Use of composed fertilizers in floating system.

摘要

In floating system, a soilless cultivation technique very interesting for the low installation and running costs, the employment of composed ready-to-use fertilizers may simplify considerably the preparation of the nutrient solution. Normally, in soilless systems the nutrient solution is prepared mixing and diluting concentrated solutions (generally not less than three), previously made using numerous single mineral salts and acids. In the trials described in this paper, some leafy vegetables were grown in floating system with a nutrient solution prepared using either single mineral salts (standard nutrient solution) or composed fertilizers. In the first trial, carried out in spring, loose-leaf lettuce (Lactuca sativa L. subsp. secalina), leaf beet (Beta vulgaris L. var. cycla) and rocket (Eruca sativa Miller) were grown, and Osmocote Start 12+11+17+2MgO+microelements, a controlled release fertilizer, was used as composed fertilizer. In the second trial, carried out in autumn, only rocket was grown and two composed fertilizers were used: Osmocote Start and Plant Prod 15+15+30+microelements, a water soluble fertilizer. With Plant Prod rocket provided the same yield obtained with the standard nutrient solution and a significant reduction of leaf nitrate content was achieved. Osmocote Start when used in spring did not cause differences in plant growth respect to the standard nutrient solution for any of the tested species, while in autumn (rocket cultivation) it caused a reduction of leaf fresh matter production. Probably, such reduction was due to a release rate, which is temperature-dependant, too slow to support suitably plant growth. In rocket plants grown with Osmocote Start leaf nitrate content decreased strongly compared to the plants grown both with the standard nutrient solution and with Plant Prod.