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Phalaris brachystachys (short-spiked canary grass) is considered to be among the most troublesome cereal weeds in Mediterranean areas. A bioeconomic model, based on population dynamics, competition and economic sub-models, was developed to simulate the long-term economic consequence of using herbicide-based strategies: no herbicide application, full herbicide dose (standard rate) and two reduced dose rates (75 and 50% of the standard rate) to control P. brachystachys in a biennial wheat-sunflower rotation. Simulation results indicated that only herbicide application at a full dose (90% control) and 3/4 dose (80% control) produced positive economic results, with the full dose being the best strategy (EUR 98.65 ha-1 year-1). A sensitivity analysis showed that the economic outcome, in terms of annualized net return, was strongly influenced by changes in yield, price, and fixed costs. In addition, the annualized net return was more sensitive to parameter changes at reduced herbicide doses than at full rate. In the wheat-sunflower rotation system, the application of the full dose of herbicide was the most economical and stable strategy in the long-term. Reduced doses are not a recommended option from an economic point of view. Bioeconomic models provide practical insight into different management approaches for effective weed control.

RESUMO

Mulching use in agriculture has been known since 1802 as the practice of spreading dry leaves and straw on the soil to prevent erosion and water loss. Our study evaluated the mulch effectiveness in the establishment of regenerating seedlings and its contribution to the control of exotic grasses. The studies were carried out in an ecological restoration area in the municipality of Itapira-SP. The treatment with mulching consisted in chemical desiccation with glyphosate herbicide application, keeping the dry grass on the ground. In the control treatment, after chemical weeding, the grass was removed with manual mowing, exposing the soil. Eight months after implantation, we sampled all regenerating seedlings in 100 plots of 50 x 50 cm in each treatment. We considered as seedlings all individuals of tree species less than 100 cm tall. We calculated richness, abundance, similarity, and the relationship of the frequency of seedlings to the height of the mulch. We sampled eight species with 42 seedlings, with only one not identified. The highest abundance and species richness were found in the treatment with mulch (n = 34 individuals; eight species), the most abundant being Schinus terebinthifoliaRaddi (14 individuals) followed by Solanum mauritianumScop. (11 individuals), and Platypodium elegansVog. (three individuals). The presence of exoticgrasses was lower in the plots of the mulching (13%) compared to the control treatment (67%). The highest frequency of seedlings was obtained with mulch height from 21 to 37 cm. We suggest that adaptive management practices, such as the use of the mulching technique, can be implemented in ecological restoration areas, because they favor the natural regeneration of native seedlings and can contribute to the control of exotic grasses, but the height of the layer must be controlled.(AU)

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The aim of this study was to assess the effect of increasing periods of coexistence of weed plants with Urochloa ruziziensis on the canopy structure and productivity of a pasture already established with this forage species. The experiment was a randomized blocks design with four replications, and treatments consisted of seven increasing periods of coexistence of forage grass with weed plants: 0 (control), 15, 30, 45, 60, 75 and 90 days after regrowth (DAR). The main morpho-structural and productive characteristics of the forage plants were determined at the end of the experimental period (90 DAR). The ratio of the first green leaf height to the tiller height increases, while the leaf to stem ratio diminishes as the period of interaction with the infesting community increases. The number of green leaves per tiller and the tiller height diminishes as the period of coexistence with weed plants increases. The presence of weed plants interferes negatively with all parameters of the grass canopy structure and productivity of a grazing land already established with Urochloa ruziziensis, suggesting that measures of control of the infesting community should be adopted up to 17 days of regrowth of the forage plant.(AU)

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This study aimed to evaluate the impacts of different forage cutting intensities, obtained by grazing simulation, on the floristic diversity and productivity of a pasture cultivated with spreading liverseed grass. The experiment was set up in a randomized block design, with four replications and treatments arranged in a 5×2 factorial scheme, with five levels of cutting intensity of the simulated grazing (0, 25, 50, 75, and 95% of the forage canopy) associated with two levels of weed coexistence (presence and absence). The evaluations of floristic diversity, number of individuals, and total dry matter of weeds were obtained at 15, 30, 45, 60, and 90 days after grazing simulation (DAGS). All plots were evaluated at the end of the experimental period (90 DAGS) for the amount of dry biomass produced by the pasture. The results showed that higher forage cutting intensities, obtained by grazing simulation, increased the floristic diversity, the number of individuals, and the dry matter accumulated by weeds in a pasture grown with spreading liverseed grass, reducing by up to 56% theproduction of total dry matter of the forage.

