Estresse hídrico em fases fenológicas do cajueiro anão precoce em ambiente protegido.

Abstract

The cashew (Anacardium occidentale L.) plant is a native tropical species of Brazil, it is dispersed in almost all territory. Since from 1975, the cultivation of this fruit is considered of socioeconomic importance in the Northeast Brazil, principally in the States of Ceara, Piaui and Rio Grande do Norte. In Paraiba, most of the planting is still using seed, characterized by an accentuated genetic variability accompanied by low productivities, however, the increase of the cultivated area of cashew, as well as the increase of the intensive use of water of good quality, reduces its availability. Thus, there is need to accomplish a study to evaluate the water necessity of the precocious dwarf cashew (CCP 76), as well as to observe in which phenological phase the crop is more sensitive to the stress provoked by water deficit. The experiment was conducted during November 1, 2005 to November 1, 2006, in a protected ambient belonging to Department of Agricultural Engineering/CTRN/UFCG. The treatments consisted of the combinations among four irrigation depths (L1 = 40, L2 = 55, L3 = 70 and L4 = 85% of the ETc) distributed in three different stages (A. from transplanting until the flowering; B. from flowering until the beginning of the production; C - during production), besides a control, where the plants were not submitted to any water stress during the whole period. Drip irrigation system was used to apply water, for each plant three autocompensating dripperswere used for irrigation, corresponding to a total discharge of 6,9 L h"1 of water. During the study, at intervals of 30 days, the evaluations of the growth and physiological variables were made; the production variables were studied starting from the 300 days after transplanting. The growth variables curves of the plants stressed during the production phase had behavior similar to control; the physiological variables (quantum efficiency of the photosystem II and the resistance of stomata) were affected significantly only by the factor phenological phases; the plants which suffered water deficit during the flowering phase presented better indices of production, surpassing the control, except for the variables regarding the number of fruits for plant and ºBrix.