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Search Results: 1 - 10 of 11846 matches for " Villa Nova Nilson Augusto "
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Necessidades hídricas de citros e macieiras a partir da área foliar e da energia solar
Pereira, André Belmont;Villa Nova, Nilson Augusto;Alfaro, Adriane Theodoro;
Revista Brasileira de Fruticultura , 2009, DOI: 10.1590/S0100-29452009000300008
Abstract: solar energy is the primary source for photosynthesis and transpiration in such a way as to assure the expression of the crop yield potential at a given site. the current methodology aims to ease the calculation of the water amount (liters/plant/day) necessary for a localized irrigation scheduling with a minimal loss possible at both citrus and apple trees orchards by means of usual available data, such as leaf area, global solar radiation flux density, net radiation and air daily mean steam saturation deficit. taking into account that the localized irrigation system takes up far less water than sprinkler systems and also that the grant of water for irrigation is becoming more and more limited, such a work certainly comes to be of a great importance to assure the sustainability of the irrigated agriculture, especially at both arid and semi-arid regions. for the development of the proposed methodology a data set of sap flux measured by means of the heat flux approach in a citrus orchard, cultivar tahiti, with leaf areas of 48 and 99 m2, as well as in apple trees with leaf areas roughly of 5, 8, 9, 11, 16 and 21 m2 was used herein. the obtained results revealed that it is rather feasible to estimate the amount of irrigation water throughout the whole citrus and apple trees cycle by means of the criterion based on the physiological variable input, which expresses the ability of the plants to converting solar energy into water taken up in the transpiration process at the sites in study.
Coffee crop coefficient for precision irrigation based on leaf area index
Pereira, Antonio Roberto;Camargo, Marcelo Bento Paes de;Villa Nova, Nilson Augusto;
Bragantia , 2011, DOI: 10.1590/S0006-87052011000400030
Abstract: crop coefficient (kc) for coffee plantations was found to be linearly related to the leaf area index (l) up to 3, i.e., kc = b l. the basic assumption is that for irrigated trees the water use per unit leaf area (etla) is equal to the reference evapotranspiration (eto) expressed also on a unit leaf area basis of the reference surface (etla = eto/lo). as recommended by fao-56 the leaf area index (lo) for the hypothetical reference surface (grass) is equal to 2.88, then the most likely value is b = lo-1 = 2.88-1 = 0.347. however, for l > 3 (completely covered ground surface) kc decreased from a peak value (~1.05) tending to an asymptotic low value around 0.7 for l > 6, but the linear model gives unrealistic kc estimates; tentatively the empirical function kc = 1.8 l-0.5 is offered here as an initial guess due to the lack of experimental results for the interval 3.5
Potato potential yield based on climatic elements and cultivar characteristics
Pereira, André Belmont;Villa Nova, Nilson Augusto;Ramos, Valdir Josué;Pereira, Antonio Roberto;
Bragantia , 2008, DOI: 10.1590/S0006-87052008000200008
Abstract: there is currently a great deal of interest in estimating crop productivity as a function of climatic elements by means of different crop weather models. an agrometeorological model is presented based on carbon dioxide assimilation maximum rates for c3 plants, fraction of photosynthetically active radiation, air temperature, photoperiod duration, and crop parameters under tropical climate conditions. such crop parameters include leaf area and harvest indexes, dry matter content of potato tubers, and crop cycles to estimate potato potential yields. field data from observed productivity obtained with the cultivar itararé (iac-5986), grown under adequate soil water supply conditions at four different regions in the state of s?o paulo (itararé, piracicaba, tatuí, and s?o manuel), brazil, were used to test the model. the results revealed an excellent performance of the agrometeorological model in study, with an underestimation of irrigated potato productivity less than 10%.
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.
Balan?o de energia numa cultura de arroz em condi??es de sequeiro
Villa Nova, Nilson Augusto;Pereira, Antonio Roberto;Pedro Júnior, Mário Jóse;
Bragantia , 1975, DOI: 10.1590/S0006-87051975000100009
Abstract: the main objective of this study was to quantify, in a rice field grown under upland conditions, how the net radiation is partitioned among the various energy balance components, such as: latent heat, sensible heat, and soil heat fluxes, with and without advection
Método alternativo para cálculo da temperatura base de gramíneas forrageiras
Villa Nova, Nilson Augusto;Tonato, Felipe;Pedreira, Carlos Guilherme Silveira;Medeiros, Henrique Rocha de;
Ciência Rural , 2007, DOI: 10.1590/S0103-84782007000200039
Abstract: the assessment of the temperature below which plant growth ceases, known as base temperature (tb) is key in for establishing the potential yield of a plant resource at a given location, and for quantifying the fitness of a given crop for a given production system. whereas this is widely recognized, it is especially true in the case of perennial crops such as many of the forage species. this present study was aimed at developing, evaluating, and proposing a new methodological approach for the calculation of the tb of forage crops, using both temperature and daylength, as a climatic variable named photothermal unit (pu). by using two regrowth cycles and their respective amounts of forage accumulated, the value of tb can be calculated if the proportion between harvested yields and accumulated pus of both regrowth cycles are the same. yield data from two forage grass species, elephantgrass (pennisetum purpureum schum. cv. napier) and florico stargrass (cynodon nlemfu?nsis vanderyst var. nlemfu?nsis), from two field trials were used to test the proposed approach. calculated tb values were 15 and 12°c for elephantgrass and stargrass, respectively. these values are consistent with those generated by the classic method and reported in the literature.
