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| Registros recuperados: 50 | |
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| Teruel,Dioger Alexandre; Dourado-Neto,Durval; Hopmans,Jan W.; Reichardt,Klaus. |
| Devido à dificuldade de observação, quantificação e interpretação de sistemas radiculares, o estado da arte do conhecimento científico nesta área está aquém do desejável. Estas dificuldades tornam a análise e a interpretação da arquitetura de sistemas radiculares praticamente impossíveis de serem realizadas pela estatística tradicional, fazendo com que a modelagem matemática seja uma abordagem atrativa. Utilizou-se neste estudo plantas de soja, visto que a maioria dos trabalhos de pesquisa sobre a estrutura e funcionamento de sistemas radiculares de culturas comerciais tem sido realizada com um pequeno número de espécies, com ênfase nas monocotiledôneas, sendo muito poucos aqueles com dicotiledôneas herbáceas e espécies arbóreas. Estudou-se a influência da... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Glycine max; Modelo matemático; Raiz; Nutriente; Fósforo. |
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162000000400014 |
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| Oliveira,Júlio César Martins de; Reichardt,Klaus; Bacchi,Osny O.S.; Timm,Luis Carlos; Dourado-Neto,Durval; Trivelin,Paulo César Ocheuse; Tominaga,Tânia Toyomi; Navarro,Roberta de Castro; Piccolo,Marisa de Cássia; Cássaro,Fábio Augusto Meira. |
| Results of an organic matter management experiment of a sugar cane crop are reported for the first cropping year. Sugar cane was planted in October 1997, and labeled with a 15N fertilizer pulse to study the fate of organic matter in the soil-plant system. A nitrogen balance is presented, partitioning the system in plant components (stalk, tip and straw), soil components (five soil organic matter fractions) and evaluating leaching losses. The 15N label permitted to determine, at the end of the growing season, amounts of nitrogen derived from the fertilizer, present in the above mentioned compartments. |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Fertilizer; Nitrogen; N label; Soil; Sugar cane. |
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162000000300015 |
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| Dourado-Neto,Durval; Jong van Lier,Quirijn de; Metselaar,Klaas; Reichardt,Klaus; Nielsen,Donald R.. |
| 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, Mendonça derived in 1958 an equation... |
| Tipo: Info:eu-repo/semantics/report |
Palavras-chave: Actual and reference evapotranspiration; Deficit and excess water. |
| Ano: 2010 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162010000100013 |
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| Silva,Adriana Lúcia da; Roveratti,Renato; Reichardt,Klaus; Bacchi,Osny Oliveira Santos; Timm,Luis Carlos; Bruno,Isabeli Pereira; Oliveira,Julio César Martins; Dourado Neto,Durval. |
| Establishing field water balances is difficult and costly, the variability of their components being the major problem to obtain reliable results. This component variability is presented herein for a coffee crop grown in the Southern Hemisphere, on a tropical soil with 10% slope. It was observed that: rainfall has to be measured with an appropriate number of replicates; irrigation can introduce great variability into calculations; evapotranspiration, calculated as a remainder of the water balance equation, has exceedingly high coefficients of variation; the soil water storage component is the major contributor in error propagation calculations to estimate evapotranspiration; and that runoff can be satisfactorily controlled on the 10% slope through crop... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Component variability; Rainfall; Evapotranspiration; Soil water storage. |
| Ano: 2006 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162006000200001 |
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| Sadeghi,Morteza; Ghahraman,Bijan; Davary,Kamran; Hasheminia,Seyed Majid; Reichardt,Klaus. |
| Using scaling methods, a single solution of Richards' equation (RE) will suffice for numerous specific cases of water flow in unsaturated soils. In this study, a new method is developed to scale RE for the soil water redistribution process. Two similarity conditions are required: similarity in the shape of the soil water content profiles as well as of the water flux density curves. An advantage of this method is that it is not restricted to a specific soil hydraulic model - hence, all such models can be applied to RE. To evaluate the proposed method, various soil textures and initial conditions were considered. After the RE was solved numerically using the HYDRUS-1D model, the solutions were scaled. The scaled soil water content profiles were nearly... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Nielsen-similarity; Spatial variability; Invariant solutions. |
| Ano: 2011 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162011000500011 |
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| Reichardt,Klaus; Silva,José Carlos de Araújo; Bassoi,Luis Henrique; Timm,Luís Carlos; Oliveira,Julio Cesar Martins de; Bacchi,Osny Oliveira Santos; Pilotto,João Eduardo. |
