Adriano Jakelaitis

Manejo de plantas daninhas no consórcio de milho com capim-braquiária (Brachiaria decumbens)

The objective of this work was to evaluate the effects of nicosulfuron and atrazine mixture on weeds, corn and Brachiaria decumbens intercrops, cultivated under no-tillage and conventional tillage. Six nicosulfuron doses (0, 2, 4, 8, 16 and 24 g ha-1) in mixture with atrazine in the dose of 1.500 g ha-1 were evaluated, plus two controls, represented by both species in monocrop. Seminiferous propagation of the annual weeds was efficiently controlled by applying nicosulfuron in 8 g ha-1 in mixture with atrazine, regardless of the management systems. The perennial species (Artemisia verlotorum and Cyperus rotundus), of vegetative propagation, were not controlled by the herbicide mixture, regardless of the applied dose. Larger infestations of these species were observed under the conventional system. B. decumbens biomass was reduced in the intercrop with corn, when compared to its control in monocrop, presenting a greater reduction when submitted to the largest doses of nicosulfuron, in both planting systems. No difference was observed in the production of grains and corn straw, in function of the treatments studied, under both planting systems.

Dinâmica populacional de plantas daninhas sob diferentes sistemas de manejo nas culturas de milho e feijão

Com o objetivo de avaliar a dinâmica populacional de plantas daninhas por meio de parâmetros fitossociologicos, realizou-se este trabalho com as culturas de milho e feijao em cultivos sucessivos, no periodo de novembro de 1998 a maio de 2001, em um Argissolo Vermelho-Amarelo Câmbico, fase terraco, em Vicosa-MG. A comunidade de plantas daninhas era composta por Amaranthus deflexus, Brachiaria plantaginea, Cyperus rotundus, Galinsoga parviflora, Mucuna aterrima e Oxalis latifolia. Os tratamentos foram constituidos de dois sistemas de manejo do solo (plantios convencional e direto) e duas finalidades de uso da cultura do milho (grao e silagem), em blocos com quatro repeticoes. No plantio convencional, antes da semeadura das culturas, o solo foi arado e gradeado, e, no plantio direto, foi realizada a dessecacao das plantas daninhas com herbicidas sistemicos. As avaliacoes de plantas daninhas na cultura do milho foram realizadas antes e apos a aplicacao dos herbicidas nicosulfuron e atrazine em pos-emergencia (aos 20 e 55 DAE, respectivamente) no ano agricola 1999/00, e apos a aplicacao de atrazine e metolachlor em pre-emergencia (aos 20 DAE) em 2000/01. Em se tratando do feijoeiro, as avaliacoes tambem foram feitas antes e apos a aplicacao dos herbicidas fluazifop-p-butil e fomesafen, em pos-emergencia aos 20 e 40 DAE, respectivamente. A dinâmica populacional foi avaliada por meio do uso de parâmetros fitossociologicos baseados na densidade, frequencia e biomassa das especies amostradas. Verificou-se aos 20 DAE, antes da aplicacao dos herbicidas em ambas as culturas (milho e feijao), maior densidade e importância relativa das especies dicotiledoneas no plantio direto. No plantio convencional constatou-se maior densidade, dominância e importância relativa de Cyperus rotundus. Apos aplicacao dos herbicidas seletivos, Cyperus rotundus foi a especie de maior importância relativa em todos os sistemas estudados. Em ambas as finalidades de uso do milho, Cyperus rotundus teve sua populacao reduzida no plantio direto, quando comparado com o convencional.

Efeitos de sistemas de manejo sobre a população de tiririca

Em experimento conduzido em campo, de novembro de 1998 a maio de 2001, sobre Argissolo Vermelho-Amarelo Câmbico de alta fertilidade, em Vicosa-MG, foram avaliados os efeitos de sistemas de manejo do solo na populacao de tiririca (Cyperus rotundus). Na area experimental, antes da instalacao do experimento predominava infestacao alta (720 ± 130 plantas m-2) de tiririca. Os tratamentos foram constituidos de dois sistemas de manejo do solo (plantios convencional e direto) e duas finalidades de uso da cultura do milho (grao e silagem), cultivados com feijao de outono-inverno em sucessao a cultura do milho, em blocos com quatro repeticoes. No plantio convencional, antes da semeadura das culturas, o solo foi arado e gradeado, e, no plantio direto, foi realizada a dessecacao das plantas daninhas com glyphosate + 2,4-D. As avaliacoes das manifestacoes epigeas da tiririca na cultura do milho ocorreram aos 20 e 55 dias apos a emergencia (DAE) no ano agricola 1999/00 e aos 20 DAE em 2000/01 e, para o feijoeiro, aos 20 e 40 DAE. A avaliacao do banco de tuberculos foi realizada apos a colheita do milho, no ultimo ano de conducao, determinando-se a densidade, a biomassa e a porcentagem de brotacao dos tuberculos coletados. Verificou-se reducao das manifestacoes epigeas da tiririca no sistema de plantio direto em ambas as finalidades de uso da cultura do milho durante todo o periodo de conducao do ensaio. Tanto no milho cultivado para grao quanto para silagem, constatou-se elevada reducao do banco de tuberculos no plantio direto, com predominio de tuberculos dormentes, em relacao ao plantio convencional.

