Manejo cultural da mamoeira: época de plantio, irrigação, espaçamento e competição de cultivares.

Abstract

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 Ceará, 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.