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Search Results: 1 - 10 of 14375 matches for " Amanda Posselt;Cao "
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Soil aggregation in a crop-livestock integration system under no-tillage
Souza, Edicarlos Damacena de;Costa, Sérgio Ely Valad？o Gigante de Andrade;Anghinoni, Ibanor;Carvalho, Paulo César de Faccio;Oliveira, Eric Victor Ferreira de;Martins, Amanda Posselt;Cao, Eduardo;Andrighetti, Marcelo;
Revista Brasileira de Ciência do Solo , 2010, DOI: 10.1590/S0100-06832010000400033
Abstract: grazing intensities can influence soil aggregation, which can be temporarily and permanently affected. the objective of this study was to evaluate the aggregate stability in water at the end of a soybean cycle and during pasture development in a crop-livestock integration system under no-tillage and grazing intensities. the experiment was initiated in 2001, in a dystrophic red latosol, after soybean harvest. treatments consisted of pasture (black oat + italian ryegrass) at heights of 10, 20 and 40 cm, grazed by young cattle, and a control (no grazing), followed by soybean cultivation, in a randomized block design. soil samples were collected at the end of the soybean cycle (may/2007), during animal grazing (september/2007) and at the end of the grazing cycle (november/2007). the grazing period influences aggregate distribution, since in the september sampling (0-5 cm layer), there was a higher proportion of aggregates > 4.76 mm at all grazing intensities. soil aggregation is higher in no-tillage crop-livestock integration systems in grazed than in ungrazed areas.
Attributes of irrigated rice as affected by soil sodicity and potassic fertilizer application
Carmona, Felipe de Campos;Anghinoni, Ibanor;Holzschuh, Marquel Jonas;Martins, Amanda Posselt;
Revista Brasileira de Ciência do Solo , 2011, DOI: 10.1590/S0100-06832011000300023
Abstract: soils of the coastal plains of rio grande do sul, brazil, are affected by salinization, which can hamper the establishment and development of crops in general, including rice. the application of high doses of kcl may aggravate the crop damage, due to the high saline content of this fertilizer. this study aimed to evaluate the effect of k fertilizer management on some properties of rice plant, grown in soils with different sodicity levels, and determine which attribute is best related to yield. the field study was conducted in four albaqualfs with exchangeable na percentages of 5.6, 9.0, 21 and 32 %. the management of kcl fertilizer consisted of the application of 90 kg ha-1 k2o broadcast, 90 kg ha-1 k2o in the row and 45 kg ha-1 k2o in the row + 45 kg ha-1 k2o at panicle initiation (pi). plant density, dry matter evolution, height, spad (soil plant analysis development value indicating relative chlorophyll contents) index, tiller mass, 1,000-grain weight, panicle length and grain yield were evaluated. the plant density was damaged by application of k fertilizer in the row, especially at full dose (90 kg ha-1), at three sodicity levels, resulting in loss in biomass accumulation in later stages, affecting the crop yield, even at the lowest level of soil sodicity (5.6 %). all properties were correlated with yield; the highest positive correlation was found with plant density and shoot dry matter at full flowering, and a negative correlation with panicle length.
Ciclagem e balan？o de potássio e produtividade de soja na integra？？o lavoura-pecuária sob semeadura direta
Ferreira, Eric Victor de Oliveira;Anghinoni, Ibanor;Andrighetti, Marcelo Hoerbe;Martins, Amanda Posselt;Carvalho, Paulo César de Faccio;
Revista Brasileira de Ciência do Solo , 2011, DOI: 10.1590/S0100-06832011000100015
Abstract: nutrient cycling and balance in integrated crop-livestock systems (icl) are processes that involves soil, plant and animal components, beyond fertilization. animal management, by modifying soil biotic and abiotic conditions, also influences this process as it affects the residue decomposition rate. the objective was to evaluate potassium (k) cycling and balance in an icl system with grazing (black oat and ryegrass) intensities in the winter, followed by soybean cultivated in the summer. the experiment was conducted as of may of 2001 in an area in the state of rio grande do sul - brazil, on a rhodic hapludox (oxisol), under no tillage since 1991. the treatments consisted of continuous bovine grazing intensities at a pasture height of 10, 20, 30 and 40 cm, and a control (no-grazing), in a randomized block design, with three replicates. the forage/soybean cycle of 2007/08 was evaluated in this paper. to calculate k cycling, the contents accumulated in pasture, soybean and animals in one pasture-soybean cycle were considered, and the balance, "in the field" and "in the soil", of k inputs (fertilizer) and outputs (soybean grains and animal tissue) and the k remaining in plant and soil, respectively, were calculated. potassium cycling increased with increasing grazing intensity and the balance, despite negative, with a higher deficit in areas with higher grazing intensity, did not influence soybean yield.
