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Search Results: 1 - 10 of 9822 matches for " Dourado-Neto Durval "
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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.
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.
General procedure to initialize the cyclic soil water balance by the Thornthwaite and Mather method
Dourado-Neto, Durval;Jong van Lier, Quirijn de;Metselaar, Klaas;Reichardt, Klaus;Nielsen, Donald R.;
Scientia Agricola , 2010, DOI: 10.1590/S0103-90162010000100013
Abstract: the original thornthwaite and mather method, proposed in 1955 to calculate a climatic monthly cyclic soil water balance, is frequently used as an iterative procedure due to its low input requirements and coherent estimates of water balance components. using long term data sets to establish a characteristic water balance of a location, the initial soil water storage is generally assumed to be at field capacity at the end of the last month of the wet season, unless the climate is (semi-) arid when the soil water storage is lower than the soil water holding capacity. to close the water balance, several iterations might be necessary, which can be troublesome in many situations. for (semi-) arid climates with one dry season, mendon?a derived in 1958 an equation to quantify the soil water storage monthly at the end of the last month of the wet season, which avoids iteration procedures and closes the balance in one calculation. the cyclic daily water balance application is needed to obtain more accurate water balance output estimates. in this note, an equation to express the water storage for the case of the occurrence of more than one dry season per year is presented as a generalization of mendon?a's equation, also avoiding iteration procedures.
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,
Abstract: Com o objetivo de estimar o volume de água por hectare retido na folhagem da cultura de milho para fins de quimiga o (alvo folha), é proposto um modelo, tendo sido conduzido um experimento em que foi avaliada a intercepta o de água pela parte aérea das plantas de milho sob diferentes laminas de irriga o aplicadas via piv central. Foi semeado um híbrido de milho, em três densidades, obtendo-se assim três arranjos espaciais diferentes. As avalia es foram realizadas em 3 estádios fenológicos: i) 4-5 folhas; ii) 8 folhas e iii) 14 folhas. A quantidade de água retida nas folhas das plantas foi estimada subtraindo à massa total da planta medida após a passagem do piv , a massa de matéria seca e a água constitutiva das plantas. Para a análise estatística dos resultados, utilizou-se um delineamento experimental em parcelas subdivididas no tempo, com quatro repeti es. O tratamento principal foi a popula o de plantas e o subtratamento a data de amostragem. A área foliar foi avaliada em cada amostragem. A fenologia e o desenvolvimento relativo da cultura foram avaliados periodicamente. Os resultados permitiram verificar que o modelo proposto é utilizável.
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,
Abstract: Com o objetivo de elaborar um modelo matemático para estimar o acúmulo de matéria seca, e prever as épocas de florescimento e do ponto de maturidade fisiológica da cultura de feij o, em fun o da temperatura média diária do ar, foi conduzido um experimento em Piracicaba-SP (22o42?30'? de latitude Sul, 47o38?00'? de longitude Oeste e 546 m de altitude) utilizando o cultivar IAC-Carioca sob dez tratamentos (diferentes níveis de nitrogênio e água). Em fun o dos resultados obtidos, verificou-se que o modelo sugerido é utilizável para o que foi proposto.
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