Just getting ready to prepare my raised beds for planting vegetables at a later stage. Is it possible to use fresh horse manure or how old has it to be. I can also get seaweed from the shore but don't know if I can use it at this stage, will it break down in the soil in time so that I can plant my seeds at a later stage.
Better to let manure rot undercover (old plastic /carpet etc) to avoid leeching of nutrients. Fresh manure can be used on established plants. I have seen gardens with cabbage/sprouts/caulies with fresh manure without any problems.You can use fresh manure mixed with water to make a nutrient "drink" for plots. Use when plants are well-established and avoid leaves.
Also you can spread fresh manure & seaweed after the growing season, lightly fork it in and break it up. It should rot over winter.
My father used to collect seaweed from Dun Laoghaire harbour. He brought it home and put it in a trench he dug in the garden, covered it and left it there for six months. I think he usually collected the seaweed in September as it's at its most nutrient dense in the Autumn. He learnt that from his stint as a teacher in one of the Aran Islands as he stayed in Connemara.