332 resultados para Gossypium hirsutum.
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Nitrous oxide emissions were monitored at three sites over a 2-year period in irrigated cotton fields in Khorezm, Uzbekistan, a region located in the arid deserts of the Aral Sea Basin. The fields were managed using different fertilizer management strategies and irrigation water regimes. N2O emissions varied widely between years, within 1 year throughout the vegetation season, and between the sites. The amount of irrigation water applied, the amount and type of N fertilizer used, and topsoil temperature had the greatest effect on these emissions. Very high N2O emissions of up to 3000 μg N2O-N m−2 h−1 were measured in periods following N-fertilizer application in combination with irrigation events. These “emission pulses” accounted for 80–95% of the total N2O emissions between April and September and varied from 0.9 to 6.5 kg N2O-N ha−1.. Emission factors (EF), uncorrected for background emission, ranged from 0.4% to 2.6% of total N applied, corresponding to an average EF of 1.48% of applied N fertilizer lost as N2O-N. This is in line with the default global average value of 1.25% of applied N used in calculations of N2O emissions by the Intergovernmental Panel on Climate Change. During the emission pulses, which were triggered by high soil moisture and high availability of mineral N, a clear diurnal pattern of N2O emissions was observed, driven by daily changes in topsoil temperature. For these periods, air sampling from 8:00 to 10:00 and from 18:00 to 20:00 was found to best represent the mean daily N2O flux rates. The wet topsoil conditions caused by irrigation favored the production of N2O from NO3− fertilizers, but not from NH4+ fertilizers, thus indicating that denitrification was the main process causing N2O emissions. It is therefore argued that there is scope for reducing N2O emission from irrigated cotton production; i.e. through the exclusive use of NH4+ fertilizers. Advanced application and irrigation techniques such as subsurface fertilizer application, drip irrigation and fertigation may also minimize N2O emission from this regionally dominant agro-ecosystem.
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Alternaria leaf blight is the most prevalent disease of cotton in northern Australia. A trial was conducted at Katherine Research Station, Northern Territory, Australia, to determine the effects of foliar application of potassium nitrate (KNO3) on the suppression of Alternaria leaf blight of cotton. Disease incidence, severity and leaf shedding were assessed at the bottom (1-7 nodes), middle (8-14 nodes) and the top (15+ nodes) of plants at weekly intervals from 7 July to 22 September 2004. Disease incidence, severity and shedding at the middle canopy level were significantly higher for all treatments than those from bottom and top canopies. Foliar KNO3, applied at 13 kg/ha, significantly (P < 0.05) reduced the mean disease incidence, severity and leaf shedding assessed during the trial period. KNO 3 significantly (P < 0.001) reduced the disease severity and leaf shedding at the middle canopy level. Almost all leaves in the middle canopy became infected in the first week of July in contrast to infection levels of 50-65% at the bottom and top of the canopy. Disease severity and leaf shedding in the middle canopy were significantly (P < 0.05) lower in KNO 3-treated plots than the control plots from the second and third weeks of July to the second and third weeks of August. This study demonstrates that foliar application of KNO3 may be effective in reducing the effect of Alternaria leaf blight of cotton in northern Australia.
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In the northern grain and cotton region of Australia, poor crop growth after long periods of fallow, called 'long-fallow' disorder, is caused by a decline of natural arbuscular-mycorrhizal fungi (AMF). When cotton was grown in large pots containing 22 kg of Vertisol from a field recently harvested from cotton in Central Queensland, plants in pasteurised soil were extremely stunted compared with plants in unpasteurised soil. We tested the hypothesis that this extreme stunting was caused by the absence of AMF and examined whether such stunted plants could recover from subsequent treatment with AMF spores and/or P fertiliser. At 42 days after sowing, the healthy cotton growing in unpasteurised soil had 48% of its root-length colonised with AMF, whereas the stunted cotton had none. After inoculation with AMF spores (6 spores/g soil of Glomus mosseae) and/or application of P fertiliser (50 mg P/kg soil) at 45 days after sowing, the stunted plants commenced to improve about 25 days after treatment, and continued until their total dry matter and seed cotton production equalled that of plants growing in unpasteurised soil with natural AMF. In contrast, non-mycorrhizal cotton grown without P fertiliser remained stunted throughout and produced no bolls and only 1% of the biomass of mycorrhizal cotton. Even with the addition of P fertiliser, non-mycorrhizal cotton produced only 64% of the biomass and 58% of the seed cotton (lint + seed) of mycorrhizal cotton plants. These results show that cotton is highly dependent on AMF for P nutrition and growth in Vertisol (even with high rates of P fertiliser), but can recover from complete lack of AMF and consequent stunting during at least the first 45 days of growth when treated with AMF spores and/or P fertiliser. This corroborates field observations in the northern region that cotton may recover from long-fallow disorder caused by low initial levels of AMF propagules in the soil as the AMF colonisation of its roots increases during the growing season.