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This study aimed to evaluate the impacts of different forage cutting intensities, obtained by grazing simulation, on the floristic diversity and productivity of a pasture cultivated with spreading liverseed grass. The experiment was set up in a randomized block design, with four replications and treatments arranged in a 5×2 factorial scheme, with five levels of cutting intensity of the simulated grazing (0, 25, 50, 75, and 95% of the forage canopy) associated with two levels of weed coexistence (presence and absence). The evaluations of floristic diversity, number of individuals, and total dry matter of weeds were obtained at 15, 30, 45, 60, and 90 days after grazing simulation (DAGS). All plots were evaluated at the end of the experimental period (90 DAGS) for the amount of dry biomass produced by the pasture. The results showed that higher forage cutting intensities, obtained by grazing simulation, increased the floristic diversity, the number of individuals, and the dry matter accumulated by weeds in a pasture grown with spreading liverseed grass, reducing by up to 56% theproduction of total dry matter of the forage.(AU)

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In ecological restoration, one of the main challenges is to develop new methods, techniques, and incentives that both favour and reduce maintenance costs in restoration projects. Besides, post-planting maintenance is often neglected hampering seedling survival over time owing to alien grasses, which compete strongly with native plants for resources. To solve these issues, recently, an innovative technology called Nucleário has been developed in Brazil. Aiming to hinder alien competition filters, the Nucleário also attempts to condition a better microenvironment, reducing drought stress through the water storage tank, decreasing temperatures, which facilitates the survival and growth of seedlings in areas under restoration. Another method used to decrease alien grasses, which is inexpensive, is seedling crowning using cardboard lowing maintenance needs in restored areas. Cardboard has similar functions to Nucleário, such as protecting soil against loss of water and nutrients and reducing competition with invasive exotic grasses. Therefore, comparing them also with traditional manual weeding (i.e., clean-weeded crown by hoe), we aimed to verify which technique is most cost-efficient for seedling crown maintenance of Dipteryx alata Vog., which is an indigenous tree species with high economic value owing to its nuts. We tested three techniques in areas under restoration in the Cerrado, in the Environmental Protection Area "Córrego Guariroba" located in Campo Grande, Mato Grosso do Sul, Brazil. We monitored seedlings submitted to the three methods in the wet and the dry periods for biotic (competition with exotic grasses, herbivory, and growth) and abiotic (moisture and soil temperature) indicators. We observed that the Nucleário was the treatment that maintained the highest soil moisture, resulting in a larger canopy area. However, these effects do not reflect increases in the survival rate, diameter, and height of the seedlings. None of the treatments was effective in reducing herbivory. Nucleário was the most effective treatment in reducing the competition of seedlings with invasive grasses. Cardboard presented an implementation value 21.5 times lower than Nucleário and 1.2 times than manual crowning. Given the high purchase price, the Nucleário's cost-benefit ratio was very high compared to the crowning of cardboard and the manual weeding, which discourages us from recommending it for this species with high survival rates. Its project can be revised to decrease herbivory rates, as well as its efficiency tested in the short and long term in different ecosystems and species, particularly species susceptible to water stress.

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Um dos fatores que comprometem o rendimento do algodoeiro cultivado, mesmo em cultivo em diferentes épocas de semeadura, é a interferência exercida pelas plantas daninhas. O objetivo desse trabalho foi avaliar o desenvolvimento inicial do algodoeiro quando submetido à competição com gramíneas. Foi realizado um experimento com delineamento inteiramente casualizado em esquema fatorial de 3x5, sendo elas, Urochloa brizantha cv. Marandu e Piatã e Urochloa ruziziensis; e com cinco densidades de plantio, ou seja, ausência de gramínea, 163,53; 81,79; 54,51 e 40,88 cm² para cada planta de gramínea e com cinco repetições, totalizando 75 parcelas ou vasos. Após 30 dias da semeadura foram determinados os seguintes parâmetros: ISPADAL – índice spad do algodoeiro; CEAL – condutância estomática do algodoeiro; APAL e APG – altura de planta do algodoeiro e gramínea; NFAL – número de folhas do algodoeiro; MSPAAL e MSPAG – massa seca da parte aérea do algodoeiro e gramínea; MSRAL e MSRG – massa seca de raiz do algodoeiro e gramínea. O desenvolvimento inicial do algodoeiro foi comprometido com a presença das gramíneas do gênero Urochloa. É necessário o controle de gramíneas do gênero Urochloa na cultura do algodoeiro. A espécie Urochloa ruziziensis causou mais danos na cultura do algodoeiro.

