Many naturally-derived products are used as growth promoters or biostimulants on vegetables, even if their mechanisms of action are not still now completely clarified. Among them, seaweeds and seaweed products are inserted as admissible organic fertilizers in the Annex I of the Reg. (EC) No. 889/2008, even if their biostimulant properties are not recognized in organic farming.
After a previous bioassay on maize germination for defining the optimal water dilution ratios of the filtrate seaweed extract (FSE), in the present research we applied the FSE at two diluted doses to a greenhouse organic lettuce, for assessing its biostimulant effect on vegetable growth and nutrient uptake.
The greenhouse pot trials were conducted on Lactuca sativa L., by applying FSE at 1/250 and 1/500 v/v water dilutions. After 90 days, root fresh/dry weight, shoot fresh/dry weight and dry matter, number of leaves, LAI, specific leaf fresh/dry weight, total dry biomass, leaf macro and micro elements (P, K, Ca, Mg, Fe, Na, Mn, Cu, Zn, B) content and total chlorophyll were determined.
Obtained results indicated that FSE plays a role in promoting the increase of lettuce shoot dry weight and related nutrient uptake, with particular efficacy in relation to P and K macroelements. This property is better expressed at the highest dilution, confirming that the biostimulating activity of the formulate acts without any nutritional effect: thus, the FSE appears to be a good opportunity for promoting the early-stage development for organic nursery productio
