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Search Results: 1 - 10 of 9278 matches for " Veronica Acosta-Martinez "
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Microbial Compositions and Enzymes of a Forest Ecosystem in Alabama: Initial Response to Thinning and Burning Management Selections  [PDF]
Fritz A. Ntoko, Terrence G. Gardner, Zachary N. Senwo, Veronica Acosta-Martinez
Open Journal of Forestry (OJF) , 2018, DOI: 10.4236/ojf.2018.83021
Abstract: Prescribed burning and tree thinning are commonly used restoration practices for US forests management to increase forest productivity and enhance plant and animal diversity. The impact of these practices in Alabama’s Bankhead National Forest (BNF) to soil microbial components and overall forest soil health are unknown. We hypothesized that microbial assemblages and enzyme activities are continuously changing in forest ecosystems especially due to management selections. Therefore, the objective of this study was to assess changes in microbial community compositions (fungal vs bacterial populations) via fatty acid methyl ester (FAME) profiling and several enzyme activities (β-glucosaminidase, acid phosphatase, arylsulfatase, β-glucosidase, xylanase, laccase, and manganese peroxidase) critical to soil organic matter (SOM) dynamics and biogeochemical cycling. In this forest, heavily-thinned plots without burning or less frequent burning treatments seemed to provide more favorable conditions (higher pH and lower C:N ratios) for C and N mineralization. This may explain a slight increase (by 12%) detected in fungi:bacteria (F:B) ratio in the heavily-thinned plots relative to the control. Thinned (lightly and heavily) plots showed greater ligninolytic (laccase and MnP) activities and lower β-glucosidase and β-glucosaminidase activities compared to the no-thinned plots probably due to increase depositions of woody recalcitrant C materials. We observed significant but negative correlations between the ligninolytic laccase and manganese peroxidase (Lac and MnP) enzymes respectively, with MBC (?0.45* and ?0.68** respectively) and MBN (?0.43* and ?0.65** respectively). Prescribed burning treatment reduced microbial biomass C and N of the 9-yr burned plot/lightly thinned plotsprobably due to depletion of labile C sources with the high temperatures, leaving mostly recalcitrant C sources as available soil substrates. Gram-positive bacteria (i15:0, a15:0, i17:0, and a17:0), actinomycetes (10-Me17:0, 10-Me18:0), AMF (16:1ω5c), and saprophytic fungi (18:1ω9c), largely contributed to the microbial compositions. This study bridges knowledge gaps in our understanding of microbial community compositions and enzyme-mediated processes in repeatedly burned and thinned forest ecosystems.
Evaluation of Stable Isotopes of Water to Determine Rainwater Infiltration in Soils under Conservation Reserve Program  [PDF]
Timothy S. Goebel, Robert J. Lascano, Veronica Acosta-Martinez
Journal of Agricultural Chemistry and Environment (JACEN) , 2016, DOI: 10.4236/jacen.2016.54019
Abstract: The Conservation Reserve Program (CRP) is a USDA program introduced in 1985 to reduce soil erosion by increasing vegetative cover of highly erodible land. Participation in the CRP is done via contracts (10 - 15 years in length) and currently the total area of land under contract is set to decline as per the 2014 Farm Bill. The Texas High Plains (THP) leads the US with >900,000 ha enrolled in CRP. A potential long- term benefit of CRP is to increase soil organic matter and to improve soil structure leading to increased water infiltration. Our objective was to evaluate the feasibility of using stable isotopes of water to measure and compare infiltration of rain in land under CRP management to land under continuous dryland cotton in the THP. For this purpose we selected two sites, with soils in the Amarillo series, enrolled in CRP, one for 25 years and the second site for 22 years. Results from several rain events showed that stable isotopes of water are a method that can be used to evaluate the depth of rainwater infiltration for soils under CRP and dryland management.
Crop and Soil Responses to Using Corn Stover as a Bioenergy Feedstock: Observations from the Northern US Corn Belt
Jane M. F. Johnson,Veronica Acosta-Martinez,Cynthia A. Cambardella,Nancy W. Barbour
Agriculture , 2013, DOI: 10.3390/agriculture3010072
Abstract: Corn ( Zea mays L.) stover is a potential bioenergy feedstock, but little is known about the impacts of reducing stover return on yield and soil quality in the Northern US Corn Belt. Our study objectives were to measure the impact of three stover return rates (Full (~7.8 Mg ha ?1 yr ?1), Moderate (~3.8 Mg ha ?1 yr ?1) or Low (~1.5 Mg ha yr ?1) Return) on corn and soybean ( Glycine max. L [Merr.]) yields and on soil dynamic properties on a chisel-tilled (Chisel) field, and well- (NT1995) or newly- (NT2005) established no-till managed fields. Stover return rate did not affect corn and soybean yields except under NT1995 where Low Return (2.88 Mg ha ?1) reduced yields compared with Full and Moderate Return (3.13 Mg ha ?1). In NT1995 at 0–5 cm depth, particulate organic matter in Full Return and Moderate Return (14.3 g kg ?1) exceeded Low Return (11.3 g kg ?1). In NT2005, acid phosphatase activity was reduced about 20% in Low Return compared to Full Return. Also the Low Return had an increase in erodible-sized dry aggregates at the soil surface compared to Full Return. Three or fewer cycles of stover treatments revealed little evidence for short-term impacts on crop yield, but detected subtle soil changes that indicate repeated harvests may have negative consequences if stover removed.
