Here's a link to an article about veganic gardening from

A little excerpt:

Soil conditioners and fertilizers that we use include: lime, gypsum, rock phosphorus, dolomite, rock dusts, rock potash, wood ash, hay mulches, composted organic matter (fruit and vegetable rinds, leaves, and grass clippings), green manures or nitrogen-fixing crops, liquid feeds such as comfrey or nettles, and seaweed (fresh, liquid or meal) for trace elements. Seaweed is best used harvested fresh from the sea as opposed to washed up and sitting on beaches.