Growth, relative chlorophyll content and concentration of inorganic solutes in sunflowers plants supplemented with marine macroalgae organic residue

Resumo

One effect of the tidal dynamics is the accumulation during of large volumes of macroalgae the low tide, named “arribadas algae”. The objective of this work was to analyze the effects of using arribada alga eorganic residues (AAOR) on the initial growth of sunflower plants, where the following were evaluated: plant growth, relative chlorophyll content and inorganic solids content (Na, K, Cl and NO₃). The algae were collected on Praia do Pacheco in Caucaia, state of Ceará, Brazil, washed in running water and placed to dry in the sun for seven days, then dried in a forced circulation oven at 80 ºC and crushed. The sunflower seeds were sown in 5 L plastic buckets, containing: 1) 100% (in volume) of sand; 2) sand + 100% of nitrogen recommendation - NR in commercial fertilizer (80 kg of N.ha^-1); 3) sand + 50% of the NR in macroalgae; 4) sand + 100% of NR in macroalgae; and 5) sand + 150% of the NR in macroalgae. The use of AAOR improved the growth of the analyzed variables in relation to the plants grown in substrate with sand or sand + fertilizer. The best results were observed at 50% of the NR in AAOR. The addition of increasing concentrations of AAOR allowed a greater accumulation of beneficial ions such as K and NO3 while no significant differences were observed for toxic ions such as Na and Cl in relation to plants supplemented with fertilizer or sand. The use of AAOR in substrates can be an alternative to fertilizers in plant cultivation since it reduces production costs besides being a sustainable destination.