Effect of surfactant modified zeolite (SMZ) added in propagating substrate for the germination of some vegetables

Abstract

The effect of using propagating substrate (PS) as a sole growing medium, zeolite-added PS and surfactant-modified zeolite (SMZ) added PS for the germination and growth of okra (Abelmoschus esculentus), white radish (Raphanus sativus) and pakchoy (Brassica chinensis) was studied. SMZ was prepared by modifying clinoptilolite type zeolite with cationic surfactant hexadecyltrimethyl ammonium (HDTMA). SMZ can easily adsorb anionic nutrients such as phosphate, nitrate and nitrite due to HDTMA bilayer formation on zeolite surfaces that reversed negatively charged of zeolite surfaces to positive charge. This can be shown by the results in a controlled release and plant growth studies. The application of SMZ in PS reduced the amount of nutrients leached out from PS compared to zeolite added PS and only PS. The amount of nutrients in SMZ(15)-PS(50) (ratio of SMZ(15): propagating substrate (50)) showed the lowest leaching due to the greater tendency to hold the nutrients and also released them slowly. There were significant difference (P < 0.05) in growth parameters of three types of vegetables grown in different substrates. The mean of height, fresh mass and dry mass of A. esculentus, R. sativus and B. chinensis grown on SMZ(1)-PS(50) were significantly higher than those of zeolite added substrate. The results implicitly suggested that the studied plant showed better response if SMZ was used as a controlled release nutrients in propagating substrate rather than the unmodified zeolite.