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Search Results: 1 - 10 of 9678 matches for " Dourado-Neto "
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Estimativa do coeficiente de cultura do cafeeiro em fun??o de variáveis climatológicas e fitotécnicas
Villa Nova, Nilson Augusto;Favarin, José Laércio;Angelocci, Luiz Roberto;Dourado-Neto, Durval;
Bragantia , 2002, DOI: 10.1590/S0006-87052002000100013
Abstract: with the objective of proposing a new approach to estimate the crop coefficient (kc) for coffee, a field experiment was carried out at the crop production department of esalq, university of s?o paulo, piracicaba, brazil (latitude: 22o43'30"s, longitude: 47o38'00"w and altitude 580 m). the method was based on the estimates of crop transpiration as function of weather and crop variables (plant density, leaf area and weeds management). the cultivar mundo novo iac 388-17 grafted on the cultivar apoat? iac 2258 was planted on the spacing of 2.5 m x 1.0 m (4,000 plants.ha-1). from 15 to 40 months of age, at intervals of 60 to 150 days, crop water consumption was estimated through a water balance procedure, assuming a uniform water status of the crop. leaf area of two plants was assessed in 18 occasions during the experimental period, using the equipment li-cor 3100 (lambda corporation, ne, usa). the values of kc had a dynamic behavior with the increase of the transpiring surface as a function of leaf area and planting density. the presence of weed caused increases on kc up to 30 months after planting. comparing the values of kc available in the literature to the ones obtained in this work, the present approach provided consistent results, with the advantage of allowing the simulation of other planting density conditions within the limit of 4,000 plants.ha-1 evaluated.
Modelo matemático para estimar o acúmulo de matéria seca e prever as épocas do florescimento e do ponto de maturidade fisiológica da cultura de feij?o
Pimenta, Hudson Santos;Fancelli, Ant?nio Luiz;Dourado-Neto, Durval;
Scientia Agricola , 1999, DOI: 10.1590/S0103-90161999000400019
Abstract: with the objective of developing a mathematical model to estimate the effect of daily air temperature on the growth (dry matter accumulation), and forecast the flowering and physiological maturity dates of the common bean, an experiment was carried out at piracicaba, sp, brazil (22o42?30'?, 47o38?00'? w and altitude: 546 m) using the cultivar iac-carioca, in ten treatments (different levels of nitrogen and water). the results showed that the proposed model can be used for its purpose.
Estimativa do volume máximo de calda para aplica??o foliar de produtos químicos na cultura de milho
Basanta, Maria del Valle;Dourado-Neto, Durval;García y García, Axel;
Scientia Agricola , 2000, DOI: 10.1590/S0103-90162000000200014
Abstract: with the objective of estimating the volume of water retained by corn leaves per unit area (ha) for chemigation purposes, a simple model is proposed. a field experiment was carried out to obtain the water interception on the aerial corn plant parts under a center pivot irrigation system. three plant populations were used to obtain different designs, the measurements having been performed at three phenological stages: i) 4-5 leaves; ii) 8 leaves and iii) 14 leaves. the water mass retained by the corn leaves was obtained considering the total plant mass (measured after irrigation), the plant dry weight and the plant constitution water mass. treatments were arranged in a split-plot design, with four replications. main plot treatment was plant population and subplot treatment was sampling date. total plant leaf area was evaluated for each sampling period. phenology and the relative crop development were evaluated periodically. results indicate that the proposed model can be used for this estimate.
Qualidade de cultivares de alface produzidos em hidroponia
Ohse, Silvana;Dourado-Neto, Durval;Manfron, Paulo Augusto;Santos, Osmar Souza dos;
Scientia Agricola , 2001, DOI: 10.1590/S0103-90162001000100027
Abstract: the purpose of this research was to define the centesimal composition of six lettuce cultivars (aurora, brisa, lívia, mimosa, regina and ver?nica) using four nutrient solutions. the experimental design was carried out in santa maria, rs, brazil, consisting of entirely randomized subdivided parcels. the used spacing was 0.18 m between array and 0.25 m among plants. it was observed that the ueda solution should not be used for the lettuce production in nft system, due to the high dry mass production and, consequently, high caloric value, content of lipids and fibers, depreciating the quality of the final product, in spite of its low nitrate content. the lettuce production in the nft system using the castellane-araújo, furlani and bernardes solutions maintained the nutricional quality (protein, ethereal extract and fiber, mineral residue contents) equivalent to the lettuce produced in soil, but presenting smaller caloric value. therefore, the hydroponic lettuce is a healthy food for maintaining and improving its centesimal composition for being a product of low caloric value, easy cleaning and high durability.