One of the factors that compromise the yield of cultivated cotton, even in cultivation at different sowing times, is the interference exerted by weeds. The objective of this work was to evaluate the initial development of cotton when submitted to grass competition. An experiment was carried out with a completely randomized design, in a factorial scheme of 3x5, being Urochloa brizantha cv. Marandu and Piatã and Urochloa ruziziensis and with five planting densities, that is, absence of grass, 163,53; 81.79; 54.51 and 40.88 cm² for each grass plant and with five replications, totaling 75 plots or vessels. After 30 days of sowing, the following parameters were determined: ISPADAL - cotton spad index; CEAL - stomatal conductance of cotton; APAL and APG - plant height of cotton and grass; NFAL - number of cotton leaves; MSPAAL and MSPAG - dry mass of the aerial part of the cotton and grass; MSRAL and MSRG - dry mass of cotton and grass roots. The initial development of the cotton plant was compromised with the presence of grasses of the genus Urochloa. It is necessary the control of grasses of the genus Urochloa in the cotton crop. The Urochloa ruziziensis species caused more damage to the cotton crop.

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RESUMO

Um dos fatores que comprometem o rendimento do algodoeiro cultivado, mesmo em cultivo em diferentes épocas de semeadura, é a interferência exercida pelas plantas daninhas. O objetivo desse trabalho foi avaliar o desenvolvimento inicial do algodoeiro quando submetido à competição com gramíneas. Foi realizado um experimento com delineamento inteiramente casualizado em esquema fatorial de 3x5, sendo elas, Urochloa brizantha cv. Marandu e Piatã e Urochloa ruziziensis; e com cinco densidades de plantio, ou seja, ausência de gramínea, 163,53; 81,79; 54,51 e 40,88 cm² para cada planta de gramínea e com cinco repetições, totalizando 75 parcelas ou vasos. Após 30 dias da semeadura foram determinados os seguintes parâmetros: ISPADAL índice spad do algodoeiro; CEAL condutância estomática do algodoeiro; APAL e APG altura de planta do algodoeiro e gramínea; NFAL número de folhas do algodoeiro; MSPAAL e MSPAG massa seca da parte aérea do algodoeiro e gramínea; MSRAL e MSRG massa seca de raiz do algodoeiro e gramínea. O desenvolvimento inicial do algodoeiro foi comprometido com a presença das gramíneas do gênero Urochloa. É necessário o controle de gramíneas do gênero Urochloa na cultura do algodoeiro. A espécie Urochloa ruziziensis causou mais danos na cultura do algodoeiro.(AU)

One of the factors that compromise the yield of cultivated cotton, even in cultivation at different sowing times, is the interference exerted by weeds. The objective of this work was to evaluate the initial development of cotton when submitted to grass competition. An experiment was carried out with a completely randomized design, in a factorial scheme of 3x5, being Urochloa brizantha cv. Marandu and Piatã and Urochloa ruziziensis and with five planting densities, that is, absence of grass, 163,53; 81.79; 54.51 and 40.88 cm² for each grass plant and with five replications, totaling 75 plots or vessels. After 30 days of sowing, the following parameters were determined: ISPADAL - cotton spad index; CEAL - stomatal conductance of cotton; APAL and APG - plant height of cotton and grass; NFAL - number of cotton leaves; MSPAAL and MSPAG - dry mass of the aerial part of the cotton and grass; MSRAL and MSRG - dry mass of cotton and grass roots. The initial development of the cotton plant was compromised with the presence of grasses of the genus Urochloa. It is necessary the control of grasses of the genus Urochloa in the cotton crop. The Urochloa ruziziensis species caused more damage to the cotton crop.(AU)

