Cultural handling of the mamoneira: time of plantation, irrigation, espaÃamento and competition to cultivate.

A mamoneira à uma planta oleaginosa arbustiva, e o Ãleo de suas sementes possui inÃmeras aplicaÃÃes industriais. Contudo, na atualidade tem-se dado Ãnfase ao seu emprego na produÃÃo de combustÃvel renovÃvel (biodiesel). O que reveste a cultura de grande importÃncia econÃmica e ambiental. Desse modo, foram conduzidos dois ensaios experimentais durante os anos de 2003, 2004 e 2005, com o objetivo de avaliar o comportamento da mamoneira cultivada em diferentes Ãpocas, espaÃamentos e sob condiÃÃes irrigadas e de sequeiro. Os trabalhos foram conduzidos na Fazenda Experimental Vale do Curu, que pertence ao Centro de CiÃncias AgrÃrias da Universidade Federal do CearÃ. No primeiro experimento a mamoneira cv. âBRS 149 Nordestinaâ foi semeada em quatro Ãpocas, combinadas com dois regimes de irrigaÃÃo. No segundo experimento, foram testadas duas cultivares (BRS 149 Nordestina e Mirante 10) semeadas em trÃs espaÃamentos e em duas Ãpocas distintas. Verificou-se que a antecipaÃÃo da semeadura para janeiro de 2004 com o uso da irrigaÃÃo promoveu incrementos na produtividade de grÃos e no nÃmero de racemos por planta, os quais possuem maior tamanho, peso e nÃmero de frutos. A suplementaÃÃo hÃdrica foi mais vantajosa no inÃcio do crescimento da cultura do que apÃs o tÃrmino da estaÃÃo chuvosa. As sementes dos racemos secundÃrios e terciÃrios possuem maior teor de Ãleo e massa de sementes. No experimento de 2005 foram obtidos os seguintes resultados: a Ãpoca de plantio associada à irrigaÃÃo promoveu aumentos da altura da planta, do nÃmero de ramos laterais e do nÃmero de internÃdios, alÃm de retardar o florescimento e aumentar a produtividade de grÃos. O nÃmero de racemos e de frutos por racemo reduziu com o plantio de sequeiro. Os racemos que mais contribuÃram com a produtividade total foram os secundÃrios seguidos dos terciÃrios. A cv. Nordestina apresentou maior massa e teor de Ãleo das sementes do que a cv. Mirante 10. Em mÃdia sob condiÃÃes irrigadas a massa das sementes aumentou, independente do espaÃamento ou da cultivar utilizada. Por outro lado, a antecipaÃÃo do plantio associada à irrigaÃÃo reduziu o teor de Ãleo das sementes.The castor bean is an oil seed crop, and the oil present in the seeds has several industrial applications. Recently it has been suggested to be used as a renewable fuel (Biodiesel). As a consequence the crop has assumed a relevant ecological and economic importance. Two field studies were conducted in 2003, 2004 and 2005, with the objective of evaluating the behavior of castor bean grown at different times and spacing and under irrigated and rainfed conditions. The experiments were carried out at the "Fazenda Experimental do Vale do Curu", belonging to the Universidade Federal do CearÃ, Brazil. In the first experiment the castor plant cv. BRS 149 Nordestina was sown at four different times of planting combined with two irrigation regimes. In the second experiment, two cultivars were evaluated (BRS 149 Nordestina and Mirante 10) seeded in three plant spacing and two different times. Irrigation was more profitable at the beginning of the cycle, prior the rain season than at the end of the rain period, at the end of the plant growth cycle. The combination of the anticipation of the sowing in January of 2004 with the use of irrigation promoted increments in the seed yield and number of racemes for plant and higher weight and number of fruits per raceme. Irrigation yielded better results when was associated with the earliness of planting, as compared with application of water at the end of the raining season. The seeds of the secondary and tertiary racemes possessed greater oil content and seeds weigh. When sowed in December of 2003 the primary racemes produced very light seeds. In the experiment of 2005 the following results were observed: the combination of anticipation of sowing with irrigation promoted increases of the height of the plant, number of lateral branches and the number of internodes, delayed flowering and increased grain yield. Under rain red conditions the number the number of fruits per raceme was reduced. Secondary racemes were responsible for the higher proportion of total seed yield, followed by the tertiary racemes. The cv. BRS 149 Nordestina showed higher seed weigh and oil content. Under irrigation condition the weigh of the seeds increased, independent of the spacing or cultivar used. The early planting associated with the irrigation practice reduced the oil content of the seeds