Multi-Location Study of Soil Enzyme Activities as Affected by Types and Rates of Manure Application and Tillage Practices
Veronica Acosta-Martinez,Maysoon M. Mikha,Karamat R. Sistani,Phillip W. Stahlman,Joseph G. Benjamin,Merle F. Vigil,Richie Erickson
Agriculture , 2011, DOI: 10.3390/agriculture1010004
Abstract: Significant amounts of manure are produced in the USA; however, information on the changes in ecosystem services related to soil biogeochemical cycling for agroecosystems supported with organic amendments such as manure is limited. A multi-location field study was initiated in Colorado (CO), Kansas (KS) and Kentucky (KY), USA in loam soils to evaluate the effects of manure and tillage practices on enzyme activities that are key to biogeochemical cycling such as β-glucosidase (C cycling), α-galactosidase (C cycling), β-glucosaminidase (C and N cycling) and phosphomonoesterases (P cycling). The treatments were as follows: (i) two years of beef manure applications to a fine sandy loam at different rates (control: 0, low: 34 kg N ha ?1 and high: 96 kg N ha ?1) and tillage practices in CO; (ii) three years of beef manure applications to a silt loam at different rates (0, low: 67 kg N ha ?1 and high: 134 kg N ha ?1) and tillage practices in KS and; (iii) three years of poultry and dairy manure applications to a silt loam with different tillage practices at the same rate (403 kg N ha ?1) in KY. Tillage practices (none vs. conventional) had no effect on the enzyme activities. Principal Component Analyses (PCA) grouped all enzyme activities with the high beef manure application rate after the first year in CO at 0–5 cm. By the second year, the low and high beef manure rates differed in enzyme activities for the KS soil with no difference between the low rate and control in CO. Since the first year of the KY study, acid phosphatase activity was greater in the poultry treated soil compared to dairy or the control; whereas, C cycling enzyme activities were similar in soil treated with dairy or poultry manure. For all studies, PCAs for soil samples from 5–10 cm depth did not reveal treatment separation until the second year, i.e., only high application rate differed from the other treatments. Results of the study indicated significant responses in C and P cycling enzyme activities to manure applications within two years, suggesting potential benefits to soil biogeochemical cycling essential for the productivity of agroecosystems supported with organic fertilizers.
Understanding and Enhancing Soil Biological Health: The Solution for Reversing Soil Degradation
R. Michael Lehman,Cynthia A. Cambardella,Diane E. Stott,Veronica Acosta-Martinez,Daniel K. Manter,Jeffrey S. Buyer,Jude E. Maul,Jeffrey L. Smith,Harold P. Collins,Jonathan J. Halvorson,Robert J. Kremer,Jonathan G. Lundgren,Tom F. Ducey,Virginia L. Jin,Douglas L. Karlen
Sustainability , 2015, DOI: 10.3390/su7010988
Abstract: Our objective is to provide an optimistic strategy for reversing soil degradation by increasing public and private research efforts to understand the role of soil biology, particularly microbiology, on the health of our world’s soils. We begin by defining soil quality/soil health (which we consider to be interchangeable terms), characterizing healthy soil resources, and relating the significance of soil health to agroecosystems and their functions. We examine how soil biology influences soil health and how biological properties and processes contribute to sustainability of agriculture and ecosystem services. We continue by examining what can be done to manipulate soil biology to: (i) increase nutrient availability for production of high yielding, high quality crops; (ii) protect crops from pests, pathogens, weeds; and (iii) manage other factors limiting production, provision of ecosystem services, and resilience to stresses like droughts. Next we look to the future by asking what needs to be known about soil biology that is not currently recognized or fully understood and how these needs could be addressed using emerging research tools. We conclude, based on our perceptions of how new knowledge regarding soil biology will help make agriculture more sustainable and productive, by recommending research emphases that should receive first priority through enhanced public and private research in order to reverse the trajectory toward global soil degradation.