Atividade microbiana do solo após aplicação de herbicidas em sistemas de plantio direto e convencional

This study evaluated the effect of the herbicides fluazifop-p-butyl and fomesafen in five concentrations (0.0; 1.05; 2.10; 4.20 and 8.40 µg g-1) and their mixture (Robust®) on microbial activity in soil submitted to no-tillage system (NTS) and conventional planting system (CPS). Samples in Erlenmeyer of 250 mL were treated with herbicide and wetted to field capacity. After every four days, microbial respiration was quantified through CO2 left by the soil. Metabolic quotient (qCO2) and carbon of microbial biomass (CMB) were determined 20 days after incubation. Under NTS, microbial activity increased with fluazifop-p-butyl and decreased with up to 4.20 µg g-1 of fomesafen. Herbicide effect on soil microbial respiration and CMB under CPS was below that observed under NTS.CMB increased with the increase of fluazifop-p-butyl concentration and decrease of fomesafen concentration. The mixture (Robust®) did not influence CMB under NTS, but it was reduced under CPS in higher concentrations. Under NTS, qCO2 increased with the herbicide concentrations, without, however, varying between them. Under CPS, herbicide mixture provided a higher qCO2. In general, the herbicides provided a negative effect on microbial biomass, proportional to the concentrations applied, being smaller in soil under NTS than in soil under CPS.

Effects of herbicide and insecticide interaction on soil entomofauna under maize crop

Abstract The aim of this study was to evaluate the impact of the herbicide mixture nicosulfuron+atrazine, with or without the insecticide chlorpyrifos, onto soil entomofauna under maize crop. The treatments, applied 25 days after maize emergence, were represented by a weeded control without insecticide and herbicide, a weeded control with chlorpyrifos, and mixtures of nicosulfuron+atrazine, with or without chlorpyrifos. Arthropods populations, on the soil surface, as well as inside the soil under maize, were principally represented by mites (Arachnida: Acari), decomposer collembolans (Hexapoda:Parainsecta:Collembola) and predator ants (Hymenoptera:Formicidae). The nicosulfuron+atrazine mixture with chlorpyrifos and the isolated chlorpyrifos reduced the population dynamics of all insect groups on the soil surface compared to the weeded control. In the soil, mite and ant populations were reduced after application of the herbicide mixture with chlorpyrifos and of the isolated chlorpyrifos.The aim of this study was to evaluate the impact of the herbicide mixture nicosulfuron + atrazine, with or without the insecticide chlorpyrifos, onto soil entomofauna under maize crop. The treatments, applied 25 days after maize emergence, were represented by a weeded control without insecticide and herbicide, a weeded control with chlorpyrifos, and mixtures of nicosulfuron + atrazine, with or without chlorpyrifos. Arthropods populations, on the soil surface, as well as inside the soil under maize, were principally represented by mites (Arachnida: Acari), decomposer collembolans (Hexapoda:Parainsecta:Collembola) and predator ants (Hymenoptera:Formicidae). The nicosulfuron + atrazine mixture with chlorpyrifos and the isolated chlorpyrifos reduced the population dynamics of all insect groups on the soil surface compared to the weeded control. In the soil, mite and ant populations were reduced after application of the herbicide mixture with chlorpyrifos and of the isolated chlorpyrifos.

Ação de herbicidas sobre o crescimento de estirpes de Rhizobium tropici

This work aimed to evaluate the growth of Rhizobium tropici BR322 and BR 520 strains, used as inoculant on common bean in Brazil, in yeast extract manitol (YM) medium supplemented with different herbicides (bentazon, metolachlor, imazamox, fluazifop-p-butyl, fomesafen and paraquat). Fluazifop-p-butyl and fomesafen were evaluated pure and in a commercial mixture with concentration varying from 0.0 to 49.23 mg L-1. Cell growth was assessed by optic density readings in a spectrophotometer at 560 nm, being later converted to colony forming units per mL. Paraquat caused higher inhibition of cell growth, followed by the commercial mixture fomesafen and fluazifop-p-butyl. For the other herbicides, growth reduction was not significant. In general, BR 520 strain was more tolerant to the tested herbicides, except to paraquat. The herbicide concentration I50, (which decreased Rhizobium growth in 50%) could not be determined in the fomesafen concentrations tested, isolated or mixed to fluazifop-p-butyl. The highest reduction of 31.1% was observed in BR322 at the maximum tested concentration of the commercial mixture.

