in coal mines, but also an important clean energy. Understanding the deformation characteristics of coal measures and the occurrence of gas is the basis for coal mine gas disaster prevention and coalbed methane development. Taking the North China coal measures as the research object, taking the tectonic evolution and control as the main line, using the theory of plate tectonics, tectonic evolution and step by step control of gas-occurring structures, the deformation characteristics of the North China coal-measures and the law of coal mine gas occurrence were systematically studied. The …


Plastic Deformation-Based Constitutive Relation Of Coal Damage And Permeability Model, Wu Xuehai, Li Bobo, Wang Xin, Gao Zheng, Li Jianhua, Xu Jiang Dec 2021

Plastic Deformation-Based Constitutive Relation Of Coal Damage And Permeability Model, Wu Xuehai, Li Bobo, Wang Xin, Gao Zheng, Li Jianhua, Xu Jiang

Coal Geology & Exploration

Coal and gas outburst induced by mining disturbance is one of the main gas dynamic disasters in coal mine production. In order to systematically explore the evolution characteristics of coal damage and the law of gas seepage under mining disturbance, the whole stress strain–seepage experiment under different gas pressures was carried out. The generalized Hooke's law was modified by considering the effects of gas adsorption and thermal expansion, the plastic deformation-based constitutive relation of coal damage was established, and the piecewise permeability model considering the damage was further constructed. The results shown that the coal permeability can be divided into …


New Method And Optimization Research On Water Sealing Outside Casing Based On Water-Swelling Rubber For Stratified Pumping, Zheng Xianghua, Yuan Wei, Luo Yunxiang, Cheng Cong Dec 2021

New Method And Optimization Research On Water Sealing Outside Casing Based On Water-Swelling Rubber For Stratified Pumping, Zheng Xianghua, Yuan Wei, Luo Yunxiang, Cheng Cong

Coal Geology & Exploration

Stratified pumping test is a key technique for hydrogeological exploration. To solve the problems of low efficiency and poor reliability and controllability of the traditional water-sealing methods outside casing for stratified pumping, a water-swelling rubber was developed based on high water absorption of the sodium polyacrylate resin, and a new approach based on water-swelling rubber was proposed and optimized by the response surface methodology in this paper. With the water swelling ratio of the rubber as response index, a surrogate model was constructed by the Box-Behnken experimental design to study the influence of different process parameters, working condition parameters, and …


Discussion On The Water-Preserved Coal Mining By Dewatering-Reflooding Water Curtain In Open-Pit Coal Mines, Li Ying, Yang Zhuo, Wu Tong Dec 2021

Discussion On The Water-Preserved Coal Mining By Dewatering-Reflooding Water Curtain In Open-Pit Coal Mines, Li Ying, Yang Zhuo, Wu Tong

Coal Geology & Exploration

To suppress the attenuation of groundwater resources caused by drainage and control the influence range of coal mining on groundwater resources, the coal mining technology with water curtain was adopted. Taking an open-pit coal mine as the background, this paper established a sand trough recharge platform to carry out physical experiments, and used a numerical method to simulate the irrigation area, so as to analyze the formation and variation of the dewatering-reflooding water curtain. Physical experiments were carried out to observe the formation of a fixed head boundary by water injection curtain which prevented the expansion of funnel, the influence …


Interfacial Shear Behavior Of Gabion Reinforced Coal Gangue And Stability Of Embankment Slope, Yang Guolin, Chen Zi'ang, Duan Junyi, Zhang Yu, Zhang Zhen Dec 2021

Interfacial Shear Behavior Of Gabion Reinforced Coal Gangue And Stability Of Embankment Slope, Yang Guolin, Chen Zi'ang, Duan Junyi, Zhang Yu, Zhang Zhen

Coal Geology & Exploration

In order to make full use of coal gangue generated in coal mining and support the carbon neutral policy, the road section K128+573–K128+740 of Anshao Highway (Anhua-shaoyang, Hunan Province)was filled by coal gangue, and the embankment slope was enhanced by gabion net. The basic characteristics of coal gangue were obtained by its chemical composition and gradation, and shear characteristics of gabion reinforced coal gangue were tested by large-scale direct shearing instrument. Finally, the influence of reinforcement and its method on the stability of reinforced coal gangue embankment was found out by finite difference method. The experimental results show that after …


Prediction Model Of Water Inrush From Coal Floor Based On Ga-Bp Neural Network Optimized By Ssa And Its Application, Yin Huiyong, Zhou Xinlong, Lang Ning, Zhang Lifeng, Wang Mingli, Wu Tao, Li Xin Dec 2021

