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Search Results: 1 - 10 of 248784 matches for " Paulo Cezar R.;Dias "
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Acúmulo de nutrientes e método para estimar doses de nitrogênio e de potássio na fertirriga??o do piment?o
Fontes, Paulo Cezar R.;Dias, Emerson N.;Gra?a, Rodrigo N.;
Horticultura Brasileira , 2005, DOI: 10.1590/S0102-05362005000200022
Abstract: shoot nutrient uptake curves were characterized and a model was developed to estimate nitrogen and potassium rates to be applied in sweet pepper (capsicum annuum l.) fertigation in unheated greenhouse. the experiment was carried out from march to december using a randomized blocks design with 16 treatments and 6 replicates. each treatment corresponded to a sampling time accomplished every 14 days from transplanting (dat) up to 224 dat. at that time, fruit yield and shoot dry weight were 51960 and 6130 kg ha-1 respectively. total nutrient accumulation in the shoot, expressed in kg ha-1, was: 247 for k, 193 for n, 114 for ca, 42 for mg, 23 for p, 23 for s, 1.2 for fe, 0,31 for b, 0.29 for cu, 0.27 for zn and 0,26 for mn. uptake curves and uptake rates (ta) are presented for each nutrient. based upon ta, a model is proposed to estimate n and k rates to apply in pepper plant fertigation in unheated greenhouse.
Dinamica do crescimento, distribui??o de matéria seca e produ??o de piment?o em ambiente protegido
Fontes, Paulo Cezar R.;Dias, Emerson N.;Silva, Derly José Henriques da;
Horticultura Brasileira , 2005, DOI: 10.1590/S0102-05362005000100020
Abstract: the nutrient uptake, the partitioning of dry matter and sweet pepper fruit yield were characterized under unheated greenhouse conditions. the experiment was carried out from march to december, and the randomized block design was used with 6 replicates and 16 treatments. seedlings of elisa cv. were transplanted to the field in 1 x 0.6 m spacing on april, 27th. each treatment corresponded to a sampling time accomplished every 14 days from transplanting. at 224 days after transplanting (dat) to the plastic house, the pepper plants presented 91 cm of height with a leaf area of 9056 cm2 plant-1 and 189, 79 and 109 g plant-1 of fruit dry matter, stem and leaves, respectively, also presenting an absolute growth rate with maximum value of 4.11 g m-2 day-1. plant growth was continuous along the plant cycle and fruits accumulated the highest amount of dry matter. total ripened fruit yield was 51,960 kg ha-1 or 232 kg ha-1 day-1 of crop permanence in the greenhouse. marketable fruits were represented by 92.8% of the total yield.
Estimativa da área da folha da batateira utilizando medidas lineares
Silva, Marcelo CC;Fontes, Paulo Cezar R;Viana, Rafael G;
Horticultura Brasileira , 2008, DOI: 10.1590/S0102-05362008000100016
Abstract: the objective of this experiment was to determine the most appropriate model to estimate potato leaf area through the leaf length and width. 300 leaves of 300 potato plants, cv. monalisa were collected in an aleatory way, 21 and 56 days after the plant emergence (dae). in laboratory, the length (c), width (l) and area of each leaf (af) were measured. the data were submitted to the regression analysis with the af value as a dependent variable and the leaf length and width values as the independent variables. three statistical models were tested (linear, exponential and logarithmic). potato plant af was more precisely estimated (r2 = 0,88), using the two measures, l and c (af = 0,2798**lc + 71,267); however, for better speed and workability, potato plant af, was adequately estimated by measuring leaf l or c and using equations af = 0,0479**l + 10,777 (r2 = 0,83) or af = 0,0659**c + 12,979 (r2 = 0,82). the evaluated foliar area, 21 dae, using linear model was of 234,41 cm2, and the measured real value, was of 185,52 cm2. at 56 dae, the evaluated foliar area using the linear model was of 175,60 cm2, and the measured real value, was of 176,01 cm2. with one of the proposed models, the potato leaf area can be estimated in real time, quickly and without collecting the leaf.
