The effect of fertilizer application on farming of the seaweed <i>Undaria pinnatifida</i> (Laminariales, Phaeophyta)

Abstract

SUMMARY A slow‐release ammonium phosphate fertilizer coated with porous plastic was tested on Undaria pinnatifida (Harvey) Suringar as a possible solution to the nutrient deficiency in seawater that causes quality and yield deterioration in seaweed farming. The yield of U. pinnatifida within the fertilized area was 17–40% greater than that of the control area (unfertilized area). In addition, two harvests were possible per season and the quality of harvested U. pinnatifida was also better than that outside the fertilizer diffusion area. The released NH 4 ‐N did not increase the concentration of NH 4 ‐N outside the farming area. Therefore, this fertilizer increased yield and improved quality without causing water pollution.