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Se determinó la influencia de las prácticas de rotación de cultivos y control de malezas sobre la dinámica de las malezas, y el crecimiento, desarrollo y rendimiento en el cultivo de Soya y Algodón, en terrenos del Centro Experimental del Algodón, ubicado en el municipio de Posoltega, Departamento de Chinandega, se estableció el presente ensayo durante la época de postrera de Agosto 1991 a Enero 1992. Se utilizó un diseño bifactorial en parcelas divididas en bloques completamente al azar con cuatro repeticiones siendo los factores en estudios los siguientes: Factor A: Rotación de cultivos (Soya sin inocular-Algodón, soya inoculada-algodón, soya inocutada-soya inoculada, soya sin inocular-soya sin inocular, Ajonjolí-Algodón.) Factor B: Métodos de control de malezas (Control químico, control período crítico, control limpia periódica.). Las rotaciones de soya redujeron la abundancia total de malezas predominando la especie Desmodiun canum. La menor cobertura y menor biomasa fue reflejada por la rotación Soya sin inocular-Soya sin inocular, no obstante la menor diversidad se encontró en la rotación Soya inoculada-Soya inoculada. El control limpia periódica disminuyó la cobertura y abundancia, pero presentó una biomasa intermedia respecto a los otros controles y una diversidad similar. En el cultivo de soya para la variable de altura de planta, diámetro de tallo, número de nódulos por planta y número de nudos no existen diferencias significativas, lo mismo para las variables de rendimientos. En el cultivo del algodón se obtuvo diferencias significativas para las variables de crecimiento y rendimiento. En cuanto a las variables de crecimiento y rendimiento la rotación ajonjolí-algodón reflejó los siguientes valores diámetro de tallo (4.1 mm), altura de planta (134.0 cm), rendimiento Kg/ha (1758). La rotación Soya sin inocular-Soya sin inocular reflejó diámetro de tallo (4.3 mm). altura de planta (65.7 cm) y rendimiento de 1553 kg/ha registrando los mejores resultados.
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Este estudio fue realizado en el Centro experimental de Algodón (C.E.A), Nicaragua; con el propósito de determinar el periodo crítico de competencia en algodón (Gossypium hirsutum L.) y las malezas. Dos experimentos fueron sembrados en agosto de 1991. En el experimento 1 (períodos libres de malezas) los tratamientos, 7 en total, consistieron en mantener parcelas libres de malezas desde la siembra hasta 14, 28, 42, 56, 70 días después de la siembra. Un tratamiento fue dejado enmalezado durante todo el ciclo y otro fue dejado libre de maleza. En el experimento 2 (períodos con competencia) a las malezas les fue permitido competir por diferentes períodos comenzando los controles a los 14, 28, 42, 56 y 70 días después de la siembra. un tratamiento fue dejado enmalezado durante todo el ciclo y otro fue dejado libre de maleza. Los resultados obtenidos muestran que bajo las condiciones experimentales, el algodón necesita 70 días libres de malezas para obtener buenos rendimientos y es capaz de soportar 42 días de competencia sin ver mermado sus rendimientos de manera significativa. El período crítico de competencia encuentra entre 42 y 70 días después de la siembra. El mejor resultado fue obtenido cuando las malezas fueron controladas en dos ocasiones, la primera 42 días después de la siembra y la segunda 70 días después de la siembra.