Deficit irrigation at different growth stages of the common bean (Phaseolus vulgaris L., cv. Imbabello)
Calvache, M.;Reichardt, K;Bacchi, O.O.S.;Dourado-Neto, D.;
Scientia Agricola , 1997, DOI: 10.1590/S0103-90161997000300002
Abstract: to identify specific growth stages of the common bean crop at which the plant is less sensitive to water stress, in which irrigation could be omitted without significant decrease hi final yield, two field experiments were conducted at "la tola" university experimental station, tumbaco, pichincha, ecuador, on a sandy loam soil (typic haplustoll). the climate is tempered and dry (mean air temperature 16°c and mean relative humidity 74%, during the cropping season) 123 and 109 mm of rainfall were recorded during the experimental cropping periods (july to october), of 1992 and 1994, respectively. the treatments consisted of combinations of 7 irrigation regimes including normal watering; full stress; (traditional management practice); single stress at vegetative stage; flowering; seed formation and ripening, and of 2 levels of applied n (20 and 80 kg/ha). these 14 treatment combinations were arranged and analysed in a split-plot design with 4 replications. the plot size was 33.6 m2 (8 rows, 7 m long) with a plant population of 120,000 pl/ha. irrigation treatments were started after uniform germination and crop establishment soil water content was monitored with a neutron probe down to 0.50 m depth, before and 24 h after each irrigation. the actual evapotranspiration of the crop was estimated by the water-balance technique. field water efficiency and crop water use efficiency were calculated. yield data showed that the treatments which had irrigation deficit had lower yield than those that had supplementary irrigation. the flowering stage was the most sensitive to water stress. nitrogen fertilization significantly increased the number of pods and gram yield. crop water use efficiency (kg/m3) was the lowest with stress at the flowering period, and the yield response factor (ky) was higher hi treatments of full stress and stress at flowering. in relation to the traditional management practice adopted by farmers, only treatments of normal watering and stress at maturation ha
Influence of photoperiod and air temperature on the growth, flowering and maturation of soybean (Glycine max (L.) Merrill)
Camara, G.M.S.;Sediyama, T.;Dourado-Neto, D.;Bernardes, M.S.;
Scientia Agricola , 1997, DOI: 10.1590/S0103-90161997000300017
Abstract: with the purpose to evaluate the effect of short (12 hours) and long (13 and 14 hours) photoperiods and air temperature regimes (winter and summer growing seasons) on soybean behaviour, greenhouse experiments were installed at the federal university of vi?osa, brasil, from june 1984 to december 1985. in each experiment, under a completely randomized design with 12 treatments (soybean cultivars) and eight replicates: duration of vegetative period from emergency to stage r1 or flowering (dvp, in days); plant height (ph, m); number of nodes per plant at stage r1 (nnp); and duration of soybean cycle from emergency to stage r7 or physiological maturity point (dc, days), were evaluated. the results permit to conclude that: the vegetative period from emergency to flowering and the juvenile period are significantly affected by the photoperiod and temperature differences; shorter photoperiods or higher temperatures anticipate flowering; longer photoperiods under the same temperature regime or higher temperature under the same photoperiod regime result in higher plants.
