Germinação e crescimento inicial da mamoeira irrigada com águas salinas.

Abstract

Being the castor bean a plant with satisfactory production capacity under low precipitation conditions it is an important alternative for the Brazilian semi-arid. In this region, with loss in the castor bean, crop yield, in comparison to other crops may be considered resistant to adverse climate, constituting thus one of the few alternatives of work and income for the farmers of the region. Although it is tolerant to drought, its cultivation is encouraged under irrigation, because usually the irrigation is the only way to guarantee the agricultural production in tropical areas of hot and dry climate, as is the case of the semi-arid Brazilian Northeast An appropriate irrigation management is necessary to prevent salinity problems; most of the available irrigation waters contains high salt, being frequently found values of the order of 0.2 to 5.0 dS m"1. Furthermore, being a plant of vigorous and easy propagation, little is known about its management. Considering the lack of information regarding the effects of the salinity on different phenologic phases and on the production, the present study aims to verify the use of saline water in the castor bean crop variety BRS 149-Nordestina, in its germination phase and initial growth. The study was conducted in the greenhouse of the Agricultural Engineering Department of the Center of Sciences and Technology of the Federal University of Campina Grande, during the period of July to September of 2003. The experimental design adopted was a randomized block, consisting of the combination of five levels of salinity of the irrigation water (Ni=0,7; N2=l,7; N3=2,7; N4=3,7 and N5=4,7 dS m"1) and five proportions between Na:Ca (PIi=9,5:0,5; PI2=7,5:2,5; PI3=5,0:5,0; PI4=2,5:7,5; e Pl5=0,5:9,5), factorily-combined resulting in 25 treatments, with three replications. The experiment lasted 80 days. The salinity did not influence the variables such as, the percentaage of germination, dry phytomass of root, leaf area ratio and photosynthesis efficiency JJ. The number of leaves, plant height, leaf * area, stem diameter, dry aerial phytomass during the cycle and water consumption had a linear decrease with the increase of electrical conductivity of the irrigation water. The root/aerial part ratio and the tension of water retention in leaves increased linearly with the salinity stress. The plant height and aerial phytomass were influenced positively with the decrease of Na and the increase of Ca in the irrigation water.