Leftover food, chipped bark, garden compost, leaf moulds and manure should be mixed together using a compost heap and spread throughout your garden so you are not solely relying on sunlight and water to make the crops grow. Manure isn’t something that should make you feel ill when thinking about it, it is sold in stores or you could just let chickens roam around in the garden so don’t think you have to scoop this from the toilet. You could use dead animals or meat products as others do but these cannot be put in the soil. Yet, left for a couple of weeks in the bin, maggots will soon appear which is what you use to help fertilize your garden.