Αξιολόγηση ποιοτικών χαρακτηριστικών βιολογικών και συμβατικών σπορόφυτων με τη μέθοδο της επίπλευσης

Abstract

Float system as a method of development of seedlings in organic agriculture is a relatively newone and it is characterized by profitability and sustainability. The two “key” factors thatdiscriminate the organic form the conventional float system nursery are the fertilization and plantprotection.The first series of experiments were focused on the effects of three substrates (mixture ofpeat-vermiculite in portions 2:1, 1:1 and 1:2) on the growth of tomato and lettuce. Theexperiments were conducted under the completely randomized experimental design. Resultsrevealed some significant differences between the plant species. In particular, in the case oforganically grown tomato, there were not any significant differences among the three substrates interms of root growth. The type of the substrate had a significant effect on the fresh weight ofseedlings, with the portion 1:1 showing the highest values. It has also to be noted that seedlingquality under the organic system was higher than the one of the conventional system, since itresulted to plants of smaller height, higher root growth and lower moisture content. Organicallyproduced seedlings of lettuce and tomato had higher root length and diameter than theconventionally grown ones, respectively.Effects of shading were also studied in both systems, organic and conventional. In bothsystems seedlings were grown under no (0%) and 30% shading. Several plants were tested(tomato, lettuce, basile, tobacco, minth, melon). In most cases, our results showed that shading didnot have any significant effect on the growth of seedlings. Above-ground part development washigher in the conventional float system, while organic production favoured root growth. In thecase of conventionally grown tomato, shading reduced root growth (p<0.05). In lettuce, leaf areaand root surface were significantly lower under shade in organic and conventional seedlings,respectively. In the other plant species, shading did not have any significant effect on root and leafarea.Regarding arbuscular fungi (AMF) colonization, this was higher in the organically grownplants, while the impact of shading was not significant. Concentration of the most trace elements(Fe, Zn, Mn) has not been affected by shading. The only exception was the negative effect ofshading on the concentration of Cu in the organic float system.For the evaluation of organic fertilization, three different fertilizers were studied: Fishfert,Rhizocyn, Fishfert and Rizocyn, while inorganic fertilization was also included. The resultsshowed that the growth characteristics of the biologically produced seedlings are similar to thoseof the conventional seedling where tomato, lettuce and melon tested.Some of the conclusions were:1. The process organic seedlings produced with float system was evaluated and found thatthe produced organic seedlings are comparable and in some cases better growth compared withconventional seedlings.2. The effect of shadowing (level studied) was not significant for most studied in thisresearch characteristics and clearly needs further investigation3. The fertilization of seedlings grown in organic hydroponic seedbed using fish remainssolutions did not undercut the lubricating algae residues and standard mineral fertilization.4. The type of the substrate supports the growth of plants in seed trays for organically orconventionally produced seedlings with the method of flotation with different ratio of peat-perlitemixture demonstrate the 1/1 as the most effective.This study demonstrates the feasibility of organic seedling production with float system, since inmany cases the development and qualitative characteristics of the produced seedlings did notundercut the corresponding conventional plant. Further investigation of the effect of differentagronomic practices and the evaluation of the method in the light of the growth and productivityof seedlings transplanted to field conditions.