Use of Organic Fertilizers for Lettuce Plug Plant Production

Vegetable crop production in conventional intensive agricultural systems commonly requires high fertilization rates. Recent data show that organic vegetable production in Italy is expanding rapidly. The increasing number of growers involved in organic vegetable production has created a demand for organically produced seedlings. The aim of this study was to evaluate the effects of different levels of organic fertilizers [commercial organic fertilizers permitted by the European Council Regulation (EEC) No 2092/91] applied to lettuce seedlings on seedling growth and yield. Romaine lettuce seeds of cultivar 'Gretta R' were sown on March 2007 in polystyrene plug trays in an unheated greenhouse on the Northern coast of Sicily. At the second leaf stage, seedlings were sub-irrigated with various concentrations (3, 6, or 9 g L-1) of an organic water soluble fertilizer (Kappabios, Serbios (R)) containing N 3% and K2O 6%. At the end of March 2007, four leaf stage plug plants were field transplanted in black polyethylene film mulched plots at a density of 6.6 plants per m(2). One week after transplanting, young plants were foliar sprayed with various concentrations (1.5, 2.5, or 3.5 g L-1) of an organic water soluble fertilizer containing 14% N (Azobios, Serbios (R)). Higher fertilization rates positively influenced seedling growth in the greenhouse and resulted in higher yields and larger head weight relative to the control seedlings growth, yield and head weight.