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Search Results: 1 - 10 of 208526 matches for " L.;Rizzardi "
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Potencial alelopático de extratos aquosos de genótipos de canola sobre Bidens pilosa
Rizzardi, A.;Rizzardi, M.A.;Lamb, T.D.;Johann, L.B.;
Planta Daninha , 2008, DOI: 10.1590/S0100-83582008000400002
Abstract: the objective of this experiment was to evaluate the effect of aqueous extract of plants of canola genotypes on the germination and radicle length of hairy beggartick (bidens pilosa). the treatments consisted of genotypes of canola hyola 420, hyola 401, hyola 43, hyola 60, hyola 61, y 3000, h 1432, dln 03-02, dln 03-04, sdh 03-01, sdh 03-07, sw-2797, and sw-eclipse. the concentrations of aqueous extract of 100, 75, 50, 25 and 0 % were tested. a completely randomized experimental design was used in a factorial 12 x 4 (genotypes and extract concentrations) with four replications. the experiment was carried out in plastic boxes containing ot the bottom blotter paper moistened with the aqueous extract, where the hairy beggartick achenes were seeded. seven days later, the number of germinated achenes was evaluated and the length of radicles measured. the results showed that the canola extracts negatively influenced achene germination and radicle length. the effects increased with increased extract concentrations. at low concentration, some genotype extracts presented a stimulating effect. the results showed that the variability among canola genotypes was only evident at low extract concentrations.
Controle de plantas daninhas em milho em fun??o de quantidades de palha de nabo forrageiro
Rizzardi, M.A.;Silva, L.F.;Vargas, L.;
Planta Daninha , 2006, DOI: 10.1590/S0100-83582006000200008
Abstract: the objective of this study was to evaluate the effect of the amount of turnip (raphanus sativus var. oleiferus) crop residue on weed control in corn. the experimental design was a split-plot, in randomized blocks, with four replications. the treatments tested were 0, 6, and 9 t ha-1 of turnip crop residues, fallow period (the amount of residues was equivalent to the amount of natural vegetation residues), arranged as main plots, and six weed control periods (corn plants with 1, 2, 4, 5, 6, and 7 developed leaves), besides two controls (one without weeds and another without weed control), arranged as subplots. interactions occurred between residue amounts and control periods in relation to the degree of weed control. the best control period was achieved when the corn plants presented from 2 to 4 developed leaves. corn grain yield was higher in the control plots with no weed control than in the plots with 9 t ha-1 of turnip crop. chemical control did not increase corn grain yield, when the amount of turnip crop was 9 t ha-1.
Influência das coberturas vegetais antecessoras de aveia-preta e nabo forrageiro na época de controle de plantas daninhas em milho
Rizzardi, M.A.;Silva, L.F.;
Planta Daninha , 2006, DOI: 10.1590/S0100-83582006000400007
Abstract: the objective of this work was to assess the effect of rape and black oats as cover crops on chemical weed control timing in corn under no-till. the experiment was arranged in a complete block design, with the treatments in subplots and four replications. the main treatment plots were cover crops and the subplots the chemical weed control timings, according to corn growth stages (1, 2, 3, 4, 5 and 6 leaves). two control plots, one with and the other without total weed control were added to the experiment. weed chemical control was performed in postemergence with the association of the herbicides nicosulfuron + atrazine (sanson 0.8 l ha-1 + primóleo 0.3 l ha-1). when chemical control was applied, the cover crop black oat showed to be more efficient on corn grain yield. rape was found to require more criterion as to the correct timing for weed control, while black oat allowed more flexibility. the best time for herbicide application ranged from the corn growth stages of two to three leaves.