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To evaluate the effects of herbicide rate, cultivar, and spatial pattern on rice grain yield and weed suppression, a field experiment was conducted on a lowland rice field at the Rice Research Station of Tonekabon, north of Iran, in 2011. The experimental design was a split plot-factorial where the whole plot portion was a randomized complete block with three replicates. Main plots were pretilachlor rates (0, 0.5, 1, 1.5, 2 L ha-1 of pretilachlor). The subplots were factorial combinations of two crop spatial patterns (uniform and wide-row planting patterns, 20× 20 and 30 × 13 cm, respectively) and two traditional rice cultivars ('Hashemi' and 'Deylamani'). Regardless of cultivar and spatial pattern, rice grain and biological yields, panicle number per m2, leaf area index, and herbicide efficacy increased, while weed biomass decreased with increasing pretilachlor application rate. Rice grain and biological yields, panicle number per m2, leaf area index, and herbicide efficacy were significantly greater in uniform planting pattern than in wide-row planting pattern when averaged over cultivars and pretilachlor rates. Moreover, uniform planting pattern of rice plants suppressed weeds 39% better than wide-row planting pattern as averaged across pretilchlor rates and cultivars. 'Deylamani' produced grater grain and biological yields, panicle number per m2, leaf area index than 'Hashemi' as averaged across pretilachlor rates and spatial patterns. This experiment illustrated that uniform spatial pattern increased weed suppression, herbicide efficacy, and grain yield.

Para avaliar os efeitos da taxa de herbicida, cultivar e padrão espacial em arroz produção de grãos e supressão de plantas daninhas , um experimento de campo foi realizado em um campo de arroz irrigado na Estação de Pesquisa do Arroz de Tonekabon , norte do Irã, em 2011. O delineamento experimental foi uma fração de lote - fatorial, onde toda a parte de enredo foi em blocos casualizados com três repetições. As parcelas foram as taxas pretilaclor (0, 0.5, 1, 1.5 , 2 L ha-1 de pretilaclor) . As subparcelas foram combinações fatoriais de dois padrões de culturas espaciais (uniformes e padrões de plantio em toda a linha, 20 × 20 e 30 × 13 cm , respectivamente) e duas cultivares de arroz tradicionais (' Hashemi ' e ' Deylamani ') . Independentemente de cultivar e padrão espacial , grãos de arroz e os rendimentos biológicos , número de panículas por m2 , o índice de área foliar e eficácia do herbicida aumentou, enquanto a biomassa de plantas daninhas diminuiu com o aumento da taxa de aplicação pretilaclor . O grão de arroz e os rendimentos biológicos , número de panículas por m2 , o índice de área foliar e eficácia do herbicida foram significativamente maiores no padrão de plantio uniforme do que em toda a linha de plantio padrão quando calculados sobre cultivares e taxas pretilaclor . Além disso, o plantio uniforme padrão de plantas de arroz suprimida ervas daninhas 39% melhor do que em toda a linha de plantio padrão como média entre as taxas de pretilchlor e cultivares . ' Deylamani "produzido grão ralador e os rendimentos biológicos , número de panículas por m2 , índice de área foliar do que" Hashemi ", como média entre as taxas de pretilaclor e padrões espaciais. Este experimento mostrou que padrão espacial uniforme aumento supressão de plantas daninhas , eficácia do herbicida , e rendimento de grãos.

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A interferência de plantas daninhas na cultura do girassol pode reduzir significativamente a produtividade de aquênios. O objetivo deste trabalho foi determinar o período anterior à interferência e o período total de prevenção à interferência da comunidade infestante sobre a produtividade de aquênios e rendimento de óleo da cultura do girassol. O experimento foi conduzido em campo, no município de Botucatu (SP), no ano agrícola de 2007/2008. O delineamento experimental foi o de blocos casualizados, com quatro repetições. Os tratamentos foram compostos por parcelas constituídas por períodos de controle e de presença de plantas daninhas. Para os períodos de controle, a cultura foi mantida livre das plantas daninhas pelos períodos crescentes de 7, 14, 21, 28, 35, 42, 49 e 110 dias após a emergência (DAE) do girassol. Para os períodos de convivência, a cultura foi mantida na presença da comunidade infestante pelos mesmos períodos. Foram avaliadas as seguintes variáveis: diâmetro de capítulos, produtividade de aquênios, rendimento de óleo de girassol, densidade e matéria seca das plantas daninhas. O período anterior à interferência foi de 35 DAE da cultura para a produtividade de aquênios, sendo que o período total de prevenção à interferência estendeu-se até 24 DAE. Para o rendimento de óleo, o período anterior à interferência foi de 25 DAE, enquanto que o período total de prevenção à interferência prolongou-se por 14 DAE.

