The use of organic materials as fertilizer and their degree of maturity can generate positive or negative effects on the germination and growth of crops. The maturation and stabilization of these organic materials can avoid the generation of phytotoxic effects on the seeds. In addition to this, the use of dilutions for these organic fertilizers can greatly reduce these negative effects on the germination and growth of the seeds. An evaluation trial of three commercial organic fertilizers was established at the Cryobiology Laboratory of the University of Panama, to study the phytotoxic effect of diluted extracts from organic fertilizers using the phytotoxicity test on lettuce seeds as a bioindicator plant and using different components and degrees of stabilization and their dilutions on the relative germination percentage, the relative root growth and the germination index of lettuce plants. The results obtained showed that the organic fertilizer from poultry manure with non-stabilized sawdust (T3) diluted to 25% was the best response for the growth variablesevaluated in the plant, followed by the pelletized fertilizer from poultry and bovine manure (T2) diluted to 25%. This indicates that the 25% dilution of immature organic fertilizers decreases their phytotoxic effect by reducing the presence of harmful compounds on sensitive seeds such as lettuce. This evaluation procedure for organic fertilizers is fast, economical and allows the safe use of composting products available on the market.
