I am not sure how this green fertilizer really works. Adherents of organic gardening in Germany, where this smelly liquid made from weeds is called "Jauche" claim that it turbo charges the soil with beneficial micro-organisms. It is intentionally mixed aerobic / anaerobic composting. Perhaps it contains both aerobic and anaerobic organisms in sufficient quantities to seed the soil well. I also think it may contain a lot of nutrients. I read in the literature about anaerobic digestion, that grass has more nutrients than cow manure, as the cow's stomach has extracted a lot of the useful stuff. I'm assuming weeds will likewise have a lot of nutrients. The German website mentioned below states that liquid green manure contains a lot of Nitrogen and Potassium, and provides adequate nutrition for most plants. They also say it can be used as a compost starter, and a nettle brew can be used pure as a foliar spray against insects, but not on light feeders like carrots as it contains too much Nitrogen. Real officionados use particularly good composting weeds like nettles to make the brew. Dandelions, onions, garlic and Camomile are also good. I use what ever I've pulled out.
This is one of the easiest ways of making organic garden fertilizer. It is like a brewing process that cannot go wrong. It will enliven the soil, and make your plants perky fast. Trust the nation of brewers to have come up with a nutritious form of liquid in order for their garden denizens not to feel left out.
Place some plants in a bucket of water. For a more beneficial green fertilizer you can use nettles, comfrey, those weeds with good compost starting and or nutrient profiles. I’ve mostly used any weeds I can find, including pesky things like morning glory that can resurrect itself from seemingly dead sticks and old dry vines, and whose life force I want to remove in a terminal sort of way before using it as mulch. Anaerobic rotting does this. Chop up the plants, immerse in stood water and stir vigorously once a day.
Very soon, and notably this is partially anaerobic, casting doubt on the reputed slowness of anaerobic processes, very soon it will begin to emit the fragrance of cow manure. The smell will cling to all exposed skin for a long time, so do wear gloves if the whiff of dairy farming will have negative repercussions in your life.
Continue to stir daily until the biological perfume subsides. You will see that only the stringy, leached plant fibers remain and everything else has liquified. Indeed, this is how flax fibers were extracted from the plant in the past. When your brew is no longer so smelly, dilute ten to one and water your plants. This plant beer will make your soil very happy, boosting soil life and adding trace elements. In my experience it also makes the plants take on a healthy glow and get a bit unruly.
A week later I did some weeding and added the weeds to the brew, necessitating a larger bucket. In time the smell became powerful, drifting dangerously around the neighbourhood. I wondered if the suggestion that the smell eventually subsides is just another fairy story. To prevent my neighbours becoming offended, or thinking I was processing real manure, I had to terminate the brewing, which was nearly complete, and had had its full effect on the weeds and morning glory