Prediction Model Of Water Inrush From Coal Floor Based On Ga-Bp Neural Network Optimized By Ssa And Its Application, Yin Huiyong, Zhou Xinlong, Lang Ning, Zhang Lifeng, Wang Mingli, Wu Tao, Li Xin

Coal Geology & Exploration

With the increase of coal mining depth, coal production process is faced with complex water inrush mechanism and variable water inrush main control factors, and the uncertainties among the factors make the prediction of floor water inrush more difficult. In order to accurately predict the risk of floor water inrush, aiming at the small sample and non-linear problem of floor water inrush, firstly, genetic Algorithm is used to optimize the initial weights and thresholds of network random assignment, and then Sparrow Search Algorithm with strong search ability and good stability is selected to optimize the weights and thresholds for the …


Study On The Microscopic Mechanism Of The Loess Improved By Quicklime, Xie Xiao, Wang Luyao, Deng Lejuan, Zhang Guowei Dec 2021

Study On The Microscopic Mechanism Of The Loess Improved By Quicklime, Xie Xiao, Wang Luyao, Deng Lejuan, Zhang Guowei

Coal Geology & Exploration

To investigate the influence of lime content on loess strength and its microscopic mechanism, different proportions of lime were used to improve loess. Through direct shear test, mercury intrusion porosimetry and scanning electron microscopy, the strength characteristics and microstructure changes of compacted loess and modified loess with different lime contents were analyzed qualitatively and quantitatively, and the microscopic mechanism of lime-improved loess was analyzed in depth. The results show that the shear strength parameters of lime-improved loess increases first and then decreases with the increase of lime contents. The cohesive force and internal friction angle reach the maximum when the …


Application Of Unmanned Aerial Vehicle In Surface Soil Characterization And Geological Disaster Monitoring In Mining Areas, Long Linli, Liu Ying, Zhang Xuyang, Su Yongdong, Chen Xiaoyang Dec 2021

Application Of Unmanned Aerial Vehicle In Surface Soil Characterization And Geological Disaster Monitoring In Mining Areas, Long Linli, Liu Ying, Zhang Xuyang, Su Yongdong, Chen Xiaoyang

Coal Geology & Exploration

With the emergence and development of UAVs and the improvement of the miniaturization and intelligence of various sensor, UAVs equipped with sensors have become an efficient tool for obtaining spatial data. Because UAVs are low cost, short revisit period, fast and efficient, light and flexible, simple operation, and high temporal and spatial accuracy of image acquisition, it is widely used in mining land damage monitoring. Using "UAV, Inversion, Soil Monitoring, Surface Collapse, Ground Fissure" as keywords, this paper summarizes the academic papers of the search system in the web of science, CNKI, and Google Scholar from January 2010 to May …


The Development Law Of Surface Cracks In Shallow Coal Seam Mining Through Double Gullies Terrain, Sun Xueyang, Zhang Huixuan, Lu Mingjiao, Li Cheng, Miao Lintian Dec 2021

The Development Law Of Surface Cracks In Shallow Coal Seam Mining Through Double Gullies Terrain, Sun Xueyang, Zhang Huixuan, Lu Mingjiao, Li Cheng, Miao Lintian

Coal Geology & Exploration

In order to protect the ecological environment of the mining area in the Yellow River Basin, the mining-induced surface crack development law was summarized from the parameters of surface crack development location and development morphology during mining of the working face passing through the double gullies terrain by using a combination of numerical simulation experiments, similar material simulation experiments and theoretical analysis in the context of the working face 125203 of Anshan Coal Mine in Miaohagu Mining Area of Fugu County. Through theoretical analysis, the relative position function T of surface cracks in shallow coal seam mining through double gullies …


Numerical Analysis Of The Effect Of Different Soil Types And Water Content On Heat Transfer Performance Of Horizontal Buried Pipes, Zou Hang, Pei Peng, Hao Dingyi, Wang Chen Dec 2021

Numerical Analysis Of The Effect Of Different Soil Types And Water Content On Heat Transfer Performance Of Horizontal Buried Pipes, Zou Hang, Pei Peng, Hao Dingyi, Wang Chen

