The research was conducted on broccoli, lettuce and celery on the circulatory system of hydroponics which grows vegetables in the nutrient solution of the Horticulture Research Institute. Seven studied substrates included: (1) - Substrate from soil Institute (for reference - called the original substrate); (2) - Smoked rice husk substrate; (3) - Coconut fiber substrate; (4) - Mixture of 50 percent smoked rice husk and 50 percent original substrate; (5) - Mixture of 50 percent coconut fiber and 50 percent original substrate; (6) - Mixture of 50 percent smoked rice husk and 50 percent coconut fiber substrate; (7) - Mixture of 1/3 original, 1/3 smoked rice husk and 1/3 coconut fiber substrate. The research results revealed that different kinds of substrates have different effects on the growth, productivity and quality of broccoli, lettuce and celery. Broccoli, lettuce and celery grown on all seven studied substrates have lower levels of nitrate, lead and cadmium than the standard level, which means they are much safer for customers. The best result can be found in the mixture of 50 percent of the original substrate and 50 percent of coconut fiber substrate for all broccoli, lettuce and celery. To be more specific, the productivity was 29.3 quintal/1000 m2 for broccoli (17.2 percent higher than the reference); 28.2 quintal/1000 m2 for lettuce (8 percent higher than reference) and 25.8 quintal/1000 m2 for celery (15.2 percent higher than reference).
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