Transpiration of irrigated apple trees and citrus from a water potential gradient approach in the leaf-atmosphere system
Pereira, André Belmont;Villa Nova, Nilson Augusto;Pires, Luiz Fernando;Alfaro, Adriane Theodoro;
Revista Brasileira de Meteorologia , 2011, DOI: 10.1590/S0102-77862011000200002
Abstract: the uptake of water from the roots of crops comes to being a physiological response of the plant to the water loss process through its stomata. getting to know the daily transpiration rates throughout the phenological cycle allows for the application of the ideal amount of irrigation water at the right moment to maximize production with environmental protection. since transpiration direct measurements at the field, mainly for trees in general, are to be of operational difficulty and relatively high cost we came up with a methodology that allows one to calculate the daily transpiration rates of apple trees and citrus orchards from variables of both the physical environment and the crop. the input data of the proposed model are air temperature, air relative humidity, photoperiod duration, and leaf area. estimated transpiration rates based on the water potential gradient between the air and leaf approach were comparable in apple trees and citrus orchards. sap flow daily values were obtained by means of the heat balance method at bordeaux, france, and piracicaba, sp, brazil. all the coefficients of determination of the regression equations obtained herein were higher than 0.93. this allows one to calculate the amount of irrigation water to be applied throughout the crop growing seasons with a high precision as a function of meteorological data and crop covering density at the sites in the study.
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,
Abstract: Com base em pesquisa realizada no cafezal do Departamento de Produ o Vegetal da ESALQ, Universidade de S o Paulo, utilizando a cultivar Mundo Novo IAC 388-17, enxertada na cultivar Apoat IAC 2258, plantada no espa amento de 2,5 m x 1,0 m (4.000 plantas.ha-1), prop s-se um método para a estimativa do coeficiente de cultura (Kc) de café. O método fundamentou-se na estimativa da transpira o do cafeeiro em fun o de variáveis climatológicas e fitotécnicas (área foliar, densidade de plantas e manejo de plantas daninhas). Entre 15 e 40 meses após a implanta o do cafezal, realizaram-se estimativas de Kc nas condi es de densidade de plantio e da área foliar do cafeeiro, bem como simula es para diferentes densidades, na presen a e na ausência de plantas daninhas. Os resultados evidenciaram a dinamica do coeficiente de cultura (Kc) com a varia o da área foliar e a densidade de plantio. O Kc estimado foi superior na presen a de mato até 30 meses após o plantio, para o espa amento adotado neste experimento. Em compara o com os dados de Kc para café indicados na literatura, o método proporcionou resultados consistentes, com a vantagem de permitir simula es para diferentes densidades de plantas. Em vista dos resultados, sugerem-se estudos adicionais da rela o entre área foliar e densidade de plantas elevada, ou seja, que ultrapasse o limite adotado neste experimento, de 4.000 plantas.ha-1.
Constru??o e avalia??o de psicr?metro aspirado de termopar
Marin, Fábio Ricardo;Angelocci, Luiz Roberto;Coelho Filho, Maurício Ant?nio;Villa Nova, Nilson Augusto;
Scientia Agricola , 2001, DOI: 10.1590/S0103-90162001000400028
Abstract: the construction of a low cost aspirated thermocouple psychrometer made of pvc tubes is described. the instrument can easily be connected to dataloggers. the aspiration is made by fans used in microcomputers and temperatures measured with cooper-constantan thermocouples. a cotton string was used to make the wet junction. its perfomance was evaluated in comparison to an assman aspirated psychrometer and a vaisala inc. capacitive higrometer, in natural and controlled environments. the results show a good agreement between measures, allowing air vapour, relative humidity, temperature and specific humidity gradients to be determined using the proposed psychrometer.
Equa es para a estimativa do índice de área foliar do cafeeiro
Favarin José Laércio,Dourado Neto Durval,García y García Axel,Villa Nova Nilson Augusto
Pesquisa Agropecuária Brasileira , 2002,
Abstract: Com o objetivo de estudar a varia o temporal do índice de área foliar (IAF) da cultura de café, utilizando um método simples e n o-destrutivo, foi instalado um experimento no Departamento de Produ o Vegetal, da Escola Superior de Agricultura Luiz de Queiroz, da Universidade de S o Paulo. Utilizou-se a cultivar Mundo Novo IAC 388-17, enxertada sobre a cultivar Apoat IAC 2258 (de 15 até 35 meses de idade), no espa amento de 2,5 x 1,0 m. Foram coletadas todas as folhas de duas plantas de café, em intervalos de 60 a 150 dias, para a mensura o da área foliar com o equipamento LI-COR (modelo 3100). Para obter a rela o funcional entre IAF e diferentes variáveis de crescimento (altura da planta, número e massa total de folhas e área foliar) e arquitetura da copa (área da se o inferior, média e superior do dossel, área lateral do dossel, diametro inferior, médio e superior do dossel, volume do dossel da planta e altura do primeiro par de ramos), assumiu-se que a parte aérea do cafeeiro tem a forma c nica. O diametro da se o inferior do dossel (primeiro par de ramos) e a altura da planta podem ser utilizadas para estimar o índice de área foliar do cafeeiro.
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