Coal Geology & Exploration

In order to reveal the heat transfer performance of the horizontal buried pipe heat exchanger in the ground source heat pump system in different soil types, this paper, based on the theoretical knowledge of soil capillary water, combined with the means of numerical simulation, discusses the influence of the difference of three-phase composition in different types of energy storage soil on the heat transfer characteristics of the horizontal buried pipe heat exchanger. The results show that under the cooling condition of 308.15 K, the outlet water temperature of the horizontal pipe in the loam soil decreases to 303.3 K and …


Evolution Law Of The Phreatic Aquifer Water Table In The Water Intake Area Of South-To-North Water Diversion Central Line In Henan Province, Jing Zhaokai, Yan Qing, Xiao Hang, Wang Panpan, Wang Huan, Li Yang Dec 2021

Evolution Law Of The Phreatic Aquifer Water Table In The Water Intake Area Of South-To-North Water Diversion Central Line In Henan Province, Jing Zhaokai, Yan Qing, Xiao Hang, Wang Panpan, Wang Huan, Li Yang

Coal Geology & Exploration

The water supply of the South-to-North Water Diversion has presented a significant impact on the phreatic aquifer water table and the water consumption structure in the intake area of Henan Province. This paper firstly reviews the previous changes of groundwater level burial depth in the plain area of Henan Province, and by collecting and counting the monitoring results of shallow groundwater level in the receiving area of Henan Province from 2008 to 2018, we quantified and partitioned the changes of shallow groundwater level in the receiving area of Henan Province before and after the water supply of the South-to-North Water …


Case Study On The Effects Of Seismic Exploration Beneath The Goafs Of Different Ages, Zhang Zhao, Yin Quanzeng Dec 2021

Case Study On The Effects Of Seismic Exploration Beneath The Goafs Of Different Ages, Zhang Zhao, Yin Quanzeng

Coal Geology & Exploration

With the continuous development of coal resources, the upper group of coal in some coal mines has been mined out, and it is urgent to solve the detection problem of the lower group of coal. Affected by the goaf formed by the upper group of coal, the seismic energy absorption and scattering attenuation of the lower group of coal are significant, and the signal-to-noise ratio of the data is low. The detection of the lower group of coal under the goaf by 3D seismic exploration is still in the exploration stage. In this paper, the 3D seismic exploration project of …


Factors Affecting The Attitude Accuracy Of Wireless Electromagnetic Wave Mwd System, Wang Xiaobo Dec 2021

Factors Affecting The Attitude Accuracy Of Wireless Electromagnetic Wave Mwd System, Wang Xiaobo

Coal Geology & Exploration

In broken soft coal seams of coal mine where hydraulic driving directional drilling is used, hole collapse and hole wall instability are easy to occur. Electromagnetic wave measurement while drilling system is suitable for gas driving drilling, so it is widely used in broken soft coal seams. The accuracy of drilling trajectory is the key to gas drainage effect in broken soft coal seams. In the use of electromagnetic wave measurement while drilling system, the phenomenon of insufficient accuracy and large error of trajectory measurement appears irregularly. In order to solve this problem, this paper analyzes all the factors that …


Mechanism And Effect Analysis Of Enhanced Gas Drainage With Large Diameter Double Boreholes, Zhang Chunhua, Zhang Zijian, Nian Jun, Jiao Dengming Dec 2021

Mechanism And Effect Analysis Of Enhanced Gas Drainage With Large Diameter Double Boreholes, Zhang Chunhua, Zhang Zijian, Nian Jun, Jiao Dengming

Coal Geology & Exploration

To study the mechanism of enhanced gas drainage with large diameter double boreholes, numerical models of single holes with different diameters and double ø350 mm holes were established by using the RFPA2D-Gas software in working face 30110 of Shiquan Coal Mine, Shanxi Province. Stress distribution, damage and fracture, gas permeability evolution and gas migration law of the coal around the hole were analyzed, and then the extraction effect of double ø350 mm holes was investigated. Simulation results show that the pressure relief radii of the ø100 mm, ø250 mm, ø350 mm and double ø350 mm holes are 0.25 …


Intercomparison Of Salinity Products In The Beaufort Gyre And Arctic Ocean, Sarah B. Hall, Bulusu Subrahmanyam, James H. Morison Dec 2021

Intercomparison Of Salinity Products In The Beaufort Gyre And Arctic Ocean, Sarah B. Hall, Bulusu Subrahmanyam, James H. Morison