Financial Management – Payment Card Fraud Can Happen to You
Richard Rizzardi
Optometry & Vision Development , 2008,
Abstract:
Altera??o das características biológicas dos biótipos de azevém (Lolium multiflorum) ocasionada pela resistência ao herbicida glyphosate
Vargas, L.;Roman, E.S.;Rizzardi, M.A.;Silva, V.C.;
Planta Daninha , 2005, DOI: 10.1590/S0100-83582005000100018
Abstract: the identification of ryegrass biotypes resistant to glyphosate is causing changes in weed management in apple orchards. three experiments were carried out to determine the gr50 of the biotypes, to grass herbicides and dry matter accumulation. the first experiment tested different rates of glyphosate. their effects on gr50 dry matter accumulation by the biotype were assessed. in the second experiment different rates of glyphosate and grass herbicides were tested: glyphosate, haloxyfop-r, diclofop, fluazifop-p, fenoxaprop-p and paraquat. a third experiments was carried out under glasshouse conditions to determine the curve of dry matter accumulation. the results showed gr50 of 287.5 and 4,833.5 g e. a. ha-1 of glyphosate for the sensitive and resistant biotypes, respectively. the results showed that the resistant factor (rf) was 16.8 and that the resistance mechanism alters the biological characteristics of the resistant biotype affecting its sensitivity to grass herbicides.
Identifica??o de biótipos de azevém (Lolium multiflorum) resistentes ao herbicida glyphosate em pomares de ma??
Vargas, L.;Roman, E.S.;Rizzardi, M.A.;Silva, V.C.;
Planta Daninha , 2004, DOI: 10.1590/S0100-83582004000400017
Abstract: glyphosate is a wide spectrum herbicide used for over 15 years in apple orchards in vacaria-rs for weed control in rows of trees. usually, 3 to 4 applications per year are made at a rate of 720 to 1080 g a.e. glyphosate ha-1 (2 to 3 l ha-1 of commercial product). ryegrass (lolium multiflorum) is a common weed in orchards and traditionally sensitive to glyphosate. however, in the last years, some ryegrass plants have not been found to show significant toxicity symptoms after treatment with glyphosate, suggesting that they acquired resistance to this product. to evaluate the response of a ryegrass plant population to glyphosate, one field and two greenhouse experiments were carried out. the field experiment treatments had increasing rates of glyphosate (0; 360; 720; 1,440; 2,880; 5,760 and 11,520 g a.e. ha-1), in addition to the herbicides paraquat, glufosinate-ammonium, haloxyfop and diclofop-methyl as standards, sprayed at two different vegetative growth stages of ryegrass. the greenhouse experiments had increasing rates of glyphosate (0; 360; 720; 1,440; 2,880 and 5,760 g a.e. ha-1) plus the above listed check herbicides sprayed on biotypes considered resistant and on plants of one susceptible biotype. in the second greenhouse experiment, glyphosate rates (720; 1,440; 2,880; 720 + 720 and 720 + 1,440 g a.e. ha-1) were sprayed in single and sequential applications, in addition to the herbicides paraquat, glufosinate-ammonium, haloxyfop, clethodim, sethoxydim, diclofop-methyl, fenoxaprop, fluazifop, paraquat + diuron, atrazine + simazine, trifluralin, and metolachlor. toxicicity to the herbicides was assessed at 15, 30 and 45 dat (days after treatment). overall, the field and greenhouse experiment results showed that the susceptible biotype is easily controlled by glyphosate and by the other postemergence herbicides tested, independent of the vegetative growth stage. in addition, the results showed that the resistant biotype, similarly to the susceptible biotype, is
Resistência de azevém (Lolium multiflorum) ao herbicida glyphosate
Roman, E.S.;Vargas, L.;Rizzardi, M.A.;Mattei, R.W.;
Planta Daninha , 2004, DOI: 10.1590/S0100-83582004000200018
Abstract: italian ryegrass (lolium multiflorum) is cultivated as forage and/or cover crop in no-till system. however, it is also a serious weed in wheat and other winter cereals in southern brazil. experiments were conducted at greenhouse and field conditions to evaluate the susceptibility of two ryegrass biotype to glyphosate as well as the efficacy of other herbicides on the post-emergence control of the species for sowing wheat under no-till system. the experimental design was a completely randomized design for the greenhouse experiment and a completely randomized block design for the field experiment. herbicides with different mechanisms of action were evaluated on the weed control: glyphosate, glufosinate, clethodim, haloxyfop-r and diclofop, paraquat and paraquat+diuron. the results obtained under greenhouse conditions indicated the glyphosate susceptible biotype was controlled by the rate of 360 g e.a. ha-1. the resistant ryegrass biotype had no reduction in dry matter production and less than 15 % phytotoxicity caused by glyphosate up to 1,440 g e.a. ha-1. however, glyphosate rates between 1440 and 5,760 g e.a. ha-1 reduced dry matter accumulation and resulted in toxicities under45%. under field conditions, the best lolium multiflorum control was given by clethodim 79.2 g ha-1 and diuron + paraquat at 300+600 g ha1, respectively. the results obtained in these studies indicated that the population was composed predominantly by a biotype resistant to epsps inhibitor herbicides.
