Critical periods of weed control in naturally green colored cotton BRS Verde

Cotton with naturally colored fiber is increasing as a commercial crop due specially to its textile processing with reduced environmental impact, as dying is not necessary. The critical period of weed control and the weed community were studied in a field with the naturally green colored fiber cv. BRS Verde cultivated in Missao Velha, Brazil. Without weed control during all the cycle, a reduction of 82.9% in yield was observed. The critical period of weed control was between 31 and 74 days after emergence for a reduction of 5% in yield. The weed community was composed of 21 species, with higher relative importance and dominance of monocotyledonous species. The beginning of the critical period was found to be more influential on yield than the ending. Thus, defining the right moment to start weed control can be more important to yield than determining the moment to cease it. (C) 2011 Elsevier B.V. All rights reserved

Selectivity of Pre and Postemergence Herbicides in Single or Combined Applications in Castor Crop

One of the main challenges in castor crop (Ricinus communis L.) production is efficient weed management mainly due to limited options of selective herbicides. This study evaluated the selectivity of herbicides applied alone or in combination in pre- and postemergence applications in castor crop. Two field experiments were carried out under irrigation conditions in a semi-arid region of Northeast Brazil. It was found that the visual symptoms of phytointoxication of the herbicides used on castor were mild in both experiments. Consequently, there were no significant interferences on plant height, number of racemes, and grain (seed) yield. Pre-emergence applications (g ha−1) of trifluralin (1800), pendimethalin (1500), clomazone (750), clomazone + trifluralin (750 + 1800), and clomazone + pendimethalin (750 + 1500) followed by chlorimuron-ethyl in postemergence (15 g ha−1) are selective to castor. The application (g ha−1) of pendimethalin + clomazone (1000 + 500) in pre-emergence, associated with chlorimuron-ethyl (10 and 15), metamitron (2800 and 4200), ethoxysulfuron (60 and 80), or halosulfuron-methyl (75 and 112.5) in one or two applications in postemergence, as single or split applications, in an interval of 14 days, are selective to castor crop

Semillas de Spondias tuberosa oriundas de frutos cosechados en cuatro estadios de maduración y almacenadas

Las condiciones climatológicas que son peculiares de la región semiárida ofrece de forma natural plantas propicias a la explotación humana, las cuales se destaca la Spondias tuberosa Arruda Câmara, cuyo fruto es cosechado de forma extractivita y desordenada, poniendo en riesgo su perpetuación. El propósito de esta investigación fue analizar el tiempo de almacenamiento de semillas, el ambiente y el estadio de maduración del fruto que sea más adecuado a una buena propagación de esa especie fructífera. El ensayo se llevó a cabo en casa de vegetación del Centro de Ciencias Agrarias, CCA, Areia, PB. Se utilizó un diseño experimental de bloques al azar, en esquema factorial 5 x 2 x 4, con cuatro repeticiones. Las variables estudiadas fueron el porcentaje de germinación, vigor, número de brotes, altura de plantas, diámetro y longitud de túbera. Semillas mantenidas bajo condiciones ambientes, durante ocho meses de almacenamiento alcanzaron mayor uniformidad de germinación, potencial germinativo (90%) y vigor (0,505). Las semillas más adecuadas a la optimización de buena germinación fueron aquéllas oriundas de frutos maduros (87%) y muy maduros (90%)

Períodos de interferência das plantas daninhas na cultura do girassol em Rondônia Periods of weed interference in sunflower crop in Rondônia