Faculty Publications

Salinity is the primary determinant of the Arctic Ocean’s density structure. Freshwater accumulation and distribution in the Arctic Ocean have varied significantly in recent decades and certainly in the Beaufort Gyre (BG). In this study, we analyze salinity variations in the BG region between 2012 and 2017. We use in situ salinity observations from the Seasonal Ice Zone Reconnaissance Surveys (SIZRS), CTD casts from the Beaufort Gyre Exploration Project (BGP), and the EN4 data to validate and compare with satellite observations from Soil Moisture Active Passive (SMAP), Soil Moisture and Ocean Salinity (SMOS), and Aquarius Optimally Interpolated Sea Surface Salinity …


Analysis Of Some Farm Driving Variables And Its Relation With Milk Production In A Pastoral Dairy Farm Of Buenos Aires, Argentina, J. L. Rossi, A. Ayala Torales, G. Acosta, V. A. Deregibus Dec 2021

Analysis Of Some Farm Driving Variables And Its Relation With Milk Production In A Pastoral Dairy Farm Of Buenos Aires, Argentina, J. L. Rossi, A. Ayala Torales, G. Acosta, V. A. Deregibus

IGC Proceedings (1977-2023)

The quantity of milk solids produced determines a dairy farm income and contributes to its profit. Total pasture production, forage quality and herd consumption are factors to be managed in this production system. The outcomes of two years were analyzed. Primary production showed its dependence on climatic conditions and use of technological inputs. Forage quality was promoted through interseeding legumes, applying fertilizer and maintaining the pasture young and leafy. Total forage removed by the herd was similar in both years although pasture production decreased. It was possible to cope with seasonal variations in forage production, by varying the grazing pressure …


Effect Of Energetic Supplementation On Forage Losses In An Oat And Italian Ryegrass Pasture Under Continuous Grazing, A. Frizzo, Marta G. Da Rocha, M. R. Freitas Dec 2021

Effect Of Energetic Supplementation On Forage Losses In An Oat And Italian Ryegrass Pasture Under Continuous Grazing, A. Frizzo, Marta G. Da Rocha, M. R. Freitas

IGC Proceedings (1977-2023)

The experiment was conducted at UFSM-RS to quantify herbage losses in oat and Italian ryegrass mixture under continuous grazing by beef heifers. A continuous grazing method with variable stocking rate was utilized to maintain the same herbage mass, 1500 kg DM/ha, in all treatments. The treatments consisted of levels of energetic supplement (0, 0.7 and 1.4% of LW/day). The pasture was evaluated every 28 days, when forage not suitable for grazing was collected in points previously marked in experimental area. The daily losses of herbage mass were of 22.32, 18.98 and 21.16 kg of DM/ha/day, equivalent to 2.61, 1.91 and …


Dynamics And Production Of Forage In Winter Pasture Under Continuous Grazing With Energetic Supplementation, A. Frizzo, M. R. Freitas, Marta G. Da Rocha Dec 2021

Dynamics And Production Of Forage In Winter Pasture Under Continuous Grazing With Energetic Supplementation, A. Frizzo, M. R. Freitas, Marta G. Da Rocha

IGC Proceedings (1977-2023)

This experiment was carried out at Federal University of Santa Maria, from July 09 to November 12, 1999 to evaluate the dynamics and production of forage of oat (Avena strigosa Schreb) and italian ryegrass (Lolium multiflorum Lam) mixture. The grazing system used was continuous with variable stocking rate to maintain 1500kg/ha of herbage mass in all treatments. The heifers were subjected to different levels of energetic supplementation. They are 0, 0.7 and 1.4% of LW/day. The pasture of oat and italian ryegrass presented an accumulation rate of 45.7, 55.1 and 50.0 kg of DM/ha /day and a total …


Rotational Grazing Increases Wool And Lamb Production From Phalaris-Subterranean Clover Pastures In South Eastern Australia, A. N. Thompson, D. Borg, J. F. Graham, J. Lamb, G. R. Saul Dec 2021

Rotational Grazing Increases Wool And Lamb Production From Phalaris-Subterranean Clover Pastures In South Eastern Australia, A. N. Thompson, D. Borg, J. F. Graham, J. Lamb, G. R. Saul

IGC Proceedings (1977-2023)

Wool and lamb production from different grazing systems was compared in a Mediterranean environment near Hamilton in southeastern Australia. The grazing systems were based on combinations of fertiliser inputs and grazing methods that could promote the growth and persistence of phalaris (Phalaris aquatica) and increase animal production compared to ‘typical’ unimproved pastures. In the first 2 years of this experiment, the most productive systems more than doubled ewe stocking rate and wool production, and more than trebled lamb production per hectare, compared to ‘typical’ unimproved pasture, low fertility, set-stocked systems. The change to a well fertilised phalaris/subterranean clover …