Produtividade e qualidade de frutos de meloeiro variando número de frutos e de folhas por planta
Queiroga, Roberto Cleiton F de;Puiatti, Mário;Fontes, Paulo Cezar R;Cecon, Paulo Roberto;
Horticultura Brasileira , 2008, DOI: 10.1590/S0102-05362008000200016
Abstract: the muskmelon cultivation in southeast of brazil is possible in greenhouse but plants should be pruned. however, in this species plant growth and fruit yield are limited by both source and sink size activity. the muskmelon fruit productivity and quality in greenhouse were evaluated as affected by fruit and leaf numbers left in the plant. split plot scheme, in a randomized blocks design, with four replications were used. the plot consisted of the fruit number per plant (1 or 2). the fruits were fixed at betweenthe 6 and 80 nodes. the split-plot consisted of the leaf number left in each plant (16; 19; 22 and 25). when the plant was pruned from the 22th leaf and one fruit/plant was left, the leaf area increased as compared with plants with two fruits. independently of the number of leaves, plants with only one fruit presented larger mean fruit weight and smaller commercial yield. sink reduction (fruit number/plant) provided fruits with larger net rind, pulp thickness, length, diameter, total soluble solids, total soluble sugars and no reduced sugars. on the other hand, the number of fruits/plant did not affect the titratable acidity and the reduced sugars. except for the titratable acidity that declined and the cavity diameter of the fruit that presented quadratic answer, all the characteristics evaluated presented linear increment with the increase in the number of leaves for plant.
Características de frutos do meloeiro variando número e posi??o de frutos na planta
Queiroga, Roberto Cleiton F de;Puiatti, Mário;Fontes, Paulo Cezar R;Cecon, Paulo Roberto;
Horticultura Brasileira , 2009, DOI: 10.1590/S0102-05362009000100005
Abstract: the study was carried out in a greenhouse of the universidade federal de vi?osa, minas gerais state, brazil, from 26/09/05 to 24/01/06, to evaluate the yield and quality of the melon fruit, varying the number and position of fruits on the plant. the treatments consisted of fruit number per plant (1 and 2) and fruit position in the plant (5th - 8th node and 15th - 18th node). a randomized block design was used, in a 2 x 2 factorial scheme, with 5 replications. the 'coronado f1', variety reticulatus of the cantaloupe group was cultivated in 11.5 dm3 plastic pots with commercial coconut fiber. plants with one fruit provided higher harvest period, leaf area (la) (5th - 8th node), fruit mean mass (mmf), net rind (nr), pulp thickness (pt), fruit length (lf), diameter (df), total soluble solids, total soluble sugars (tss), no reduced sugars (snr) and smaller commercial fruit yield (pcf). fruit fixation among the 15th - 18th node led to more days to begin and to finish the harvest, la, mmf, pcf, pt, lf and df of fruits (in plants with 1 fruit), maturation index, tss, and snr and led to smaller nr and total titratable acidity and reduced sugar concentrations.
