Racionalização do uso de nutrientes para o cultivo hidropônico do tomateiro

Abstract

Hydroponics cultivation of tomato plants requires research to improve qualitative and quantitative factors involved in the productive process. The aim of this work was to study development of three commercial cultivars of Lycopersicon esculentum grown in different concentrations of Hoagland nutrient solution. The experiment was conducted in a greenhouse at Soil Department of UFRRJ, Seropédica (RJ), using the Nutrient Film Technique system (NFT). Two tomato cultivars of determined growth known as UC-82 and Saladinha and another one of undetermined growth named T-93 were supplied with 50 %, 75 % and 100 % Hoagland nutrient solution. Temperature and relative humidity in the greenhouse and the pH and electric conductivity of nutrient solutions were monitored. Two experiments were set in the greenhouse. In the first, it was evaluated the vegetative growth of young plants of UC-82 cultivar by determining the fresh and dry mass accumulation as well as the NO3 -, amino-N and soluble sugars concentration in the shoot tissues. In the second experiment it was evaluated the vegetative and reproductive growth of UC-82, Saladinha and T-93 cultivars. In this experiment it was determined the fresh and dry mass accumulation in the shoot, the fruit fresh mass, the number of fruits per plant, total fresh mass per plant, the concentration of soluble solutes (oBrix) and productivity. In the climatic conditions of Seropédica, critical environmental factors such as temperature and relative humidity reached extreme values during the day time. This indicates the need of some device to improve the thermal balance in the greenhouse. The vegetative growth of UC-82 cultivar was better in 75 % ionic strength in both experiments. The Saladinha cultivar surpassed the other cultivars in final height, fresh and dry mass accumulation in the shoots and productivity in all treatments. The nutrient concentrations poorly influenced the vegetative growth of Saladinha and T-93 cultivars. The lowest productivity was found in the UC-82 cultivar. Plant productivity was strongly dependent on the genotype. On the other hand, the nutrient solution with 75 % of ionic strength tended to increase the number of fruits per plant in Saladinha and T-93 cultivars thus positively affecting plant productivity. In the conditions of this study, high irradiance and temperatures, the 75% strength Hoagland solution showed to be more adequate for growth and productivity in all studied cultivars. The Saladinha cultivar was the most productive in the NFT system in the climatic conditions of Baixada Fluminense region.