Soil Rhizosphere Microbial Communities and Enzyme Activities under Organic Farming in Alabama
Terrence Gardner,V. Acosta-Martinez,Zachary Senwo,Scot E. Dowd
Diversity , 2011, DOI: 10.3390/d3030308
Abstract: Evaluation of the soil rhizosphere has been limited by the lack of robust assessments that can explore the vast complex structure and diversity of soil microbial communities. Our objective was to combine fatty acid methyl ester (FAME) and pyrosequencing techniques to evaluate soil microbial community structure and diversity. In addition, we evaluated biogeochemical functionality of the microbial communities via enzymatic activities of nutrient cycling. Samples were taken from a silt loam at 0–10 and 10–20 cm in an organic farm under lettuce ( Lactuca sativa), potato ( Solanum tuberosum), onion ( Allium cepa L), broccoli ( Brassica oleracea var. botrytis) and Tall fescue pasture grass ( Festuca arundinacea). Several FAMEs ( a15:0, i15:0, i15:1, i16:0, a17:0, i17:0, 10Me17:0, cy17:0, 16:1ω5c and 18:1ω9c) varied among the crop rhizospheres. FAME profiles of the soil microbial community under pasture showed a higher fungal:bacterial ratio compared to the soil under lettuce, potato, onion, and broccoli. Soil under potato showed higher sum of fungal FAME indicators compared to broccoli, onion and lettuce. Microbial biomass C and enzyme activities associated with pasture and potato were higher than the other rhizospheres. The lowest soil microbial biomass C and enzyme activities were found under onion. Pyrosequencing revealed significant differences regarding the maximum operational taxonomic units (OTU) at 3% dissimilarity level (roughly corresponding to the bacterial species level) at 0–10 cm (581.7–770.0) compared to 10–20 cm (563.3–727.7) soil depths. The lowest OTUs detected at 0–10 cm were under broccoli (581.7); whereas the lowest OTUs found at 10–20 cm were under potato (563.3). The predominant phyla (85%) in this soil at both depths were Bacteroidetes (i.e., Flavobacteria, Sphingobacteria), and Proteobacteria. Flavobacteriaceae and Xanthomonadaceae were predominant under broccoli. Rhizobiaceae, Hyphomicrobiaceae, and Acidobacteriaceae were more abundant under pasture compared to the cultivated soils under broccoli, potato, onion and lettuce. This study found significant differences in microbial community structure and diversity, and enzyme activities of nutrient cycling in this organic farming system under different rhizospheres, which can have implications in soil health and metabolic functioning, and the yield and nutritional value of each crop.
New material as support for nickel boride catalyst
D. Acosta,J. Martinez,C. Carrera,E. Erdmann
Latin American applied research , 2006,
Abstract: The main objective of this work is to study the feasibility of new materials to be used as support for boron-nickel catalysts. Potential support materials such as: silica gel, alumina, hydrothermal modified Perlites and zeolite 4A, were characterized by BET, TPR and DRX. After the addition of Ni and B, their catalytic activity evaluated with the nitrobenzene hydrogenation model reaction. The influence of operational parameters during the impregnation process such as order of reactants, speed of agitation, time of aging and it influences from the previous thermal treatment were evaluated. The results show that the adequate materials to be used as catalysts supports are the commercial silica and Rehydroxilated Perlite. It is due to the existence of superficial OH groups, which allow the anchorage of the nickel boride catalyst.
Utilización de supbroductos de la industria tequilera. Parte 7. Compostaje de bagazo de agave y vinazas tequileras
Gilberto I?iguez,Nalleli Acosta,Liliana Martinez,Javier Parra
Revista internacional de contaminación ambiental , 2005,
Abstract: En el presente trabajo se realizó un estudio de compostaje de bagazo de agave para estudiar su proceso de degradación. Para esto se pusieron en compostaje 8 pilas de bagazo bajo un sistema experimental de cuatro tratamientos con dos repeticiones por tratamiento. El primero consistió de bagazo regado con agua de la llave, el segundo de bagazo regado con vinazas, el tercero de bagazo con urea regado con agua de la llave y el cuarto de bagazo con urea regado con vinazas. Al formarse las pilas se colocaron en cada una de ellas, a diferentes niveles, 5 sensores de temperatura. El promedio de los cambios de temperatura se graficó para cada día. Cada dos meses, al remover las pilas para facilitar la aireación y la adición de agua y/o vinazas se tomaron muestras para el análisis de pH, materia orgánica y celulosa. Al final del tiempo de compostaje el material de las pilas (composta) fue sujeto a un análisis de cenizas, carbono orgánico total, nitrógeno, P, K y conductividad. Además las compostas también fueron sujetas a estudios de madurez y fitotoxicidad mediante el análisis de brote de semillas, crecimiento relativo, germinación in vitro, elongación de la raíz yprueba de Solvita . La degradación de materia orgánica (MO) y de la celulosa para los tratamientos 1 y 2 siguió una ecuación cinética de primer orden mientras que para los tratamientos 3 y 4 la degradación siguió una ecuación cinética de orden mixto. El período de compostaje para los tratamientos 1 y 2 fue de 242 días, habiendo logrado pérdidas de materia seca de 52.8 y 59.1 % respectivamente. Para los tratamientos 3 y 4 el tiempo de compostaje fue de 208 y 228 días, respectivamente, con pérdidas de materia seca de 56.7 y 63.7 % respectivamente. En las pruebas de fitotoxicidad ninguna de las cuatro compostas provocó problemas de crecimiento ni de germinación de semillas.