Capacidade de suporte de carga e umidade crítica de um Latossolo induzida por diferentes manejos
Araujo-Junior, Cezar Francisco;Dias Junior, Moacir de Souza;Guimar?es, Paulo Tácito Gontijo;Alcantara, Elifas Nunes;
Revista Brasileira de Ciência do Solo , 2011, DOI: 10.1590/S0100-06832011000100011
Abstract: different weed managements in coffee have led to structural changes, affecting the soil physical quality. therefore, information on the load bearing capacity of the soil under different weed managements is essential to establish a sustainable soil management under coffee. the objectives of this study were to: (a) assess the influence of different weed managements over three decades on the load bearing capacity of a dystroferric red latosol (lvdf) cultivated with coffee on the epamig farm in s?o sebasti?o do paraíso, minas gerais state (latitude de 20 o 55 ' 00 " s and longitude 47 o 07 ' 10 " w); (b) determine the maximum stress (σmax) exerted by a tractor; (c) establish the critical water content (θcrítica) for tractor traffic. the following weed managements were assessed: no weeding (scap); hand weeding (capm); post-emergence herbicide (hpos); mowing (ro?a); rotary tiller (enrt); tandem disk harrow (grad) and pre-emergence herbicide (hpre). in each management system 15 undisturbed soil samples were collected randomly in the coffee inter-rows in the layers 0-3, 10-13 and 25-28 cm, totaling 315 soil samples. additionally, 15 samples per layer were collected in a native forest (mata). the equipment used in coffee management was coupled to a valmet? model 68 tractor for coffee. to determine θcrítica for tractor traffic, only the stress was considered that did not exceed the internal strength of the soil expressed as precompression stress. the undisturbed soil samples were used to determine precompression stress (σp) at different volumetric water contents (θ) and then bulk density (bd). disturbed samples were used to analyze particle size distribution, organic carbon (oc) and total oxides. load bearing capacity (lbc) between precompression stress and volumetric water content was calculated (σp = 10(a+bq)) to assess the possible effects of weed management systems on soil structure. the maximum stress caused by the valmet? tractor (inflation pressure of the front tires 6
Resistência à compacta??o de um Latossolo cultivado com cafeeiro, sob diferentes sistemas de manejo de plantas invasoras
Araujo-Junior, Cezar Francisco;Dias Junior, Moacir de Souza;Guimar?es, Paulo Tácito Gontijo;Pires, Bruno Silva;
Revista Brasileira de Ciência do Solo , 2008, DOI: 10.1590/S0100-06832008000100003
Abstract: the knowledge of the pressure levels that can be applied to the soil under different weed management system (wms) is importante for coffee plantations management. the objective of this study was to evaluate the influence of different weed management systems on the susceptibility to compaction of a red-yellow latossol (oxisol) (lva) using soil support capacity (csc) models. this study was carried out at the epamig research farm in patrocínio, state of minas gerais, brazil, in a coffee plantation using ruby 1192 coffee variety in a 3.8 x 0.7 m spacing, planted in february 1999. four wms were used and the soil samples were collected in-between the rows under the following management systems: (1) no weed control (sc); (2) hoe-weeded (cm); (3) weed control with post-emergence herbicide glyphosate (hpós); (4) weed control with pre-emergence oxyfluorfen (hpré). fifteen undisturbed soil samples from each system were collected (in the layers 0-3, 10-13 and 25-28 cm) in july 2004, totaling 180 samples. the undisturbed soil samples were equilibrated at different moisture contents and subjected to the uniaxial compression test to obtain the soil csc models. results suggested that the support capacity of the lva decreases in the center of the inter rows in the following order: hpré in the 0-3 cm layer > cm in the 10-13 cm layer > sc in the 0-3, 10-13, 25-28 cm layers = hpós in the 0-3, 10-13, 25-28 cm layers = cm at 0-3 and 25-28 cm layers = hpré in the 10-13 cm layer > hpré in the 25-28 cm layer. weed control with hpré in the 25-28 cm layer was most susceptible, while hpré in the 0-3 cm layer was most resistant to soil compaction. the management systems sc and hpós in the 0-3, 10-13, 25-28 cm layers and the managements cm in the 0-3 and 25-28 cm layers and hpré in the 10-13 cm layer were equally susceptible to soil compaction.