Introduction of prognostic rain in ECHAM5: design and single column model simulations
R. Posselt ,U. Lohmann
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2008,
Abstract: Prognostic equations for the rain mass mixing ratio and the rain drop number concentration are introduced into the large-scale cloud microphysics parameterization of the ECHAM5 general circulation model (ECHAM5-PROG). To this end, a rain flux from one level to the next with the appropriate fall speed is introduced. This maintains rain water in the atmosphere to be available for the next time step. Rain formation in ECHAM5-PROG is, therefore, less dependent on the autoconversion rate than the standard ECHAM5 but shifts the emphasis towards the accretion rates in accordance with observations. ECHAM5-PROG is tested and evaluated with Single Column Model (SCM) simulations for two cases: the marine stratocumulus study EPIC (October 2001) and the continental mid-latitude ARM Cloud IOP (shallow frontal cloud case – March 2000). In case of heavy precipitation events, the prognostic equations for rain hardly affect the amount and timing of precipitation at the surface in different SCM simulations because heavy rain depends mainly on the large-scale forcing. In case of thin, drizzling clouds (i.e., stratocumulus), surface precipitation is sensitive to the number of sub-time steps used in the prognostic rain scheme. Cloud microphysical quantities, such as cloud liquid and rain water within the atmosphere, are sensitive to the number of sub-time steps in both considered cases. This results from the decreasing autoconversion rate and increasing accretion rate.
Influence of Giant CCN on warm rain processes in the ECHAM5 GCM
R. Posselt ,U. Lohmann
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2008,
Abstract: Increased Cloud Condensation Nuclei (CCN) load due to anthropogenic activity might lead to non-precipitating clouds because the cloud drops become smaller (for a constant liquid water content) and, therefore, less efficient in rain formation (aerosol indirect effect). Adding giant CCN (GCCN) into such a cloud can initiate precipitation (namely, drizzle) and, therefore, might counteract the aerosol indirect effect. The effect of GCCN on global climate on warm clouds and precipitation within the ECHAM5 General Circulation Model (GCM) is investigated. Therefore, the newly introduced prognostic rain scheme (Posselt and Lohmann, 2007) is applied so that GCCN are directly activated into rain drops. The ECHAM5 simulations with incorporated GCCN show that precipitation is affected only locally. On the global scale, the precipitation amount does not change. Cloud properties like total water (liquid + rain water) and cloud drop number show a larger sensitivity to GCCN. Depending on the amount of added GCCN, the reduction of total water and cloud drops account for up to 20% compared to the control run without GCCN. Thus, the incorporation of the GCCN accelerate the hydrological cycle so that clouds precipitate faster (but not more) and less condensed water is accumulated in the atmosphere. An estimate of the anthropogenic aerosol indirect effect on the climate is obtained by comparing simulations for present-day and pre-industrial climate. The introduction of the prognostic rain scheme lowered the anthropogenic aerosol indirect effect significantly compared to the standard ECHAM5 with the diagnostic rain scheme. The incorporation of the GCCN changes the model state, especially the cloud properties like TWP and Nl. The precipitation changes only locally but globally the precipitation is unaffected because it has to equal the global mean evaporation rate. Changing the cloud properties leads to a local reduction of the aerosol indirect effect and, hence, partly compensating for the increased anthropogenic CCN concentrations in that regions. Globally, the aerosol indirect effect is nearly the same for all simulations.
Influence of Giant CCN on warm rain processes in the ECHAM5 GCM
R. Posselt,U. Lohmann
Atmospheric Chemistry and Physics Discussions , 2007,
Abstract: Increased Cloud Condensation Nuclei (CCN) load due to anthropogenic activity might lead to non-precipitating clouds because the cloud drops become smaller (for a constant liquid water content) and, therefore, less efficient in rain formation (aerosol indirect effect). Adding giant CCN (GCCN) into such a cloud can initiate precipitation (namely, drizzle) and, therefore, might counteract the aerosol indirect effect. The effect of GCCN on global climate, especially on clouds and precipitation, within a General Circulation Model (GCM) is investigated. GCCN are aerosol particles larger than 5–10 μm in radius that can act as cloud condensation nuclei. One prominent GCCN species is sea salt. Sea salt concentrations depend mainly on wind speed but also on relative humidity, stability and precipitation history. Natural variability is much larger than the simulated one because sea salt emissions within ECHAM5 are a function of wind speed only. Giant sea salt concentrations in ECHAM5 are determined by using the tail of the coarse mode aerosol distribution with cutoff radii of 5 μm or 10 μm. It is assumed that activated GCCN particles directly form rain drops (of 25 μm size). Thereby, the added rain water mass and number stems from the redistribution of the condensed water into cloud and rain water according to the number of activated GCCN. As the formed precipitation is most likely drizzle with rather small drops a prognostic rain scheme is applied to account for the lower fall speeds and, therefore, slower sedimentation of the drizzle drops. The ECHAM5 simulations with incorporated GCCN show that precipitation is affected only locally. Cloud properties like liquid water and cloud drop number show a larger sensitivity to GCCN. On the one hand, the increased rain water mass causes an increase in the accretion rate and, therefore, in the rain production. On the other hand, very high GCCN concentrations can lead to an artificially exaggerated transfer of cloud water to the rain class which then results in a strong decrease of the conversion rate and the rain production. The introduction of the GCCN reduces the anthropogenic increase of liquid water in the atmosphere from pre-industrial to present day because clouds are precipitating faster in the presence of the GCCN. Hence, the accumulation of liquid water in the atmosphere is reduced. According to those changes in the cloud properties, the radiative budget is also changing. The GCCN cause a reduction of the anthropogenic aerosol indirect effect of about 0.1–0.25 W m 2 which corresponds to 5–10% of the total effect.