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Durante el ciclo agrícola 1988 -1989 en el centro experimental del Algodón Ubicado en la localidad de Posooltega, Chinandega se realizó un estudio con el propósito de determinar la influencia de diferentes cultivos antecedentes y métodos de control de malezas a la dinámica de las malezas y al crecimiento, desarrollo y rendimiento del cultivo del algodonero; utilizando la variedad CEA H 373.. se utilizo el diseño de parcelas divididas en bloques al azar con cuatro repeticiones y nueve tratamientos los cuales corresponden a las combinaciones de tres antecesores con tres métodos de control de malezas: se usaron los cultivos antecesores Soya sin inoculación (al), Soya inoculada (a2), Ajonjolì (a3) y los métodos de control Fluometuron 1425 cc de i.a./ha mas una limpia (b1), 2, limpia (b2) y limpias repetidas(b3). No se encontraron diferentes significativas en la influencia de los cultivos antecesores Soya sin inoculación (a1), se exibe una menor abundancia total de malezas, menor cobertura y menor biomasa permitiendo al cultivo un mejor comportamiento en su crecimiento y desarrollo. Contrario a esto el cultivo antecesor Soya sin inoculada (a2) manifestó el menor rendimiento, mayor cobertura y una abundancia total y biomasa de malezas superadas tan solo ligeramente por la originada en la influencia del cultivo antecesor Ajonjolí (a3). No hubo diferencias sustanciales en la diversidad de malezas por efecto de los diferentes cultivos procedentes como de los métodos de control de malezas. Se logró de terminar que hubo diferencias significativas en el rendimiento del algodonero en los métodos de control de malezas resultando los métodos de control químico (b1) y limpias periódicas (b3) los de mejor comportamiento. Con las limpias periódicas (b3) se produce la menor abundancia total de malezas menor a cobertura y menor biomasa. Opuesto a estos resultados, el método de una sola limpia (b2) origino la mayor abundancia total, y mayor cobertura de malezas. Al mismo tiempo este mismo método (b2) presento los menores valores para las variables de rendimientos de algodonero. Finalmente el rendimiento del algodonero se vio influenciado negativamente en 31.19 y 21.17 por la biomasa y abundancia de las malezas respectivamente.
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Se llevó a cabo el presente estudio en el centro experimental del algodón (CEA), Posoltega, con el objetivo de determinar las variedades más precoces y la fecha más óptima de siembra, manteniendo el rendimiento en el cultivo del algodón (gossypium), y observar cual es el efecto de la fecha de siembra sobre el rendimiento. Se determinó que de diez variedades, las precoces son paulikeni 73 y u-386 obteniendo su fecha media de maduración en las dos fechas con rangos de 23-25 días, se comportan como intermedias u-276, con al son y u-280 con un rango de maduración de 27-29 días en las dos fechas de siembra, el resto de variedades se consideraron como tardías, incluyendo a la variedad h-373 con rangos de maduración de 31-33 días. En la segunda fecha de siembra, obtuvieron los mejores rendimientos en producción las variedades u-280 y u-276, con respecto a la primera fecha lo obtuvieron h-373 (testigo), seguida de las variedades u-280 y u-276.
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Tesis (Doctorado en Ciencias con especialidad en Biotecnología) U.A.N.L., Facultad de Ciencias Biológicas, 2007.
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Response of cotton (Gossypium hirsutum L. cv. NIAB-78) to salinity, in terms of seed germination, seedling root growth and root Na+ and K+ content was determined in a laboratory experiment. Cotton seeds were exposed to increasing salinity levels using germination water with Sodium chloride concentrations of 0, 50, 100, 150 and 200 mM, to provide different degrees of salt stress. Germinated seeds were counted and roots were harvested at 24, 48, 72 and 96 h after the start of the experiment. It appeared that seed germination was only slightly affected by an increase in salinity (in most cases the differences between treatment were non-significant), whereas root length, root growth rate, root fresh and dry weights were severely affected, generally highly significant differences in these variables were found for comparisons involving most combinations of salinity levels, in particular with increased incubation period. K+ contents decreased with increasing salinity levels, although differences in K+ content were only significant when comparing the control and the 4 salinity levels. Na+ content of the roots increased with increasing levels of NaCl in the germination water, suggesting an exchange of K+ for Na+. The ratio K+/Na+ strongly decreased with rising levels of salinity from around 4.5 for the control to similar to 1 at 200 mM NaCl.