Controle de Digitaria horizontalis pelos herbicidas glyphosate, sulfosate e glifosate potássico submetidos a diferentes intervalos de chuva após a aplicação

The effectiveness of sulfosate, potassium glyphosate and different glyphosate formulations on Digitaria horizontalis was evaluated when the products were applied in post emergence conditions and the plants were submitted to 20 mm simulated rainfall during 50 minutes, at intervals of 1, 2, 4 and 6 hr after herbicide application. The experiment was carried out under greenhouse conditions from January to April 2000, in Vicosa, Minas Gerais, Brazil, arranged in a split split-plot randomized block design with four replications. The phytotoxic effect of the herbicides on D. horizontalis was evaluated at 3, 7, 14, 21 and 28 DAA (days after application). At 45 DAA, the shoot dry biomass was compared to the control (without herbicide). No differences were observed among potassium glyphosate, sulfosate and glyphosate formulations (Roundup Transorb®) for similar application conditions. These treatments provided lower regrowth of D. horizontalis, when the interval without rain following application was of 46 hr. Glyphosate SL and WG formulations were the most affected by rainfall in all the intervals evaluated, when compared to other herbicide treatments.

Cultivares de milho e de gramíneas forrageiras sob monocultivo e consorciação

The purpose of this study was to evaluate the performance of maize and forage grass ( Brachiaria brizantha and Panicum maximum ) cultivars under monocropping and intercropping systems. The experiment was carried out in randomized complete blocks, in a 3x4 + 7 factorial design, with four replications. The first factor consisted of three maize cultivars (AL Bandeirantes, an open pollination variety; AG 2040, a double cross; and Pioneer 30F87, a triple cross) and the second one included four forage cultivars (Marandu and Xaraes, from B. brizantha , and Tanzânia and Mombaca, from P. maximum ). The seven additional treatments consisted of the respective tested cultivars monocroppings. Maize and forage grasses were sown simultaneously, the first in rows, spaced 1.0 m apart, and the second by throwing. Hybrid Pioneer 30F87 maize yields were the highest ones, for both monocropping and intercropping systems, and maize affected dry weight gain of forages, when compared to the monocropping system. For intercropping, P. maximum forage cultivars were the most productive ones, while, for monocropping, the Mombaca cultivar presented the highest dry matter production level. KEY-WORDS: Zea mays ; Brachiaria brizantha ; Panicum maximum ; agriculture and livestock integration; pasture.

Efeitos de mistura de herbicida com inseticida sobre a cultura do milho, as plantas daninhas e a lagarta-do-cartucho

This study aimed to evaluate the effect of the tank mixture of the herbicide nicosulfuron with the insecticide chlorpirifos on the maize hybrid P30F80, weeds, and fall armyworm. The experiment was arranged in a randomized complete block design, in a 5x2+3 factorial scheme and four replications. The first factor consisted of nicosulfuron doses (0, 10, 20, 30, and 40 g ha-1) + atrazine (1.200 g ha-1) + oil (900 g ha-1) and the second of doses of the insecticide chlorpirifos (0 and 240 g ha-1). Three additional treatments were evaluated: two controls, with and without weeding, both without insecticide, and one control with weeding and insecticide. The interaction between the doses of nicosulfuron and chlorpirifos in the control of the fall armyworm was not significant. The chlorpirifos-nicosulfuron tank mixture was non-selective for the maize hybrid P30F80, reducing the number of ears and maize grain yield. Chlorpirifos did not interfere in the efficiency of weed control by the herbicides 14 and 28 days after application of these products. However, the toxicicity caused to the maize plant by the chlorpirifos-nicosulfuron tank mixture contributed to reducing the crop control of Ipomoea grandifolia and Brachiaria decumbens by maize.

Population dynamics of weeds in no-tillage and conventional crop systems

Abstract Population dynamics of weeds in successive maize and bean crops were evaluated in two soil management systems (conventional and no-tillage), for two maize applications (grain and silage), and in four consecutive growing seasons. Every year, conventional tillage consisted in plowing and harrowing before sowing. In no-tillage, chemical weed desiccation was made with the mixture glyphosate+2.4-D. To control weeds, the mixture fluazifop-p-butil+fomesafen was applied on the bean crop in all the planting seasons, and the herbicides nicosulfuron+atrazine on maize after crop emergence (1998–1999, 1999–2000, 2001–2002) and atrazine+metolachlor before emergence (2000–2001). Purple nutsedge (Cyperus rotundus) was the most important species under conventional soil tillage; while in no-tillage the dicotyledonous weed species (Amaranthus deflexus, Bidens pilosa, Euphorbia heterophylla, Galinsoga parviflora Ipomoea grandifolia) were the most relevant. Regardless of the maize use, the C. rotundus population and tuber bank, with prevailingly dormant tubers, was considerably reduced in no-tillage compared with the conventional system.