The Carrying Capacity Of Pure And Oversown Giant Star Grass (Cynodon Nlemfuensis Vanderyst) Under Different Stocking Rate In South-Western Islands Of Japan, Yasuhiro Kawamoto, T. Namihira, Y. Imura, M. Nagano Dec 2021

The Carrying Capacity Of Pure And Oversown Giant Star Grass (Cynodon Nlemfuensis Vanderyst) Under Different Stocking Rate In South-Western Islands Of Japan, Yasuhiro Kawamoto, T. Namihira, Y. Imura, M. Nagano

IGC Proceedings (1977-2023)

The objective of this study was firstly to know the potential carrying capacity, pasture production, pasture utilization of giant star grass under different stocking rates in intensive rotational grazing system, and to evaluate a carrying capacity of giant star grass (Cynodon nlemfuensis Vanderyst) pasture oversown with annual hybrid ryegrass (Lolium multiflorum X Lolium perenne) on short low productive winter pasture in South-western Islands of Japan. High herbage availability and good quality forage to bring about effective animal productions were produced by using relatively heavy stocking rates of 6 - 8 heads/ha, and achieved optimum pasture utilization of …


Residual Forage And Animal Performance From A Kikuyo Pasture Under Mixed Grazing And Supplementation, F. C. Gómez-Merino, Pedro A. Martínez-Hernández, J. Pérez-Pérez, Alfonso Hernández-Garay Dec 2021

Residual Forage And Animal Performance From A Kikuyo Pasture Under Mixed Grazing And Supplementation, F. C. Gómez-Merino, Pedro A. Martínez-Hernández, J. Pérez-Pérez, Alfonso Hernández-Garay

IGC Proceedings (1977-2023)

Five grazing strategies were compared: grazing by ewes only and mixed grazing (ewes + heifers), in mixed grazing heifers received no supplement or one of three supplements. Ruminal undegradable protein (RUP) varied among supplement: 4.25, 9.11 and 9.13%, the supplement with the highest RUP included protected methionine. All supplements were 21% crude protein and 3.0 Mcal/kg of metabolizable energy. Grazing was on kikuyu, ratio was 30 kg of ewe per 100 kg of heifer in the mixed grazing treatments. Experimental grazing lasted 84 days. Variables measured were residual forage, proline content in residual forage and liveweight gains per animal and …


Stubble Height Effects On Limpograss Pasture Characteristics And Performance Of Beef Heifers, Y. C. Newman, Lynn E. Sollenberger, W. E. Kunkle, D. B. Bates, C. G. Chambliss, A. M. Fox Dec 2021

Stubble Height Effects On Limpograss Pasture Characteristics And Performance Of Beef Heifers, Y. C. Newman, Lynn E. Sollenberger, W. E. Kunkle, D. B. Bates, C. G. Chambliss, A. M. Fox

IGC Proceedings (1977-2023)

Limpograss (Hemarthria altissima [Poir.] Stapf. & C.E. Hubb.) is a C4 species used in Florida beef production systems because of its cool-season growth, persistence on poorly drained soils, and high yield and digestibility. Animal performance on limpograss pastures, however, has been limited by low herbage crude protein (CP). This study evaluated the effect of canopy height of limpograss pastures and N supplementation of grazing cattle on sward characteristics and weight gain and blood urea N (BUN) concentration of yearling beef heifers. Under continuous stocking, six treatments were imposed that included all combinations of three stubble heights (20, 40, …


The Duration Of Regrowth Period And The Structural Traits In A Rotationally Grazed Panicum Maximum Sward, Carlos A. M. Gomide, J. A. Gomide Dec 2021

The Duration Of Regrowth Period And The Structural Traits In A Rotationally Grazed Panicum Maximum Sward, Carlos A. M. Gomide, J. A. Gomide

IGC Proceedings (1977-2023)

Panicum maximum 'cv'. Mombaça was rotationally grazed by steers. Three regrowth periods based on the number of expanded leaves per tiller: 2.5; 3.5 and 4.5, were compared. Three groups of seven tester steers, one for each treatment, grazed the replications of each experimental paddocks, the animals being removed from a paddock after 4 to 5 day grazing period when its sward leaf area index (LAI) was 1.5, on the average. Sward height and available biomass increased while tiller population density and leaf-stem ratio decreased with regrowth period. Overall averages observed for LAI and photosyntheticly active radiation interception by the end …