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Com o objetivo de determinar os efeitos de períodos de controle e de convivência das plantas daninhas na produtividade da cultura do algodoeiro (Gossypium hirsutum), cultivar Delta-Opal, realizou-se um experimento que constou de dois grupos de tratamentos. No primeiro, a cultura permaneceu livre da competição das plantas daninhas desde a emergência até 7, 14, 21, 28, 35, 42, 49, 56, 63 dias e colheita (159 dias). No segundo, a cultura permaneceu em competição com a comunidade infestante desde a emergência até os mesmos períodos descritos para a primeira série de tratamentos. Dentre as espécies de plantas daninhas encontradas na área experimental, destacaram-se a tiririca (Cyperus rotundus), o fedegoso (Senna obtusifolia), a anileira (Indigofera hirsuta) e o capim-carrapicho (Cenchrus echinatus). Pelas condições edáficas, climáticas e florísticas sob as quais foi conduzida a cultura de algodão, o Período Anterior à Interferência (PAI) dessa comunidade que reduziu em 5% a produtividade da cultura foi de oito dias após a emergência da cultura (DAE); o Período Total de Prevenção da Interferência (PTPI) foi de 66 DAE; e o Período Crítico de Prevenção da Interferência (PCPI) foi dos 8 aos 66 DAE.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Estudou-se os efeitos de herbicidas, isolados ou combinados, na cultura do algodão (Gossypium hirsutum L.) e eficiência no controle das plantas daninhas. O experimento foi conduzido na Fazenda de Ensino e Pesquisa da Faculdade de Engenharia de Ilha Solteira - UNESP em solo Latossolo Vermelho Escuro franco argilo-arenoso, localizada no município de Selvíria, Estado de Mato Grosso do Sul, Brasil. Os tratamentos testados com as doses em kg i.a/ha foram: alachlor a 2,15 e 2,58 em pré-emergência (pré), trifluralina a 0,96 em pré-plantio incorporado ao solo (ppi) isolada ou combinada com MSMA a 1,89, ou bentazon a 0,72 ou diuron a 1,20 em pós-emergência (pós) em jato dirigido, MSMA a 2,52 em pós, linuron a 1,0 em pré diuron a 1,6 em pré ou pós e testemunhas com e sem capina. O delineamento experimental utilizado foi o de blocos ao acaso com doze tratamentos e quatro repetições. As aplicações em ppi e a semeadura foram realizadas dia 11. 12.81 e as em pré dia 18.12.81, com um pulverizador costal de pressão constante (CO2) de 30 1b/pol2, com barra de quatro bicos tipo leque Albuz verde e consumo de calda de 250 l/ha. As aplicações em pós foram realizadas. no dia 27.12.81, com o mesmo pulverizador com um bico tipo defletor, polijet azul, com protetor de jato, com pressão de 40 1b/pol2 e consumo de 500 I/ha. As espécies dominantes foram capim - colchão (Digitaria sangnalis (L.) Scop) e caruru (Amaranthus viridis L.) que foram excelentemente controladas, até 90 dias após a semeadura, por alachlor, diuron em pré, trifluralina + diuron, que reduziram mais de 80% do peso da biomassa seca da parte aérea destas. Os herbicidas não causaram fitotoxicidade à cultura. A presença das plantas daninhas reduziu em 58,9% a produção de algodão em caroço.
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The cotton disease known as angular leaf spot, caused by Xanthomonas axonopodis pv. malvacearum (Xam) has been causing cotton losses in several producing regions around the world. Xam is transmitted by seeds, which may be infected both externally and internally. Infected seeds constitute the main long-distance dissemination mode of the pathogen. In view of this, the use of healthy seeds is a must. To accomplish that, detection methodologies for the bacteria must be developed be used in seed health analysis laboratories. This study aimed to develop a semi-selective medium for Xam detection in cotton seeds. The semi-selective culture medium was named MSSXAN and it was consisted of peptone (5.0 g), beef extract (3 g), sucrose (5 g), soluble starch (10 g), agar (15 g), CaCl 2 (0.25 g), Tween 80 (10 mL), distilled water (1,000 mL), crystal violet solution at 1% (150 μL), cephalexin (50 mg 1*), methyl thyophanate (10 mg*) and chlorothalonil (10 mg*) - *added after culture medium autoclaving. This MSSXAN medium shows low repressiveness to Xam and it be used for isolation of this bacteria in cotton seeds health analysis. © 2009 Academic Journals Inc.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)