Objetivou-se, neste trabalho, determinar os períodos de interferência das plantas daninhas na cultura do girassol e seus efeitos sobre o diâmetro do capítulo, teor de óleo, rendimento de óleo e produtividade. Adotou-se o delineamento experimental de blocos ao acaso com três repetições. Os tratamentos foram distribuídos em esquema fatorial 2 x 2 x 5, sendo os fatores: cultivares (Embrapa 122 e Hélio 358), modalidade de competição (na presença e na ausência de plantas daninhas) e períodos de convivência ou controle das plantas daninhas da emergência aos 15, 30, 45, 60 e 110 dias. As variáveis mensuradas foram diâmetro de capítulo, teor de óleo, rendimento de óleo e produtividade. As plantas daninhas interferem negativamente no diâmetro do capítulo, produtividade e rendimento de óleo, mas o convívio com as mesmas aumentou o teor de óleo das sementes, além de reduzir em 76,83 e 92,68% a produtividade dos cultivares Embrapa 122 e Hélio 358, respectivamente. Admitindo-se uma perda de 10% na produtividade, o período anterior à interferência (PAI), o período total de prevenção a interferência (PTPI) e o período crítico de prevenção e interferência (PCPI) para a cultivar Embrapa 122 foram de 16; 37 e 21 dias, respectivamente. Para o híbrido Hélio 358 o PAI, o PTPI e o PCPI foram de 24; 43 e 19 dias, respectivamente.<br>The objective of this study was to determine the periods of weed interference in sunflower cultivation, and its effects on the head diameter, oil content, oil yield and its productivity. The experimental design was in the randomized blocks with three replications. The treatments were arranged in a factorial 2 x 2 x 5, with the following factors: cultivar (Embrapa 122 and Hélio 358), modality of competition (in the presence and absence of weeds) and periods of coexistence and control of weed from the emergence until the 15, 30, 45, 60 and 110 days. The measured variables were head diameter, oil content, oil yield and productivity. Weeds interfere negatively in the head diameter, in the productivity, and in the yield of oil, but the coexistence with the weeds increases the oil content of seeds, as well as reduces in 76.83 and 92.68% the productivity of cultivars Embrapa 122 and Hélio 358, respectively. Assuming a 10% loss in productivity, the PAI, PTPI and the critical period of prevention and interference (PCPI) for the cultivar Embrapa 122 were 16, 37 and 21 days, respectively. For the hybrid Hélio 358 the period before interference (PAI), the PTPI and the PCPI were 24, 43 and 19 days, respectively

Adubação do algodão colorido BRS 200 em sistema orgânico no Seridó Paraibano Fertilization of colored cotton BRS 200 under organic system in Serido, in the State of Paraiba, Brazil

É grande a potencialidade do algodão colorido para ser cultivado organicamente na região semi-árida, onde as condições edafoclimáticas possibilitam o cultivo sem defensivos agrícolas. Os adubos orgânicos têm sido utilizados para melhorar as propriedades físico-químicas do solo, o estabelecimento de microrganismos benéficos e o aumento da matéria orgânica, além de ser fonte de nutrientes. O objetivo deste trabalho foi determinar níveis e forma de aplicação do esterco bovino em algodoeiro colorido BRS 200-marrom, cultivado sob manejo orgânico nas condições edafoclimáticas do Seridó Paraibano. O experimento foi conduzido em blocos ao acaso, com nove tratamentos e quatro repetições, nos anos 2000, 2001 e 2002. Os tratamentos se originaram de um fatorial (4 x 2+1), cujos fatores foram quatro níveis de esterco bovino curtido (10, 20, 30 e 40 t ha-1) em dois locais de aplicação (abaixo e ao lado das sementes), adicionado de uma testemunha absoluta sem adubação orgânica. A presença do esterco bovino incrementou a produtividade do algodão. Quando ocorreu regularidade climática, a aplicação ao lado das sementes foi mais eficiente, alcançando-se o máximo rendimento com 30 t ha-1. A uniformidade do comprimento da fibra decresceu e o índice de fibras curtas aumentou com o incremento dos níveis de adubo.<br>The naturally colored cotton has potentiality for growth in Northeast Semi-arid, where the edaphoclimatic conditions permit the cultivation without agrochemicals. Organic fertilizers have been used to improve physico-chemical properties of the soil, establishment of beneficial microorganisms, increase of the organic matter and nutrients. The objective of this work was to determine levels and forms of application of cattle manure in colored cotton BRS 200, cultivated under organic management in Seridó, in the State of Paraiba. The experiment was conducted in randomized blocks, with nine treatments and four replications, during 2000, 2001 and 2002. The treatments were originated from a factorial 4x2+1, consisting of four levels of decomposed cattle manure (10, 20, 30 and 40 t ha-1) and two sites of application (below and by the side of seeds), plus an absolute control without organic manure. Organic fertilization increased the cotton yield. Under regular climatic conditions, the sidewise application was more efficient, reaching the maximum yield with 30 t ha-1. The uniformity of fiber length decreased and the index of short fibers increased with the increment of the levels of organic manure