Potassium release kinetics from three invasive algae mixed with different media in leachate column studies

Algae can be an important source of nutrients in agriculture. The objectives of this study were to (1) estimate the potassium (K) release rate from algae, commercially prepared algal cell walls, and synthetic sources, and (2) better understand effects of polymeric chemistry and potential mechanisms among test materials. Three leachate column studies were conducted for 16 weeks. The experiments consisted of five K sources applied at 0, 112, and 336 kg K ha. At each leachate collection, half pore volume deionized water was applied and leachate samples were analyzed using a K ion selective electrode. Results from these studies showed that the amount of K released was significantly higher under synthetic K in the first 6 weeks (4100–4200 mg L) and sharply declined thereafter. Release of K from algal samples was slower in the first 3 weeks and peaked in 8 to 9 weeks (2800–3400 mg L). The release of K from agar weed Gracilaria salicornia was significantly lower than from carrageenan producer, Eucheuma denticulatum and Kappaphycus alvarezii. Another leachate study was conducted for 6 weeks using agar and carrageenan and found that K release from agar columns was significantly lower (10–12%) than from carrageenan. We conclude that the differences in release rate of K among dried algae may be explained in part by differences in cell wall composition.