Effect Of Different Strategies Of Management Of Elephantgrass On Pasture Availability And Milk Yield Of Crossbred Holstein X Zebu Cows, Fermino Deresz Dec 2021

Effect Of Different Strategies Of Management Of Elephantgrass On Pasture Availability And Milk Yield Of Crossbred Holstein X Zebu Cows, Fermino Deresz

IGC Proceedings (1977-2023)

The trial was done to study different strategies of pasture management on milk production of cows grazing Elephantgrass (Pennisetum purpureum, Schum.). The treatments were: Elephantgrass with 30 days of resting and fertilized monthly (30MF), fertilized every two months (30BF). Elephantgrass with 45 days of resting and a stubble height of 90-100 cm (45HS) or a stubble height of 40-50 cm (45LS). The stubble height for treatments 30MF and 30BF was 90-100 cm. The study was done using six crossbred Holstein x Zebu cows/treatment, with 100 days of lactation, on average. The experimental design was a completely randomized block …


Distribution And Characterization Of Rhyolites Of The Strawberry Volcanics -- Evolution Of A Major Rhyolite Field Associated With Columbia River Basalt Magmatism, Eastern Oregon, Usa, Chanel Leigh Dvorak Dec 2021

Distribution And Characterization Of Rhyolites Of The Strawberry Volcanics -- Evolution Of A Major Rhyolite Field Associated With Columbia River Basalt Magmatism, Eastern Oregon, Usa, Chanel Leigh Dvorak

Dissertations and Theses

The Strawberry Rhyolites constitute a significant rhyolite field among the largest in Oregon. Aerial coverage of approximately 386 km2 and an overall estimated volume of ~67 km3 using a median thickness for each unit. On the other hand, the total volume could be greater than 100 km3 if greater thicknesses apply. The Strawberry Rhyolites, a largely unknown mid-Miocene silicic volcanic rocks, crop out amongst voluminous flood basalt flows of the Columbia River Basalt Group (CRBG) in eastern Oregon. The eruptive activity of the Strawberry Rhyolites is currently constrained to span a period of about 2 million years, …


Effects Of Nitrogen Fertilization On The Production Of Panicum Maximum Cv. Ipr 86 Under Grazing, S. M. B. Lugão, L. R. De A. Rodrigues, E. B. Malheiros, J. J. Dos S. Abrahão, A. De Morais Dec 2021

Effects Of Nitrogen Fertilization On The Production Of Panicum Maximum Cv. Ipr 86 Under Grazing, S. M. B. Lugão, L. R. De A. Rodrigues, E. B. Malheiros, J. J. Dos S. Abrahão, A. De Morais

IGC Proceedings (1977-2023)

The experiment was conducted at the Experimental Station of Paranavaí/IAPAR-PR-Brazil, from October 1998 to May 1999, to evaluate the effects of N fertilization on Panicum maximum cv. IPR 86 pastures. Four doses of N (0; 150; 300; and 450 kg.ha-1.year-1) were applied to pastures under rotational grazing with grazing cycles (GCs) of 40 days (5 days-grazing and 35 days-rest). It was used a randomized complete block design, with split-plots, and two replications per treatment, being the N-doses studied in the main plots and the GCs in the sub-plots. In all GCs the variables dry matter of …


Effects Of Management Strategies On Seed Production And Seedling Recruitment In Birdsfoot Trefoil-White Clover Mixtures, W. Ayalá, M. Carámbula, D. F. Risso, J. Hodgson, Peter D. Kemp Dec 2021

Effects Of Management Strategies On Seed Production And Seedling Recruitment In Birdsfoot Trefoil-White Clover Mixtures, W. Ayalá, M. Carámbula, D. F. Risso, J. Hodgson, Peter D. Kemp

IGC Proceedings (1977-2023)

The effects of grazing management on seed production, seed bank size and seedling emergence patterns of Trifolium repens cv. Zapicán (WC) and Lotus corniculatus cv. San Gabriel (BFT) oversown swards were evaluated. A complete randomized block design with 4 replicate blocks was used, in which 4 grazing strategies (grazing all year (SI), summer spelling for seed production (S2), winter rest plus summer spelling (S3) and autumn rest plus summer spelling (S4)), were combined with two defoliation severalties (4 and 10 cm height post-grazing residuals). Plots of 110 m2 were grazed monthly by sheep. Seed production, soil seed bank and …