Mineral Content of Mediterranean Seaweeds, Padina pavonica L. (Pheophytae, Ulva lactuca L. and Ulva linza L. (Chlorophytae) for Biofertilizing Use

Nowadays, organic fertilizers play an important role in agriculture. They are progressively substituting chemical fertilizers to prevent their harmful impact on human health and the environment. They provide high yield, better quality products and a shorter period of harvesting crops. In this study, the mineral elements: primary macronutrient (N, PO3- and K+), secondary macronutrient: (Ca2+, Mg2+ and SO2-), micronutrient (Na+ and Cl-), alkalinity (HCO3-) and other elements (NO2- and NO-), of three seaweeds were determined: chlorophytae (Ulva lactuca, Ulva linza) and phaeophytae (Padina pavonica). The nitrogen content was the most abundant element in the three Mediterranean seaweeds [79.85 - 57.16 - 126.09 [×10³ mg L-1], respectively, with a maximum to the chlorophytae U. lactuca. This is true also for other macroelements (K and P); their values are higher in green seaweed than the brown Padina pavonica. Secondary elements (Ca and Mg) also show higher values in green algae, with a maximum value in Ulva lactuca. There is no significant difference concerning the values of microelements Na+ and Cl- between green and brown algae. The values of nitrite and nitrate are equivalent for the two green algae, while these items are virtually nonexistent in the brown algae. In conclusion, interesting values of the green alga Ulva lactuca could suggest the use of aqueous extract of this alga such as biofertilizant.