The primary aim of SeaSoilDemo was to study the effect of application of various seaweed materials in a perennial grass-clover ley and communicate with industry actors about the experiences made. Secondary objectives were to record by photos and video the performance of various seaweed materials when they were applied as soil amendments to perennial ley, and their effects on the growth of the ley (WP1); to edit visual documentation materials into presentations (WP2) and to ensure progress and scientific quality (WP3).
The project was categorized under priority area 1, "Dissemination of research and results", but also had relevance for area 3, "Business and commercialisation preparation" because we acquired experience about the practical handling and performance of seaweed material as soil amendment.
The project implied a high level of risk, because we wanted to test the maximum amount of material application over 10 years, being 2 or 4 kg DM/m2, in one rate, to see if a perennial ley could survive. The reason for this was that farmers may possibly be offered large quantities of seaweed materials at a low cost, e.g. due to exceeded shelf-life of products. With 6 out of 7 materials applied, the ley survived. Fermented material with a low content of DM, which easily leached into the ground killed off all the ley plants. Perennial weeds (coach grass, dandelion) colonised the plot, which became green for the second cut of ley. The canopy on all amended plots was not suited for ruminant feed due to high content of potassium but low of calcium + magnesium. This implies a high risk of tetany disease. The concentrations of minerals, arsenic and heavy metals were measured at NMBU. The content of arsenic in the canopy increased with application of high seaweed rates, but not the content of cadmium.
With the high rates applied, seaweed material was present on the soil surface throughout the season in several plots and made the surface smeary. Such high rates are not recommendable, for several reasons, but we are grateful that we could conduct this special experiment anyway, to demonstrate some potential consequences of high rate applications.
Three videos were produced, entitled
- Presenting the seaweed-based fertilizers in the Seasoil project (youtube.com)
- Seasoil: What happens when you apply the maximum rate of seaweed material to perennial ley? (youtube.com)
- Testing seaweed materials on perennial ley: Growth through the season (youtube.com)
The last video follows the growth on all plots from early May to late September 2023. Two Irish and three Norwegian seaweed industries provided materials for testing, and were actively involved in discussing the results and how to present them in videos and Power point presentations.
The experiment has been presented (by internet connection) on the Blue Bio e-coffee meeting on November 8, 2023; the final BlueBio meeting on March 19, 2024; for members of the Norwegian Seaweed Association on May 8, 2024; for 20 students in the international summer school conducted by the BlueBio project MariGreen on May 29, 2024; and during the SeaSoil project meeting in Ireland on June 4, 2024. It will be presented during the Seagriculture Conference in Torshavn, Faroy, on June 20, 2024.
Coordinator:
Anne-Kristin Løes, Norwegian Centre for Organic Agriculture (NORSØK)