Influência da distribuição espacial do milho e da Brachiaria brizantha consorciados sobre a população de plantas daninhas em sistema plantio direto na palha

O cultivo consorciado de milho com forrageiras tropicais no sistema plantio direto na palha pode diminuir a incidência de plantas daninhas em decorrência da elevada produção de fitomassa e da alelopatia proporcionada pela deposição superficial de palha no solo. Este trabalho objetivou avaliar a influência da distribuição espacial da cultura do milho com Brachiaria brizantha, cultivados em consórcio no sistema plantio direto na palha, sobre a população de plantas daninhas. O experimento foi instalado em condições de campo, nos anos agrícolas 2002/03 e 2003/04, na Fazenda Experimental Lageado, em Botucatu-SP. O delineamento experimental foi o de blocos casualizados em esquema fatorial simples 2 x 4, com quatro repetições. Os tratamentos foram dois espaçamentos entre linhas de milho (E1-45 cm e E2- 90 cm) e quatro modalidades de cultivo (MCS - cultivo do milho solteiro; MBL - cultivo do milho com B. brizantha na linha de semeadura; BEM - cultivo do milho com B. brizantha na entrelinha; e MBLE - cultivo do milho com B. brizantha simultaneamente na linha e na entrelinha). Foram avaliados a produtividade de matéria seca da forrageira, a caracterização fitossociológica, a incidência e o controle de plantas daninhas. O cultivo MBLE a 90 cm foi a modalidade de consorciação que proporcionou maior produção de palhada. A presença de B. brizantha em cultivo consorciado diminuiu a densidade de plantas daninhas. A utilização do cultivo consorciado do milho com B. brizantha na linha+entrelinha proporcionou índice de controle de 95%, independentemente do espaçamento utilizado.

Rikastuspajaa ja purkuistuntoa

Liite: TAMK maakunnassa

Pianon huippuosaajat kesäkurssilla : kohtauspaikkana Mänttä

Liite: TAMK maakunnassa

Työelämän kumppani maakunnassa

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Avoin AMK kaikille avoin opintopolku

Liite: TAMK maakunnassa

Milho (Zea mays) como espécie bioindicadora da atividade residual de (imazethapyr+imazapic)

Este estudo teve como objetivo avaliar a atividade residual, no solo, do herbicida (imazethapyr+imazapic) aplicado na cultura de arroz irrigado, instalado pelo sistema Clearfield® e tendo como planta bioindicadora o milho, cv. Biomatrix 2202. Os trabalhos foram realizados em casa de vegetação da Universidade Federal de Pelotas, Capão do Leão-RS. O arroz, cv. IRGA 422 CL, foi semeado em caixas de polietileno (60 x 40 x 20 cm). Quando o arroz estava em estádio de 3 a 4 folhas, foram aplicados os tratamentos com o herbicida (imazethapyr+ imazapic) a 0; 25+75; 37,5+112,5; e 50+150 g ha-1, que corresponderam a 0, 100, 150 e 200 g ha-1 no produto formulado. Após a colheita do arroz, o solo foi mantido sem irrigação por 45 dias, quando então foi semeada aveia-preta (Avena strigosa), colhida no início da primavera. Aos 360 e 540 dias após a aplicação dos tratamentos (DAA), foi transferido o solo das caixas de polietileno para dois conjuntos de vasos, onde foi semeado milho, os quais passaram respectivamente a ser identificados como experimentos safra (E1) e safrinha (E2). Nos primeiros 360 e 540 dias entre a aplicação dos herbicidas e a semeadura dos dois experimentos, o solo do E2 permaneceu sem irrigação. As plantas de milho foram colhidas, em estádios de 4 a 5 folhas. As variáveis avaliadas foram: massas secas dos sistemas radical e aéreo, altura de planta e índice de área foliar, sendo esta última avaliada somente no E2. Os dados experimentais foram submetidos à análise de variância (<0,05); havendo significância, eles foram testados por modelos de regressão polinomial. Foram observadas reduções significativas nas massas secas de raiz e parte aérea, altura de planta e área foliar do milho, cv. Biomatrix 2202, semeado até 540 DAA do herbicida (imazethapyr+imazapic) na cultura do arroz, demonstrando que o milho pode ser utilizado como indicador da atividade desse herbicida no solo.