Linear programming model to optimize the water resource use in irrigation projects: an application to the Senator Nilo Coelho Project
Frizzone, J.A.;Coelho, R.D.;Dourado-Neto, D.;Soliani, R.;
Scientia Agricola , 1997, DOI: 10.1590/S0103-90161997000300016
Abstract: the main objective of this paper was to develop a separable linear programming model, considering a set of technical factors which may influence the profit of an irrigation project the model presents an objective function that maximizes the net income and specifies the range of water availability. it is assumed that yield functions in response to water application are available for differents crops and describe very well the water-yield relationships. the linear programming model was developed genetically, so that, the rational use of the available water resource could be included in an irrigation project specific equations were developed and applied in the irrigation project "senator nilo coelho" (sncp), located in petrolina - brazil based on the water-yield functions considered, cultivated land constraints, production costs and products prices, it was concluded that: (a) the model was suitable for the management of the sncp, resulting in optimal cropping patterns and showing the water requirements; (b) for 7,424 ha of land and 66, 644,500 m3 of water available on a year basis, the shadow price of these resources were respectively, us$ 1,115.20/ha e uss 281.60/1000 m3; (c) for the total monthly water availability of 9,861,040 m3, the total annual water availability of 66,644,500 m3 became an effective restriction to the increase of the net income of the production system in the sncp; (d) maintaining the total monthly water availability of 9,861,040 m3, annual volumes lower than 88,338,983 m3 were used fully to reach the optimal solution, and that higher volumes than this limit, did not increase the net return; (e) the optimization model presented, estimated a net return of 5234 % higher than the traditional cropping pattern used hi the sncp, considering the agricultural year of 1992.
Modelagem matemática como metodologia de análise do crescimento e arquitetura de sistemas radiculares
Teruel, Dioger Alexandre;Dourado-Neto, Durval;Hopmans, Jan W.;Reichardt, Klaus;
Scientia Agricola , 2000, DOI: 10.1590/S0103-90162000000400014
Abstract: root systems are difficult to observe, quantify, and interpret, being those the reasons why the scientific knowledge about roots is so poor. these difficulties make root architecture virtually impossible to be properly analyzed and understood by classical statistics, being simulation modeling an attractive approach. the plant species studied in this paper was soybean, a herbaceous dicotyledon, since most of the structural and functional investigations on root systems have been carried out for a few monocotyledon species. insufficient phosphorus supply in agricultural soils often affects crop yield, and therefore the effects of soil p concentration on soybean root architecture were studied. the proposed simulation model is a promising methodology for root data analysis, allowing a proper visualization of different plant adaptation strategies, as reflected by different root architectures.
Altera??es estruturais do sistema radicular de soja em resposta à disponibilidade de fósforo no solo
Teruel, Dioger Alexandre;Dourado-Neto, Durval;Hopmans, Jan W.;Reichardt, Klaus;
Scientia Agricola , 2001, DOI: 10.1590/S0103-90162001000100010
Abstract: since the analytical framework and quantitative tools associated with classical statistics are not efficient to identify and interpret plant strategies for adaptation to a given soil environment, the objective of this study was to utilize concepts of topology in order to analyze the structural changes in soybean root systems in response to soil phosphorus availability. soybean plants were grown in black plexiglas boxes under controlled environment (temperature and photoperiod). the boxes were packed with substrate mixed with nutrient solution to achieve uniform p concentration for two treatments: +p (15.5 mg l-1 p) and -p (8.5 mg l-1 p). in a completely randomized experimental design, three replicates were sampled at 5, 10, 15, 20, 25, and 30 days after germination. for each treatment, plant age, and replicate, the following attributes were obtained: main root length (order 0), and average number and length of order-1, order-2, and order-3 lateral roots according to their position of origin along the main root. topological indexes were defined and calculated for both treatments, using the mean values of three replicates. indexes used in this study were efficient in detecting the structural changes performed by the soybean root systems growing under lower soil p concentration.
Software to model soil water retention curves (SWRC, version 2.00)
Dourado-Neto, Durval;Nielsen, Donald R.;Hopmans, Jan W.;Reichardt, Klaus;Bacchi, Osny Oliveira Santos;
Scientia Agricola , 2000, DOI: 10.1590/S0103-90162000000100031
Abstract: a software for the adjustment of soil water retention curves (swrc) is presented, using twelve models found in the literature.
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