Dep. de Estatistica

United States

Dep. de Estatistica

United States

Time filter

Source Type

Aspiazu I.,State University of Montes Claros | Sediyama T.,Federal University of Viçosa | Ribeiro Jr. J.I.,Dep. de Estatistica | Silva A.A.,Federal University of Viçosa | And 6 more authors.
Planta Daninha | Year: 2010

The objective of this study was to evaluate characteristics associated with the photosynthetic efficiency and water use of weed species. Treatments were composed by the species Bidens pilosa, Commelina benghalensis and Brachiaria plantaginea, sown individually in the experimental units. The experimental design was in randomized blocks in a 3 × 4 factorial, with three repetitions. Characteristics associated with water use - transpiratory rate (E), stomatal conductance (Gs), vapor pressure in the substomatal chamber (Ean) and water use efficiency (WUE) - as well as photosynthesis - internal leaf CO2 concentration (Ci), CO2 consumed during the evaluation (δC),leaves average temperature at evaluation time (Tleaf) and photosynthetic rate (A) - were evaluated. B. plantaginea showed lower E, lower WUE and higher A and Ci, differing from the other involved species. B. pilosa showed lower values of WUE, A and T when compared to the other species. According to the results, it can be concluded that B. plantaginea was more efficient in characteristics related to the photosynthesis, i.e., more efficient use of light. B. pilosa was more efficient in characteristics related to water use.


Aspiazu I.,State University of Montes Claros | Sediyama T.,State University of Montes Claros | Ribeiro J.I.,Federal University of Viçosa | Silva A.A.,Dep. de Estatistica | And 5 more authors.
Planta Daninha | Year: 2010

The objective of this work was to evaluate characteristics associated with the photosynthetic activity of cassava plants in competition with weeds or not. The trial was performed on open environment conditions, with experimental units consisting of fiber glass vases with 150 dm3 filled with Red Yellow Latosol, previously fertilized. Treatments consisted in the cultivation of cassava plants isolated and associated to three weed species (Bidens pilosa, Commelina benghalensis and Brachiaria plantaginea). After cassava shooting, 15 days after planting, a removal of the weeds excess was performed, sown at the time of cassava planting, leaving six plants m-2 of B. pilosa and four plants m-2 of C. benghalensis and B. plantaginea. At 60 days after emergence (DAE), stomatal conductance (Gs), vapor pressure in the substomatal cavity (Ean), temperature gradient between leaf and air (ΔT), transpiration rate (E) and water use efficiency (WUE) were evaluated. B. pilosa showed greater capacity to affect growth of cassava plants. B. plantaginea is very efficient in using water, especially by presenting C4 metabolism, and remains competitive with cassava even under temporarily low water status. C. benghalensis, in turn, is not a good competitor for light and apparently is not the primary cause of water depletion in the soil. The effects of weeds, in this case, were more associated with the competition. However, they were found between moderate to low. This implies that the competition established at experimental level was low.


Aspiazu I.,State University of Montes Claros | Sediyama T.,Federal University of Viçosa | Ribeiro Jr. J.I.,Dep. de Estatistica | Silva A.A.,Federal University of Viçosa | And 6 more authors.
Planta Daninha | Year: 2010

The objective of this work was to evaluate characteristics associated with the photosynthetic activity of cassava plants under weed competition. The trial was carried out under field conditions, and experimental units consisted of 150 dm3 fiberglass boxes containing red yellow Latosol, previously corrected and fertilized. Treatments consisted in the cultivation of cassava plants which were free of weed competition and associated with three weed species: Bidens pilosa, Commelina benghalensis or Brachiaria plantaginea. After manioc sprouting started, 15 days after being planted, weeds that had been sown when manioc was planted were thinned, there were then eight plants left per experimental unit in accordance with specified treatments: cassava free of competition, cassava competing with B. pilosa, cassava competing with C. benghalensis and cassava competing with B. plantaginea. Sixty days after crop emergence leaf internal CO2 concentration (Ci), leaf temperature at the time of evaluation (Tleaf) and photosynthetic rate (A) were evaluated, also the CO2 consumption rate (ΔC) of cassava plants was calculated. A correlation matrix between variables was also obtained. All characteristics associated with photosynthesis in cassava plants were influenced by weed species. Cassava was more affected by B. pilosa and B. plantaginea in which concerns its exposition to solar radiation and water, while C. benghalensis seems to mostly affect the composition of incident light on the culture, allowing cassava to anticipate imposition when competing, even before it reaches harmful levels.


Lemos J.P.,Federal University of Viçosa | Galvao J.C.C.,Campus Universitario | Silva A.A.,DFT UFV | Fontanetti A.,Federal University of São Carlos | And 2 more authors.
Planta Daninha | Year: 2012

The efficiency of using clearings to control Picão-preto (Bidens pilosa) and Trapoeraba (Commelina benghalensis) was evaluated based on the morphological and physiological characteristics of corn.An experiment under greenhouse conditions was conducted in 2009/2010.The physiological characteristics were obtained in a subdivided parcel, with four evaluations being performed throughout the corn cycle (1- before the first clearing (V3); 2- after the first clearing (V6);3- after the second clearing (V9); and 4- corn plants at the fluorescence stage), by means of Infra Red Gas Analyzer. Two clearings reduced the influence of B. pilosa and C. benghalensis weeds on the morphological characteristics of corn. The clearing did not influence the physiological aspects of the corn plants in competition with weeds. C. benghalensis caused a greater interference in the physiological characteristics of corn, reducing photosynthesis and transpiration. When not cleared, B. pilosa species had a greater capacity of interfering in corn morphology.


Lemos J.P.,Federal University of Viçosa | Galvao J.C.C.,DFT UFV | Silva A.A.,DFT UFV | Fontanetti A.,Anhanguera | And 2 more authors.
Planta Daninha | Year: 2013

Mowing is one of the most important methods used to control weeds in organic farming, under the no-tillage system. This study aimed to evaluate the effects of three weed management techniques on weed development, using the weeds Bidens pilosa and Commelina benghalensis, in competition with organic corn {mowing at the three-leaf stage (14 days after corn emergence - DACE), mowing at the three- and six-leaf stage (14 and 25 DACE), and no mowing. Single cultivation with no mowing was also evaluated for these weeds. Mowings performed at 14 and 25 DACE prevented the production of B. pilosa seeds, ensuring efficient control of this species. However, the use of this technique was shown to be inefficient in the control of C. benghalensis.

Loading Dep. de Estatistica collaborators
Loading Dep. de Estatistica collaborators