Introduction of prognostic rain in ECHAM5: design and Single Column Model simulations
R. Posselt,U. Lohmann
Atmospheric Chemistry and Physics Discussions , 2007,
Abstract: Prognostic equations for the rain mass mixing ratio and the rain drop number concentration are introduced into the large-scale cloud microphysics parameterization of the ECHAM5 general circulation model (ECHAM5-RAIN). For this a rain flux from one level to the next with the appropriate fall speed is introduced. This maintains rain water in the atmosphere to be available for the next time step. Rain formation in ECHAM5-RAIN is, therefore, less dependent on the autoconversion rate than the standard ECHAM5 but shifts the emphasis towards the accretion rates in accordance with observations. ECHAM5-RAIN is tested and evaluated with two cases: the continental mid-latitude ARM Cloud IOP (shallow frontal cloud case – March 2000) and EPIC (a marine stratocumulus study – October 2001). The prognostic equations for rain hardly affect the amount and timing of precipitation at the surface in different Single Column Model (SCM) simulations for heavy precipitating clouds because heavy rain depends mainly on the large-scale forcing. In case of thin, drizzling clouds (i.e., stratocumulus), an increase in surface precipitation is caused by more sub-time steps used in the prognostic rain scheme until convergence is reached. Cloud microphysical quantities, such as liquid and rain water, are more sensitive to the number of sub-time steps for light precipitation. This results from the decreasing autoconversion rate and increasing accretion rate.
Corrigendum to "Influence of Giant CCN on warm rain processes in the ECHAM5 GCM" published in Atmos. Chem. Phys., 8, 2949─2963, 2008
R. Posselt,U. Lohmann
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2008,
Abstract: No abstract available.
Biomassa microbiana do solo em sistema de integra？？o lavoura-pecuária em plantio direto, submetido a intensidades de pastejo
Souza, Edicarlos Damacena de;Costa, Sérgio Ely Valad？o Gigante de Andrade;Anghinoni, Ibanor;Lima, Christina Venzke Sim？es de;Carvalho, Paulo César de Faccio;Martins, Amanda Posselt;
Revista Brasileira de Ciência do Solo , 2010, DOI: 10.1590/S0100-06832010000100008
Abstract: in integrated crop-livestock systems most of the nutrient supply for a pasture is provided by animal excretions, in the form of manure or urine, stimulating the activity and accumulation of nutrients in the cells. this study was carried out in an integrated crop-livestock system under no-tillage, initiated in 2001, with the objective of evaluating the impact of different winter grazing intensities (black oat + italian ryegrass; 10, 20, and 40 cm, and a no-grazing control treatment) on microbial activity and on carbon, nitrogen and phosphorus concentration and stocks in microbial biomass in the 0-10 cm layer of an oxisol (latosol), in southern brazil, during a grazing cycle. biomass nutrient contents and stocks and microbial activity were affected by grazing intensities and by the season of the grazing cycle. microbial carbon and phosphorus contents increased in the beginning of the grazing cycle in may until the period of high phytomass production in september, after which these contents decreased, following the pasture senescence. on the other hand, microbial nitrogen decreased from may to november, possibly as a result of plant uptake of soil n. integrated crop-livestock systems under no-tillage maintain soil biological quality, and are, under adequate grazing intensity, similar to no-tillage systems without grazing influence. however, at high grazing intensities (10 cm) under water stress, this soil quality is negatively affected.
The Role of Maternalism in Contemporary Paid Domestic Work  [PDF]
Amanda Moras
Sociology Mind (SM) , 2013, DOI: 10.4236/sm.2013.33033
Abstract:

Various studies of domestic work have identified close personal relationships between domestic workers and employers as a key instrument in the exploitation of domestic workers, allowing employers to solicit unpaid services as well as a sense of superiority (Rollins, 1985; Romero, 2002; Glenn, 1992; Hondagneu-Sotelo, 2001). Likewise, other scholars have pointed out that close employee-employer relationships may actually empower domestic workers, increasing job leverage (Thorton-Dill, 1994). Ultimately, these lines are blurry and ever changing as employers continuously redefine employee expectations. Drawing from a larger study involving thirty interviews with white upper middle class women who currently employ domestic workers (mostly housecleaners) this paper explores employers’ interactions with domestic workers. Through these interviews this research elaborates on how employers and employees interact, how employers feel about these interactions, and explores to what extent these interactions are informed by the widely reported maternalistic tendencies of the past, while also considering the consequences of this.

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