Crescimento, produção e consumo hídrico do quiabeiro submetido à salinidade em condições hidropônicas

Abstract

Researches has been carried out about the use of brackish water in hydroponics. Such researches are strategic for the rational use of these waters, especially in the Brazilian Semiarid. In this context, interest arises to study regional crops with great demand and adapted to the conditions of high temperature, as the case of the okra. Okra is a culture few explored about this feasibility on hydroponic cultivation and still needs further studies to determinate this tolerance to salinity. The objective of this work was to analyze water consumption, growth, production and quality of the okra, submitted to different levels of salinity in a hydroponic system. The work was composed of two experiments. In the first one, differents genotypes were tested and their adaptation to the soilless cultivation during 60 days after seeding (DAS), it was evaluated fresh shoot mass (FSM). From experimente I the cultivar 'Speedy' was chosen, which in the second experiment was submitted to seven levels of electrical conductivity of the solution (CEsol 2,08, 4,47, 7,9, 9,46, 12,84, 14, 82, and 18.61 dS m-1). The water consumption was evaluated by daily millimetric readings of water height in the freshwater reservoir that supplied the nutrient solution, during 85 days. The efficiency of water use, dry matter (DM), plant height (H), number of leaves (NL) and leaf area (LA) were determined at 101 days after seeding (DAS). The technical viability of the okra cultivation in hydroponics is also studied. Harvesting of the mature fruits was done manually, with a typical green coloration of the mature fruits, at intervals of 2 days, during 49 days, evaluating fruit quality and yield. To evaluate the tolerance of 'Speedy' okra culture to salinity, was used mathematical models proposed by Maas and Hoffman (1977), Steppuhn et al. (2005) and the plateau model with exponential reduction. The leaf area and number of leaves were the most affected growth variables with the increase of the electrical conductivity of solution (ECsol), water consumption analysis shows a unitary linear reduction of 5.70% per unit increase (dS m-1). The water efficiency use had a maximum of 7.81 kg m-3 for ECsol of 7.08 dS m-1. The model that best explained the production was the plateau with exponential reduction with salinity threshold of 5.43 dS m-1. The fruit was the part of okra less affected by salinity.