Risco climático do cultivo da mamoeira em Estados do Nordeste brasileiro.

Abstract

Nowadays, there is an increasing necessity of new energy sources. The renewable sources, like biodiesel, appears as a clean and efficient solution to suppliment the future energy demands. In this context, castor bean, has assumed a prominent place in the world. It's characteristic of easy adaptation in semi-arid regions, and the quality of its oil are responsible for the worldwide interest in the cuítivation of the castor beans. Because of its high temperature requirement, the castor bean is very well adapted to the tropical regions. Thus, the Northeast Brazil shows up as a great castor bean seed-producing region. Having, however, most of this region is susceptible to a great instability in the pluviometric behavior. The instability of the pluviometric behavior brings uncertainties about the unirrigated plantation, conducing the farmers to suffer great losses in the plantations. Considering such characteristics, through an agroclimatologic zoning, the identification of the suitable áreas for planting and the determination of the probable time for the beginning of the Castor bean's plantation were done for the unirrigated regime, in the states of Pernambuco, Paraíba and Rio Grande do Norte. At each selected locality growing periods of castor beans are determined using averages and Markov chain probabilities of available soil moisture. Using these results, áreas suitable for the plantation of castor beans are determined. The results showed an accentuated restriction of soil water availability to castor beans culture. It was verified that, for the leveis of CAD considered and considering the altitude limitation to castor bean plantation, most of the state of Paraíba, doesn't present an adequate soil moisture condition to supply the needs of the castor beans in the whole criticai period of its development cycle. Irrigation is necessary in most of the localities in the state except for the localities of Araruna and Alagoa Nova, at ali leveis of CAD and Olho d'água district at CAD i50, CAD2oo and CAD250 leveis. The state of Pernambuco, presented more favorable conditions, to the cuítivation of castor beans under unirrigated regime, in the "Agreste", an area that surrounds Cortês, Maraial and Jucati districts, and a small area near Machados district at CAD100, CAD150 and CAD200 leveis, at CAD250, there is a small area to the North of the "Sertão", surrounding São José do Belmonte and the "Agreste" excluding Caruaru district. In Rio Grande do Norte the production of the castor beans in unirrigated regime, for ali the leveis of CAD, should be restricted to a small area in the Southwest of the state near São Miguel district and a small area near Coronel Ezequiel. The practice of the supplemental irrigation is essential for the viability of this activity in the other áreas of the state.