Temperatura cardeal e potencial hídrico na germina??o de sementes de corda-de-viola (Ipomoea triloba)
Rizzardi, M.A.;Luiz, A.R.;Roman, E.S.;Vargas, L.;
Planta Daninha , 2009, DOI: 10.1590/S0100-83582009000100003
Abstract: this work aimed to assess the effect of temperature and moisture on the germination and emergence of morning glory (ipomoea triloba) and to determine the effect of water potential and temperature on seed germination and hypocotyl and radicle elongation. thermoperiods of 9.3 and 5 (7.5); 14.3 and 10 (12.5); 19.3 and 15 (17.5); 24.3 and 20 (22.5); 29.3 and 25 (27.5); 34.3 and 30 (32.5); 39.2 and 35 (37.5) and 44.2 and 40 (42.5) and 49.2 and 45 (47.5) oc, which alternated for 14 and 10 hours, and water potentials of 0, -0.03, -0.06, -0.1, -0.2, -0.4, -0.6 and -0.9 mpa were evaluated. the germination of morning glory seeds occurred through temperature and water potential interaction whereas radicle and hypocotyl elongation was triggered by temperature. with regard to germination, the parameters of the model used to estimate cardinal temperatures and the baseline water potential were determined by probit analysis. as to elongation processes, cardinal temperatures were calculated by linear regression and their responses to temperature were described by a second-order regression equation. the mathematical models described the processes of seed germination and of hypocotyl and radicle elongation of this species as a function of hydrothermal time and temperature, respectively.
Controle de plantas daninhas em milho em fun??o de épocas de aplica??o de nitrogênio
Rizzardi, M.A.;Zanatta, F.S.;Lamb, T.D.;Johann, L.B.;
Planta Daninha , 2008, DOI: 10.1590/S0100-83582008000100012
Abstract: the objective of this study was to evaluate the influence of nitrogen application time on weed interference in maize and to determine nitrogen application effect on weed control. the trial was conducted in completely randomized blocks and split-plot design, with four replications. the treatments consisted of five systems of nitrogen application on maize: 0-0-0, 150-0-0, 75-75-0, 0-150-0 and 0-75-75, corresponding, respectively, to the applied amounts of nitrogen before sowing with four and eight leaves, and six times of weed control (maize with 2, 3, 4, 5, 6 and 7 leaves) plus two controls with and without the presence of weeds. the chemical control of weeds was performed after emergence by associating the herbicides nicosulfuron and atrazine. the weed control in v2 was not efficient due to re-infestation. anticipated applications of nitrogen increased weed density. the greatest nitrogen levels in the index-leaf occurred when nitrogen was applied in v4 and v8, regardless of weed control time. the highest grain yield and number by corn ear were obtained after weed control was performed at the phenological stage v, regardless of nitrogen application time.
Influência de doses de nitrogênio na época de controle de plantas daninhas na cultura do milho (Zea mays)
Zanatta, F.S.;Rizzardi, M.A.;Lamb, T.D.;Johann, L.B.;
Planta Daninha , 2007, DOI: 10.1590/S0100-83582007000300012
Abstract: the objective of this study was to quantify the effect of nitrogen fertilization on weed interference in maize. the experimental design used was a split-plot, in randomized blocks, with four replications. the treatments consisted of five rates of n (0, 50, 100, 150 and 200 kg ha-1) and four weed control times (maize in v2, v3, v4 and v5), two more controls without and with weeds. chemical control was performed at post-emergence with association of the herbicides nicosulfuron and atrazine. the n rates influenced the determination of weed control time. when weed control was conducted at a later time, the use of high n rates minimized the negative effect of weed interference. in the absence of n application, chemical control exerts a greater influence on maize grain yield.
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