Kaluza-Klein Consistency, Killing Vectors, and Kahler Spaces
P. Hoxha,R. R. Martinez-Acosta,C. N. Pope
Physics , 2000, DOI: 10.1088/0264-9381/17/20/305
Abstract: We make a detailed investigation of all spaces Q_{n_1... n_N}^{q_1... q_N} of the form of U(1) bundles over arbitrary products \prod_i CP^{n_i} of complex projective spaces, with arbitrary winding numbers q_i over each factor in the base. Special cases, including Q_{11}^{11} (sometimes known as T^{11}), Q_{111}^{111} and Q_{21}^{32}, are relevant for compactifications of type IIB and D=11 supergravity. Remarkable ``conspiracies'' allow consistent Kaluza-Klein S^5, S^4 and S^7 sphere reductions of these theories that retain all the Yang-Mills fields of the isometry group in a massless truncation. We prove that such conspiracies do not occur for the reductions on the Q_{n_1... n_N}^{q_1... q_N} spaces, and that it is inconsistent to make a massless truncation in which the non-abelian SU(n_i+1) factors in their isometry groups are retained. In the course of proving this we derive many properties of the spaces Q_{n_1... n_N}^{q_1... q_N} of more general utility. In particular, we show that they always admit Einstein metrics, and that the spaces where q_i=(n_i+1)/\ell all admit two Killing spinors. We also obtain an iterative construction for real metrics on CP^n, and construct the Killing vectors on Q_{n_1... n_N}^{q_1... q_N} in terms of scalar eigenfunctions on CP^{n_i}. We derive bounds that allow us to prove that certain Killing-vector identities on spheres, necessary for consistent Kaluza-Klein reductions, are never satisfied on Q_{n_1... n_N}^{q_1... q_N}.
Interactions of Soil Order and Land Use Management on Soil Properties in the Kukart Watershed, Kyrgyzstan
Zulfiia Sakbaeva,Veronica Acosta-Martínez,Jennifer Moore-Kucera,Wayne Hudnall,Karabaev Nuridin
Applied and Environmental Soil Science , 2012, DOI: 10.1155/2012/130941
Abstract: Surveys of soil properties related to soil functioning for many regions of Kyrgyzstan are limited. This study established ranges of chemical (soil organic matter (SOM), pH and total N (TN)), physical (soil texture), and biochemical (six enzyme activities of C, N, P, and S cycling) characteristics for nine profiles from the Kukart watershed of Jalal-Abad region in Kyrgyzstan. These profiles represent different soil orders (Inceptisols, Alfisols, and Mollisols) and land uses (cultivated, nut-fruit forests, and pasture). The Sierozem (Inceptisols) soils had the highest pH and contained the lowest SOM and TN contents compared to the Brown, Black-brown, and Meadow-steppe soils (Alfisols and Mollisols). Enzymatic activities within surface horizons (0–18?cm) typically decreased in the following order: forest > pasture > cultivated. Enzyme activity trends due to land use were present regardless of elevation, climate, and soil types although subtle differences among soil types within land use were observed. The significant reductions in measured soil enzyme activities involved in C, N, P, and S nutrient transformations under cultivation compared to pasture and forest ecosystems and lower values under Inceptisols can serve as soil quality indicators for land use decisions in the watershed. 1. Introduction Expected changes in global climate, land uses, population distribution, and water availability create challenges to meet societal needs for ecosystem services that agricultural, forestry, and pasture lands provide. In order to make sound decisions regarding land use, knowledge of specific properties related to soil functioning under different land use scenarios are necessary. Dynamic properties such as enzyme activities and soil organic matter (SOM) are sensitive to land management practices and can provide valuable information about important soil processes such as nutrient cycling, decomposition and formation of SOM, and overall productivity potential. Enzymatic potential in soils is influenced by inherent soil properties such as soil texture, type of clay, and drainage class that were established as soil formed as well as dynamic properties such as SOM, pH, and nutrient holding capacity. Among the various enzymes present in soil, assessment of the activities of hydrolases involved in C, N, P, and S cycling can provide information about soil fertility [1, 2] as well as the metabolic potential of soil [3, 4]. Previous studies with soils from various regions have shown that enzyme activities are sensitive to soil changes due to tillage [5, 6], cropping systems
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