| The effects of soil water spatial variability previous to irrigation and of the field capacity on the estimation of irrigation water depth are evaluated. The experiment consisted of a common bean (Phaseolus vulgaris L.) crop established on a Kandiudalfic Eutrudox of Piracicaba, SP, Brazil, irrigated by central pivot, in which soil water contents were evaluated with a depth neutron gauge, in a grid of 20x4 points with lag of 0.5 m. In a given situation, the 80 calculated irrigation water depths presented a coefficient of variation of 29.3%, with an average water value of 18 mm, maximum of 41mm and minimum of 9 mm. It is concluded that the only practical way of irrigation is the use of an average water depth, due to the inherent variability of the soil, and... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Irrigation water depth; Field capacity; Spatial variability. |
| Ano: 2001 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162001000300017 |
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| Timm,Luis Carlos; Fante Jr.,Lorival; Barbosa,Emanuel Pimentel; Reichardt,Klaus; Bacchi,Osny Oliveira Santos. |
| Para estudar a interação solo-planta utilizou-se um modelo de espaço de estados (regressão dinâmica) comparativamente à um modelo de regressão estática, em versão convencional e em versão sequencial. Para tal, foram utilizados dados experimentais de densidade do solo, macroporosidade, microporosidade e porosidade total de um solo Latossolo Vermelho Escuro, além da densidade radicular por comprimento de raiz por unidade de volume, de uma cultura de aveia forrageira. Das variáveis explanatórias estudadas, a porosidade total apresentou correlação bastante significativa com a densidade radicular, considerada como a variável resposta do estudo. Um modelo de regressão estática representado na forma de espaço de estados com estimação seqüencial forneceu um... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Variabilidade espacial; Regressão dinâmica; Regressão estática; Estimação seqüencial. |
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162000000400025 |
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| Dourado-Neto,Durval; García y García,Axel; Fancelli,Antonio Luiz; Frizzone,José Antonio; Reichardt,Klaus. |
| El presente trabajo tiene por objetivo presentar un modelo mecanístico para estimar el almacenamiento de agua en el suelo, con el propósito de prever el rendimiento agrícola para cultivos anuales no fotosensibles. El movimiento y la retención de agua en el sistema agrícola, son los atributos de interés en el estudio. El rendimiento agrícola depende de los procesos básicos de fotosíntesis y respiración. También, el rendimiento depende de la especie vegetal, nutrición de la planta, energia disponible, población de plantas, plantas dañinas y población de parásitos, principalmente. Además, la evapotranspiración actual también depende de los mismos atributos y procesos. Por lo tanto, la hipótesis base del modelo es que es posible estimar el rendimiento... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Balance hídrico; Almacenamiento de agua; Modelagem. |
| Ano: 1999 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90161999000300005 |
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| Bruno,Isabeli Pereira; Silva,Adriana Lúcia da; Reichardt,Klaus; Dourado-Neto,Durval; Bacchi,Osny Oliveira Santos; Volpe,Clóvis Alberto. |
| The use of climatological water balances in substitution to complete water balances directly measured in the field allows a more practical crop management, since the climatological water balances are based on data monitored as a routine. This study makes a comparison between these methods in terms of estimatives of evapotranspiration, soil water storage, soil available water, runoff losses, and drainage below root zone, during a two year period, taking as an example a coffee crop of the variety Catuaí, three to five years old. Climatological water balances based on the estimation of the evapotranspiration through the methods of Thornthwaite and Penman-Monteith, can reasonably substitute field measured balances, however underestimating the above mentioned... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Evapotranspiration; Soil water storage; Available water; Water deficit; Water excess. |
| Ano: 2007 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162007000300001 |
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| Timm,Luís Carlos; Pires,Luiz Fernando; Roveratti,Renato; Arthur,Robson Clayton Jacques; Reichardt,Klaus; Oliveira,Júlio Cesar Martins de; Bacchi,Osny Oliveira Santos. |
| Soil water content (theta) and bulk density (rhos) greatly influence important soil and plant processes, such as water movement, soil compaction, soil aeration, and plant root system development. Spatial and temporal variability of theta and rhos during different periods of the year and different phases of crops are of fundamental interest. This work involves the characterization of spatial and temporal patterns of theta and rhos during different climatic periods of year, aiming to verify whether there are significant temporal changes in rhos at the soil surface layer when submitted to wetting and drying cycles. The field experiment was carried out in a coffee plantation, Rhodic Kandiudalf soil, clayey texture. Using a neutron/gamma surface probe, theta... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Neutron/gamma surface probe; Wetting/drying cycles; Spatial and temporal variability. |
| Ano: 2006 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162006000100009 |
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| Registros recuperados: 50 | |
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