Weed community and growth under the canopy of trees adapted to the brazilian semi-arid region

The objectives of this work were to evaluate the floristic composition and dry biomass of weeds under the canopy of seven perennial species adapted to the Semi-Arid region of Brazil, and correlate these characteristics with growth traits of the perennial species. The following perennial species were evaluated in two experiments (E1 and E2): mesquite (Prosopis juliflora), jucá (Caesalpinia ferrea), white popinac (Leucaena leucocephala), mofumbo (Combretum leprosum), neem (Azadirachata indica), sabiá (Mimosa caesalpiniaefolia) and tamarind (Tamarindus indica). In E1, the seven species were evaluated in a random block design with four replicates and nine plants per plot. In E2, evaluation comprised four species (mesquite, jucá, white popinac, and tamarind) in a random block design with eight replicates and nine plants per plot. A circle with an area of 1.77 m² was established around the trunk of each plant, two years after they were transplanted to the permanent location. The weeds collected within this circle were cut even with the ground, classified and weighed. At this time, plant height, and crown and stem diameters were evaluated in all trees of each plot. In E1 there were no differences between tree species as to weed frequency under their canopies; however, weed growth was smaller under the canopy of sabiá trees. Mesquite and sabiá had the greatest plant height and crown diameter means, but only sabiá had the greatest stem diameter. In E2, the perennial species were not different with regard to weed frequency and growth under their canopies, but mesquite had the greatest growth, as measured by plant height (with significant results for jucá as well) and crown and stem diameter.

Multispecies weed competition and their economic threshold on the wheat crop

Two field experiments were conducted to evaluate the effects of multispecies weed competition on wheat grain yield and to determine their economic threshold on the crop. The experiments were conducted in 2002, on two sites in Iran: at the Agricultural Research Station on Ferdowsi University of Mashhad (E1) and on the fields of Shirvan's Agricultural College (E2). A 15 x 50 m area of a 15 ha wheat field in E1 and a 15 x 50 m area of a 28 ha wheat field in E2 were selected as experimental sites. These areas were managed like other parts of the fields, except for the use of herbicides. At the beginning of the shooting stage, 30 points were randomly selected by dropping a 50 x 50 cm square marker on each site. The weeds present in E1 were: Avena ludoviciana, Chenopodium album, Solanum nigrum, Stellaria holostea, Convolvulus spp., Fumaria spp., Sonchus spp., and Polygonum aviculare. In E2 the weeds were A. ludoviciana, Erysimum sp., P. aviculare, Rapistrum rugosum, C. album, Salsola kali, and Sonchus sp. The data obtained within the sampled squares were submitted to regression equations and weeds densities were calculated in terms of TCL (Total Competitive Load). The regression analysis model indicated that only A. ludoviciana, Convolvulus spp. and C. album, in E1; and A. ludoviciana, S. kali, and R. rugosum, in E2 had a significant effect on the wheat yield reduction. Weed economic thresholds were 5.23 TCL in E1 and 6.16 TCL in E2; which were equivalent to 5 plants m-2 of A. ludoviciana or 12 plants m-2 of Convolvulus spp. or 19 plants m-2 of C. album in E1; and 6 plants m-2 A. ludoviciana, 13 plants m-2 S. kali and 27 plants m-2 R. rugosum in E2. Simulations of economic weed thresholds using several wheat grain prices and weed control costs allowed a better comparison of the experiments, suggesting that a more competitive crop at location E1 than at E2 was the cause of a lower weed competitive ability at the first location.

Weeds under the canopies of tree species submitted to different planting densities and intercropping

Assessing the growth and floristic composition of species that grow under the canopy of trees is important for weed control (WC). The objective of this study was to assess two experiments (E1 and E2), when the trees were two years and one year of age, respectively. In E1, sabiá (S) and gliricidia (G) were submitted to planting densities from 400 to 1.200 plants ha-1. In E2, growing systems consisting of S, G, and neem (N) combinations were compared: SSS, GGG, NNN, GSG, NSN, SGS, NGN, SNS, and GNG (each letter represents a row of plants). A random block design was adopted, with three (E1) and four (E2) replicates. In E1, treatments were arranged as split-plots (species in plots). In E2, the degrees of freedom for treatments (8) were partitioned into growing systems (treatments that involved the same species) and between growing system groups (2). Twenty-one weed species were found in E1. Gliricidia attained greater plant height than sabiá, but these species did not differ in canopy diameter, number of weed species per plot, and weed green and dry biomass of the shoot. Higher planting densities resulted in the reduction of all those traits. Twenty-six weed species were found in E2. Growing systems that included gliricidia showed canopies with greater diameters than growing systems that included neem. There were no differences between growing systems for number of weed species per plot and for weed green and dry biomass of the shoot.