The 2011 ASHS Annual Conference

The use of organic and inorganic media in hydroponic production of vegetables has increased significantly because substrates facilitate the management of plants, since growing crops is more difficult when cultivated in soil. In the present study we evaluated the effect of five substrates [volcanic rock (tuff), perlite, two kinds of coir (one from Mexico and another from Sri-Lanka) and pine sawdust] on growth and production of two tomato cultivars (Caiman F1 and Tequila F1). Treatments were set in a completely randomized design with four replicates; the parameters measured included the volume of irrigation and leacheate water. Leacheate pH, electrical conductivity (EC) and temperature were also measured. The leaching fraction and water consumed by plants were calculated, as well as leaf area, total dry mass, and fruit yield. Compared to irrigation solutions, leachate water exhibited significant substrate effects on EC (from 1.73 to 2.53 dS·m^-1) and pH (from 6 to 7.3). Pine sawdust showed the highest difference in pH and EC between irrigation and leacheate water. The leaching fraction and water consumed by plants were affected according to the developmental stage as well as to substrate type. There was a significant direct correlation between pH and fruit yield. In Caiman F1 there was a significant positive effect of pH on total dry mass. There was a significant negative correlation between the leaching fraction and fruit yield. EC and temperature in nutrient solution had no significant effects on leaf area, dry mass, and fruit yield in the substrates evaluated.