The interference of weeds in sunflower cultivation can significantly reduce the productivity of achenes. The objective of this study was to determine the period before interference and total period of interference of the weed community on productivity and achene oil of sunflower cultivation. The experiment was conducted under field conditions in the fieldin Botucatu (SP) in the 2007/2008 agricultural year. The experimental design was a randomized complete block with four replications. The treatments were composed of portions represent periods of control and presence of weeds. For control periods, the culture was kept free of weeds by increasing periods of 7, 14, 21, 28, 35, 42, 49 and 110 days after the emergence (DAE) of sunflower. For periods of coexistence, the culture was maintained in the presence of the weed community for the same periods. We assessed the following variables: diameter of chapters, achene yield, oil yield of sunflower, density and dry matter of weeds and phytosociological indices. The period before the interference was 35 DAE culture to the productivity of achenes, and the total period of interference lasted until 24 DAE. For oil yield, the period before the interference was 25 DAE, whereas the total period of interference lasted for 14 DAE.

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This study aimed to evaluate the effects of plant densities of Urochloa decumbens on the early growth of Corymbia citriodora. The experimental design was completely randomized design with four replications, each plot consisted of a of 60 L capacity vase. The signal grass densities were 0, 20, 40, 80 and 160 plants m-2, along with one eucalyptus plant. At the end of eight months of living together increase in height and in diameter and plant dry mass of eucalyptus and signal grass were carried out. The eucalyptus characteristics were influenced by all the weed populations, the effect being more pronounced with the increasing of grass density.

O presente estudo teve como objetivo avaliar os efeitos da convivência de densidades crescentes de plantas Urochloa decumbens no crescimento inicial de plantas de Corymbia citriodora. O delineamento experimental adotado foi inteiramente casualisado, com quatro repetições; cada parcela constou de um vaso de 60 L de capacidade. As densidades de capim-braquiária foram: 0, 20, 40, 80 e 160 plantas m-2, juntamente com uma planta de eucalipto. Foram realizadas, ao final de oito meses de convivência, as avaliações de: incremento em altura e em diâmetro e massa seca das plantas de eucalipto e de capimbraquiária. Para todas as características estudadas a população infestante influenciou no desenvolvimento das plantas de eucalipto, sendo o efeito mais acentuado à medida que se aumentou a densidade de plantas de capim-braquiária.

RESUMO

This study aimed to evaluate the effects of plant densities of Urochloa decumbens on the early growth of Corymbia citriodora. The experimental design was completely randomized design with four replications, each plot consisted of a of 60 L capacity vase. The signal grass densities were 0, 20, 40, 80 and 160 plants m-2, along with one eucalyptus plant. At the end of eight months of living together increase in height and in diameter and plant dry mass of eucalyptus and signal grass were carried out. The eucalyptus characteristics were influenced by all the weed populations, the effect being more pronounced with the increasing of grass density.

O presente estudo teve como objetivo avaliar os efeitos da convivência de densidades crescentes de plantas Urochloa decumbens no crescimento inicial de plantas de Corymbia citriodora. O delineamento experimental adotado foi inteiramente casualisado, com quatro repetições; cada parcela constou de um vaso de 60 L de capacidade. As densidades de capim-braquiária foram: 0, 20, 40, 80 e 160 plantas m-2, juntamente com uma planta de eucalipto. Foram realizadas, ao final de oito meses de convivência, as avaliações de: incremento em altura e em diâmetro e massa seca das plantas de eucalipto e de capimbraquiária. Para todas as características estudadas a população infestante influenciou no desenvolvimento das plantas de eucalipto, sendo o efeito mais acentuado à medida que se aumentou a densidade de plantas de capim-braquiária.