Modelagem da capacidade de suporte de carga e quantifica??o dos efeitos das opera??es mecanizadas em um Latossolo Amarelo cultivado com cafeeiros
Silva, Arystides Resende;Dias Junior, Moacir de Souza;Guimar?es, Paulo Tácito Gontijo;Araújo Júnior, Cezar Franciso;
Revista Brasileira de Ciência do Solo , 2006, DOI: 10.1590/S0100-06832006000200002
Abstract: minas gerais state is the largest coffee producer in brazil. the state contributes with over 50 % of the total production, which is for the most part cultivated in the cerrado region. this region is outstanding in coffee production due to the advanced technology in mechanization. consequently, the machine traffic that the soils are subjected to causes concern because of the possibility of widespread soil compaction. our objectives were (a) to propose load support capacity models to a typical dystrophic yellow latosol (lad) cultivated with coffee as a function of preconsolidation pressure and moisture content; (b) to determine, through the use of this model, the influence of soil management operations on the soil structure at three depths, in the dry and rainy seasons. soil samples were taken from three depths (0 to 3, 10 to 13 and 25 to 28 cm); thirty samples were collected where there was no traffic and ten samples collected in the traffic line of each equipment, in august 2002 and march 2003, respectively, to quantify its effects on the soil structure in the rainy and in the dry seasons. the undisturbed soil samples were used in the uniaxial compression test. texture, organic matter, particle density, shrinkage limit, and plasticity limit were also determined. the load support capacity model of the lad is a function of the preconsolidation pressure and moisture content and is expressed by the equation sp = 10(2.72-1.17u) where sp means preconsolidation pressure and u means humidity. the effects of the mechanized operations in the coffee plantation were quantified by the load support capacity model and through its use it was possible to quantify the influence of the management operations in the yellow latosol structure.
Atributos físico-hídricos de um latossolo de cerrado em diferentes posi??es de amostragem na lavoura cafeeira
Gontijo, Ivoney;Dias Junior, Moacir de Souza;Guimar?es, Paulo Tácito Gontijo;Araujo-Junior, Cezar Francisco;
Revista Brasileira de Ciência do Solo , 2008, DOI: 10.1590/S0100-06832008000600002
Abstract: the soil compaction, induced by different traffic intensities, can cause damage in the soil structure, reducing the coffee plantation production. the objectives of this study was to develop a model of load support capacity for a red latosol (oxisol) under cerrado and under coffee and to investigate the effect of coffee plantation management on soil pore distribution and soil water retention, in different sampling positions in the coffee plantation. the stud site is located at 18 o 59 ' 15 '' s and to 46 o 56 ' 47 '' w patrocínio county, minas gerais state, and has been cultivated with coffee (coffea arabica l.), at a 4 x 1 m spacing, since 1995. the different sampling positions in the coffee plantation were: under canopy (ps), cart track (lt) and in the middle of the interrows (el). besides, samples were also collected in a native cerrado vegetation (mn) to obtain the soil load capacity models. disturbed and undisturbed soil samples were collected at each sampling point at a depth of 10-13 cm to assess the following physical-hydric attributes: preconsolidation pressure (σp), gravimetric moisture content (u), bulk density (ds), total porosity (pt), macropores (ma), micropores (mi), soil water retention curve, organic matter (mo), texture, particle density and liquid, plastic, and contraction limits. the results obtained suggest that the load support capacity of the soil decreases in the following order: lt > mn = ps > el. the el position was most susceptible to soil compaction due to lower load support capacity associated with subsoiling just before sampling, decreasing the soil mechanical resistance. the soil load support capacity under mn and ps was homogeneous, indicating a soil structure favorable to the development of the coffee root system. the available water in the soil was higher in el and ps and lower in lt and mn positions. the micropores of soil under lt were larger than in the el, which was disturbed by the subsoiling.
Rea??o entre fenilnitrometanos e enoato derivado do D-manitol na presen?a de TBAF ou DBU: adi??o conjugada sin-seletiva e rea??o de NEF consecutiva
Dias, Ayres G.;Pinho, Vagner D.;Costa, Paulo R. R.;
Química Nova , 2008, DOI: 10.1590/S0100-40422008000400024
Abstract: a tandem syn-selective conjugate addition - nef reaction was observed when phenylnitromethane and oxygenated derivatives were allowed to react with an enoate derived from d-mannitol at rt in the presence of tbaf or dbu. while nitro-adducts predominate after 4h of reaction, the corresponding ketones were the main products after 12-24h of reaction. the nef reaction occurred without racemization of the stereogenic center generated in the conjugate addition step.
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